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9th International Conference on WWER Fuel Performance, Modelling and Experimental Support 17-24 september 2011, Helena Resort, Burgas
CORE DESIGNS FOR NEW VVER REACTORS AND OPERATIONAL EXPERIENCE OF IMMEDIATE PROTOTYPES
I.N. Vasilchenko, V.A.Mokhov, S.B.Ryzhov OKB “GIDROPRESS”, Podolsk, Russia
Introduction An intensive development of nuclear power engineering is under way in Russia both due to the commissioning of new power units of already existing designs and due to the improvement of VVER reactor designs for the units to be constructed in the XXI century. The design of the reactor core and its components is also involved into the process of improvement. The reactor cores for new VVER reactors under construction and in elaboration have a considerable common invariable part, its parameters being chosen during the development of the commercial VVER-1000. They are the core and fuel assembly cross-section dimensions, appropriate FA shape and core arrangement. They are an important part of the whole VVER technology which has taken a significant place in the world nuclear power engineering. All further modifications are directed firstly at the adaptation to the requirements for the new reactor designs, secondly, to the achievement of the competitive economic indices. The designs of the cores for new VVER reactors based on the evolutionary principle respectively take into account all the previous improvements. Besides, these designs are developed with regard for the capability to implement the targets specified in Terms of Reference for the new reactor plants. It refers, for example, to the justification of a high fuel burnup and reactor load-follow operation. The paper covers the recent improvements analyzed in order to implement the enhanced core performances. AES-2006 reactor core design is considered from the point of view of its application and improvement in the planned VVER-TOI project and of the possibilities of using the basic engineering solutions for the cores with spectral control. The discussion of several types of mixing grids considered in the paper involves a preliminary assessment of their efficiency and the information on their introduction into pilot operation at the VVER-1000 Units. Special attention is given to the results of the operation of immediate prototypes (TVS-2 and TVS-2М) that corroborate the reliability of the design both with regard for the core geometrical stability and fuel cladding tightness.
1. Main parameters of reactor cores for the new VVER reactors A comparison of the characteristics of the reactor cores for new reactor designs are given in Table 1. It is evident from the Table that in case of a significant rise in thermal power the average linear heat rate of the fuel rod actually practically does not change mainly due to the increase in the reactor core height. The minor differences in other parameters result from the design optimization, which is described below.
Table 1 – Main parameters of V-320, AES-2006 and VVER-TOI reactor plants No. Parameter VVER-1000 AES-2006 VVER-TOI 1 Availability factor ~0,82 0,92 0,93 2 Thermal output, MW 3000 ÷3120 3200 3300 3 Average core inlet/outlet temperature: Tinlet, °С Тoutlet,°С 289 298,1 297,6
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321 329,5 329,1 4 Core inlet/outlet pressure: P outlet, MPa 15,7 16,2 16,2 5 Number of fuel assemblies, pcs 163 163 163 6 Number of fuel rods, pcs 311÷312 312 313 7 Core height, mm 3530÷3680 3730 3730 8 Average linear heat rate, W/cm 167 168 173 9 Maximum linear heat rate 448 420 420 10 Number of RCCA, pcs 61 Up to 121 94 11 Mass of fuel in the core, kg 85950 87065 87344 12 Total number of absorber rods in the core 18х61 18х121 18х79+ 16х15
2. Fuel assembly designs for the new VVER reactors The changes in the parameters of the new VVER reactors brought about some changes in FA characteristics. The new VVER fuel assembly characteristics given in Table 2 show the succession in the designs developed which allows using the considerable positive experience in FA operation as the reference one. The design measures on fuel loading increase in FAs were taken to extend the fuel cycle. Since the fuel enrichment is limited to 5% and it is necessary to maintain, if possible, the water-to-uranium ratio the only way for the fuel cycle extension is to increase the content of uranium dioxide in a fuel assembly.
