Load Following with a Passive Reactor Core Using the SPARC Design
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UPTEC ES 16 023 Examensarbete 30 hp 13 Juni 2016 Load following with a passive reactor core using the SPARC design Sebastian Leo Eile Svanström Abstract Load following with a passive reactor core using the SPARC design Sebastian Leo Eile Svanström Teknisk- naturvetenskaplig fakultet UTH-enheten This thesis is a follow up on "SPARC fast reactor design: Design of two passively metal-fuelled sodium-cooled pool-type small modular fast reactors with Autonomous Besöksadress: Reactivity Control" by Tobias Lindström (2015). In this thesis the two reactors Ångströmlaboratoriet Lägerhyddsvägen 1 designed by Lindström in said thesis were evaluated. The goal was to determine the Hus 4, Plan 0 reactors ability to load follow as well as the burnup of the neutron absorber used in the passive control system. Postadress: Box 536 751 21 Uppsala To be able to determine the dynamic behaviour of the reactors the reactivity feedbacks of the cores were modelled using Serpent, a Monte Carlo simulation Telefon: software for 3D neutron transport calculations. These feedbacks were then 018 – 471 30 03 implemented into a dynamic simulation of the core, primary and secondary circulation Telefax: and steam generator. The secondary circulation and feedwater flow were used to 018 – 471 30 00 regulate steam temperature and turbine power. The core was left at constant coolant flow and no control rods were used. Hemsida: http://www.teknat.uu.se/student The simulations showed that the reactor was able to load follow between 100 % and 40 % of rated power at a speed of 6 % per minute. It was also shown that the reactor could safely adjust its power between 100 % and 10 % of rated power suggesting that load following is possible below 40 % of rated power but at a lower speed. Finally the reactors were allowed compensate for the variations in a week of the Latvian wind power production in order to show one possible application of the reactor. Handledare: Carl Hellesen Ämnesgranskare: Staffan Qvist Examinator: Petra Jönsson ISSN: 1650-8300, UPTEC ES 16 023 Sammanfattning F¨oratt m¨otaklimathotet s˚ablir f¨ornyelsebar energi mycket vanligare i l¨andersenergisystem. Detta har i sin tur resulterat i st¨orrebehov av lastf¨oljandeenergiproduktion f¨orde tillf¨allen vinden inte bl˚asereller solen inte skiner. Idag g¨orsdetta huvudsakligen med gasturbiner, dieselgeneratorer och vattenkraft. Det ¨ardock inte alla l¨andersom har tillg˚angtill vattenkraft och gas och diesel ¨arb˚adedyrt och f¨ororenande. K¨arnkraftkan utg¨oraett alternativ d˚aden ej ¨arbaserad p˚afossila resurser. Detta kr¨aver dock att problem f¨orknippademed s¨akerhet och l˚anglivat avfall kan l¨osas. Fj¨ardegenerationens k¨arnkrafti form av metallkylda snabbreaktorer ¨ard˚aett lovande alternativ. Denna rapport bygger vidare p˚ajust en s˚adanreaktor, SPARC. SPARC, kort f¨orSafe, Passive with Autonomous Reactivity Control, ¨aren modul¨arbat- terih¨ardmed en termisk effekt p˚a150 MW som skall fungera i 30 ˚ar. Den ¨arbaserad p˚a Integral Fast Reactor (IFR) och har samma passiva s¨akerhet. F¨oratt kompensera f¨orreak- tivitetsf¨or¨andringar¨over reaktorns livscykel anv¨andsdet passiva reaktivitetskontrollsystem ARC, kort f¨orAutonomous Reactivity Control. Detta system g¨oratt reaktorn kan fungera passivt under 30 ˚arutan m¨anskligt ingripande. Denna rapport syftar till att utv¨ardera SPARC-reaktorns lastf¨oljningsf¨orm˚aga.Denna lastf¨olj- ning skall ske passivt vilket betyder att fl¨odeti h¨ardenm˚astevara konstant och inga styrstavar f˚arutnyttjas. D¨armeds˚akommer reaktorn endast styras med hj¨alpav temperatur˚aterkoppling fr˚an˚angcykeln. F¨oratt kunna utf¨oraen dynamisk simulering av reaktorn s˚am˚astedessa temperatur˚aterkoppl- ingar best¨ammas. Detta gjorde med neutrontransport simuleringar i SERPENT, ett 3D Monte Carlo program. Tv˚akategorier av ˚aterkopplingar best¨amdes, de line¨araoch icke- linj¨ara.De linj¨arabestod av den radiella, axiella och kapslingsexpansions˚aterkopplingen samt kylmedel˚aterkopplingen. De ickelinj¨aravar Doppler˚aterkopplingen och ARC-˚aterkopplingen. I en del av dessa simuleringar s˚abest¨amdes¨aven utbr¨anningarav neutronabsorbatorn i ARC- systemet. Man kunde avg¨oraatt utbr¨anningenav neutronabsorbartorn var f¨orsumbar. Samtliga˚aterkop- plingar visade sig vara negativa och stora vilket resulterar i en stabil reaktorh¨ard. Dessa ˚aterkopplingar implementerades sedan i den lastf¨oljningssimuleringarna. Dessa simuleringarna omfattades av reaktorn, sekund¨arakylmedelscirkuleringen och˚anggenerator.Matarvattenfl¨odet anv¨andesf¨oratt styra effekten i ˚anggeneratornoch fl¨odeti ˚angcykeln anv¨andsf¨oratt re- glera ˚angtemperaturen. Tre simuleringar utf¨ordes. F¨orstett stegsvar f¨oratt avg¨orahur snabbt reaktorn kan lastf¨olja,d¨areftertestades reaktorns effektgr¨anser,slutligen gjordes en lastf¨oljningmot vindkraftproduktion som "proof-of-concept". Med denna enkla reglering p˚avisadesdet att SPARC-reaktorn effektivt kunde kompensera f¨orvariationerna hos 60 MW vindkraft. N¨arreaktorn opererar mellan 100 % och 40 % kan effekten anpassas med hastighet av 6 % av m¨arkeffekten per minut. Reaktorn kunde ¨aven reglera sin effekt ned till 15 MWt dock med reducerad hastighet under 40 MWt. Det ¨artroligt att ˚angcykeln kommer att vara begr¨ansadef¨oranl¨aggningensl¨agstaeffekt. 