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Nuclear Engineering Handbook

Kenneth D. Kok

Boiling Water Reactors

Publication details https://www.routledgehandbooks.com/doi/10.1201/9781315373829-5 Kevin Theriault Published online on: 21 Oct 2016

How to cite :- Kevin Theriault. 21 Oct 2016, Boiling Water Reactors from: Nuclear Engineering Handbook CRC Press Accessed on: 28 Sep 2021 https://www.routledgehandbooks.com/doi/10.1201/9781315373829-5

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The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The publisher shall not be liable for an loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 . Reactor ...... Core Design 3.3 . Nuclear Assembly Boiler ...... 3.2 ...... 3.1 Introduction CONTENTS Theriault Kevin Boiling Water Reactors 3 ...... Core Design 3.3.4 of Fuel Assembly Description ...... 3.3.3 Core ...... Configuration 3.3.2 ...... 3.3.1 Introduction .. Control Rod Drive System ...... 3.2.5 ...... Lines Steam Main 3.2.4 ...... Description Summary 3.1.5 Economic Simplified ...... BWR 3.1.4 3.1.3 ABWR ...... BWR-6 Product ...... Line 3.1.2 Water Boiling Reactor ...... Background 3.1.1 .. Reactor Water System ...... Recirculation 3.2.3 Reactor Assembly ...... 3.2.2 ...... 3.2.1 Introduction 3.3.4.5 Core Thermal Hydraulics Core ...... Thermal Power Local ...... 3.3.4.5 Distribution Relative Assembly3.3.4.4 Power ...... Distribution ...... Distribution Axial 3.3.4.3 Power ...... 3.3.4.2 Distribution 3.3.4.1 ...... Fuel Channel ...... Features Bundle 3.3.3.5 Fuel ...... Bundle 3.3.3.4 of Fuel Basis ...... Rods Design 3.3.3.3 Fuel Rod ...... 3.3.3.2 3.3.3.1 ... Safety/Relief Valves ...... 3.2.4.1 Valves Piping ...... and Motors and Pumps ...... 3.2.3.5 Jet of ...... Feature the Pump Safety 3.2.3.4 Jet Principle of ...... the Pump Operating 3.2.3.3 3.2.3.2 ... Jet Assembly...... Pump 3.2.3.1 ...... Dryer Steam Core Shroud ...... 3.2.2.3 Reactor Vessel3.2.2.2 ...... 3.2.2.1 104 104 108 108 109 106 103 102 102 102 112 101 113 113 113 113 110 110 111 111 114 114 114 85 88 99 99 98 98 96 96 97 87 87 87 91 91 Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 86 3.4 Reactor Auxiliary Systems ...... Reactor Auxiliary 3.4 3.5 Instrumentation and Controls ...... and Instrumentation 3.5 3.4.9 RHR System RHR ...... 3.4.9 3.4.8 ECCS ...... RCIC System ...... 3.4.7 SBLC System ...... 3.4.6 Emergency Equipment System Cooling ...... 3.4.5 Water Cooling Closed System ...... for Reactor Service 3.4.4 Pools Cleanup and System Containment Cooling and Fuel ...... Building 3.4.3 RWCU System ...... 3.4.2 ...... 3.4.1 Introduction Reactor Control Reactivity ...... 3.3.5 .. Nuclear System System Protection ...... 3.5.5 Plant Shutdown ...... 3.5.4 Power Operation ...... 3.5.3 ...... Plant Startup 3.5.2 ...... 3.5.1 Introduction 3.4.9.1 LPCI ...... Automatic Function Depressurization LPCS System3.4.8.3 ...... HPCS System ...... 3.4.8.2 3.4.8.1 Supplementary Control Reactivity ...... Control Rod Nuclear Characteristics 3.3.5.3 Control ...... Rods 3.3.5.2 3.3.5.1 ...... Reactor Stability 3.3.4.11 ...... Localization Strain ...... Limits Damage and Limits Operating between Margin 3.3.4.10 Control Reactivity ...... 3.3.4.9 ...... Core Nuclear Characteristics 3.3.4.8 Thermal-Hydraulic Analysis...... 3.3.4.7 3.3.4.6 ...... Annunciation and Reset Power ...... 3.5.5.6 Distribution Separation ...... Divisional 3.5.5.5 ...... Function Actuation Features Safety Engineered 3.5.5.4 Nuclear System ...... 3.5.5.3 Isolation Function Reactor Trip ...... 3.5.5.2 Function 3.5.5.1 Average Power Monitor Range ...... Power Local Monitor3.5.4.4 Range ...... Monitors Range ...... Intermediate 3.5.4.3 Monitor Range ...... Source 3.5.4.2 3.5.4.1 Reactor Feedwater Control System ...... Relief Function Pressure 3.5.3.6 Turbine3.5.3.5 Valve Bypass ...... System Control3.5.3.4 ...... Flow Control ...... Recirculation 3.5.3.3 Control Rod Adjustment3.5.3.2 ...... 3.5.3.1 Turbine ...... Startup Operation ...... and Reactor Startup 3.5.2.2 3.5.2.1 Nuclear Engineering Handbook Engineering Nuclear 122 122 123 134 134 128 128 128 130 130 127 133 133 133 133 129 129 129 129 126 120 135 135 135 138 136 124 121 121 13 137 137 137 131 131 131 115 117 117 119 119 119 118 118 118 116 116 114 7 Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Boiling Water Reactors 600–1400 MWe gross. Principal design features include600–1400 MWe features design Principal gross. or support systems. Powertive buildings output approximately capabilities range from respec of the size the BWR-5 product without the increasing in line used as vessels sure BWR-6 productThe capable is line of producing 20 Line BWR-6 Product 3.1.2 power fossil-fueled found in to that plants. similar BWR generation substantially cycle is power 1955 to in equipment business offer it commercially. Aside its heat from source, the atomic an advantages established and simplicity of control design its and inherent in separator steam dryer. and internal the tions: innova technical two by introducing drum steam external of the ABWR was elimination thetheultimately that step path to first its down led of way The simplicity turbine. to the generator steam andsecondary flowedbefore making a then an elevated to drum steam reactor BWRs. was generated but Steam the in characterizes cycle that steam direct not the upon cycle, was dual based BWR. enough, design steam was, The not atrue interestingly Referdesign. to Table 3.1 to evolution the see offirst 1 simplification.The Dresden BWR, nuclear supply the in supply chain. led to partnerships continued has base Union, Toshiba, Hitachi, Kraftwerken Consolidation industrial of Electric. the General and operation in globally. of number units total former vendors Current and ASEA-Atom, are about comprises design 25 (ABWRs)BWRs This construction. under currently explored be later. will This bundles. fuel of the envelope the in water and region fuel boiling the in heatsystem with generation occurring simplicity. mind: in one purpose with changes lutionary followed 1960, in BWR of subsequently the design evo underwent aseries then since and Dresden BWR, I, large-scale first for The safely produceagrid. and electricity cessfully (1957) Vallecitosthat The BWR could Jose, plantsucplants San confirmed near California. first theBWR 5 MWe The program. nuclear be to plant built was submarine Plant Vallecitos developed 1950s the technology in United for the the States Navy in nuclear its origins has The boiling water reactors boiling The Boiling Water3.1.1 Reactor Background 3.1 Introduction General Electric selected the BWR as the most promising nuclear power most BWR promising the the as concept selected because Electric General twoand areas:containment reactor key in systems simplified been BWR has The design approximately are worldThere the 92 operational in BWRs today several and advanced cycle nuclear a direct is latter the BWR that PWR and is the between major difference The • separators capacity dryers. steam and from Increased • capability. coolant circulation Compact increased pumps with jet • ...... Rod Control Information and 3.5.6 nals arrangement. nals improvements and vessels reactor inter pressure in standard in More bundles fuel ...... Interlocks and Bypass ...... Backup Protection 3.5.5.8 3.5.5.7 (BWRs) nuclear plant, like the pressurized water(BWRs) reactor (PWR), pressurized nuclear plant, the like more power from the same size pres % more size power same the from of the % of the - 138 138 139 87 - - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 88 touches on the design and systematically reduce systematically and capital design touches on the proved costs, which to ahighly be to put finishing the 3 was of Phase purpose The features. design and new technologies development ofof the testing the and took place, engineering included more detailed ABWR of most the which 2, concept. feasibility in Phase the studydesign determined that and easier more efficient. significantly nance plant would that mainte the design into capital make the incorporate cost features and attention was lay paid that reduce to systematically ahead, special challenges economic the improvements Safety were, always, techniques. as struction top priority. the Anticipating of worldwide BWRs, operating (2) available (3) and new technologies, new con modular blendment was aBWR to design effort of plant (1) included that acareful features best the PowerElectric Company (TEPCO) 3.1 and (Figures 3.2). develop of the stated purpose The Development ABWR of the of took 1980s the Tokyo place the sponsorship the under during ABWR 3.1.3 Development of the ABWR occurred in a series of steps. Phase 1 was a conceptual was aconceptual of 1 steps.Development aseries Phase in ABWR of the occurred • Improved operator–machine interface systems for better control Improved plant. of for interface systems the better operator–machine • • • ESBWR ABWR BWR/6 BWR/5 BWR/4 BWR/3 Product Line Product Evolution GE BWR of the 3.1 TABLE BWR/2 BWR/1 electronics technology. electronics latest the solid-state incorporating systems Improved control instrumentation and heat output bundle. per increased permits and of fuel length per kilowatt rating previous 7 the as outline external same the within dles 8 in arranged and rods, longer active fuel length fuel in Smaller-diameter First Commercial Commercial First Operation Date Operation ne eiwTBD Under review 1996 1978 1977 1972 1971 1969 1960 Passive ECCS Natural circulation Improved ECCS:high/lowpressure flooders Advanced control room, digitalandfiber optic technology Fine-motion control rod drives Reactor internalpumps Kashiwazaki-Kariwa 6 Solid-state nuclearsystemprotection system Compact control room Confrentes Valve flowcontrol Improved ECCS Tokai 2 Increased powerdensity(20%) Vermont Yankee Improved ECCS:sprayandfloodcapability First jetpumpapplication Dresden 2 Large direct cycle Plants purchased solelyoneconomics Oyster Creek Initial commercial-size BWR Dresden 1 Representative Plant/Characteristics Nuclear Engineering Handbook Engineering Nuclear 7 design. This lowers× 7 design. the This × 8 bun - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 ABWR major systems. ABWR major FIGURE 3.1 F/D Hx Tank FPC control system Standby liquid SPCU HPCF Hx RHR Fuel pool xHx Hx Suppression pool RIP demineralizer Water clean-upsystem Reactor Horizontal FMCRD Filter vent RPV (F/D) RHR RHR HPCF Hx exchanger RCIC Heat (Hx) control unit Hydraulic CRD drain pump drain tank HP heater HP heater feedwater heater High-pressure turbine High-pressure pump water Feed Condenser separator Moisture reheater pressure turbine Low- feedwater heater Low-pressure CBP demineralizer Condensate Condensate filter Gland steam CP condenser air ejector Steam jet Generator Off-gas system storage pool Condensate

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Boiling Water Reactors Water Boiling 89 Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 gram. The key goals, all of which were of which follows: key achieved, goals, as all The are gram. conclusion. 17,later year on September that adecade of development bringing work to asuccessful review. Permit, May Establishment in 1991. An was or issued license, Excavation began reviews. respective their to discuss ings (NRC). Commission Nuclear NRC,the the Regulatory fact, and in MITI held several meet United ABWR of review the States the the by in with forconducted some parallel time in and, interestingly, time were at Trade this started (MITI),International also Industry and of agency, Japanese the regulatory with activities Ministry Licensing the began. ing structed would ABWRs. be structed to con be units next Kashiwazaki-Kariwa the that 1988 when TEPCOend in announced endeavor. fortuitous hindsight, and, in successful development The to an came phases 90 ABWR reactor assembly. ABWR reactor FIGURE 3.2 The key design objectives for the ABWR were established during the development ABWR for the the objectives key design wereThe during established pro By 1991, complete concluded MITI and was its essentially design licensing detailed the With the selection of the ABWR for the K-6&7 projects, the detailed project engineer project detailed ABWR of the the With selection forK-6&7 projects, the the • Less than one unplanned scram per year per scram one unplanned than Less • factor Plant of availability 87 • of 60 years life Design • 3 2 20 7 6 8 16 17 5 26 21 15 14 25 10 22 12 13 11 24 9 27 1 19 23 18 4 % 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 — — — — — — — — — — — — — — — — — — — — — — — — — — — Control rods Fuel assemblie Local powerrangemonito Fine-motion controlroddrives Reactor internalpumps(RIPs) Steam dryerassembly Shroud headandsteamseparatorassembly Shutdown coolingoutlet Low-pressure flooder(LPFL) HPCF couplin High-pressure coreflooder(HPCF)sparger Feedwater sparger In-core instrumentguidetube In-core housin Control rodguidetube Control roddrivehousing Fuel supports Top guide Core plat Core shroud Forged shellring RIP penetration Vessel bottomhead Vessel supportskir Feedwater nozzl Stem outletflowrestrictor Vessel flangeandclosurehead e g s g s e s t Nuclear Engineering Handbook Engineering Nuclear s s r s - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Boiling Water Reactors nonexistent. condensate supply and bysteam radioactive virtually system the is particles turbine to the power reactor during vessel only the generation. from Carryover exists ofsteam long-lived N16,primarily of radioactivity the the avery short-lived that so of 7 s) (half-life isotope 3.6.for Figure aBWR shown system in is basic heat The deaeration condenser balance cycle with condensate and demineralization. generator. employs turbine steam to the turbine The a conventionaldirected regenerative water, top vessel, of the the and recirculation separated in rated from is dried which steam, reactor core, the Water producing through satu circulated instrumentation. is and trols con necessary and requirements to accommodate safeguard systems operational and the generator feedwater and supply nuclear auxiliary core the are with system. Associated of anuclear core located aconventional areactor vessel inside and consisting tem turbine sys cycle BWR 3.5) system generation (Figure utilization asteam steam direct is and The Description Summary 3.1.5 Table product lines. described of table 3.2 is the acomparison key for features the The economic simplified economic The BWR Economic Simplified 3.1.4 U.S. NRC. are key goals The 3.3 and(Figures 3.4).the publication by production certified ofESBWR As this the being is simplified the wellBWR as as programs, (SBWR) construction and development program The steam produced steam The nuclear by core the is, of course, radioactive. is radioactivity The • < limit radiation exposure personnel Operating • of 18–24 months interval Refueling • • of 48 months schedule Construction • 10 of Radwaste that the generation than less • Radwaste generation < • • Construction schedule of 48 months schedule Construction • • < limit radiation exposure personnel Operating • of 18–24 months interval Refueling • year per scram one unplanned than Less • of 60 years life Design • factor Plant of availability 95 • Cost advantage technologies generating over load base typical competing • BWRs (goal < (goal BWRs by atReduced core least frequency afactor damage calculated of 10 over previous cally complex systems cally safety 20 BWRs (GoalBWRs < by atReduced core least frequency afactor damage calculated of 10 over previous reduction in capital% reduction in cost ($/kWh) versus previous 1100 MWe typi BWRs class 10 l0 − 6 6 /year) /year)

BWR 100 m ESBWR) builds on the very successful ABWR technology (ESBWR) ABWR very technology successful on the builds % 3 /year best operating BWRs operating % best 1 Sv/year 1 Sv/year - 91 - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 ESBWR major systems. ESBWR major FIGURE 3.3 F/D Hx Tank pool coolingsystem N Fuel andauxiliary 2 F/D Hx Standby liquid Vent tostack control system PCCS Suppression GDCS pool H NRHx RHx shutdown coolingsystem Reactor watercleanup/ FMCRD RPV Filter/demineralizer SRV control unit Hydraulic Suppression DPV pool condenser Isolation Backup Vent tostack spray from FAPCS Backup makeup fill connection Post LOCA from CRDS Backup makeup CRD pump pump water Feed High pressureturbine High-pressure Feedwater FW heaters heater #4 Open FW 5, 6,and7 pump boost feedwater heaters Low-pressure 1, 2,and3 condenser separator Moisture reheater Main pressure turbine Low- Main con- den ser Condenser Condensate demineralizer Condensate pump Condensate air ejector Circulating Steam jet Generator filter water Off-gas system storage tank Condensate

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Nuclear Engineering Handbook Engineering Nuclear 92 Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 ESBWR reactor pressure vessel and internals. and vessel pressure ESBWR reactor FIGURE 3.4 ing or at each refueling operation. hydraulic The or ating refueling each control drive rod system, incorporates which load fuel vessel prior open to initial an with drive allow drives testing and control and rods without bottom-mounted removal and control drives of refueling allow rod Bottom-entry achieve thesuperiorload-following capabilityoftheBWR. through thecore without changingcontrol rod position.ThisuniqueBWR feature helps The BWRcore powerlevelisfurtheradjustablebychangingtherecirculation flowrate level ismaintainedoradjustedbypositioningcontrol rods upanddownwithinthecore. high.Thepower in diameterand 14 ft (4.3 m) (4.9 m) forming acore arrayabout16 ft A 1220-MWe assembliesand177 control rod BWR-6 core consistsof748 fuel assemblies, rods contained within thereactor vesseland cooled bytherecirculating watersystem. Boiling Water Reactors The BWR is the only light water light only BWR the The is reactor system employs that control rods. bottom-entry The nuclearcore, thesource oftheheat,consistsfuelassembliesandcontrol 93 - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 oto omSystem-based Severe accident Control room In-core monitor Control and Alternate Emergency AC Containment heat Shutdown heat Isolation makeup Welded plate Primary Fine-motionCRDs Reactor vessel LockingpistonCRDs ECCS Control rod drives Recirculation Feature BWRs to Previous of Key ESBWR Features Comparison 3.2 TABLE 94 Direct cycle reactor system. reactor cycle Direct FIGURE 3.5 mitigation calibration instrumentation shutdown removal removal water containment RPV system inside Recirculation Reactor pumps vessel o pcfclyadesdInerting,drywell flooding, Not specificallyaddressed TIP system Two nonsafetyD/G Analog, hardwired, single Three safety-gradeD/G Two SLCpumps Three safety-gradeD/G Two-division RHR Two-division RHR RCIC Mark III—large, low Two-division ECCSplus Two externalloop