Table 2 – Comparative parameters of fuel assemblies № Parameter VVER-1000 VVER-1200 VVER-TOI
1 Fuel assembly type TVS-2, (2M) TVS-2006 TVS-TOI 2 Cladding temperature, t clad °C 352 - 355 355 355 3 Fuel rod diameter/ spacer grid pitch, mm 9,1/12,75 9,1/12,75 9,1/12,75 4 Central tube yes no no 5 Number of absorber rods in RCCA, pcs 18 18 18 or 16 6 Maximum width across flats, mm 235,1 235,1 235,1 7 Number of channels, pcs 19 19 18 8 Mass of fuel in a FA, kg 505-527 534 536 9 Pellet dimensions douterxdch, mm 7,57х1,4; 7,6х1,2 7,6х1,2 7,6х1,2
3. Description of the main parameters and properties of fuel assemblies
As the operating experience of the TVS-2(2M) with a rigid welded skeleton is being gained, lesser grounds remain to consider its alternatives in the new designs (Fig. 1). The experience has shown that this design has design and process parameters close to the optimal ones. First and foremost, it is the arrangement of the bundle. The spacer grid pitch is 340 mm. In respect to the flow turbulization there is a sufficient number of the spacer grids in a VVER-1000 FA to ensure the power level of 104-107% without mixing grids. From the point of view of rigidity the quantity of the spacer grids with the above mentioned pitch is sufficient to guarantee the stability of the fuel assembly shape and the reliability of the fuel rod spacing. Besides, the process of bundle assembling has been mastered at the Manufacturer’s. The thermo-mechanics of the components is also acceptable. As a result of development of the cell shape, the pressure loss coefficient was obtained that does not significantly influence the reactor core flow rate.
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Thus, a sufficiently good balance between the mentioned factors has been achieved. The other designers of alternative FA designs for VVER-1000 reactors are expected to come to a similar bundle arrangement. The FA top and bottom nozzles have also been proven with respect to their design and technology. The latest embodiment of these components is cast. With the obvious external difference the nature of their design remains unchanged (Fig. 2). Nowadays, the introduction of TVS-2 (2M) top and bottom nozzles into the TVSA design corroborates the recognized quality of these components. The fuel assembly design developed for AES-2006 Project is presented in Ref. /1/. All the engineering solutions of TVS-2M design were embodied in it. Some distinctive features are related with the elongation of the core and the fuel rod by 50 mm and the installation of an additional off-centre tube to locate the in-core instrumentation sensors (similar to V-392 plant design). The first alteration brought about mounting one more spacer grid (13 pcs. total), the second change caused some asymmetry in the fuel bundle arrangement. A large scope of work was performed to ensure VVER fuel licensing. Extensive studies and experimental justification were implemented for the FAs of TVS-2 and TVSA designs. The fuel rods of the standard design have been in regular operation within the TVSA for 6 years. A 5-year burnt-up TVSA fuel assembly from Kalinin NPP was studied in SSC RIAR, ref. /2/. Special in-pile test programs for refabricated fuel rods CYCLE, LOCA and RIA were performed in MIR reactor, and also oxidation experiments and high burn-up fuel thermostability tests were performed in hot cells /3-7/. On the basis of Fig.1- FA general view these FA studies the SSC RIAR specialists /2/ made a conclusion on the retention of operability in VVER fuel rods with burn-up up to 72 MWd/kgU. The fivefold margin for the cladding oxide film thickness and the eightfold margin of the cladding hydride content after 6 years of operation were determined experimentally. The design requirements for the gas pressure inside the cladding and for cladding deformation due to the in-service Fig. 2 – TVS-2M bottom nozzle made of a casting dimensional changes in the pellets are not exceeded. As a result of the tests performed on VVER fresh and spent fuel rods data were obtained that were needed to confirm meeting the requirements of the new regulatory document NP-082-07. The in-pile tests in the MIR reactor and the bench tests (in the hot cells) were performed to study the spent fuel under LOCA. Acceptable thermal stability of the fresh and spent fuel rods under LOCA was confirmed, the data for software verification were obtained. Fuel rod tests under the load-follow operating conditions were realized at power level of 100-40-100% /7/.
