Safety. Economy. Design Criteria for the HTR Core. Jan Leen Kloosterman, Physics of Nuclear Reactors, TU-Delft

Transcription

1 Design Criteria for the HTR Core Jan Leen Kloosterman, Physics of Nuclear Reactors, TU-Delft Delft University of Technology Challenge the future Safety Economy Design Criteria for the HTR Core 2 54

2 What is Nuclear Safety? Target: no health hazard to the public or personnel Subtargets: No one near the boundary should take shelter or be evacuated No need for moving mechanical components to ensure this target Exposure to plant personnel significantly lower than current international values Koster etal, Nucl. Eng. Des. 222(2003) 231 Design Criteria for the HTR Core 3 54 Safety design philosophy Top level regulatory criteria ALARA Fundamental safety functions Control of reactivity Removal of (decay) heat from the core Confinement of radioactive material Defense in depth Prevention of off-normal event Control of off-normal event Mitigation of off-normal event Design Criteria for the HTR Core 4 54

3 Safety classification in defense of depth Prevention systems Mitigation systems 1. Systems that can cause damage to the core if not working properly (inwp) 2. Systems that can cause fission product release inwp 3. Systems that can trigger off-normal events inwp 1. Systems to stop the reactor rapidly and remove residual heat 2. Systems to reduce radiation exposure to the public 3. Countermeasures and systems in off-normal states Design Criteria for the HTR Core 5 54 Fission product containment SiC IPyC OPyC Tangential Stress [MPa] Fast neutron dose [E>0.1 MeV 1e25 nm2] Design Criteria for the HTR Core 6 54

4 Fission product containment HTR LWR Design Criteria for the HTR Core 7 54 Fission product containment Considered to be a safe lower temperature limit Design Criteria for the HTR Core 8 54

5 Decay heat production 1) Fission products decay β ( ) γ ( ) production 8 MeV/fission, -rays 7 MeV/fission 2) Actinide decay ( ) ( ) U min and Np days Much more important for irradiated MOX fuel 3) Delayed neutron induced fission Comparable to fission products decay; time span? 4)Spontaneous fission Much more a shielding problem than decay heat ( ) 5) Activation of structural materials only few % of FP decay heat Design Criteria for the HTR Core 9 54 Decay heat production β 0 0 P() t P0 exp( t) ρ λ exp ρ β t β ρ0 β ρ0 Λ Design Criteria for the HTR Core 10 54

6 Decay heat production Decay power (MW/ MW) Decayenergy(MWd) Time (d) Source: ORNL Design Criteria for the HTR Core Decay heat production Produced heat after 0.5 day amounts: MWd 400 MWs = 400 fps Heat reservoir in BWR o Fuel from operating temp to 100 C 9 o o Coolant from 286 C to 100 C 112 ( ) Energy fps Reactor vessel and internals 43 Pershagen, Light Water Reactor Safety, 1989 J.L.Kloosterman, FJOH summerschool, 2000 Design Criteria for the HTR Core 12 54

7 Pebble-bed reactor core design? Design Criteria for the HTR Core Reflector savings core reflector δ vacuum x = 0 x = a x = a+ b Design Criteria for the HTR Core 14 54

8 Reflector savings 1 1 DB C mc b δ = a(bare) a(refl) = tan LR tanh BmC DR LR ( ) Thick reflector b L R DC δ δ = L R D R b = 2 L R b L R Design Criteria for the HTR Core Reflector savings Duderstadt and Hamilton, Nuclear Reactor Analysis, 1976 Design Criteria for the HTR Core 16 54

9 Low leakage core design H R τ is a measure for the rms distance travelled until the neutron reaches the thermal energy range 2 L is a measure for the rms distance a thermal neutron travels until is is absorbed 2 M is migration area P = P P NL FNL TNL 1 1 = 1+ B τ 1+ B L BM g g 2 2 g Design Criteria for the HTR Core Low leakage core design H R φ+ B φ = g 2 1 φ φ 2 r + + B 0 2 gφ = r r r z φ ( rz, ) =R( r) Ζ( z) H = 1.85 R φ ν r π z, = 0 cos R H 0 ( r z) A J B 2 0 g 2 2 ν π = + R H Design Criteria for the HTR Core 18 54

10 Reactor core design DLOFC Passive decay heat removal calls for long tall reactor cores Design Criteria for the HTR Core Reactor core design Design Criteria for the HTR Core 20 54

11 Reactor core design? Volume x2 Power +20% Ben Said etal, Nucl Eng Des, 236(2006) 648 Core diameter limited by shutdown capability RPV diameter decay heat removal Design Criteria for the HTR Core Reactor core design Passive decay heat removal calls for long tall reactor cores Or Cores with a fuel-free central column Design Criteria for the HTR Core 22 54

12 Reactor core design Ben Said etal, Nucl Eng Des, 236(2006) 648 Design Criteria for the HTR Core Reactor core design Ben Said etal, Nucl Eng Des, 236(2006) 648 Design Criteria for the HTR Core 24 54

13 Neutron flux profile Fast Thermal Brian Boer, TU-Delft Design Criteria for the HTR Core Reactor core design T mid PBMR results DLOFC Brian Boer, TU-Delft Design Criteria for the HTR Core 26 54

14 Reactor core design T max PBMR results DLOFC Brian Boer, TU-Delft Design Criteria for the HTR Core Pressurized and Depressurized LOFC Brian Boer, TU-Delft Design Criteria for the HTR Core 28 54

15 Maximum core height Fission 6.4% 135 I β 135 β 6.6h Xe 9.2h 135 Cs ( n, γ ) ( b) Xe [ Xe] ρ Φ Positive feedback! Φ Design Criteria for the HTR Core Design Criteria for the HTR Core 30 54