Core channel pressure, notinerted HPCS jet pumps recirculation systemwith Heaters Feedwater and dryers Separators BWR/6 Steam pumps pumps Drain Feed Heaters Turbine prtrts-ae Operatortask-based Operator task-based A-TIP system Digital, multiplexed,fiber Passive Two SLCpumps Nonsafetysystem Three-division RHR Three-division RHR RCIC Compact, inerted Four-division, passive, Extensive useofforged Three-division ECCS Vessel-mounted reactor containment venting optics, multiplechannel rings internal pumps Extraction steam Demineralizers PL LP LP HP ABWR Moisture separator and reheater Condenser Nuclear Engineering Handbook Engineering Nuclear Inerting, drywellflooding, Gamma thermometers Digital, multiplexed,fiber Two SLEaccumulators Isolation condensers, Compact, inerted Extensive useofforged Fine-motion CRDs Natural circulation core catcher optics, multiplechannel combined withRWCU passive rings gravity-driven Generator Condensate pumps ESBWR Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 changes of up to 25 changes turbine. the flow steam Power on load in to demands accommodate changes varying flow reactor water the control with automated systempermits recirculation conjunction in control and system regulator pressure turbine of integration the boilers. The to most fossil pumps. recirculation the of deliver BWRthe can at least 10 most BWR of boilers, loss-of-coolantconditions. emergency under the Like design safety inherent the contribute to also thereactor The jet pumps vessel. flowwithin recirculation of pumps generate the reactor vessel. the of These pumps inside tion about jet two-thirds applica BWR the of of is the product any boiler).cal feature line unique and important An greater than any gravity or mechanical system carry out rapid system carry control insertion. rod or any mechanical gravity than greater force far accumulators provide that insertion arod control of Pressurized rods. the tioning position, at provides rod selected of posi the the and positive locking driving mechanical Boiling Water Reactors Typical heat balance diagram. Typical heatbalance FIGURE 3.6 The BWR operates at constant pressure and maintains constant steam pressure similar similar pressure steam constant BWR maintains The operates and pressure at constant The core flowThe the feedwater theof sum flowof a (typiis recirculation the BWR flow and 08H Ah =0.8 P =Pressure,psia M =Moisture,% F =Temperature, H =Enthalpy,Btu/lbm # =Flow,lbm/h Turbine cycleuse Other systemlosses Cleanup losses Pump heating Core thermalpower Legend Wd =100.0% % of rated power accomplished be can automatically by recirculation 527.6 H 532.9 F 2.100E+04 # power in a natural recirculation mode without operation recirculation % power anatural in 48.0 H 77.0 F 49.0E+06 MWt 1040 526.9 1912 Total core flow P 1913.3 MWt 1912.0 H # −1.1 −2.7 Control roddrive 5.1 feed flow * ConditionsatupstreamsideofTSV Carryunder =0.35% 8.414E+06 # Main steamflow 410.1 H 431.4 F Main feedflow demineralizer Clea syst nu em 8.300E+04 # 8.300E+04 # 8.331E+06 # p 8.352E+06 # 1190.8 H* 526.8 H 414.6 H 410.1 H 532.2 F 435.5 F 431.4 F 0.42 M* 983 P* * 95 - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 The following auxiliary systems are used as backup as (standby) used are systems or systems: emergency following auxiliary The plant for operation: normal used are systems tem. Several auxiliary out control settings. rod altering flow alone,control thus providing automatic load-followingthecapability with for BWR 96 principal components follows: as principal nuclear of are boiler the generator.to produce, turbine by power the steam control and the contain, The required necessary equipment of instrumentation the nuclear and assembly boiler consists The 3.2.1 Introduction Nuclear Boiler Assembly 3.2 The nuclear boiler system is supported by the specialized functions of its auxiliary sys of its auxiliary functions nuclear supported system boiler specialized The by is the • Low-pressure core spray (LPCS) system • core spray High-pressure (HPCS) system • • • • • system RHR • Reactor (RCIC) core isolation cooling system • Standby control liquid (SBLC) system • Radioactive system waste treatment • water cooling Closed system for reactor service • system filtering and cooling pools containment and Fuel building • residual of the heat Shutdown removal function (RHR) system cooling • Reactor water cleanup (RWCU) system • • • • • Automatic depressurization Automatic cooling pool Suppression spray Containment condensing Steam (LPCI) injection coolant Low-pressure lic system for insertion and withdrawal and control of rods the systemlic for insertion Control rod drive system guides and isolation valve, outboard containment suppressors,including its restraints, and lines steam Main core flow controlling and providing suppressors;piping devices, and its in suspension and restraints, used system recirculation water Reactor structure support core separators dryers, steam core and spray,recirculation, feedwater and spargers and and internals vessel Reactor : Safety/relief isolation valves; containment and piping up to and : Control rods, control rod drive mechanisms, and hydrau and : Control rods, control drive rod mechanisms, : Reactor pressure vessel,: Reactor pumps for jet pressure reactor water : Pumps; control equipment and isolation valves; Nuclear Engineering Handbook Engineering Nuclear - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Reactor assembly. Reactor FIGURE 3.7 corrosion-resistant alloys. All major internal componentsremoved be reactor of can the major internal corrosion-resistant alloys. All drive rod of assembly. the of for of removal housing bottom ease each maintenance the and used at is operations. joint Aflanged drives do refueling with not interfere bottom-entry The welded are housings, head which bottom reactor of to vessel. the the drives mounted within coupled plant below are operation. core during rods the tubes The to guide control the rod providesguide lateral support assembly. top for of fuel the each core plateThe top provides at The top tube. of control the lateral each guide rod guidance head bottom by reactor of vessel. the ported acontrol the drive nozzle rod penetration in support its fuel sup weight piece, tube, with is guide the Each and of bears assemblies four fuel support tubes. guide orificed on mounted the top control on an of corerod rests the rods, up control drive rod control housings, makes assembly drives. and that rod fuel Each control includes the reactor pumps. jet assembly The also the and assemblies, dryer and core,the shroud, assembly, top the guide the core plate the assembly, separator steam the components reactor 3.7) reactor ofassemblyThe ofvessel, (Figure the its consists internal Reactor Assembly 3.2.2 Boiling Water Reactors Except for the Zircaloy in the reactor core, these reactor internals are stainless steel or other or steel other stainless are reactor core, reactor the internals Except in Zircaloy for these the may into and withdrawn be assemblies Control fuel occupy spaces alternate rods between Jet pump/recirculation Low-pressure coolant In-core fluxmonitor Vent andheadspray Vessel supportskirt Core spraysparger Jet pumpassembly Control roddrives injection inlet water inlet Core sprayinlet Fuel assemblies Steam outlet Control roddrive Shield wall Recirculation Core plate Control blade Core shroud Top guide Core sprayline Feedwater sparger Feedwater inlet Steam separator Steam dryer Steam dryerliftinglug water outlet hydraulic lines assembly assembly 97 - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 wall to prevent the jet pump outlet flow from bypassing the core and to form a chamber to preventchamber wall andthe a to core pump outlet form jet flow the from bypassing plenum. peripheral shroud of support shelf weldedThe the is inlet the into vessel to the peripheral shroud of support shelf the the below core elevation the coolant to the introduce penetrate separator the assembly.steam diffusers on aflange with discharge Thejet pump mates turn guide, in the top on thewhich withflange mates a thea flange top shroud at of plenum following connections; by formed core of shroud the is the discharge The annulus. tothe upward separate from the the downward a barrier core flow through flow the to provides core and the surrounds that structure steel stainless acylindrical, shroud is The Core Shroud 3.2.2.2 the space of flooding permits (reactor which well) above drywell, the rounding vessel. sur the vessel and the between seal the is feature design head Another the for refueling. removing when lines the steam in joints flanged to break need the eliminating thereby welded are operation. vessel body, outlet to Steam the lines refueling the to simplify ing vessel pedestal, which is integrated with the reactor building foundation. reactor building the integrated with is which vessel pedestal, bolted cylindrical is steel and which to aconcrete skirt, mounted on asupporting vessel is The loads, thrusts. reaction jet loads, and control drive earthquake rod reactions, including combined to take designed are adjacent and attachments, supports, sections shell their Totion. integrity, monitor Vessel used. system seal is detection aleak supports, internal power and include conditions cold cooling, opera and These heating hydrostatic testing, demonstrated without to perform conditions. been detectable operating at leakage has all throughout its lifetime. design safety and of operability requirements the vessel to meet evaluation coupled the materials, permits program, acontinuing with of high-quality selection initial The irradiation. after of vessel materials performance power reactors,Electric-designed considerable and data have on the accumulated been have vessel. conducted most Such programs General radiation-induced been in in changes evaluating for of and aprogram monitoring impact specimens and tensile for irradiating made are Provisions properties. material and to of enable monitoring exposure periodic vessel the located samples within are Vessel material. vessel wall surveillance material vessel reduces by core the radiation the downward shroud and the experienced between water feedwater and recalculating waterlight space reactor, carries that annulus the and vessel. of BWR the have vessels lowest integrity the of any neutron exposure structural over not is used cladding its steel surfaces. interior stainless throughout its lifetime, operating environment to steam asaturated vessel head exposed is weld steel overlay to corrosion. the stainless Since with resistance to provide necessary the low except interior vessel is of on the clad for the alloy is steel, material nozzles base which removable head. full-diameter a single The vessel with a pressure reactor vessel is The Reactor Vessel 3.2.2.1 basis. on aroutine support controlassemblies, performed fuel rods, pieces is and plant. of removal the The in-core assemblies, life of components fuel other the as such components removal would these that a major require it not task,is and is expected during piping. removal core inlet plate The the assembly top of and guide the injection assembly core shroud, pump, the jet coolant the high-pressure and pump diffusers, except jet the 98 Many features have been incorporated in the design of the vessel and its associated pip its associated vessel and of design the the have incorporated in Many features been system seal This O-rings. of metal concentric two consists seal vessel headThe closure to maximize selected are advanced and fabrication steels techniques Fine-grained Nuclear Engineering Handbook Engineering Nuclear - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 motor, aflow control valve,twoand shutoff valves. coupled a directly water-cooled a pump with (air–water)reactor vessel, containing each to the reactor of core. loops two the system external consists The coolant through required 3.8) system (Figure reactor the of water the to circulate recirculation is function The Reactor Water Recirculation System 3.2.3 down comer annulus. recirculation the into separators then the and pool surrounding to the drains and troughs by asystem removed of is carried Moisture and unit. integral arigid forming members ing support to bottom top and attached are vanes vanes. These drying the outward through operation separatorsposition vessel by head. during the flows the from Steam upwardand assembly, support dryer vessel wall the the inward from extending it held and is down in Pads installation. assembly during dryer for vessel provide of the inside the alignment sides top and the wet of plenum. the forms steam assembly and Vertical on the guides reactor vessel above the separator mounted assembly in steam is dryer the steam The Steam Dryer 3.2.2.3 flow.down comer annulus standpipes the the to join of stage each separator surrounds of pool that enters the the and wet plenum the into steam belowpasses dryer. the separated water The lower the exits end leaves then stages. separator steam the The at top and the three of each the in steam the forces water separate the from avortex centrifugal to establish the aspin wherein mixture the standpipe giving on vanes the impinges through rator, rising steam–water the mixture sepa each steel. In separators madesteam have are of and stainless no parts type moving bolt of the compression expansion and sleeve.flow-axial differential fixed The through established torque. is loading its nut Final and top nominal to guide only the tightened is in shroud up head. the Atee-bolt engages making in to engage threads it unnecessary makes which assemblies, of the removal installation the and water during tool manipulation under minimum-depth operations with reactor bolts refueling to access the during direct the Thelong-bolt objective of pins. is with to positioned locating provide design finally and guide rods with core shroud flange on the separator aligned the is base installation, by along hold-down bolt of for removal above ease extension and separators. the During devices. separator The boltedreplacement assembly is core shroud to flange the sealing a gasket or other and contactnotrequire does is a metal-to-metal core shroudand flanges separator the assembly between plenum seal cover The region. the core of discharge the pipe. andthe separator top core steam forms flange shroud onof the The assembly rests separator steam located atarray top of of standpipesstand the a three-stage each with plenum. inlet recirculation of region the mounted the below is coretion in the neutron absorber of (sodium the core. pentaborate) the Anozzlefrom injection for the solu or removalcore of spray fuel installation nozzles do the spargers and with not interfere spray provided spargers are spray with ring nozzles for separator steam top core the corebase. of the The and space the the between shroud in fault and of conditions normal operation. loads in pressure and seismic system, the and weight the separators, shroud, of shroud steam support the pump The the jet carries the the eventin re-flooded be core, the of a can around accidentloss-of-coolant which (LOCA). Boiling Water Reactors The steam separator of steam adomed weldedThe assembly on top consists is of base which an Two spargers, one for for ring other HPCS, LPCS core the the mounted and inside are the injection of cooling water. of cooling injection the The 99 - - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 lines, joins the water leaving the separators, and flows downward in the annulus between the waterthe the separators, the leaving between joins flows and lines, annulus the in downward Water drain piped routed support turbine. is the to tray the through dryer of in the collected top vessel body nozzles of located is the the end and near line steam leaves vessel through the water removed. is steam saturated where The adryer any remaining through passes and the separatorfromseparated towater the separators.is array ofopens The fixed steam steam aboveenters aplenum separator bounded by core located and the the directly dome, which steam–water The where mixture it heated atwo-phase, steam–water becomes is and mixture. channel fuel the inside rods coolant water fuel individual The along the assemblies. passes fuel support fuel each in the piece among provide piece. distribution the flow desired Orifices the nose through fuel bundle each to supportfuel individually where flowdirected the is upward, intothe andenters where tubes itturns thedriveguide control flows rod between lower the between side suction plenum the pump.a barrier jet and of the flow The of water core shroud support the shelf, in welded forms which are openings into pump diffusers jet intothe lower core discharged The plenum. to finally be diffuser, the in diffuse then and mix flows two where these pump throat downwater jet comer the the into to drawn be region in where, pump throat jet of the due process, it exchange to amomentum induces surrounding stage initial intothe thejet nozzlepump from flowdischarged is nozzles. This vessel inlet the to returned and pipes connected, are of anumber riser to which amanifold through tributed nozzles. There, it at pressure, pumped dis is ahigher recirculation two the vessel through the from Approximately core vessel wall. of flow the core the taken shroud and is one-third path for core of amajor coolant flow. the portion circulation pumps, jet system. havetion The which provide no parts, moving acontinuous internal 100 BWR vessel arrangement for jet pump recirculation system. recirculation pump jet for arrangement BWR vessel FIGURE 3.8 The recirculation pumps take suction from the downward flow in the annulus between the the between downwardannulus the the from suction flowin pumps take recirculation The High-performance jet pumps located within the reactor vessel are used in the recircula the in used reactor vessel are the pumps located jet within High-performance Recirculation Jet pumps Manifold inlet Shutoff control valve valve Flow Nuclear Engineering Handbook Engineering Nuclear Recirculation Recirculation Shutoff valve pump outlet - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Jet pump assembly. pump Jet FIGURE 3.9 pipe. The jet pump assembly is composed of two jet pumps and contains no parts. moving pipe. contains of pumps composed and pump jet assembly two jet is The riser from flew a single supplied of pumps is jet pair Each driving wall. vessel inner the core shroud and the 3.9) between region pumps (Figure jet The annular the located in are Jet Assembly Pump 3.2.3.1 flow. recirculation vessel as the from exits remainder the pumps and jet enters the downward the flow joins and above of water. annulus the downwardthis of flow Aportion Feedwater vessel wall. core the shroud and added spargers located is system through to the Boiling Water Reactors and supports nozzle assembly Hold-down Inlet and tailpipe Reactor vessel and supports Mixer Recirculation inlet Inlet riser Core support Restrainers Core shroud assembly Restrainers nozzle-1 perjet Diffuser Jet pump pump riser wall 101 Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 the control room for motor windings, bearing oil reservoirs, and cooling water. cooling and reservoirs, oil control for room the bearing motor windings, water locatedcooling in are system. Temperature alarms high-temperature recorders and provided closed is the cooling from for motor reservoir oil bearing bearing the in coils through water and Cooling speed. cooling air–waterstant cooler to the for motor windings motor induction to operate designed squirrel-cage at con three-phase, enclosed, totally control room. the in water activate temperature alarm cooling recorded,and for pump an are on high each and cavity. seal of temperature the cavity controls the of the temperatures reactor service The water cooling water system closed for the from circulate that coils Cooling seals. shaft all of event failure of agross unlikely the in leakage minimizes pump casing the located in bushing Athrottle pressure. pump operating maximum capable against is and of sealing differential pressure total of the portion equal an motor pump. the carries from seal Each without the removing cartridges replaced spare readily be with can which or cartridges, power. poweredpumps operate are auxiliary and from speed at constant powered are a low-frequency and from motorstartup generator Following set. startup, the pumps operate steel. The at 25 of stainless constructed are and type seal mechanical mounted, vertically centrifugal, pumps are reactor recirculation The Motors and Pumps 3.2.3.4 preventthethe can corelevel that to of re-flooding the thejet top pump.at of break line the coreis recirculation height.of no There two-thirds than at flooding no less of post-accidentallows feature jet with a pump design capability safety coreThe flooding Safety Feature of the Jet Pump 3.2.3.3 flow for load rates following.required of spectrum head static into head. pump system accommodates jet full readily The the converts dynamic the This to slow relatively section streams. the ing velocity mixed high mix the from located is downstream completed. essentially Adiffuser is mixing because section mixing end of the the near decreases rate The rise of pressure mixing. by the caused transfer the and velocitymomentum of profile the because rearrangement occurs rise where apressure section, mixing the merge in streams two nozzle. These inlet tion flow reducedthe the is converging