IAEA Technical Meeting on Priorities in Modelling and Simulation for Fast Neutron Systems

Transcription

1 IAEA Technical Meeting on Priorities in Modelling and Simulation for Fast Neutron Systems Modelling and simulation of severe accidents in GEN IV reactors, research tools used in the Institute for Energy and Transport at the European Commission s Joint Research Centre. A. Flores y Flores, V. Matuzas, L. Ammirabile, H. Tsige Tamirat, K. Tuček, A. Lazaro Chueca European Commission Joint Research Centre Institute for Energy and Transport Alain.Flores-y-Flores@ec.europa.eu 1

2 Established in institutes in 5 countries 2,845 permanent and temporary staff 1,398 scientific publications in

3 Projects where the JRC-IET has been involved Lead-cooled European Advanced DEmonstrationReactor (LEADER), The objective of LEADER was to demonstrate a feasibility of an LFR (at low operating temperature < 500ºC) to comply with the Generation IV goals The main goal was to develop designs of ALFRED LFRdemonstratorand ELFR industrial plant The Collaborative Project on the European Sodium Fast Reactor (CP- ESFR), The objective of CP-ESFR was to establish the technical basis of a European sodium fast reactor plant. 3

4 Lead-cooled European Advanced DEmonstrationReactor (LEADER), In LEADER, IET contributed among others to the task on the definition and neutronic characterisation of the ELFR core analyses of partial fuel sub-assembly blockages in ALFRED with the SIMMER-III code analyses of Unprotected Loss-of-Flow and Unprotected Transient-Over-Power transients with the TRACE code organised Safety Workshop, which initiated an early, pre-licensing discussion with representatives from regulatory authorities & TSOs 4

5 Examples of JRC involvement in: LEADER Partial fuel sub-assembly blockages (75% coolant flow area) in ALFRED were analysed with the SIMMER-III code Unprotected Loss-of-Flow in ALFRED was analysed with the TRACE code 5

6 JRC-IET contribution to CP-ESFR JRC-IET contributed to CP-ESFR subprojects on core & fuel cycle design and on safety concept options and PR&PP (SP2 & SP3) Methodology for design analysis based on Monte Carlo method (MCNP) for neutronics and subchannel analysis for thermal-hydraulics (COBRA) Implementation of a coupling scheme between a thermal-hydraulics and a neutronic 3D models for a Sodium Fast Reactor design (TRACE-PARCS) 6

7 Radial Power peaking Power density [W/cm 3 ] Temperature [ºC] Core radius [cm] Coolant T Clad T Outer fuel T Avg fuel T Inner fuel T Height [m] 7

8 Multi-physics coupled neutronics and thermohydraulics analysis using TRACE-PARCS Cross sections generated by Monte Carlo based code Serpent 3D Thermohydraulic vessel model Initial approach 2 groups Current version 7 groups 8

9 Projects where the JRC-IET is involved JASMIN: Joint Advanced Severe Accidents Modelling and Integration for Na-cooled Fast Neutron Reactors Objectives of JASMIN Development and validation of a joint European computer code for modelling of initiation phases of severe accidents in liquid metal cooled fast reactors: ASTEC-Na Focus on SFRs; further extensions are planned for applicability to LFRs JRC/IET in JASMIN Leads task on the development and qualification of the neutronics model in ASTEC-Na Contributes to the benchmarking/validation of the fuel pin mechanics model in ASTEC-Na Contributes to integration and dissemination activities 9

10 CABRI A4 Transient Over Power (TOP) Fresh UO2 fuel pin (solid) The highest energy TOP of the CABRI A series experiments Energy release 1.86 kj/g at the axial peak power point TOP characteristics Peak power MW 8968 Peak power (Fissile) W Time of peak ms 53.9 P max /P Injected reactivity $ 2.1 Time of scram ms 105 Energy release in the test pin (at 130 ms) KJ/g 1.86 Energy release in the test pin (at 250 ms) KJ/g 1.95 Channel inlet flow rate g/s Temperature at the lower end of the fissile length (T in ) C 400 Temperature at the upper end of the fissile length (T out ) C 579 Na temperature rise along fissile length C 179 Max. linear power rating W/cm