16 Xenon oscillations Design Criteria for the HTR Core Xenon oscillations Strydom, Nucl Eng Des, 238(2008) 2960 Design Criteria for the HTR Core 32 54

17 Maximum core height 1 β 1 β Ott and Neuholt, Introductory Dynamics of Nuclear Reactors Design Criteria for the HTR Core Maximum core height Migration area: ( L diffusion length, τ Fermi age) 1 = L + τ = Squared prompt fission chain length: L = = 6M β β PFC 6 = β 2 Prompt fission chain length: PFC 30 Any core larger than 30M is loosely coupled and therefore sensitive to Xenon oscillations M L M Design Criteria for the HTR Core 34 54

18 Maximum reactor core height Duderstadt and Hamilton, Nuclear Reactor Analysis, 1976 Design Criteria for the HTR Core Maximum reactor core height Q Pressure drop: Pumping power: Q H Δp ρ ΔT ( In practice Δ p< 0.02 p) 2 3 Δp P = m ρ 2 Kugeler and Schulten, Hochtemperatur Reaktortechnik, 1989 Design Criteria for the HTR Core 36 54

19 Reactor core layout m 11 m Concrete Middle column Reflector RPV RCCS Core Core barrel Design Criteria for the HTR Core Gas coolant choice L AC A S = π DL D Q m Mass flow Power Pressure drop Pumping power Gas law m = ρ VA ( ) Q = m C T T = hsδt p P out in 1 4f L V 2 D Δp P = m ρ 2 Δ = ρ ρrt P = M Melese and Katz, Thermal and Flow Design of Helium-cooled Reactors, ANS, 1984 Design Criteria for the HTR Core 38 54

20 Gas coolant choice L AC A S = π DL D Q m Q A c C P c 3 = molar heat capacity M = molar mass P M Melese and Katz, Thermal and Flow Design of Helium-cooled Reactors, ANS, 1984 Design Criteria for the HTR Core Gas coolant choice Tabor, Gases Liquids and Solids, 1979 Design Criteria for the HTR Core 40 54

21 Gas coolant choice Gas Power for fixed frontal area (Q/A c ) Heat transfer area for fixed flow area Pressure for a given system pressure Helium CO H Steam Air Melese and Katz, Thermal and Flow Design of Helium-cooled Reactors, ANS, 1984 Design Criteria for the HTR Core History of gas-cooled reactors Design Criteria for the HTR Core 42 54

22 Early Gas-Cooled Reactors X-10 reactor in Oak Ridge, MW, air-cooled 2 MW reactor in Saclay, 1951, N 2 cooled (later CO 2 ) Calder Hall reactors, 1953, CO 2 cooled 166 MWe reactor in Tokai, 1966, CO 2 cooled Magnox and AGRs in the UK, CO 2 cooled Design Criteria for the HTR Core History of High Temperature Reactors Reactor Power (th/e) T in T out Pressure Operation Power name (MW) ( 0 C) ( 0 C) (bar) period density (MW/m 3 ) Dragon 20 / AVR 46 / Peach Bottom 115 / Design Criteria for the HTR Core 44 54

23 History of High Temperature Reactors Reactor Power (th/e) T in T out Pressure Operation Power name (MW) ( 0 C) ( 0 C) (bar) period density (MW/m 3 ) Dragon 20 / AVR 46 / Peach Bottom 115 / FS Vrain 842 / THTR 750 / Design Criteria for the HTR Core History of High Temperature Reactors Reactor Power (th/e) T in T out Pressure Operation Power name (MW) ( 0 C) ( 0 C) (bar) period density (MW/m 3 ) Dragon 20 / AVR 46 / Peach Bottom 115 / FS Vrain 842 / THTR 750 / HTR-Modul 200 / MHTGR 350 / Design Criteria for the HTR Core 46 54

24 History of High Temperature Reactors Reactor Power (th/e) T in T out Pressure Operation Power name (MW) ( 0 C) ( 0 C) (bar) period density (MW/m 3 ) Dragon 20 / AVR 46 / Peach Bottom 115 / FS Vrain 842 / THTR 750 / HTR-Modul 200 / MHTGR 350 / HTTR 30 / HTR / Design Criteria for the HTR Core History of High Temperature Reactors Large HTGRs (3000 th) FS Vrain (330 e) THTR (300 e) MHTGR (140 e) HTR-Modul (80 e) PBMR (165 e) HTRPM (210 e) AVR (15 e) Peach Bottom (40 e) Dragon (20 th) HTTR (30 th) HTR-10 (10 th) Design Criteria for the HTR Core 48 54

25 Current developments PBMR Koster etal, Nucl. Eng. Des. 222(2003) 231 HTR-PM + Zhengy and Shi, HTR2008, Washington Design Criteria for the HTR Core Future developments: Radial cooling solid T coolant T [ C] 0 [ C] Z [cm] Z [cm] R [cm] R [cm] Boer etal, HTR2008, Washington Design Criteria for the HTR Core 50 54

26 Future developments: Radial cooling Boer etal, HTR2008, Washington Design Criteria for the HTR Core Future developments: Wall paper fuel 1070 Temperature [ C] PBMR fuel Wallpaper fuel Pebble Radius [m] Marmier etal, HTR2008, Washington Design Criteria for the HTR Core 52 54

27 Future developments: Optimization Effect of recycling Effect of fuel zoning Average power density [MW/m 3 ] Radial position [cm] Brian Boer, TU-Delft Design Criteria for the HTR Core Summary Power distribution Coolant choice Core geometry Design Criteria for the HTR Core 54 54