as accelerated sucthrough further is pressure, which at nozzle outlet. the flow suction The enters constriction of velocity the because at a low is andaccelerated high high flowto a pressure theat a section entersnozzle driving The Operating Principle of the Jet Pump 3.2.3.2 conditions. collective operating flow and individual under rates their varying to ascertain approximately pumps is jet 19 ft (5.8 m). monitors pump flow jet passages Instrumentation at lower the section weldedcal is end that of shroud support. the overall the into The length cylindri in a straight terminating section gradual is a conical diffuser The jet pump flange. removable the upper removed split be the end. nozzle assembly The can by disconnecting at lower the section drive nozzle the entrance at end and of pipe adiffuser section with assembly, mixer inlet The a replaceable a diffuser. and component, a constant-diameter is 102 The drive motorThe water-cooled avertical for pump is each (air–water heat exchanger), acartridge into built seals of multiple assembly consists seal mechanical pump shaft The mixer, ports, a nozzle five assemblyinlet with of an discharge pump consists jet Each Nuclear Engineering Handbook Engineering Nuclear of rated speed during % of rated during speed - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Cross section of reactor internal pump. internal of reactor section Cross FIGURE 3.10 and pumps and installation of reactor internal pumps (Figure 3.10). pumps (Figure of reactor internal installation pumps and and ESBWR The transitions of valve to provide reliable stem packing seal. ahighly vessel water valves steel level have considerations necessary. double stainless are The sets operation. reactor pressure No special refueling the with parallel in allows maintenance flow of the control downstream is valve. side other suction the the This pump and of the electrohydraulic with actuator.valve aball-type is shutoffoccur. The valves motor-operated bypass and are gate valves flow the and control prevent apipe were if break pipe to may forces of aresult whipping action that jet as arise to piping restrained is recirculation reactor vessel. to the at All point of attachment the stresses resultant constant-support minimizing hangers, thereby hung using pumps are loop valves, piping piping, of The welded associated is and recirculation The construction. Valves Piping and 3.2.3.5 Boiling Water Reactors The ABWR design enhancements include elimination of the external recirculation loops recirculation external of the include elimination ABWRThe enhancements design flowsideThe the controlpump.of discharge Onethe shutoffvalve is on valveis on Terminal Purge water box Pump shaft Impeller Motor casing auxiliary impelller Cooling water Coupling stud Secondary seal pressurization RPV Motor rotor inlet water inlet connector rust disk outlet Ard Cable Motor cover Auxiliary cover Speed sensor Lower journal Stretch tube Upper journal Stretch tube Stator water ring bearing bearing Piston ring Diffuser Diffuser nut Secondary rust bearin Cooling seal water inlet pads g 103 Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 is by the control by operator.is room the transient the levels normal after of valve to their valve pressure set operation resetting and to stay allows them longer Manual open to accommodate before swings. closing pressure automatically, valves other of changed the valves, closing for is the pressure set the which two these with conjunction tocycles alevel not In reopen. valves relief where other will the to alower pressure pressures the set at actuation level, normal limiting thereby initial their following closing) (opening and pressures set normal of automaticallyfeature changing isolation event, line steam valves two amain (oneing abackup other) to the have the by core decay heat until the RHR system steam condensing function is initiated. is function condensing system steam by RHR core decay the heat until reactor not shutdown) is availablecondenser after aheat as sink generated steam to release event (in the may main used be the valves. function of the pressure-relief The tightness valve, leak reset aspring assuring shutoff than pressure provides differential ahigher valves point of the set re-closing the at lower the function, point forpressure-relief set the below for that operation (spring-actuated) of valves By operating safety for the function. point is set function pressure-relief The pressure. closing to apreset falls when pressure supply valve. each Valves power-actuated are that automatically close pressure upon high or room power-actuatedtrol automatically Separate pressure. power upon high circuits sure falls to 96 falls sure pres when inlet close and valves point pressure at set open spring function, For safety the by analysis: determined cases transient pressurization following two the to accommodate valves system. most The sized severe the are of reactor primary the ize provides power-actuated function to relief system. valve depressur The opening primary reactor of overpressure provides the against protection function pression pool. safety The sup pressure safety/relief to the The directly valves valves dual-function discharging are Safety/Relief Valves 3.2.4.1 line. steam of amain arapid of abreak to case protect against core of in uncovering the safeguard engineered an additionalas line included each steam in is Aflow-restricting nozzle maintenance. removalof forease line and for test steam main the to valvesrelief flange-connected are safety/ The penetration. one outboard and containment of the one inboard line, steam Two containment. the on each from zontally isolation valves air-operated installed are vessel, of the downward elevation axis to the where emerge they hori to the vertical parallel welded are run vessel nozzles and to the lines nozzles. steam steel Carbon four vesselthrough several below the feet reactor vessel from flange the exits Steam Steam Lines Main 3.2.4 pumps. recirculation reactor for need the mode eliminates and circulation mode to anatural aforced recirculation from 104 To limit the cycling of valveTo dur relief actuation cycling to the one valve initial limit subsequent to their For the pressure-relief function, the valves are power-actuated manually from the con valves the the power-actuated from are manually function, For pressure-relief the • • valve position switches, and reactor scrams from an indirect scram indirect valve an from position reactor switches, scrams and on based scram isolation valves, of line direct steam failure main ofClosure all rect scram valve closure, failure ofthesteambypasssystem,andreactor scramsfrom anindi- Turbine tripfrom turbinedesignpower, failure ofdirect scramonturbinestop of spring set point pressure. set % of spring Nuclear Engineering Handbook Engineering Nuclear ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 is sufficient to establish the necessary pressure barrier, both are initiated in the control in initiated are barrier, both pressure the necessary establish sufficient to is standby AC and power. poweredsions are auxiliary either divisions two of from the While volume. divi pressurized Both the from containment the into directed is leakage in and effectively eliminated Out is leakage environs. the and barrier containment the between barrier apressurized to establish used are outboard divisions containment and inboard isolation valves containment following aLOCA. steam Independent containment main control system to prevent the possiblecould through of leak which nuclear release steam abackup isolation as valve. to the shutoffvalve The functions and valve of leakage part is valve. oftion the control may room operate each valves. control posi the indicate room the the Lights in the located Independent switches in except remote means. opened manual by manual be valves variable. cannot initiated, isolation and is measured continue to Once close for each sensors independent two tripping has channel each independent channels; two comes from for closure signal temperature. The building turbine (7) high and (outside containment), the (6) low vacuum condenser procedurallybypassed), (unless temperature tunnel line steam (5) differential turbine, ambient to and the high inlet (3) line, line, steam the from steam tion flowmain the(4) high in rate low atpressure tion system scram trip circuit when the valve when the circuit closes. trip systemtion scram reactor protec the into a signal valve independentEach position initiating an switch has supply, air ofloss the power pilot to the valves, electrical loaded of the failure spring. and valve of the closure pilot the upon valves. accumulator in to assist valve air Each an has or of loss power of on loss pressure pneumatic globe valves closed to to the fail designed barrier. isolation valves The spring-loadedcontainment are piston-operated pneumatic pool. suppression the safety/reliefselected control reactor to room the valves pass water from opened are to nozzles,to occur, reactorline vessel floods to a the level steam abovemain the vessel Forwater this reactor suppression lines. vessel to the the valve from pool via discharge vessel, safety/relief to pass valves for used be automatic used can depressurization system and/or RHR the water reactor the into LPCS injecting the system pumps are tor shutdown of LPCI when to cool period function the reactor the water during and switches from different power different sources. from switches control power redundant room for from is manual at actuation signal any The pressure. confirmed. been acceptable and should HPCS reactor system the vessel level initiation initiation the have automatic delayed is operator to the allow 90to 120 s from depressurization to terminate system and/or RHR the LPCS adequately the system can of core. cool initiation the The of reduced is to apoint where system LPCI pressure function the primary the until open valves The not simultaneous. need be remain signals Initiation or LPCS system running. low systemand RHR the reactor waterof function of one level LPCI confirmation and pressure valves drywell automatically of These open pressure. high closure upon signals to apreset falls pressure Valves the surization. until open automatically open remain and depres power powered initiate different sources, from either can of which logic channels valves LOCA conditions. These have system assumed under independent two primary Boiling Water Reactors A shutoff valve is used in each steam line outboard of the external containment isolation containment outboard external of the A shutoff line steam each valve in used is The isolation valvesThe upon close (1) low water reactorlevel vessel, the (2) in radia high isolation valves, containment two one outside has and one inside line the steam Each In the unlikely event that the RHR shutdown suction line is unavailable during reac shutdown unavailable event during is RHR the that line suction unlikely the In power valves for manually to be open The automatic actuated used can depressurization safety/reliefSelected automatic the of the with valves depressurization associated are 105 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 below. advantages Some of the bottom-mounted detailed ofanism. the are drive arrangement head,sel vessel head the removed or without drive with mech the removing for refueling, uncoupled be control below can vessel without rod The from the the reactor removing ves core over length. at entire increments rods the position intermediate the can mechanism drive The withdrawal insertion. control of rod, the but withoutunintentional restricting tube to indexpreventthe engagein collet fingers The notches ments by acollet mechanism. piston, and coupled tube index incre An at control to locked rod, the scram. fixed are condensate water fluid. operating uses the as Accumulators provide for energy additional a double-acting hydraulic is piston that control drive rod mechanism locking-piston-type The interconnections. necessary controls with and system, instrumentation and entire the ahydraulic ahydraulicnisms, power for drive control each mechanism, unit supply for nism are made at ports in the face flange. housing the of made the at are in ports nism drive to mecha the Hydraulic servicing. and connections accessiblereadily for inspection yet are and they head.vessel bottom refueling Here, during no cause interference they thereactor on mountedhousing on a flanged entry, are drives which upward-scramming bottom- are drive mechanisms The signal. any other overriding latter the with function ascram and function latching and apositioning perform drive mechanisms The nisms. moved drive mecha are by rods piston-type hydraulicallyThe vertically actuated, locking reactor. down the safely shutting and level of quickly provide means and principal the overall control control the thus core. reactor rods power throughout the These spersed of movable use by the Positive- control inter control maintained rods is core reactivity Rod Control Drive System 3.2.5 boundary.ment pressure - level contain the to establish to apredetermined lines steam main the in pressure the raise to admitted is air cleared, interlock is the point. interlock When set pressure air the than points. interlock set permissive the within reactor vessel are supply levels air pressure of the the the and unless initiate not actually system will The occurred. aLOCA that has determined it been has after switch byroom aremote manual 106 The control of drive rod severalThe system locking-piston consists control drive rod mecha greater is pressure line steam the if closed isolation valves line remain steam main The • • • • reactor vessel. the may that in be material foreign drives from the deposits within contamination the minimizes drivesthe waterthrough high-purity continuous inflow of The problems. maintenance and leakage hydraulic inherent special systems, their with thefor need fluid of operating water eliminates the use as The of reactor quality function. scram the reliability, in particularly provides operational high This of drive mechanisms. types known of all margins force operating forces piston and drive scram provides highest locking the The to drive components.exposure least possible the neutron a neutron reactorwater shield, yielding as the while in of the use maximum makes arrangement Such an servicing. and for inspection more accessible them removed location reactor. makes the from this Furthermore, operative are and even head when drives do refueling the is The with not interfere Nuclear Engineering Handbook Engineering Nuclear ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Fine-motion control rod drive cross section. cross drive rod control Fine-motion FIGURE 3.11 control drive rod system to asimple drive motion control fine rod (Figure 3.11). flux shaping. and startup, maneuvering, during of control degree flexibility to core give operator and the the maximum in the tribution power of to number give drives optimum suppliedThe dis the selected areactor is with Boiling Water Reactors Enhancement of the ABWR of the ESBWR and Enhancement complex converts the from mechanical-hydraulic • • resultant fuel economy fuel resultant BWR. for the and flux shaping below core from provides the Control axial best entry rod the wear problems and eliminated. attendant systems are their and seals push rod or shaft reactor vessel. the into leakage allow Dynamic which piston seals, nal intersimpleuse water fluid, operating drivesthecan the as high-purity By using Guide tube Leak-off piping Outer tube Scram line sensing magnet Ball check Ball screw Bayonet couplingtype sensing spring Ball nut Separation Labyrinth seal Separation Separation valve inlet socket coupling) probe (to controlrod Brake CRD spud guide tubebasecoupling) support (tocontrolrod Bayonet couplingtype internal CRDblowout Position indicator Full-in mechanism probe (PIP) Buffer sensing magnet Scram position FMCRD housin Hollow piston Back seat Middle flange Spool piece Synchro signal Seal housing Motor generator g - 107 - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 ABWR configuration. core FIGURE 3.12 ule cell is shown in Figure 3.13. Figure shown in is cell ule in 3.12,Figure is variables.shown basic the core The configuration fuel mod and a single combination of an optimum represents core design final resulting considered, the that and cyclefueleconomics, are affect conditions, may which significantly changing properly that of variables combination design to certain be evaluates continually this Electric from have design withGeneral dataoperating scope verified plants. by been comparison employed this andcalculations in analyses heatDesign the operating pressure. andflux, fuel, heat core of and the transfer, flow teristics distribution, void content, cladding stress, core power level, density, exposure nuclear fuel charac thermal-hydraulic characteristics, reliability, improved excellent and performance, cycle economy. fuel factors contribute achievement to the These of experience. high operating variables and proper of on the combination design many based BWR is of design the fuel coreThe and 3.3.1 Introduction Design Core Reactor 3.3 108 Several important features of the BWR core design are summarized below. BWR summarized of the core are design features Several important moderator-to-fuel as parameters design such are volume section ratio, this in Discussed • • and hydrideand at improved long in buildup. performance results cladding This corrosion temperature-dependent associated and temperature Zircaloy mizing mini advantageousBWR significant, of the are in factors watertral chemistry lowand coefficients, The neu heat temperature, coolant saturation high transfer levels. stress and reduce temperatures cladding cycle reactor (approximately of a direct level [6900 kPa]) characteristics 1000 psia moderate The results. test pressure experimental experience, and operating limits, on conservative application based is design of stress BWRThe core mechanical LPRM assembly Control rodassembly Peripheral fuelassembly Fuel assembly Nuclear Engineering Handbook Engineering Nuclear - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Fuel module (cell). module Fuel FIGURE 3.13 core. Important components of this arrangement are described in the following sections. the in described are arrangement core. components of Important this reactor coolant flows vessel. the The the locatedupwardthrough and within assemblies fuel many upright containing an cylinder as reactor core BWRThe of arranged the is Configuration Core 3.3.2 Boiling Water Reactors • • • • ability to overrideability xenon to follow load. of control, xenon ease power spatial radial stability, the the distribution, the and the of self-flattening to control for opposed rods loadas inherent the following, of coolant flow use advantages. the are of anumber BWR inherent the These has negative large of the Because moderator (void) density coefficient reactivity,of powercritical limit. the than less nificantly power bundle peak at the that so rated designed sig reactor is is conditions The and reliability. state of operation operation. for operational flexibility allow Provisions nonoptimal aworst core represents the expected sizing in power used design The distribution to values proven assembly irradiation. fuel similar in are outputs thermal of (approximatelinear and13.4 kW/ftmaximum fluxes [44 kW/m]) Thefuel.heat design of quantities proven significant of by statistically irradiation BWR applied have the design criteria in been mechanical and basic thermal The thermal stresses. hydrides of migration the to cold reduce and zones cladding BWR core minimize throughout the temperatures cladding fuel relatively The uniform exposures. Part lengthrod Fuel rod Water rod Tie rod - 109 Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 UO approximately is pellets of 95 the density immersion to The size. grinding (0.23 mm) diameter gap between the pellet and the tube. the (0.23 mm) and pellet the gap between diameter a 9-mil in result dimensions selected bundle. The fuel of the handling