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The impulse tests of VVER fresh and spent fuel rods resulted in an experimental data array for fuel with a burnup to 67 MWD/kgU, which is now being analyzed for justification of average radial fuel enthalpy in RIA used as an acceptance criterion. In view of the considered possibility to uprate the power of VVER-1000 reactor core up to 110% of nominal, the task of determination of the fact of coolant boiling on the cladding surfaces is quite acute. Within the framework of the challenge the specialists of Kurchatov Institute are working on the improvement of the in-core instrumentation system for reactor core parameter monitoring and registration of local boiling by the in-core detectors /8/.
4. Modernization proposals
Meanwhile there is still a potential for design improvement. These improvements involve possible reducing of margins, meeting the needs of new fuel cycles, and also standardization and technological simplifications. Due to a number of risks in the way to these design improvement, the introduction of these improvements is a rather long process with a trial operation supposed to be involved. What are these improvements, their risks and challenges? First of all, it is an increase in fuel charging and the accompanying thinning of the fuel rod cladding. The state-of-the-art in fuel manufacturing and operation allows considering this issue as the most urgent one. Besides, some experience has been gained in the operation of claddings of 9,1x7,93 mm and pellets of 7,8 mm in diameter without a centerline hole, respectively. For their wide application it is necessary to finalize the work on the confirmation of the current safety criteria for this type of fuel within the scope of ref. /9/. In particular, a confirmation or a determination of the new values for permissible specific average radial enthalpy is required. It is known that the values used for the fresh and irradiated VVER-1000 FA were obtained for pellets with centerline holes and they demonstrate the availability of margins of this criterion for the reactivity-initiated accidents (RIA) in the VVER. It is probably expedient to use these pallets for basic operation of the power unit where extension of the fuel cycle is an important requirement and necessity. For load-follow conditions of the unit the pellets of Dout/dch = 7,6/1,2 mm can be used because in this case the fuel cycle is extended. Besides, the conditions of fuel-to-cladding interaction become more complicated. Some parameters of the new fuel cycles developed so far are given in Tables 3, 4. The analysis of the results obtained by the specialists of RRC “Kurchatov Institute” shows that the utilization of the standard fuel (enrichment 4,95%, pellet diameter 7,6 mm, fuel rod core height 3680 mm, centerline hole 1,2 mm) can ensure a maximum fuel cycle of 600 eff. days. At this, refueling of half the core (theoretically of 82,5 FA) is required. It allows implementing 12- and 18-month cycles, but a 24-month cycle is not possible. In a 12-month cycle the achieved average burn-up per a FA is 60 MWD/kgU and the maximum burn-up is about 65 MWD/kgU. At the utilization of the fuel rod with a high uranium content (enrichment 4,95%, pellet diameter 7,8 mm, fuel rod core height 3680 mm, no centerline hole) the fuel cycle increases by 7,5% at the same level of average enrichment. In case of refuelling of half the core the maximum fuel cycle is 625 - 645 eff. days (make up fuel enrichment 4,8-4,95%), which allows implementing a 24-month cycle.