1 Executive summary In this report the load following abilities of the SPARC-reactor was investigated. It was fueled both with enriched uranium and transuranic waste. The reactor was simulated in SERPENT to determine the feedbacks. These were implemented in dynamic simulation of the reactor, secondary circulation and steam generator. From this it could be determined that: • The reactor has only negative feedbacks of which multiple are strong. • The reactor was able to load follow at 6 % of rated power per minute between 100 % and 40 %, which is the same as modern reactors. • The reactor was able to regulate its power between 100 % and 10 % but at slower rate. 2 Contents 1 Introduction 5 1.1 Scope to the thesis . 5 1.2 Background . 5 2 Nuclear reactors 8 2.1 Nuclear reactions . 8 2.2 Reactor kinetics . 9 2.3 Reactor design . 10 2.4 Reactivity feedbacks . 10 2.5 Load following . 13 3 The SPARC reactor 15 3.1 The basic design . 15 3.2 The components . 15 3.3 The ARC-system . 19 3.4 The plant . 22 4 Methods 25 5 Results 27 5.1 Feedbacks . 27 5.2 Load following . 29 5.3 Lithium absorber burnup . 36 6 Discussion 38 A Reactor parameters and lithium data 41 B Feedback coefficients 44 B.1 Thermal expansion . 44 B.2 ARC-level . 45 B.3 Cladding feedback . 46 B.4 Coolant feedback . 47 B.5 Radial expansion feedback . 48 B.6 Axial expansion feedback . 50 B.7 Doppler feedback . 52 B.8 ARC system feedback . 53 3 Glossary ρ Reactivity ARC Autonomous Reactivity Control BOC Beginning Of Cycle BWR Boiling Water Reactor EBR Experimental Breeder Reactor EOC End Of Cycle IFR Integral Fast Reactor LWR Light Water Reactor MOC Middle Of Cycle keff Effective Criticality PWR Pressurised Water Reactor PID Proportional, Integral and Derivative SFR Sodium cooled Fast Reactor SPARC Safe, Passive with Autonomous Reactivity Control TRU Transuranic Waste 4 1 Introduction 1.1 Scope to the thesis This thesis is a follow up on "SPARC fast reactor design: Design of two passively metal-fuelled sodium-cooled pool-type small modular fast reactors with Autonomous Reactivity Control" by Tobias Lindstr¨om(2015). The goal of this thesis is to evaluate if the two reactors designed in the above mentioned thesis are able to load follow and to determine the burnup of the neutron absorber used in the passive control system. To be able to determine the behaviour of the reactors under changing load it is necessary to determine the reactivity feedback coefficients. This is done by modelling the core in Serpent, a Monte Carlo simulation software for 3D neutron transport calculations. By varying parameters in this model the reactivity feedback coefficients for the radial, axial, cladding and coolant expansion as well as the Doppler coefficient and the autonomous reactivity control (ARC) system feedback is determined. These reactivity feedbacks are then implemented in a dynamic model of the reactor, primary and secondary coolant loops and the steam generator. These components are designed with parameters appropriate for a reactor of this size, i.e., 50 MWe. The load following ability of the system is then evaluated by letting the plant balance hourly wind power production. The step response of the system is also evaluated to determine how quickly the reactor can respond. Finally the steady state tem- peratures of the reactor will be determined at different loads. From these results the reactor's ability to load follow and any limitations on its operations can be determined. 1.2 Background The development of 4th generation nuclear reactors offers an opportunity to address many of the problems with current energy production and current nuclear power. They are able to mitigate climate change while supporting renewable power in the grid. Furthermore they aim to solve the problem with long term nuclear waste, provide proliferation resistance while remaining safe. This section is intended to introduce the reader to these subjects. Since the beginning of the last century the average temperature of the Earth has risen by 0.8 oC. 13 of the 14 warmest years have been recorded in the 21st century. The warming is changing the climate, both on land and in the sea. The warming oceans are also fuelling stronger hurricanes and typhoons. They also paradoxically cause more frequent and stronger droughts as well as more frequent floods. As oceans warm they expand, which together with melting land ice causes the sea levels to rise [1]. Most of this warming can be attributed to the release of greenhouse gases by human activity such as burning of fossil fuel, land usage and manufacturing. Without reduction in emissions of greenhouse gases it is very likely that the warming will exceed 3 oC with significant impact on the environment and human well being [1].