pre-irradiation the place in during pellets the plenum keeps a downward spring force pellets; this on the ablethe a fission gas as in is plenumplenum. space A located to exert plenum spring active (3.8 m), to height an stacked of (241 mm) 150 in. top 9.5 in. the avail with of tube diameter, 160-1/4 in. (4.07 m) long, a32-mil are with pellets (0.81 mm) The thickness. wall 0.483 in. is (12.3 mm) tube Zircaloy end plugs Zircaloy The tube. end of in ing each the in andsealed by ated, weldthree atmospheres, under back-filledof a withpressure helium A fuel rod consists of UO consists rod A fuel Rod Fuel 3.3.3.1 3.15). control (Figure and rods 3.14) components: two (Figure only assemblies fuel BWR essentially The core comprises of Description Fuel Assembly 3.3.3 110 UO sintering by and compacting manufactured GE14 fuel assembly. FIGURE 3.14 A fuel rod is made by stacking pellets into a Zircaloy 2 cladding tube, which is evacu is tube, which 2 cladding aZircaloy into pellets made is by rod stacking A fuel 2 density. Channel fastener Spacer positioning water rod Upper spacer Lower spacer Finger spring Fuel rod Channel (tie) 2 pellets and a Zircaloy 2 cladding tube. UO tube. cladding 2 aZircaloy and pellets 2 powder in cylindrical pellets and and pellets powder cylindrical in (partial length) Lower tieplate (standard) Expansion springs Water rod Fuel rod Fuel rod Nuclear Engineering Handbook Engineering Nuclear % of of theoretical 2 pellets are are pellets - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 array by lower upper plates. and tie lower The plate tie anosepiece,intothe fits has which (10 asquare spaced supported are and in which 100 rods, contains bundle fuel Each Bundle Fuel 3.3.3.3 a BWR environment. in fuel affecting accommodation mechanisms of the its conservative in is design rod cladding. fuel and Overall fuel between expansion tial tube to accommodate todifferen fuel provide the sized is sufficient pellet volumewithin rod. fuel of the analysis stress and design mechanical the (ASME) Vessel in aguide as Pressure Engineers and Boiler Code, used III, is Section of Mechanical Society American vessel. The apressure as designed is BWR rod The fuel Design of Basis Rods Fuel 3.3.3.2 rod. ABWR control FIGURE 3.15 Boiling Water Reactors The rod is designed to withstand the applied loads, both external and internal. The fuel fuel The applied internal. and the loads, external to withstand designed both is rod The Sheath Coupling Handle socket Center post Roller transitio absorber Neutron Roller Lower rods n × 10) 10) 111 - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 are water rods, that is, tubes of Zr-2 cladding without water UO ofare Zr-2 cladding rods, is, that tubes (diagonally bundle Two each opposite control blade) the within foursome interior the in rods operation, lower handle; by during the the assembly hangs plate tie rods. fuel supports the operations when the handling support weightrods fuel the assembly during of only the upper on the end plug to hold installed is assembly tab together. the tie These locking and hexagonal steel nut upper plate the tie Astainless casting. extend through and plate casting have end bundle plugs lower each the into threaded in screw eight rods which The tie tie operations. handling normal during material of the yield strength the to staydesigned within are considerations. parts these Mechanically, strength flowand mechanical to satisfy designed are and steel plates tie fabricated stainless bundle. are Both from fuel the fordle transferring Thetie coolant flowfuelupper rods. han supporttheplate a fuel has piece distributes to and 112 The design has two important features: important two has design The Features Bundle 3.3.3.4 below. described characteristics the with designed are rods fuel The poison. blended burnable are gadolinium bundle each with in rods bundle. Selected fuel of the part central the in used is uranium gaps; enrichment higher water the nearer rods the in and rods corner in used are rods uranium Low enrichment cycle refueling. to equilibrium of transition ease and margins, economy, of fuel balance optimal coreU-235. an achieves operating initial of design the The from that of natural uranium, 0.711 wt uranium, of that natural from or average four ranging of core three are enrichments, initial the in enrichments bundle wt approximately 2.0 within the holes in the upper tie plate to accommodate differential axial thermal expansion. thermal upper plate axial the holes tie the in to accommodate differential within by sliding lower axially the to expand them seated in plate rods tie fuel allowing the while located overplates. spring expansion Inconel top end plug the An keeps rod of fuel pin each tie havethe rods fitintoin anchor holes which standard pins, the and rod spacer-capture end plugs The rods. tie the of as the length same the pellets of fuel tube asingle having rods standard are abundle 54 fuel in rods rod-to-rod spacing. remaining The to maintain springs position spacer.Inconeleach of with axial the equipped fuel spacers are rod The fixing seven of to each spacer the locked thereby assemblies, mechanically rod, being positioning spacer- interior. the bundle as the water serves One also rod within moderating material lower the rod, introducing upper water and thus the ends, allowing to driven be through Three types of rods are used in a fuel bundle: tie rods, water rods, and standard fuel rods. rods, rods. bundle: water tie fuel afuel standard in rods, and used are of rods types Three Different U-235 enrichments are used in fuel bundles to reduce power bundles local fuel peaking. in used are U-235 enrichments Different The initial core has an average enrichment ranging from approximately from average 1.7 wt ranging an core has enrichment initial The • • fittings, end Mechanical enrichments of each for one the Poison individual fuel rods. fuel individual removal replacement, the and of permits design required, if structural unique The direction. axial the in to expand free is rod rod; forces fuel on afuel each external places design bundle minimum The high-enrichment possible to complete any it with not assembly bundle of is mechanically afuel reactor,in a reactivity.reaction therebyits decreasing chain fission the from : A material that absorbs neutrons unproductively absorbs that neutrons : Amaterial hence removes and them % rods in positions specified receiveto specified a positions lowenrichment. in rods U-235 depending on initial cycle requirements. Individual fuel Individual fuel cycle requirements. on initial depending U-235 % U-235, of approximately to amaximum 2.2 wt End fittings are designed so that so are designed : End fittings 2 fuel. Small holes located are at Small fuel. Nuclear Engineering Handbook Engineering Nuclear % U-235 to % - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 shape throughout an operating cycle. operating shape throughout an power reactorlocate operates the approximately that control so with rods axial same the to procedure is operating The peaking. lower the core of in reducesaxial the fuel part the depletion greater and of the cycle, exposure accumulated operating end of higher an the lower the core. of control in of the rods the part At fraction alarger by locating the peaking axial areduction of this control permit rods cycle, operating early of an part bottom-entry the lower for the power aBWR core.acteristic to of in have the part peak During axial the char of voids core, upper of presence anatural steam of the the is the part Because there in Distribution Axial 3.3.4.2 by withdrawal of control to compensateaffected for burnup. rods fuel cycle, operating throughout an even at steady-state power operation, are full they because assembly divided average byan the heat rod fuel flux that factorsat plane. vary Peaking heatin rod fuel flux plane at a horizontal maximum factor the is power local The peaking heatassemblyfueldivided flux theof a maximum by averagethatassembly. heat in flux divided reactor by core the average assembly power. factor the is power peaking axial The assembly average fuel relative maximum factor the power assembly is power peaking divided several into power is design componentsThe for distribution convenience. The Power Distribution 3.3.4.1 at and conditions 100operating most designed, core limiting the under is core. the order objective In to accomplish this without to damage the reactor reactor operations transients and in accommodate changes to reactor operate designed coreThe is at to rated powermargin sufficient with design Design Core 3.3.4 to locate bundles of possible leaks. the pling fuel sam fast in-core permit also technology. and newest channels the The meet requirements to changed be thecan reload fuel thus separatelyanddesign be can orificed bundle fuel rod assemblies. the controlguide serve to also and fuel bundle core coolanteach flow the through direct channels fuel acore The to cell. properlysides within space channel of assemblies four the by washer. alock upper plate tie secured acapscrew Spacer and located on are two buttons to the reusable channel the attaches aguard) and fastener assembly of (consisting a spring fitthe lower seal on tie asliding channel plate makes The surface. reusable channel The its outer dimensions are 5.455 in. are its outer (138.6 mm) dimensions fabricated from Zircaloy 4; tube asquare-shaped assembly. is afuel called is channel The channel afuel and bundle of bundle; combination afuel fuel the the encloses channel A fuel Channel Fuel 3.3.3.5 Boiling Water Reactors The use of the individual fuel channel greatly increases operating flexibility because the because flexibility operating greatly increases channel fuel individual of the use The • • transient. 0.1 than Less (44 kW/m). heat generation linear rate, core, of the any part < is maximum in The of the core experiences transition boiling during the worst expected worst the expected during boiling transition core% of experiences the % of rated power, below. detailed bases the to meet × 5.455 in. (138.8 mm) × 166.9 in. (4.2 m) long. 13.4 kW/ft 113 - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Central UO Central Core Thermal Hydraulics 3.3.4.5 center bundle. of the located afuel in are enrichments water located the near are gaps, higher and enrichments bundle. Lowera fuel uranium in enrichments of reduced several power is use by uranium local the The distribution Local Power Distribution 3.3.4.4 cycle. operating throughout an approximately power radial same the shape to maintain used also procedure is ating Acontrol care. of oper- voids rod of center the core steam greater bundles because the in aBWR reduced is in distribution or radial peaking maximum-to-average bundle The fuel Relative Power Assembly Distribution 3.3.4.3 114 conductivity data, the maximum temperature is approximately is temperature 3400 conductivity data, maximum the heat generation linear rate of 13.4 kW/ftat maximum the (44 kW/m). on published Based power factors input above as to the distribution computer output The program. of the by providing reactor power, analyzed are cases flow,enthalpy, inlet and appropriate Individual channels. assemblyfuel the flow leakage and around bypass with paths inlet reactor, the fuelregion of plenum orifices, the of along flow the characteristics and flow factors and reactorrestrictions, of core, friction the assembly dimensions, fuel zone orifice each in assemblies of number fuel represented, including core are design reactor of awhole. core the the as geometric, hydraulic, The characteristics thermal and of hydraulic and characteristics thermal the toA computer analyze used is program Thermal-Hydraulic Analysis 3.3.4.6 core life. in condition times at all boiling transition condition the operating and most limiting the between maintained is margin that such uncertainties defined, been accommodating has basis design fuel core and The from nucleatetransition theboiling. of the onset conservativelyOverheating is as defined accelerated and cladding ofmay the values corrosion. reach could that weakening cause in possiblyboiling peaks the(and temperature film in temperature ding boiling) transition cladThe temperatures. cladding fuel higher in results occurs, which powers,boiling film swept is away blanket steam the bycoolant flow, higher the bundle At again. still rises then as temperature nucleate to the drops then boiling occurs, heat of the transfer blanketing suddenly steam as rises which temperature surface cladding fuel unstable byfested an to BWR operate. designed the is which mani mode is Transition in of heat boiling transfer the efficient extremely is boiling. Nucleate film boiling and boiling, transition ate boiling, stability margin. the flow increases assemblies fuel all of orificing The increased. is power assemblies fuel zone, inner so higher flowthe the core periphery, to the than orifices more restrictive has assembly removal replacement. and fuel by fuel affected are andnotsupport the in pieces are located orifices These assemblies. Three types of boiling heat transfer must be considered in defining thermal limits: limits: nucle thermal defining must considered be heat in transfer of boiling types Three The zones. dividedouter core orifice two into assemblies,fuel is zoneThe located of near Core orificing : Fixedaccomplish orifices fuel control the among of core distribution flow 2 temperature : The maximum UO maximum : The 2 temperature will occur in new fuel operating operating new fuel in occur will temperature Nuclear Engineering Handbook Engineering Nuclear ° F (1871 F ° C). - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 ture, UO ture, actual core and fuel design, and that design correlations are applicable. are correlations design that design, and fuel core and actual computer the rations adequately that have made programs to been ensure the represent spacer and configu fuel-rod-to-fuel-rod clearances fuel-rod-to-fuel-assembly-channel and zone. orifice each in assemblies power ratio (MCPR) nodes average for the power 24 axial at peak as many and as fuel heat of the fluxes, analysis quality, critical steam a detailed andmaximum void fraction, and types severaltheamongchannel flowdistribution calculated includes the program Boiling Water Reactors 3 powerat all levels. rated power, At full voids steam the equivalent to are approximately The steam voidimportance. and is component negativeof large coefficients is prime tivity plant operations, void normal steam the componentDuring moderator of the reac density Coefficient Moderator Reactivity Density 3.3.4.7.3 U-238. the in capture by resonance neutron absorption higher in reactor power UO increases, is coefficientnegative and reactorWhen in prompt power opposing effect, its transients. water-moderated light all in As Doppler reactors, fuel low-enrichment the and reactivity Coefficient Reactivity Fuel Doppler 3.3.4.7.2 voids.steam maycoefficienttwo intobe broken components:thatthat and due dueto temperature to the ficientand moderator Thecoefficient. moderator reactivity reactivity density density fuelDoppler the importance: coef are of coefficients primary aBWR,In reactivity two Coefficients Reactivity 3.3.4.7.1 BWR. for the by Electric oped General computer on mathematical and codes devel nuclear industry throughout the information of sources current best the from on nuclear data based selected are Nuclear calculations Core Nuclear Characteristics 3.3.4.7 be met. will objectives thermal-hydraulicthe thatperformance confirming considered in of gap composition gas effect width pellet, and and the on gap conductance, have been factor duepower buildup to U-235 depletion, peaking of plutonium of surface the near local reduction in of including irradiation, effects havediation performed. Thermal been % reactivity. In addition, fuel thermal design calculations, including calculation of fuel rod tempera rod of fuel calculation including calculations, design addition,In thermal fuel as such details assembly design fuel with models used analytical of the Comparisons • • • xenon effect, thereby increasing power apower after decrease. xenon increasing thereby effect, xenonwith reactivity, excellent BWR the of capability the the core overriding has capability override Xenon below.tages listed advan operating the void in steam results due void steam effect to the This effect. negative and large The moderator coefficient density powerat operating levelsis moderator the cold,at is smallest coefficient zero power in-channel condition. negative is of conditions operation. for all The channel fuel the waterof the within moderator the coefficient that such is assembly design reactivity fuel density The 2 pellet thermal expansion characteristics, and rate and of UO characteristics, expansion thermal pellet 2 : Because the steam void reactivity effect is large compared large is void steam effect the : Because reactivity temperature increases with minimum time delay, time minimum resulting with increases temperature 2 swelling dueswelling to irra - 115 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 by gadolinium mixed into a portion of the UO of the aportion into mixed by gadolinium for burnup. fuel pensation cycles, supplementary operating For the control provided all is on calculating a reactivity less than 0.99 than less areactivity on calculating reactor, operating the based met in core is be design condition the can this that assurance core, order the from withdrawn in to provide control strongest fully rod the greater with condition at reactor when is the (cold), ambient temperature power, zero xenon, zero and or burnup depletionfuel effects. to provide only for compensation used is of reactivity form poison solid burnable the in cold the from shutdown load condition. control Additional condition full reactivity to the The movable (B The boron-carbide Reactivity Control 3.3.4.8 116 heat generation not exceed 13.4 kW/ft rate will (44 kW/m). mately 16 kW/ft (52.5 kW/m). power linear operation, full maximum the normal During (82 kW/m).ft heat generation approxi is linear rate The transient worst for the expected approximately is 25 kW/ strain of amount cladding generation to this cause rate required heat value. linear excess of The this in is old cladding Zircaloy irradiated for in damage to occur. Available not is expected damage - below fuel which thresh data the indicate that ing value of MCPR and the operating limit is termed the operating the margin termed value is ing of MCPR limit operating the and MCPR operate an with > typically will fuel MCPR is = limit operating value for this A typical limit. operating worst of produces the normal transient the effects for the margin tional to MCPR go below the transient, not avalue is permitted of approximately 1.06. addi An state. worst the So, boiling expected during actual the detecting and predicting in tainties this limit, a statistical margin of approximately margin 6 a statistical limit, this byto definition, corresponds MCPR This, =1.00. boiling. of transition additiononset In to the is conservativelyfuel as damage region, defined boiling film well the into until occur cladding fuel thedue to to of overheatingis not expected weakening Although significant Two mechanisms that could result in fuel damage (i.e., damage fuel Two could that in result perforation mechanisms cladding) are of the Margin between Operating Limits Damage Limits and 3.3.4.9 Supplementary solid burnable poisons are used to assist in providing reactivity com providing reactivity in to assist used are Supplementary poisons solid burnable The movable control rod system is capable of maintaining the reactor in a subcritical movable a subcritical The reactor in the control capable system rod is of maintaining A value of 1 • • • • Severe overheating cladding fuel of the • reactor thermal-hydraulic stability. stabilityThermal-hydraulic by capability flow load changing (or moderator density) control. Doppler fuel to provide the effect load, in void than larger the must is and be effect control changing flow by Load characteristic. xenon stability high stabilityXenon expansion Fracture of the fuel cladding due to excessive strain resulting from UO from due cladding fuel of to excessive resulting the Fracture strain plastic strain of Zircaloy cladding is conservatively defined as the limit limit the conservatively is as of cladding defined Zircaloy % plastic strain : The steam void reactivity is the primary factor in providing the providing the factor in primary void the steam is : The reactivity : The negative contributor: The to important void an is effect 4 C) sufficient to control are provide control rods reactivity : Because the fuel Doppler reactivity opposes a change achange Doppler opposes fuel the reactivity : Because % , or a1 1.30. The difference between the actual operat actual the 1.30. between difference The 2 reload rods. fuel stuck rod stuck on the % margin is made% is to uncer allow forvarious the 1.23. During full power operation,1.23. full the During Nuclear Engineering Handbook Engineering Nuclear . condition. 