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Table 3 – TVS-2M and TVS-2006 fuel cycle parameters Fuel cycle 4x1 5х1 3х1,5 TVS-2M TVS-2М AES-2006 AES-2006 AES-2006 Fuel assembly type without without FA FA FA blankets blankets Number of make-up FAs, pcs 42 36 36 60 78 FA average enrichment, % 4,79 4,83 4,83 4,89 4,69 Fuel residence time (without ~343 323,9 310 477,6 509-513 power effect), eff. days
Unloaded FA burn-up,
MWd/kgU
- average 55,8 58,5 58,4 51,9 48,4 - maximum 59,7 67,2 64,2 60,3 56,4 Specific consumption of natural 0,199 0,187 0,191 0,214 0,240 uranium, kg/MW eff. days
However it should be taken into consideration that apart from solving the above-mentioned tasks on licensing assurance and introduction of such pellets, re-analysis (or replacement, which is preferable) is required for spent fuel storage racks to ensure the guaranteed nuclear safety. The parameters of some fuel cycles for the VVER-TOI reactor are given in Table 4. The fuel cycles utilizing fuel with increased initial enrichment (>5%) and also the versions with erbium are of particular interest here. These measures provide a possibility of implementing a 24-month fuel cycle in principle. The possibility of their introduction into the VVER-TOI design is being studied now. Table 4 – TVS-TOI fuel cycle parameters (thermal output 3300 MW) Fuel cycles 12 18 months (3х1,5) 24 months months
(4х1) UO2 gadolinium erbium erbium Number of make-up FA, pcs 42 76 60 60 79/84 FA average enrichment, % 4,79 4,762 5,523 5,720 6,340/6,320 Fuel residence time (without 332,7 512,5 503 503 686/647 power effect), eff. days Unloaded FA burn-up, MWd/kgU - average ‐ maximum 54,4 47,5 59,3 59,3 58,5 52,3 69,5 68,3 68,1 Specific consumption of natural 0,199 0,227 0,213 0,221 0,249/0,248 uranium, kg/MW·eff. days
The issue of unit power uprating is of current importance for both operating VVER reactors and the designs that are being elaborated. There is no doubt that safety assurance is a paramount requirement in this process. The power uprating by 10% Nnom is now accepted as a reference value for the operating Units and as a target value for the designed ones. It sets
Fig. 3 – Mixing grid of the “Vikhr”(“Vortex”) type and coolant flow pattern
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particular tasks before the core and fuel designers and reduces the number of the considered versions when choosing the mixing grids to the most acceptable ones with respect to the process criteria. To increase CHF density several mixing grid versions have been developed for a standard TVS-2M bundle. They are not purposed for fuel rod spacing mainly due to the following reasons: 1) in the fuel rod spacing assembly, where the contact weakens during operation it is expedient to minimize the transverse component of coolant flow; 2) experiments show that a standard spacer grid is to some extent a turbulence promoter. Thus, more turbulization assemblies appear in the new design of a fuel rod bundle. The analytical calculations and experimental studies performed by IPPE, OKB “GIDROPRESS”, RRC “Kurchatov Institute” and other organizations shows that the efficiency of the turbulence promoters differs in the areas with different steam content. In the area with subcooled liquid the grid providing mass transfer between the cells is more efficient, and in the area with high steam content the grid turbulizing the flow inside a cell is more efficient. Fig. 4 – Mixing grid of the “Row-by-row run” type and These grids were named accordingly: coolant flow pattern “Row-by-row sector run” grid and “Vikhr” (“Vortex”) type grid (Fig. 3, 4). The issue of arrangement of these grids in a bundle is of interesting. The arrangement of the grids in the upper spans moves the point of the departure from nucleate boiling downwards in case of the cosine power profile, therefore the following arrangement is now accepted (see Fig. 5).
Row-by-row run “Vikhr”(“Vortex”)
Fig.5 –Arrangement of mixing and spacer grids
The pressure loss coefficient of the proposed mixing grids is ∼ 1,5 times as high as that of the spacer grids, and the installation of 4 mixing grids increases the pressure loss coefficient by ∼ 8%.
5. Proposals on TVS-TOI design The requirement for VVER-1200 optimization has also been reflected in the FA design. It deals with the optimization of the number of RCCA drives and the number and the coordinates of the in-core instrumentation system (ICIS) sensors. A coincidence of the coordinates of RCCA drives and ICIS detectors takes place in 12 core cells. The patterns of RCCA and ICIS sensor positioning are given in Fig. 6.