2 thermal thermal - - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 ficient for safe and stable operation. This ratio is selected to andficient selected providestableratiois forsafe operation. This cold coefficients, lattice remains relatively constant at varying reactor relatively power at levels. varying constant remains by providing apower xenon spatial aids stability cores. shape, Flow control which further advantagexenon. for BWR large, of This of the majoris loosely importance coupled nuclear power of in result Current BWR beyond coefficients instability designs thewell range of tor load do following variables which not tend to encourage xenon spatial oscillations. stable reac to have to select and region, it important power is well-damped distributions reactor Even load performance. the following and restrict in and occur will oscillations sible core damage. pos have they with power caused mayuntil not peaking known be of oscillations such provided, is at presence ing the core averaged instrumentation in-core values and, unless core. not evident the are They when look phenomena local within are Xenon oscillations control provide complete knowledge of adequate core and conditions control capability. adjustment brought for reactivity and local void about steam local control and by rods the of for monitoring core conditions local ioncore. addition, chambers of in-core In use the brought about negative primarily high bythe is the of powercharacteristic This coefficient of oscillations. to such damping provide that margin alarge characteristics has Electric core, possibly and core. of economics BWR the by reduce designed fuel The General as the the in power local peaking load increased cause following performance, restrict it can of reactor. any possible a condition type such shouldIf in occur, theoretically reactor is that Doppler a of coolant variation flow coefficient ratiofor load permitting by following. load following capability. advantage BWR The moderator-to- takes large of its inherently ratio alarge of moderator-to-Dopplerit desirable is to maintain coefficient for optimum load Doppler opposes the changes, Because material. reactivity fuel the fer heat through heat conduction to water subsequent formation of voids the steam and must always trans it, caused power that the opposes while and change temperature fuel in achange with BWR. Doppler of appears simultaneously feedback the The stability tors reactivity to the negative inherent moderator and constant major contribu time are feedback fuel large The Reactor Stability 3.3.4.11 to-cladding localized strain. improvementsdesign below have listed made for been 8×8 BWR/6 fuel to reduce pellet- reactorfuel operation.The normal fuelperforations rod of during number significant cally but statisti asmall cause can (ridging) atinteraction interfaces cracks pellet pellet and due to pellet-to-cladding localization strain that fuel for 7×7 BWR It was determined Strain Localization 3.3.4.10 Boiling Water Reactors The water-to-fuelThe consideration coef volume from reactivity of the ratio determined is spatial power ofxenon the small, becomes too magnitude coefficient the If reactivity of phenomenon of xenon oscillatory concentration an throughout is the Xenon instability • • reduces which ridging. chamfered, is pellet fuel The • • cladding ductility. heat improved procedure of cladding is the treatment The to reduce variability the 13.4 kW/ft (44 kW/m), ridging. and distortion reduces which thermal 18.5 kW/ft heat from generation decreased linear is maximum The (60.7 kW/m) to ridging. 2:1 to from ratio decreased is 1:1, length-to-diameter pellet fuel The reduces which 117 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 to an inserted fresh fuel assembly to verify subcriticality and predicted excess reactivity excess reactivity predicted and subcriticality assembly to verify fuel fresh inserted to an adjacent withdrawn Control are refueling. rods during core reactivity on the tests periodic control permits made alterations of reactor core. are to mechanical the use reactivity The demonstrated when capacity experimentally is This withdrawn. worth control fully rod maximum the core with continuously the subcritical tocapability shut down maintain and control the system the has changes, for To reactivity credible times. a margin all permit adequate that so control designed system rod The is shutdown available is capability at Control Nuclear Rod Characteristics 3.3.5.2 several through leakage flow flowthat leaks uppaths: of recirculation operable and reactor vessel open. intact the to left be for with tests control function entire bottom-mounted the The drives permit control of functions. the remainder the disturbing without blade refueling each its drive from or during detached permits to attached be tion rod-to-drive of connec design the The or rapid regulation insertion. for scram reactivity positioning axial allow that bottom-mounted, hydraulically drive mechanisms actuated to connected are They ascram. from forces resulting dynamic the to withstand designed (prompt shutdown) Control mechanically therefore elements regulation. are or reactivity rods. other the than exposure somewhat a highercycle ments, forand experience power neutron duty used flattening, groups power ofThese control ele significant flattening. top affect core of and the the in voids steam to counterbalance reactor, amanner such positioned in are near-cylindrical of bottom the the enter rods, of from which The rods. patterns of selected manipulation operationcontrol. reactor of Power during controlled by core the is the in distribution nuclear performance. and havethey demonstrated excellent mechanical rods service, in were first the placed since years the procedures. During manufacturing used. Over the years, Over the used. B replaced 2 BWRs, the has and Electric General all ment in control reference 1961. ele standard in the been service into has design this then, Since Control rods (Figure 3.15)Control (Figure rods B using Control Rods 3.3.5.1 Control Reactor Reactivity 3.3.5 cycle costs. fuel for minimum volume optimum to the close is ratio selected for design load good xenon spatial in stability, following and water-to-fuelmargin the of allowance to considerable the parallel In transients. startup precludewhich detrimental 118 Control rods are cooledControl core by are (bypass) leakage the rods flow.The core leakage flow is made available be rods for all reactor that scram requires control function reactivity The of reactivity power shaping and distribution dual functions control perform rods The • Holes in the core Holes plate the in flow for bypass control • core plate between shroud area and The • support fuel piece core plate and between area The • support fuel piece and assembly tie nosepiece fuel between area The • assembly nosepiece fuel and channel fuel between area The • assembly (lower Four nosepiece fuel holes in plate) tie • 4 C control have by rods tested produced quantity been routinely in 4 C compacted in stainless steel tubes were introduced tubes steel C compacted stainless in boron-steel rods previously rods % boron-steel Nuclear Engineering Handbook Engineering Nuclear - - -

Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 Boiling Water Reactors sisting of Gd sisting fission from product andbuildup con self-shieldedU-235 depletion. poison A burnable reactivity fuel in decrease linear almost the matches burnup poison from tive reactivity desirable posi It the also that is requirements. U-235 enrichment initial to penalize exists must poison depleteburnable completely residue no cycle that poison one so operating in asupplemental and rods poison. burnable movable of the effects combined of met by the control use are core control requirements core. initial The initial the in fresh is fuel of the all because core requirements equilibrium to considerably be designed core are excess of the in initial of the control requirements The Supplementary Reactivity Control 3.3.5.3 affected. not significantly would not occur. It (or aone-way is is time control that fast scram insertion) rod device in rate damage of fuel acontrol that so rod insertion velocity reactivity and fall free the limit low the accident. of probability drop arod against protects assembly and It to designed is excessivelyyielding to prevent rod high used worth. configurations abnormal proceduralcontrols are and proceduralpatterns and withdrawal patterns Preplanned to about of for control any increment notch 0.0003 dk/k withdrawn. insertion reactivity the to limit set are rods of spacing the and dimensions increment notch effective. The power about be 0.01 dk operation atypical will worth of pattern in arod maximum The core, operating average the effective. an in worth abouttion be 0.005 dk control will rod low frequency of control rod changes reduces the possibility of operator reducespossibility error. the oflow control changes rod frequency operation, control movement rod for little depletion of required reactivity. is resulting The control burnup. daily and rod fuel altered to provide normal are In patterns more uniform improves thus and plantcontrol safety. control response rod rod the Every 2–3 months, to follow used rapid is of which on speed load reducesfunction, requirements changes, flow The irradiation. of aresult control fuel as occur which long-term changes, reactivity plant. of the life the during to occur expected are which transients, all in damage against thereactor sufficient to are protect rates on scram control insertion rod The fuel. of the core. Called the reactor the core. auxiliary systems Called reactor protect the reactor well water of as vessel as the the in chemistry controland the clean awater basically which reactor is the boiler,Because required are systems process 3.4.1 Introduction Systems Reactor Auxiliary 3.4 desired characteristics. Gd characteristics. desired distribution of the burnable poison. burnable of the distribution cycle. operating depletes the It possible in is to improve by spatial power distributions essentially poison reactivity. the that so in concentration selected The is increase linear Only a few materials have nuclear cross sections suitable for burnable poisons. An ideal suitable An for have poisons. burnable sections afew materials nuclear cross Only control of the rod part integral an is device which a mechanical is velocity limiter The With the normal control rod patterns required to maintain an acceptable an power distribu to maintain required control patterns rod With normal the control for of for power shaping and shim distribution primarily used Control are rods 2 O 3 dispersed in a few selected fuel rods in each fuel assembly provides fuel each the in rods fuel afew selected in dispersed 2 O 3 depletes as a cylinder with decreasing radius to provide decreasing with depletes a acylinder as , these systems may systems divided be general two into , these 119 - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 washing and precoating operations are controlled from a local panel. The cleanup system panel. The alocal from controlled operations are precoating and washing the closed cooling water cooling system closed forthe reactor service. operation reactor vessel blowdown. and normal water by Cooling supplied is NRHX to the units to toapproximately cool reactor water flow120 filter-demineralizer the to designed is NRHX The duty NRHX. the of the increasing correspondingly and exchanger this capability of reduced,is the cooling flowtherebyRHX reducing the to return tion, the opera this During denser, or waste or tank. surge alternately waste to collector tank, the removed reactor by the blowdown from con- cleanup main system the to the through reactor. the to side shell the regenerative of the heat (RHX), exchanger where it heated is before returning through The flowunits. continues filter-demineralizer the it through cooled, is then and regenerative through pumped nonregenerativeand and (NRHXs) heat where exchangers Underline. operation, water normal the removed is at pressure and reactor temperature feedwater the through returned and line pump suction reactor recirculation the through plant operations. normal operation, Water during well as as removed is reactor the from startup, operated be shutdown, system during can h. The refueling and imately 3–3.5 periods of increasing water volume. of increasing periods system system during provides fortion, the water ameans primary removal the from fission products, corrosion products,soluble and other In insolubleaddiand impurities. reactor by water RWCU removing of high the quality purpose The to system maintain is RWCU System 3.4.2 plant operation. abnormal ing where ECCS dur areas the (whichsystems equipment located) required service is also are (blow water cooling down). area depressurization service the system and essential The system, HPCS system, LPCS the RHR of the system, the automatic and LPCI function the lead of fission toECCS release environs. the core and products damage wise of to consists could that other situations emergency of postulated to consequences mitigatesystems the (ECCS), systems core emergency to cooling as referred commonly safety as designed are systems, process system. Other RHR of the suppression the function and pool cooling system (hot standby), RHR of the SBLCtem, the function condensing system, steam the plant operation abnormal RCIC include during the used systems sys Backup auxiliary condition. shutdown;and accommodate that systems and or provide abnormal of an case backup in nuclear startup operations, boiler for normal categories: including necessary systems 120 The operationThe RWCS control of back the room. Filter resin main the from controlled is water volume, of increasing times other and excess water normally is startup During The cleanup system is sized to process the water the to process volume cleanup sized systemThe is approx reactor of system the in plant operation normal include during used systems Auxiliary • Off-gas treatment system Off-gas treatment • Radioactive system waste treatment • system RHR of the shutdown The function cooling • water cooling system closed for The reactor services • system filtering and cooling pools containment and building fuel The • RWCU The system • Nuclear Engineering Handbook Engineering Nuclear ° F during F during ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 systems containing radioactive products and the service water system that is the final heat water radioactive final the service system is products that the and containing systems primary the nuclear to system provide equipment. is between Its barrier asecond purpose water water site uses tem piped the to provide service from source for selected aheat sink water of cooling aseparate, sys loop. system closed consists The forced circulation This Cooling Water Closed System for Reactor Service 3.4.4 water surface the it recycle pool. and to the devices remove These of aportion by several skimmers. surface minimized is pool walls removed thereactor from Deposition the the internals floors, vessel. of andwaterat line pool walls, to clean used be pools, can swimming in used to that vacuum system, similar operation. normal Aportable underwater pool during upper the not containment stored in accidental by or never valve pipe an Fuel can break. exposed be is opening assemblies fuel Pool building. fuel the filtered water locatedcontinually. in usually normally is pool water water. level. plant service cooled Heat by are essential exchangers fuel below normal the building fuel the located in heatare system pumps and exchangers pool. the The stored in is of assemblies number spent fuel normal the more if than needed but may be required not system normally are heat heat RHR ing exchangers exchangers. transfer of fuel and equipment between pools. equipment and of between fuel transfer of water, the operations full to pools permit the removed gates the refueling are during for work drained be vessel flange level. pool at can pressure upper the containment With slot, the in the pool. With gate the transfer inserted holding fuel pool,well, fuel the and the pools. these located at top of the skimmers from fed is tank surge skimmer The tank. surge skimmer the from taken pumps is circulating for pool. suction the The containment the in and fuel storagethe in pool mounted diffusers through it flow the discharging by returns and pool filters fuel and heat pool water the exchangers loops circulate through Pumping tion. piping, valves,instrumenta therequired andand heat exchangers; filter-demineralizers; pumps of circulating consists cleanup systems and pool. equipment The cooling for the upper to the containment heat heat transferred cooling loadspent drywell fuel well as as cleanup system and accommodates the cooling pools containment and building fuel The System Cleanup Pools Cooling and Containment Fuel Building and 3.4.3 any following signals: of the reactor automatically the isolated from is of by motor-operated closure isolation valves on Boiling Water Reactors Because there are no drain connections at the bottom of the fuel storage fuel of at bottom the the pool, spent the connections no drain are there Because water service may become radioactive corrosion itEssential products because collects The RHR system heat exchangers are also available also to system supplement are heat RHR exchangers The pool cool fuel the aremovable with ashield wall pool has reactor upper the The gate containment between • High differential temperature across the system’s the across temperature differential High ventilation system • and outlet inlet system between flow High ratedifferential • cleanup system the equipment area in ambient temperature High • • Low reactor water level • NRHX the after temperature High • SBLC solution injection solution SBLC 121 - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 .. Emergency Equipment Cooling System3.4.5 duty. plant startup to handle capability,power adequate cooling is operating, Extra load spares requirements. all with waterthe cooling water system closed satisfies plant’s of The service intake. perature full shrinkage and to provide and for water adding makeup inhibitors. ameans and shrinkage ously to for accommodate radioactivity. used system is volume swell tank and Asurge waterclosed loop theis cooling system,in,monitored continu wouldwhich confined be Any possible radioactive foregoing the reactor equipment from leakage would to, be and equipment: following the generally service turn water in cooling which system closed forto the reactor service water plant The service pumps provide heatcould leaks. from result exchanger coolant plant into of effluentsthat radioactive possibility discharge the eliminating thereby sink, 122 tor control room. reac the from initiated manually system is operation The of this inserted. be cannot rods rated power control situation the operation that cold postulated to the the condition in SBLCThe control aredundant system system is capable reactor down the from of shutting SBLC System 3.4.6 EECS. by the serviced equipment being system pump, system cooled equipment any standby core by and cooling being ventilation LPCS system the system system pumps pump pump, or and oneRHR RHR HPCS the overheating. ating of component, any least single two failure service On EECS the will reactor system, prevent coreLPCS the ICS and RHR systems, the equipment required as AC ofloss external power, EECS the provides HPCS for and the cooling ventilation and coolers.motors upon pump Upon seal ventilation, may and as of loss such occur normal LPCS HPCS system pump cooler and pump motor systems the RHR and pump seal and shutdown emergency and normal plant. of system the provides The water cooling for the system equipment emergency The cooling The closed cooling water system design temperature depends on the maximum tem water maximum cooling on the depends system temperature closed design The • Radwaste concentrated waste tank • Radwaste concentrator condensers • • Off-gas system glycol coolers • pump coolers Cleanup recirculation • coolers Drywell • • coolers sump Clean • Nonregenerative cleanup heat exchanger • pump motor coolers Reactor recirculation • coolers pump seal Reactor recirculation • Control drive supply rod pumps Control drive supply rod pumps coolers Sample (EECS) services certain equipment required for equipment required (EECS) certain services Nuclear Engineering Handbook Engineering Nuclear - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 charge of the pump. of the charge supplied dis is condenser the from seal gland lube for cooler and the the oil and tions opera modes. water operating to Cooling the for turbine pump and automatically returns mode, test the control in system the while initiation system requires the If undisturbed. reactor operation and test the remains during closed reactor feedwaterthe remains line valve to discharge Thethe condensate to storageline tank. flowreturn test afull through plant condensate discharging operation and the storage from by suction drawing tank reactor feedwater to the line. aconnection reactor vessel through suppression to the water exhausts pool.reactor makeup the into vessel and pumped The is decay of the a portion source).emergency driven heat the with is from steam turbine The (second heat RHR exchangers the source), in condensed steam suppression or the pool (an capable condensate systems: (first other the storage isolated from of being source), tank the pump supplies water makeup one following sources of from the turbine-driven tem. The sys isolated of standby primary conditions the safe automaticallyinitiated to maintain low one-out-of-two-twice level, logic, apredetermined RCIC the ing utilizing system is reactor due vessel drops the generation toin steam continued by decay heat. Upon reach event the In desirable feedwater limits. unavailable, becomes water within the sure level valves automatically (or vessel pres by operator control room) the from action maintain reactor vessel inventory. the to maintain required condenser, feedwater the main and to the system steam provides the water makeup directs at areduced rate due core fission to the systemproduct bypass decayturbine heat.The hydraulic potential on system damage initiation. to eliminate and response quick shutoff of water valve discharge the to ensure full pump and the piping the between keeps leg Awater initiation. system system. deliversafter The RHR 30 s rated flowwithin of operation the the shutdown of the allowing function cooling depressurized, vessel is reactor water reactor the inventory necessary until the feedwater system by maintaining allows for completesystem also plant shutdown of conditions normal under of loss the feedwater from and condenser flow. makeup steam turbine the isolatedbecomes from The event the standby condition vessel the in the nuclear in boiler the maintains then and the theto core sufficientreactorcool vessel inwater pressure RCIC The system maintains RCIC System 3.4.7 control room. the in annunciated are monitored, conditions are storage abnormal and tank solution above level liquid the and system temperature. temperature saturation The in the heaters automatically pentaborate Electric SBLC solution the stored the keep in is in tank. reactor sodium coolant. core the of The wherebottom the with the into it mixes injected is needed. is chemical xenon at operating of level core control is normal liquid the that when injection assumed temperature, voids,ering xenon, shutdown It Doppler and is equilibrium, effect, margin. cold shutdown to hold and reactor shutdown when the consid adequate an with margin piping, valves, necessary valves; instrumentation. tion the and and tank; atest capacity positive of displacement full storage steel apair injec pumps and tank; stainless Boiling Water Reactors A design flow functional test of the test of RCIC normal flow maysystemA design functional performed be during condenser, relief event main the the the reactor isolatedIn vessel becomes from the plant operation, normal generation steam during Following continues areactor scram pentaborate of form sodium the solution. boron in is It used control liquid chemical The SBLCThe hot condition operating the adequate to system reactor is from the to bring of a consists equipment and The SBLC for the reactor building the located system is in pump pump 123 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 objectives is outlined in the following paragraphs. the in outlined is objectives performance and requirements ECCSs various of capability the functional totional meet accidents. break opera of The line (fragmentation)damage spectrum entire the across cladding aggregate ECCS fuel The of the reactor core to protect the designed against is functions: following ECCS system. The the to perform designed is automatic primary of the depressurization system, LPCS HPCS RHR and of systems, the and ECCSThe LPCI function the comprises ECCS 3.4.8 supply automatically steam is The isolated upon: turbine system to the control governor, of the adjust and power flow and match to decay heat generation. steam manual operator The select can required. is system initiation controller if the from signal governor mode test possible the but is when in automatically repositioned demand by the a flow from positioned controller. byis signal demand operationtheManual controlof levelmum operating acontrol and governor automatic with set-point adjustment, which ate by power DC station batteries. the from to oper water designed pumps are cooling systems. Systemexternal valves auxiliary and 124 The turbine and pump automatically and shut turbine The down upon: Two to its maxi speed the control governor include systems aspeed limiting turbine RCICThe AC system operates independently power, of auxiliary air, plant or service • • (off-site) or without with external Function power sources • • • • • temperature area High • supply pipe two steam across drop the elbows pressure in Large line • • pressure exhaust turbine High • Low pressure pump suction • water High reactor level vessel the in • Turbine overspeed • water with the capability of dissipating the rejected heat for a minimum of 30 days heat for aminimum rejected the water of capability dissipating the with of cooling sources secure from and periods for protection longProvide time this power during plant operations testing cal, ECCSs the of by all acceptablePermit wherever testing including, methods, practi systems ing by protection atProvide least independent, two this automatically cool actuated system pipe systemboiler nuclear up equivalent largest boiler abreak to, to the including, and nuclear of the failure Prevent for fragmentation any cladding mechanical fuel logic) High pressure between the turbine exhaust rupture diaphragms(two-out-of-two logic) (two-out-of-two pressure reactor Low signal isolation Automatic Nuclear Engineering Handbook Engineering Nuclear - - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 own diesel generator diesel own shown. as HPCS completely system The is tion. power independent its of sources, having external diesel-generator capable capacity is LPCI spray of set and the full of func accommodating power,regular on-site operation from standby AC is power standby the sources, and of redundancy. degree ahigh assuring further ECCS of the broken features divisions, are segregated into safeguard forengineered the operational availability. equipment wiring and maximum Electrical to assure maintained ECCS up separation the of make equipmentThe redundant that systems various of is the decay containment. heat the from forremoval therequirement and of objectives theperformance satisfies combinations two ECCS active support the oran passive system, in one or following of its the essential failure provides (floodingand spraying). phenomenological two methods cooling HPCS of system LPCSA combination the or the system plus ECCS any other two pumps requirement: functional the satisfies combinations event ECCS, of the a pipe the part In is of in that a break any one following four of the the system objectives: of requirements functional the satisfies combinations three lowing and high drywell pressure. drywell high and or of a combination indicators low pressure showing reactor vessel waterdrywell level low reactor indicating vessel water are that levelsystem upon signals redundant or high Boiling Water Reactors The powerThe AC for operation ECCS of the regular power from is Upon sources. of loss After the first 10 min following the initiation of initiation operation first thethe eventthe the in ECCSof andfollowing 10 min After of During the first 10 min following initiation of initiation operationthe ECCS,following of first the any10 min the one folof During operationThe ECCS of the network automatically is activated reactorby protection the • • • • • • • • • with one heatwith exchanger, 100 and HPCSEither system LPCS the or the system, one systemLPCI loop RHR of the waterservice flow Two at system LPCI with loops least one 100 RHR heat of and the exchanger LPCSthe system HPCS system, the and operationThe automatic of the function, depressurization one system LPCI loop RHR of the HPCS system, the and operationThe automatic of the function, depressurization LPCS system, the system and RHR one LPCI operation loop ofThe automatic of the the function, depressurization system RHR the LPCI two and loops of operationThe automatic of the function depressurization LPCS system, the system (failure and RHR of 3) division LPCI loops of the three operationThe automatic of the function, depressurization LPCS system, one system LPCI and (failure loop RHR of of 2) division the HPCS system, the the operationThe automatic of the function, depressurization system LPCItwo (failure loops RHR of of 1) division the HPCS system, the and operationThe automatic of the function, depressurization service water% service flow % 125 - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 service mode of presence upon ECC the service signal. demand suppression to the pool. controlline system The provides automatic for to the the transfer flow suppressionreturn pressure afull pool with containment primary the from is suction shutdown,plant the During condensate to storageline pump tank. flowreturn afull with plant condensate operation, the storage normal from is pump suction tank down. During flowintothereactor permits and vessel. pressure flowthe is into systemsystemhead pump nuclear exceeds until placed operationbypass activation system. of Alow the initial during may as such occur HPCS system pressure the exceeds thereactor thereactor backflowwhen from pressure vessel pressure vessel preventsstartup, operation, line shutdown. and valve discharge Atestable the check in provides system also for The remote-manual containment. primary the in pressure high low reactor indicating vessel water independent level signals from redundant orinitiated water air,vice cooling emergency or system. the automatically system Operation of is the ing the lines and to avoid and lines the hydraulicing hammer. of condensate to avoid water full times delays at fill all time in equipment maintained are operator stops the control it. manually room the from Systemsystem until piping and supply inexhaustible an water operation continued ofing HPCS of cooling the allowing suppression level the to into weir wall then pool, and provid thereby drywell to the drains suppression containment pool.the Water inventory nuclear system boiler the lost from Uponstorage supply, depletion of tank. this water system automatically the from transfers operation. plant during tested of capability to provide being the system with operating an necessary tion vessel, a motor-drivenpressure pump, generator, diesel valves, piping, instrumenta and boiler. nuclear the provides rates for of for all coolant from loss adequate depressurization and core cooling for design ECC, total of the part integral which HPCS an system The is assemblies. fuel the reactor located vessel above the inside asparger ring nozzles mounted in from assemblies aspray as water makeup jetted The over fuel is of assemblies. the fuel area of the the area water makeup down the into uncovered this due to of loss coolant inventory by directing system prevents (fragmentation) damage cladding fuel event the core becomes in the vide event water makeup the in of of aloss reactor coolant inventory. addition, In HPCS the purpose The System HPCS 3.4.8.1 driven condensate pumps. electrically driven available feedwater be additional would coolantthe source from pumps, still this of turbine- case the In of sizes. break break, for agivenlocation spectrum postulated of the a water the level, itor the maintain vessel couldat upon least refill depending cumstances room. control the in annunciate system alarms All standby sources. the from restart system will of operation, process going into the or the in operating system is the power while failure event the control In others. of but room the normal from automatic all pre-empt signals 126 The HPCS system can be tested during normal plant operation normal or plant when shut during tested the is be HPCS systemThe can The HPCS system can operate independently of normal auxiliary AC operate HPCS power, systemThe can independently auxiliary of normal plant ser condensate the water HPCS of from systemCooling the is foroperation testing the and spray with HPCS systemThe includes asparger reactor ring nozzles located the inside Although the feedwaterAlthough the not ECCS, system of is considered the apart some under cir operation and The switch of ECCS key hand possible lock a local from also pumps is of the HPCS system is to depressurize the nuclear to system boiler pro the and HPCSof to system depressurize the is Nuclear Engineering Handbook Engineering Nuclear ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 open pipe capped. core spray the through sparger. spool removed piece The is the and prior to plant startup (removablenection reactor vessel the into spool piece) system, discharged is RHR to the close, which pre-empts all others, in the event the others, operation in that LPCS of all required. the system is close, pre-empts which or motor-operatedair- valves) control valve room. the The to in indicated receives is asignal control position valve room. of the The ated the in by switch (as for akey locked all true is power Amotor-operated the service. while plant in valve is flowis andoper controls bypass operatorsystem the stops to continue to operate it. manually until the spray allowing closed loop a establishes flows intothethen suppression This chamber. control room. main the from initiated operation be The system of can the pressure. pump discharge the than greater is reactor vessel vessel pressure whenthe the precludes backflowfrom containment located the inside line valve discharge the check in flow the decreases, ratevessel pressure A testable of increases. waterthereactor to vessel valve. the across reactor the As differential pressure a permissive pump and oftion the erators.) automatically opens upon activa line motor-operated The valve discharge the in gen standby diesel of the starting initiate one-out-of-two-twice signals logic. same (The low-reactor-water indicating nals level a and/or using both drywell, the in pressure high from the standby diesel generator. standby diesel the from power, electrical of normal spray the system may operated be (automatically or manually) event hydraulic the In potential of complete on system damage initiation. loss eliminate to and response of water quick valve to ensure full injection the pump and the between by alow-flowthe suppression leg to line pool. Awater bypass or valves test injection or closed reactor vessel pressure high operation against during ing adequate net positiveensures overheat- head. suction from protected system pump is The water level suppression of pump, minimum the oftion to the the chamber, respect with The eleva flushing. and system for testing of RHR to water the connectable and for cooling suppression containment pool to for the its supply connected system tested. is The being to provide of capability operation the mentation with asystem for necessary required above core, the amotor-driven pump, motor-operated valves, piping, valves, instru and water reactor level vessel at the reduced necessary the vessel pressure. in the maintain ECCS operation of reduced systems the the other of and been the prove inadequate to nuclear boiler.the operation into system has goes reactor The once vessel pressure the fordesign ECC, provides which for adequate rates for of all core coolant from loss cooling total of located the part abovea sparger ring integral reactor core. the an system is The spray of from water jets assemblies nozzles mounted fuel down in the into by directing accomplished is event the effect uncovered core is of loss by the cooling coolant. the The LPCS of to the system prevent is (fragmentation) damage cladding function fuel The in System LPCS 3.4.8.2 control room. the in alarm an initiates comparison this in core. increase the An across drop pressure spray the with core of between area bottom the the sparger pressure and in difference the Boiling Water Reactors To plant shutdown, during for allow system testing reactor water, con atemporary via suppression to the pool line capableA bypass of rated core spray flow testing permits level to the and weir of wall the Water drywell the in reactor vessel collects the lost from The operation of the LPCS system pump is initiated from independent, from operationThe LPCS sig redundant of initiated the system pump is spray LPCS with The system reactor includes vessel asparger the ring nozzles located in by comparing determined reactor vessel is to the piping of the internal integrity The pump keeps the piping the pump keeps 127 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 back to the pressure suppression pressure back to the pool. flow plant the pumping reactor operation vessel and the normal by during bypassing time < vessel gage is pressure or cool down nuclear reactor when system the startup normal during not is required tion approaches (138 Pa). 