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On the basis of a decision taken jointly with NRC “Kurchatov Institute” the design with two types of RCCA is being developed as the basic version. The first type is similar to the existing one (Fig. 7), with 18 absorber rods, and the second one has 16 absorber rods (Fig. 8). The number of such RCCAs is 15 pcs, respectively. AES-2006АЭС-2006 VVER-TOIВВЭР ТОИ RCCA with 18 ARs RCCA ОР СУЗ с ОР СУЗ с ------18 ПЭЛ 15- 15- 16- 16- 16- 16- RCCA & - - 8 - 9 - 0 - 1 - 2 - 3 - - ОР СУЗ и 14- 15- 15- 15- 15- 15- 15- 15- 15- ICISдатчики - 9 - 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - СВРК 13- 14- 14- 14- 14- 14- 14- 14- 14- 14- sensors 9 0 1 2 3 4 5 6 7 8 ------ICIS 12- 12- 13- 13- 13- 13- 13- 13- 13- 13- 13- - 8 - 9 - 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - sen- 11- 11- 11- 11- 12- 12- 12- 12- 12- 12- 12- 12- - 6 - 7 - 8 - 9 - 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - Датчикsor 10- 10- 10- 10- 10- 10- 10- 11- 11- 11- 11- 11- 11- СВРК - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 0 - 1 - 2 - 3 - 4 - 5 - 8- 9- 9- 9- 9- 9- 9- 9- 9- 9- 9- 10- 10- 10- 9 - 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 0 - 1 - 2 7- 7- 7- 7- 8- 8- 8- 8- 8- 8- 8- 8- 8- - 6 - 7 - 8 - 9 - 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 6- 6- 6- 6- 6- 6- 6- 6- 7- 7- 7- 7- 7- 7- 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 0 - 1 - 2 - 3 - 4 - 5 4- 5- 5- 5- 5- 5- 5- 5- 5- 5- 5- 6- 6- 9 0 1 2 3 4 5 6 7 8 9 0 1 ------RCCAОР with СУЗ с 3- 3- 3- 4- 4- 4- 4- 4- 4- 4- 4- 4- 16 ПЭЛ и 7 - 8 - 9 - 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 16 ARsдатчиками and 2- 2- 2- 2- 3- 3- 3- 3- 3- 3- 3- 6 7 8 9 0 1 2 3 4 5 6 СВРК ------ICIS sensors БезNo ОР 1- 1- 1- 1- 2- 2- 2- 2- 2- 2- СУЗRCCAs 6 - 7 - 8 - 9 - 0 - 1 - 2 - 3 - 4 - 5 7- 8- 9- 1- 1- 1- 1- 1- 1- - - 0 - 1 - 2 - 3 - 4 5 No RCCAsбез ОР СУЗ 1- 2- 3- 4- 5- 6- Fig. 6 – Comparison of RCCA and ICIS positioning patterns
In this case one guide tube is used for ICIS sensor arrangement. This version excludes asymmetry of the fuel rod bundle and results in rod-by-rod power flattening. The number of fuel rods in such FA is 313 pcs. The core power distribution and outlet temperature are measured using neutron and temperature measuring channel (instrumentation tube).
GT GT IT НК НК ИК ITИК
твэл Fuel rod твэл Fuel rod
Fig. 7- RCCA arrangement in the Fig. 8- RCCA arrangement in the VVER-TOI FA VVER-1200 FA
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6. Results of TVS-2 (2M) operation The information given in Table 5 provides comprehensive data on the number of TVS-2 (2M) and engineering solutions that are now in trial and commercial operation at the Units. It is worth mentioning that so far no leaky TVS-2M have been observed since they were introduced in 2006. It is probably due to the modernization of the inlet part of TVS-2M in comparison with TVS-2 where cases of loss of fuel rod integrity (gas leaks) were observed.