20 psi containment the vessel and LPCI of func the availability The thereactor between pressure flowthedifferential insidecorethe shrouddeliver when full capability. cooling desired the pumps The to obtain bus second to the connected pump are LPCS an pump and RHR third system), the to and one bus connected pumps are RHR two not operating. Using asplit for arrangement pump power bus supply power (essential with one pump flowmaintained is required the that pumps so RHR the achieved by sizing aLOCA. after for water cooling desired reactor level vessel required the in HPCS system or level of depletion the of reactor vessel water) maintain restore and will nuclear of system boiler the (depending matic depressurization of upon the operability LPCS the system, HPCS system, with the and/or conjunction in LPCI function The auto 3.4.9.1 LPCI objectives. these to satisfy tions made system following operational func is up the RHR of with subsystems various The ECCS. of the system part of follow: the objectives design integral The an systemstandby) is shutdown RHR of the abnormal and LPCI conditions. function The system removes RHR The residual heat generated (including hot core by normal under the RHR System 3.4.9 blowdown initiate can control at room the from any time. operator itself. The corrected condition or has the blowdown erroneous are signals the if automatic the operator allows to bypass the receipt coincident of time the signals after delay Atime of pressure. approximately drywell 2 min high reactorlevel vessel and the in LPCS system. Blowdown activated is automatically of low upon coincident water signals and/or operation the LPCI of function the reactor vessel, the permitting the depressurizes tion) upon of loss blowdown coolant over The breaks. agiven range of or line liquid steam (fragmenta damage cladding operation fuel HPCS of system the for against protection system and/or RHR of the to alternate the LPCI an function as LPCS the system functions Blowdown, safety/relief selected through operation the valves, of with the conjunction in Automatic Depressurization Function 3.4.8.3 128 In conjunction with the LPCS system, redundancy of capability for core cooling is LPCS of is for the capability system, core with redundancy cooling conjunction In • • • To suppression limit pool water temperature • • ity when necessary to provide capability when additionality cooling necessary To cleanup system and capac cooling pools supplement containment and fuel the unavailable (hot standby) is condenser main To decay that so residual reactor condense steam and heat may removed be the if shutreactor servicing is and down for refueling To remove decay heat the nuclear sensible heat system boiler and the while from (fragmentation) sufficiently core cooled is a the LOCA tothat so prevent damage cladding fuel necessary,To if water the reactor level vessel after the maintain, restore in and 135 psi (931 kPa). at tested be any pumps can of the operability The Nuclear Engineering Handbook Engineering Nuclear - - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 follows: plant acold of the from standby condition as startup for is operational sequence the The Reactor Startup Operation and 3.5.2.1 plant acold of the from standby condition. operator startup The controls the manually plant acold of the from standby conditionStartup to apower the producing condition requires Plant Startup 3.5.2 to improve used are load response. changes pressure trolled aboutto bring However, reactor opposite power change. desired to the changes con small tend to load changes response operation in throttle by caused turbine changes pressure generatorbine power output. BWR operated The is because reactor at pressure constant tur the in flow new steam the change to producethe reactor pressure,desired admitting nearly constant valve admission to maintain turbine adjusts regulator the pressure initial rate or reactor of moving by power control the the As rods. turbine output the changes, performance oftheplantislocatedincontrol room andlocally. plant. Thecontrol oftheplant isfrom thecontrol room. Instrumentation formonitoringthe the monitoringofprocess fluidsandgases,formonitoringoftheperformance prevention oftheoperation oftheplantunderunsafeorpotentiallyconditions, The instrumentation of the BWR is generally associated with the control of the reactor, the 3.5.1 Introduction Controls and Instrumentation 3.5 Boiling Water Reactors Power flow reactor water in output recirculation BWR by controlled the is changes from • • • reactor of monitor Monitoring to record the and reactor behavior • Movement power desired the level of control to attain rods • • brought Pumps to rated speed • pumps reactor of water the Startup recirculation • recirculation pumps operating at pumps operating low (25 speed recirculation 32 to approximately withdrawn reactor. of the further are achieve They criticality to schedule toaccording a predetermined withdrawn manually Control are rods dropped. has current starting the after and speed pump motor full the nears motor low to the generator frequency power when sets transferred and auxiliary from pump motors, pump motors started the recirculation are the start generator cannot sets low-frequency the Because motor started. pumps are reactor waterThe recirculation approximately 25 to position, corresponds flowwhich The controlminimum theset valves are at flowrequired flow reactor of water the controlManipulation recirculation valves to providethe raised is usually limited by conditions of thermal expansion of the reactor of vessel. the expansion by of conditions thermal limited usually is raised % of rated power reactor water the with flowthe and control open fully valves % of rated flow. % ). rate The at power which level is 129 the - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 130 combination of these two methods. two ofcombination these ment of or control automatic rods, manual flow, adjustment of reactor recirculation or a output, power adjust the by output manual adjusted system requirements is the to meet producing asubstantial is system and electrical to the generator the synchronized After is Power Operation 3.5.3 of amount load applied. is asmall and synchronized is unit valve the admission after control turbine of normal the assumes regulator pressure initial The turbine. controls the the andgovernor period initial this flow bypass controls the regulator during pressure tial ini system. The the with synchronized is unit the which achieved after rated is speed until turbine the to flowgraduallytransferred valves.is bypass the This through condenser the a the floware reactor to flowaccomplished steam from of and steam establishing first by condenser, turbine of the main heating the in established vacuum is apartial After started. is vacuum pump applied mechanical is the steam available, and is reactor seal steam shaft the When turbine. rotates gear the turning the increased, being reactor is temperature the While Turbine Startup 3.5.2.2 compensated for bynormally control adjustment. rod floware adjustment, by effects recirculation loadreactivity long-term changed transient is Although coefficients. control rod reactivity themovement when is notrequired changing evaluated are to compensate periodically, for startups, curves operating during usually withdrawal, excessive rod would an which in power-to-flow result unscheduled ratio.The to prevent withdrawal Arod used interlock is curves. operating to established adhering reactor power, may two adjustment, or of acombination the change positioning, rod while operation, flowlower During desired. control as patterns power rod other and ratings of flow relationship established are the at and pattern, to powercurves is Other plotted. flow rod in reduced same theis steps point, at recirculation for established this is pattern flow.full andflow rated is curve to recirculation power. the first point rod The of When a reactor power relating power established is operation, curve operating initial an During • • • • • • At approximately 32 are used throughout the power throughout above the used range usually are 21 power to the range. powerdiate range, The criticality from range neutron monitors and/or monitor interme the channels ing channels range monitoring intermediate criticality. neutron count range up The through subcritical the in used are channels monitor nuclear behavior the reactor. of the Neutron Counting channels monitoring powerchange to used level. flowis normally Above approximately 75 power to change level. used normally are approximatelyBetween 38 automatic. Above approximately 65 % ofratedcore flow, the recirculation flowcontrol is position. minimum position from in powercontrol flow valve levelchanges control by by of recirculation is manual From approximately 30 at rated speed. power operated and to auxiliary pump transferred recirculation the and closed % of rated power, reactor water the flow control valves are % to approximately 40 % of rated power, reactor water in recirculation change and approximately% and 75 % of rated power, control of the % of rated power, control rods % Nuclear Engineering Handbook Engineering Nuclear of rated power. - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 approximately 25 reactor that power in over BWR output varied unique be The is can apower range of Recirculation Flow Control 3.5.3.2 25 of more than increases reduction and requiring or weekly load shifts reactor power, in changes large daily as such of movementrod making method normal the is steps). heatup and conditions. Control to Continuous subcritical movement limited usually is steps (notch continuously withdrawn be incremental or or groups rod can in rods Single tern. pat operated be a symmetrical Control one can at groups in of rods or rods four a time, in converse occurs. the effect inserted, acontrol is rod When pressure. aconstant to maintain valves admission sufficiently turbine the to open regulator pressure initial sure, the causing rate reactor pres to raise ends boiling in withdrawal. rod by increase caused the The reactivity in change the formation just balances steam increased the until Reactor power increases then core reactivity. increases Withdrawing and acontrol reducesneutron absorption rod the Control Adjustment Rod 3.5.3.1 Boiling Water Reactors normal operation. A signal from the initial pressure regulator is provided to the turbine provided is regulator turbine to the pressure initial the from operation.normal Asignal for required provide functions two turbine the reactor and the between Control signals System Control 3.5.3.3 control valve turbine to move the causes which position. toward raised closed point is the set in theis load demanded, pressure If a produce decrease turbine. flow steam the extra to lowered point is set reactor water systemto demanded, and pressure the flashes is the in load in output. increase an If turbine in produced for ademand achange is when there is regulator pressure point of the set automatic, system. the trol An in change temporary automatic of the of response speed load the con to increase reactor used system the is in governor controller. master to turbine storage the the energy The water of capability the control valves. turbine to reposition the regulator pressure initial flowthe causes recirculation in change the from reactor powerthe resulting change adjustment causes valve of the to zero, signal error position to reduce signal and error the controller. position each valve of with the actual resulting associated the The with pared com is controller of for valve. the signal each controller position adjusts This setting the supplied master is controller. the master to from the Asignal mechanism governing speed reactor power, operator the the from from or aloadsignal error signal ademand speed manner. asimilar reduced in flow powerreduced,is stant the power level recirculation established. When levelis is anew negative volume con aconsequent and core steam effect, with the the reactivity in generation steam reactor rate power the causes increases increased level The to increase. core, of the reactivity which the voids steam the removing at increases afaster rate. This flowthereduces the temporarily core in volume recirculation by in of steam increase rated power second. per allows reactor for and the load maneuvering following at and lowing rates of up to 1 flowfor used without load any folmethod the movementnormal is This of control rods. The rate of power increase is limited to the rate at which control rods can be withdrawn. rate withdrawn. to be the at rate control can The rods limited which is of power increase Automatic load control accomplished is by supplying from aspeed-load signal error adjustmentflow The flow of the therecirculation rate.control valvechanges change To Reactor accomplished negative power is the by using change powerAn coefficient. of the operating power operating % of the level by adjustment reactor of recirculation the % of rated power. of % of 131 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 flow combination in the flowin 28 automaticbetween lies combination region flowThis range. control at load may any power in demand initiated be change level or reactor water recirculation load at in demand power operating to capability accept changes the levels. large The generator supplying turbine is loads. house only the Automatic load following provides reduced powerreadily to the any load level daily level including following, during where of rated power would to xenon override subject be considerations.) Power levels be can (Early due above ascent lowed. xenon to spatial oscillations. 95 no restrictions are There 68 75 speed-load error. the outputcancel turbine to a thelevel will that valves increase sufficiently to open to admission turbine the instructing regulator, asignal pressure sends which initial by the sensed is of pressure increase reactor The pressure. in rateing aslight increase causes moderator. of the density core effective faster,the steam the raising thus increased The thereactor power flow increases output sweepingby increased out bubbles fromsteam flow flow. control reactorin recirculation valvewider, to open Theincrease an causing flowand steam power reduceto tends thereactor pressure level.increased thatthe fact by flowlimited steam is allowable increased The transient duration of this the flowreactor steam from the to aspeed-loadvessel. by response error increasing initial rapid speed-load of the gives alimited error. afunction is This of which time, for alength rapidly to open them and amount by an valves, admission instructing turbine sent to the system flowvalve flowtherecirculation the to controller.demand increase controller to master the causes and regulator pressure initial of the setting pressure the in decrease a causes momentary in flowsignal master tor the and controller.increase The regula pressure initial to the apositive transmitted speed-load is increased, is signal ting recirculation flow required to meet the system power to meet flowrequirements. required recirculation reactor flowthe master necessary to the establishes controller load mechanism governing speed- the from anearly reactor Asignal pressure. constant valvesadmission to maintain 132 can be adjusted to increase power adjusted level. be up desired to increase tocan the for Step up demands to 25 the control rods until there level to to rated that core corresponding rise flowandremain automaticthe flow reducedcontrol initially), system flow the (assuming power will level new power range of to the match tion exceed the that demand. demands For load increase system capacity. reactor operator The would anew control establish configura rod then system provides bypass steam additional up capability bypass to the system, main the flow. thethe thatForrange of exceed automatic loadreduction demands flow control margins during the slower changes in base power base slower the by load in level daily during following. changes required margins operator unit The would automatic adjustrejection. desired control to the preserve rods load or grid reserve for spinning simultaneously providing margins while regulation, line tie by in flowthe required load rapidwater demand control changes meets recirculation operation, such automatic During load reactor daily and following requirements. rejection, load reserve, grid spinning regulation, line tie of meeting purpose combined the with automatic an participation in system dispatch control allows full ganged rods nation with control. flow powerthe at rated core flowis accommodated by automatic reactor waterrecirculation Daily load following system flowvalve flowtherecirculation the to controller demand increased causes The to be asignal causes regulator pressure initial of the setting pressure the Decreasing If, while under normal load, the turbine speed decreases or the speed-load set or the changer decreases speed load,If, normal under turbine while the Automatic dispatch operation % % of rated power corefrom flow and approximately rate65 ranging (constant 40 flowandbetween control valvesetting) : Essentially any practical daily load daily anybe practical following profilefol can : Essentially : Automatic flow reactor waterin combi control recirculation % and rated and power at rated core Nuclear Engineering Handbook Engineering Nuclear % to approximately % and and % of of % ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 maintained through the bypass valve and the generator is disconnected from the system. the from valve generator bypass the the and disconnected is through maintained value, flow load steam reducedis is to aminimum turbine oftion control After rods. For plant shutdown, normal reactor power plant and output reduced inser are by manual Plant Shutdown 3.5.4 feedwatersingle pump. flowwater to accommodate recirculation reduced feedwater flow ofa failure by caused water level, flow, steam and feedwater flow. reactor vessel from modes signals of plant all operation.ing control system The utilizes levels dur predetermined vessel within water the the in reactor vessel to maintain the into reactor feedwaterThe control system automatically flow controls the reactorof feedwater Reactor Feedwater Control System 3.5.3.6 control by operator. is room the transient following the levels normal of valve to their valve pressure set Manual operationswings. resetting and allows to for stay which them longercally open to accommodate before closing pressure automati valves other of changed the valves, two closing for is the pressure these set the with conjunction to cycles alevel not In reopen. pressure valves relief where other will the to alower pressures the set at actuation level, normal limiting thereby initial their ing follow closing) (opening and pressures set normal of automatically feature the changing isolation event, line steam valves two amain (one during tion abackup other) to the have direct spring action for the safety function. safety for action the spring direct by and function, valve relief forrelief the operated its is signal overpressure own from suppression to the safety/ Each chamber. drywell the inside lines steam the from steam safety/relief the function, system to For relieve excess pressure. the this valves discharge bypass or stop turbine of valves admission the failure and sudden turbine of the closure operate safety/relief isolation valves steam or the valves main of the following closure system will This transients. to control pressure large used is function relief A pressure Pressure Relief Function 3.5.3.5 rate reactorthe of system. the of cooling decay the to heat control and condenser to the to discharge It tripped. used is been has bine flow is varied as the turbine is brought underthe control turbine of up governor.theto speed speed its flowas is varied reactor steam allows power the level turbine This the while to held be turbine. the constant valves. admission turbine of the closure is loadsuddenly turbine or complete neutronthereduced flux when high by from partial valves admission to prevent turbine reactor apressure-induced the scram as of response valve bypass about speed the same needs the To function, direction. this closing perform valves moved admission are rapidlyrate turbine when of reactor the pressure the of rise in to reduce is the function primary The basic functions. three to perform tor system, used is valve, regula modulating-type A fast response, pressure bypass steam by controlled the Turbine Bypass Valve 3.5.3.4 Boiling Water Reactors The reactor feedwaterThe control reduction for of system provides the reactor signal the To limit the cycling ofTo safety/relief cycling the limit valves actua to one valve initial subsequent to their The third function of the bypass valve tur bypass of the to the help is control after reactor pressure function third The of valve startup bypass of to the control during is reactor pressure function second The 133 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 The intermediate range is from about from range is l0 intermediate The Intermediate Range Monitors 3.5.4.2 activation minimized. and burnup counters are of the (0.61 m)mately 2 ft a low placesthat counters in below neutron fluxso the core. the This lap with the intermediate range monitors. intermediate lap the with provide and over range to achieve criticality provide necessary the will positions selected of travel; limits however, their motor be can driven to any position within or two three before movement occurs necessary. normally counters counters is of The the Criticality into the core through inverted thimbles. A range from below level source Arange from the to 10 inverted thimbles. core through the into move which to about chamber mid-plane each the core of bydrive the mechanisms, the inserted range,is source neutron fluxmonitored the fission the are by In counters,which Source Range Monitor 3.5.4.1 detectors. probebers. system Atraversing provides in-core neutron of for calibration the periodic range;intermediate voltage power method, local range; variance ion DC cham and range counting, source used: of are neutron monitoring types power ranges. Three and intermediate the in provides monitoring and period optimum startup the during to control movement rod sensitivity location of provides detectors core. maximum This reactor the inside detectors all with range by suitable channels, neutron monitoring cold reactorto to get the the shutdown condition. system heat RHR to exchangers the condenser main the from switched be can heatthe sink reduced sufficiently been regulator. vessel gage has sure pressure After 1135 psi (930 kPa), pres initial of the lowering setting by controlled of the periodically cool normally down is condenser. rate cooled reactor The down is main the of to by the and steam release inserted control are rods all planned, vessel are to access the requiring functions or other refueling low level (about 0.01 but fission powerreducedis maintained to a is condition, condensing steam criticality hot valve. standby the or bypass to kept in reactor be is the If turbine the through denser reduced toReactor alow power level, con further to the decay is the heat and rejected is 134 10 covered. similar to those used for the source range fission counters. source for the used to those similar to reduce and drive activation. positioned mechanisms with life are They expected their radiation have signal. relatively on the effect little neutron flux to measure at lower used is power cable levelsandbecause gamma leakage ambient reactor of temperature core, the high AC the the located in componentchambers With chamber. generated small adetection due of in neutron random pulses to the nature AC of the use makes component method). method or Campbell of voltage, This is which valuemonitored square avoltage by mean asystem as (also using method known variance When the reactor reaches the power the reactor reaches the range, moved countersWhen are the to a position approxi Reactor power is monitored from the source range up through the powerReactor the power range up operating source through monitored the is from As startup progresses and the count rate the and approach top meter range (about of progresses the the startup As These fission chambers are also withdrawn during full power operation to maintain powerfull operation maintain to withdrawn during also are chambers fission These 6 cps), downward withdrawn counters are apparent the to give in adrop count rate. of rated power is sufficient to maintain operating temperature). operating % of rated powerIf maintain sufficient to is 8 to 1.5 × 10 13 nv. range,is neutron flux the this In Nuclear Engineering Handbook Engineering Nuclear 9 nv is - - - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 variables, separation of divisions, and online testability.variables, separation online of and divisions, actuator logic logic. and system providesnational of The indication major analog for the combi and output conditioning, device to inputs, actuation signal include sensors, which solid-state nuclear system systemThe protection uses integrates the following functions: the integrates condition. system The unsafe or potentially to prevent action dition, unsafe initiates an system monitors operation con that the reactor, of abnormal the an upon which, sensing actuating and alarm electrical nuclear a four-channel system systemThe protection is Nuclear System System Protection 3.5.5 reactor system. protection the to operate in used trips also are monitors displayed are these and from core. throughout output the The signals distributed 24 detectors as many as power core by from the itor averaging bulk in measures signals Four average power range monitors (APRMs) average the measure power level. mon Each Average Power Range Monitor 3.5.4.4 (depending on reactor size). assemblies in-core fixed for group of each seven used to is nine ciated drive mechanism computer. to the its core.of asso and data directly the goes The traversing One chamber length axial thealong fluxreadings obtains withdrawn is chamber data the as taking then detector assemblies. to different many to directed be traversing the ion chamber permits mechanism indexing The containment. located the inside mechanism indexing to an connect reactor vessel and the beneath seals nozzles and the through pass at upper the end. tubes The nearly extends sealed top is core active of of to and the tube the the portion guide calibration Each chambers. calibrate fluxthe and to vertical profiles to obtain a traversing ion chamber reactor of vessel. bottom the the replaced individually tors through are by caused of burnup itsdetec These fissionable sensitivity material. reduction of chamber to thecompensate for adjustment amplifier ofgain controls permit output. the Internal linear with a amplifier to aDC connected is planes. ion Each chamber horizontal four in lie and direction axial an spaced in uniformly are a traversing chambers ion The chamber. tor’s adisplay with together position or of rod group board of of the control the rods. bench for movement,selected adjacent the from displayed are opera detectors readings on the the 1 cover arange of about chambers core. throughout the pattern These auniform in arranged power are the which In range,chambers, is in-core neutron flux ion monitored fixed by Local Power Range Monitor 3.5.4.3 Boiling Water Reactors % Fully inserting the traversing ion chamber into one of the calibration guide tubes and and tubes guide one into calibration of the traversing the ion chamber inserting Fully of insertion the assembly permits in-core fixed each included in tube guide calibration The tube for guide and calibration a chambers fission four contain each assemblies Detector –125 Engineered feature safety actuation Nuclear system isolation trip Reactor pressure boundary that penetrate the containment barrier containment the penetrate that boundary pressure its are exceeded its are % of acontrol rated or rod group of When scale. control power is rods on alinear : Monitors reactor lim operation shuts and reactor down when the certain : Isolates the reactor vessel and all connections of the primary primary of the connections all reactor: Isolates vessel and the : Actuates engineered safety feature systems feature safety engineered : Actuates electronic technology from sensor sensor from technology electronic - 135 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 nuclear system system. protection logic,division or not asystem prevent component protective of action the normal will the channel, of trip Failure asingle ited channel. for for 10 s. trip each used is switch reset One operator, by the reset amanual automatically is logic which requires inhib The to scram. or failure scrams could that possible cause of false interactions possibility the precluding equipment other physically from are and other each separated from channels trip four The of power loss asingle on the source. ascram cause power and not trip butelectrical will of on loss shut trip where design reactor. it down the will fail-safe of system the is The control to of the rods rapid the nuclear system systemThe protection initiates insertion Reactor Trip Function 3.5.5.1 equipment. actuated of the state could in restoration that achange cause of not power transients introduce will logicnel, leaves Subsequentor associated state equipment the actuated of unchanged. the (such coreof emergency loss cooling) as power functions to a sensor, its chan energized logic automatically or associated produces output.its atrip channel, For de- normally of loss power For action. to functions, asensor, trip such provide fail-safe will function) to reverts automatic status. channel input removed, is manual input the amaintained When input retained. momentary is identity most of The recent the logic. inputs may or maintained. momentary Manual be operated valves. motorsthe operate that valves drive pumps, and supply or air control the to pneumatically solenoid breakers,tors, control and power pilot circuit valves. to turn devices Actuation in on a solid-state power turn into gate operates that seals activation devices, contac as such provides that asignal logic circuitry action, the of acombination inputs requires When exceeded, bistableis the puts logic. decision to out the asignal level output preset the the with point generator of When pared aset abistable unit. in trip com is logic. decision signal to the conditioned Each analog go directly signals digital the compatible are that solid-state the conditioners conditioning, with logic. to signals After if necessary, modified,in signal are signals digital and analog Both channels. different operator the allow absolute the not to see only value in to compare but readings also switches). or limit variablesswitches drive inputs for indicators, important Analog which (such (such or digital control pressure analog be process transmitters) as as can Sensors 136 Upon loss of AC power functions, which are normally energized (such reactorUpon trip the as of energized loss AC normally are which power functions, are prevented conflicts by exclusive switch manual close OR and open Simultaneous inputs. various compares with that made logic decision is upThe of solid-state circuitry follows: as are nuclear for system system the protection functions bases Logic • • • twice logic. twice on aone-out-of-two based is initiation taken systems feature safety Engineered function. isolation valves of aone-out-of-two logic nuclear and for system remainder twice taken on two-out-of-four based isolation is steam barrier logic for main containment the penetrating Nuclear system isolation by lines isolation process valve in closure logic. two-out-of-four for automatic initiation Reactor trip control reactor shutdown and on a based is Nuclear Engineering Handbook Engineering Nuclear - - - -

Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 gency core cooling consist of three groups: of three consist core cooling gency tion is divided divisions. four into is tion AC nuclear for system system. the protection Power power DC and required are distribu Power Distribution 3.5.5.5 buffered. and devices, indicators, computer, annunciators, the as such and external isolated similarly are to or panel. cabinet Connections at receiving the electrically buffered or and panel cabinet to divisions. allocated outputand are systems various of the logic, sensors, divided reactor The quadrants. four into vessel, to is the which relationship puts, physically both electrically. by and their established Physical are separation divisions for reactor trip, used are separations isolation, ECC and Four divisional out inputs and Divisional Separation 3.5.5.4 system) RCIC the and systems. nuclear of boiler the automatic system, the function and RHR oftion the depressurization include ECCS the features (HPCS system, LPCS safety system, LPCI func engineered The Engineered Safety Features Actuation Function 3.5.5.3 source. supplied same the from Control line. power same the motive and operatedin power valve electrically for are an protective Separate action. routes reliable different, power valves two from feed sources or system componentsafety. circuit not does prevent of sensor Failure asingle normal Valve clears. nal position (except nontestable valves) check control room. the in indicated is automatically not reopen sig when the will and valves initiated, fully close been lation has iso control Once room. override the Automatic controlfrom signals. manual signals closure isolation valvesAll except nontestable valves capable check are control of remote manual separateof ECCSs. the ECC of each part during to open be are valves, for required those are ment which required andequip fluids.The process oflogic and steam release preventing thereby the tainment, nuclear system systemThe protection provides of valves forclosing the to conisolate the Nuclear System Isolation Function 3.5.5.2 Boiling Water Reactors Connections between divisions are isolated optically at the output of the originating at output isolated optically the are originating of the divisions between Connections fail- multichannel, isolationPower are containment with control associated and systems emer to isolated be during required, are and containment the penetrate which lines, The Reactor coolantReactor pressure isolation boundary Closed system isolation Containment isolation nected directly to the containment atmosphere. containment to the directly nected con they nor are boundary reactor of neither coolant pressure the part are they atmosphere. containment and drywell the penetrate barrier. containment and drywell the penetrate reactor vessel and : These are lines that do not connect to the reactor vessel to but the do that not connect lines are : These : These are the lines that penetrate the containment. However, containment. the penetrate that lines the are : These : These are lines that connect directly to the to the directly connect that lines are : These - 137 ------Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 modes and interlocks provided. interlocks modes and system operational modes. protection various for of the the the Following are bypassing and operation reactorAn interlocking mode control on the controls the panel switch Interlocks Bypass and 3.5.5.8 as follows: as supplyair due to operation back-up of the valve. scram of loss by the control would rods associated scrammed be the properly then scram, during valves. pilot supply valvesment scram to any operate scram air of If the failed all from Two solenoid instru to remove valves used main de-energized are the normally three-way Protection Backup 3.5.5.7 involved,are it out occurred. of they sequence events prints which the in outand,several identificationhaveif prints the sensors, scram variables of which caused trip. computer The also channel the caused which or sensors, sensor particular the mine the thatoperator so deter can used are trip signals annunciation Sufficient reset. manually out to lock until channel that causes and annunciated is of any channel trip A momentary Annunciation Reset and 3.5.5.6 AC power solenoid isolation valves. steam scram for pilot the valves main the and 138 Conditions activate monitored inputs that and nuclear system system the protection are inverter suppliedAn AC either the provides from bus battery DC or bus the emergency Low pressureLow at the turbine inlet detection Leak High radiation steam main activity near line steamMain line isolation Turbine stop valve closure and turbine control valve fast closure High in water level the scram discharge volume trip.reactorcause a will neutron flux High High pressure in the reactor vessel Low water level in water level the reactorLow vessel High pressure in the drywell system isolation. system nuclear system and isolation. areactor cause trip will lines a reactor trip. control areactor cause trip. valve turbine of will the fast closure and areactor cause volume trip. will discharge scram automatic function. tor initiate and depressurization RCIC the LPCS HPCS and systems, the initiates system. and initiates function, reactor, nuclear system causes isolation, activates automatic the depressurization RHR system. RHR HPCS system, LPCS the the system, the and automatic function, depressurization : Excessive leakage will cause nuclear cause : Excessive system isolation. will leakage : The closure of the main steam line isolation valves will cause cause isolation valves line will steam main of the closure : The : Abnormal drywell pressure trips the reactor, the the trips pressure initiates drywell : Abnormal : Low pressure at the turbine inlet will cause nuclear cause will inlet at turbine : Low pressure the : High pressure in the reactor vessel will trip the reac the trip reactor vessel will the in pressure : High : Alow water the reactor level vessel trips the in : High radiation levels near the main steam steam radiation: High main levels the near : High water: High control level drive rod the in : Turbine stop valve closure Nuclear Engineering Handbook Engineering Nuclear - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5 is monitored. is operated be Up simultaneously. can a time. to rods four agang position in of rod The each available data monitored, are is operator these to the computer. and the and valves hydraulic accumulators scram on the of and the status indicated. control The is unit puter operator. to the and switch reed input invalid by of caused afailed an detection The com process available to RC&I the of them the parts to other makes data function, and decodes these function position control rod information to room. the The transmitted and multiplexed are containment the inside signals These aseparate channel. feeding switches drive piston. the inside Two spaced (76 mm) are every 3 in. switches dual of each the with request. applied are to agiven movement rod restrictions which determining considered in are point of excessive to generating the withdrawn be fuel.the heat in Unit conditions flux accident. drop rod Attial power higher levels, movement rod it cannot limits rods that so of apoten consequences the limit which restrictions, to adherence operating enforces also movementto the operator addition of the In rods. to enabling to move function rods, this operator. by requested motion rod the as trol relevant is which It information, displays all con to effect is (RC&I) control information rod of function and the purpose primary The Information Rod and Control 3.5.6 value.of flow reactor power a exceeds predetermined to recirculation properlyoperating proper on the range. and ratio Control the withdrawal blocked rod if is are units all that range neutron monitors intermediate to ensure on the used are Interlocks Boiling Water Reactors The speed and capacity of the RC&I function permit the control of more than one at rod control of the more capacity permit than and RC&I of speed the The function atube within contained switches reed glass of by sealed aseries Rod sensed position is Run standby and Startup Refuel Shutdown mitted by procedures. operating mitted may accomplished be where for maintenance per some instruments individual removed. are bypasses However, function other all and of bypassed bypassing isolation valves line closed. steam main the with serviced equipment being are associated and turbine the while of about 5 maximum forto withdrawn be purposes. test withdrawn. be none and can inserted work must fully rods be performed. All : This mode is for normal operation. The intermediate range flux scram is scram range flux operation. mode for intermediate is normal The : This : This mode is used during refueling operations. It control allows refueling asingle rod during mode used is : This : This mode is for use when the reactor is to be shut down and maintenance to shut reactor be when mode is for the is use down maintenance and : This : This mode is for starting up of the reactor and bringing it to a up bringing reactor of and the mode for is starting : This % rated power. reactor critical the keeping permits It also - 139 - - - Downloaded By: 10.3.98.104 At: 04:20 28 Sep 2021; For: 9781315373829, chapter3, 10.1201/9781315373829-5