Table 5 – Introduction of 18-month TVS-2M fuel cycle Units of Balakovo NPP Units of Rostov NPP Year of charge Total number 1 2 3 4 1 2 2003 54 54 – – – – – 2004 162 54 54 54 – – – 2005 217 55 54 54 54 – – 48 TVS-2 2006 164 6 TVS-2M 55 – 55 – – with blankets 2007 271 54 48 55 60 54 – 60 TVS-2M 2008 222 60 54 – 48 – with blankets 2009 264 – 72 72 72 48 – 67 TVS-2M with blankets, 1 TVS-2 163 TVS-2M 66 TVS-2M 67 TVS-2M 2010 418 – 6 of them have 54 TVS-2M without with blankets with blankets mixing grids with blankets blankets and ADF 67 TVS-2M 61 TVS-2M 48 TVS-2M 67 67 TVS-2M 2011 without – – without without 176 with blankets blankets blankets blankets 1839 397 410 356 308 205 Total number comprising: comprising: comprising: comprising: comprising: comprising: 163 TVS-2M by April 2011 1289 TVS-2 265 TVS-2 343 TVS-2 289 TVS-2 241 TVS-2 151 TVS-2 550 TVS-2M 132 TVS-2M 67 TVS-2M 67 TVS-2M 67 TVS-2M 54 TVS-2M Achieved burn- TVS-2 50,36 46,90 51,84 50,67 43,82 – up, MW·d/kg U TVS-2M 46,69 – – – – – *It is scheduled to be charged in the core during Preventive maintenance-2011 Besides, the TVS-2M geometry stability is observed which is supported by the stable operational parameters (RCCA drop time and the RCCA pulling force, forces at fuel assembly reloading).
7. Analysis of the possibility of application of the basic design in VVER-600SC and VVER- 1000S At present a new type of VVER reactors with spectral control is being considered /10/. Boron regulation of reactivity is excluded in this reactor, which is an evolutionary development of VVER. The “detrimental” absorption of neutrons by absorber is compensated by their use in plutonium fission isotope breeding and also by neutron spectrum hardening. Neutron spectrum hardening in the core is obtained by changing the water-to-uranium ratio during operation. The task is solved based on the engineering judgment by installation of movable displacers (made of zirconium or filled by depleted uranium) into the fuel assemblies. The analogue of this solution is the application of absorber rod clusters (RCCA) in VVER reactors. The reactors of spectral control type belong to an evolutionary development of VVER reactors (SUPER-VVER of evolutionary type). The cores of VVER-600 and VVER-1000 reactors are taken as the basis. The letter “S”
Fig. 9 – VVER-600S FA cross-section
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introduced into the reactor designation implies the application of spectral control. The first fuel assembly patterns have been developed for 600MW and 1000MW reactors. The fuel assembly cross-section is given in Fig. 9. This embodiment is based mainly on the TVS-2M engineering solutions: honeycomb spacer grids, rigid welded skeleton (spacer grids+tubes), detachable top nozzle. A new solution is only required to damp the movable components, which weigh significantly more than those of the VVER RCCAs. The pitch of fuel rod arrangement in FA is reduced from 12,75 mm to 11,64 mm. Insertion of displacers into the fuel assembly at the initial stage allows reaching water-to-uranium (W/U) ratio close to 1. Withdrawal of the displacers from the FA results in W/U ratio ≈ 2. It is expedient to make the displacer rods in the form of a fuel rod bundle with a lower enrichment of fuel (natural or waste uranium). The calculations and design studies have been performed for the cores of VVER-600 and VVER-1000 reactors with an introduction of the spectral control principle. The VVER-600 fuel assembly cross-section is given in Figure 9. Due to the arrangement of the displacers with the main parameters preserved (such as fuel rod diameter and FA width across flats) the heating surface was reduced, and therefore a calculation was performed for a reduced thermal power of 1600 MW. The research performed by RRC “Kurchatov Institute” and OKB “GIDROPRESS” has shown that the application of the spectral control core instead of the initial version of VVER-600 core result in: - reduction in natural uranium consumption by 12,5 %; - reduction in fuel component in the electricity cost by ~ 3%; - refrain from boron control. Research and development activities are under way at the moment aimed at using the spectral control in VVER-1000 reactors. More appreciable advantages of the spectral control core can be expected after the transition to (U,Pu)O2 fuel in a closed fuel cycle. These studies are preliminary, and it is expedient to continue the work on the calculation analysis of the cores with spectral control for VVER-1000 and VVER-1200 reactors both with uranium oxide (UO2) and (U,Pu)O2 fuel. The other design versions with the arrangement of the displacers in fuel assemblies and the application of fuel rods of smaller diameter (6,8 mm instead of 9,1 mm) and/or with increased number of fuel assemblies in the core (211 instead of 163) inside a larger vessel are also considered. In the last case it is possible to increase the core thermal output up to 3600 MW using (U,Pu) O2 fuel.
Conclusion. The TVS-2 (2M) design is the main one development of the new core designs including VVER-TOI reactor. Its basic engineering solutions can be also used for a more essential VVER modification with spectral control. Further improvements should be concerned with fuel cycle improvement. The following directions are determined in this process: increase in fuel charging in FA and initial enrichment, study of the application of the erbium burnable absorber and axial profiling. Now a design version with heat-and-mass transfer intensifiers is being introduced. The work on the development of the evolutionary SUPER-VVER reactor with spectral control is under way in close cooperation with NRC “Kurchatov Institute”.
References 1. Yu.G.Dragunov, S.B.Ryzhov, I.N.Vasilchenko et al. “Core design for AES-2006 reactor plant”, 5th International Scientific and Technical Conference “Safety Assurance of NPP with WWER”, May 29 – June 1, 2007, Podolsk, FSUE OKB “GIDROPRESS”, 2007.
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2. V.S. Polenok, D.V. Markov , V.А. Zhitelev State and parameters of the VVER fuel rods with a burnup up to 73 MW⋅d/kgU. 4-th Russian - Hungarian - Finnish seminar on June, 19-20, 2007 in the "Коlоntaеvо" vacation center, and also in the Collection of theses of the 8th Russian Conference of Reactor Materials Science, RIAR, Dimitrovgrad, May 21-25, 2007. 3. V.A.Tsykanov, L.N.Andreeva-Andrievskaya, V.G.Asmolov et al. Study of light water reactor fuel behaviour under accident conditions. 7th Russian Conference of Reactor Materials Science, RIAR, Dimitrovgrad, September 8-12, 2003. 4. I.V.Kuzmin, L.N.Andreeva-Andrievskaya et al. Study of thermal stability of VVER-1000 spent fuel rod simulators with undistorted and distorted cladding, 7th Russian Conference of Reactor Materials Science, RIAR, Dimitrovgrad, September 8-12, 2003. 5. A.V.Alekseev, V.A.Ovchinnikov, I.V.Kiseleva, V.N.Shumeev. Results of VVER fuel rod tests under rod ejection accident conditions. Nuclear power, 2007. 6. A.V.Alekseev et al. Methodical support and experimental research of VVER-1000 fuel rod behaviour under RIA conditions in MIR reactor. Scientific and Technical Conference-2010. New generation fuel for nuclear power plants. Results of modernization, operation experience and directions of further development. Collection of theses, М., November 17-19, 2010, p. 42. 7. A.V.Goryachev et al. Conditions and results of VVER-1000 in-pile fuel rod tests with burn- up of 50 MW⋅d/kgU and cyclic power variation. Scientific and Technical Conference-2010. New generation fuel for nuclear power plants. Results of modernization, operation experience and directions of further development. Collection of theses, М., November 17-19, 2010, p.43. 8. A.E.Kalinushkin, Yu.M.Semchenkov. Current trends in VVER in-core instrumentation system development. Scientific and Technical Conference-2010. New generation fuel for nuclear power plants. Results of modernization, operation experience and directions of further development. Collection of theses, М., November 17-19, 2010, p.41. 9. Analisis of differences in fuel safety criteria for WWER and western PWR nuclear power plants. IAEA, Vienna, 2003. 10. V.A.Sidorenko “VVER- near and distant future prospects”, Rosenergoatom, No. 8, p. 3-9, 2009.