11 CABRI A4 timeline 90 A4- Scenario A fuel ejection at pin failure 56ms/49 cm BFC B,C axial fuel sweep-out following the Nainterface D upward relocation of fuel temporarily (15ms) deposited around the breach E,F internal, centre-directed fuel motion G temporary fuel accumulation, fed by E and F H,J fuel transport out of the cm BFC-zone 80 fissile height [cm] Rapid pin failure and fuel melt Central zone of 45cm has lost fuel Significant axial expansion Time after TOP trigger [ms] Final state 11

12 CABRI A4 modeling results Values obtained during steady state simulation close to experiment Still some problems to model evolution of accident Peak power not reached 12

13 [0.00] TOP triggering [45.0] Axial expansion becomes visible [53.9] Peak power [55.5] Clad rupture and fuel ejection at 48.6 cm BFC [55.5] First fuel-coolant interaction [56.0] Top of the pin has risen by about 12mm [75.5] Fuel ejection at 46.7 cm BFC [78.0] Second FCI CABRI A4 modeling results 13

14 Application of SIMMER III Within WP2.2 SIMMER III calculations are performed additionally 14

15 CABRI AGS0 Transient Over Power (TOP) MOX fuel pin (solid) Preiradiated 2.95 % at Pre-pulse only Energy release 0.44 kj/g at the axial peak power point TOP characteristics Peak power MW Time of peak ms 403 P max /P Time of scram ms 455 Energy release in the test pin (at ms) KJ/g 0.44 Channel inlet flow rate g/s 147 Temperature at the lower end of the fissile length (T in ) C 400 Temperature at the upper end of the fissile length (T out ) C 580 Na temperature rise along fissile length C 180 Max. linear power rating W/cm

16 CABRI AGS0 The pin did not fail No fuel relocation and no residual elongation observed Fuel cross-section examination at PPN showed that partial fuel melting had occurred The uppermost pellet of the fissile column was broken-up with a gap of about 1 mm and other smaller interpellet gaps (<1/2 mm) were observed along the fissile column. The maximum temperature reached during the transient was 707 C at TFC. 16

17 AGS0 modeling results Inlet and outlet rates are close to the experimental values Experimental reports contain limited information on mechanical fuel pin behavior 17

18 CABRI BI1 Loss-of-flow (LOF) MOX fuel pin (solid) Pre-irradiated 1 % at 24mm inter-pellet gap in the fuel pin LOF characteristics Core power MW 18.8 Fissile power W Max. linear power rating W/cm 600 Channel inlet flow rate g/s 160 Temperature at the lower end of the fissile length (T in ) C 400 Temperature at the upper end of the fissile length (T out ) C 580 Na temperature rise along fissile length C 180 Coupling factor 535 LOF flow Q(t)=Q 0 /(1+t /7) 18

19 CABRI BI1 timeline [0.0] LOF [20.2] Boiling onset at the top of the fissile column. [25.80] Fuel ejection 510mm BFC. The mass expelled was about 4 gram. [26.50] Ejection of molten fuel at 460mm BFC started, the mass involved was around 2 grams. [26.65] SCRAM (6.450s after boiling onset) [26.2] Maximum displacement of 5mm [26.55] The upper fuel segment moved downward 12mm Before the experiment there was a gap of 24mm in the fuel. The gap closed partially 350ms after the scram. Fuel melt. The radiograph has showed that almost all the pellets remained intact after the experiment. Some fuel melt took place. Clad melt. The clad melted between the levels and (i.e mm BFC) 19

20 CABRI BI1 modeling results Boiling onset 21.2 s (20.2 s experiment) Flow recovery 60 s (90 s experiment) 20

21 BI1 decanting options Decanting rule suddenly or continuously 21

22 Also the JRC-IET is involved in the ESNII+ project JRC IET activities within WP6 (Core Safety) Subtask ASTRID core safety coefficients. JRC use the MCNPX stochastic code. Subtask ASTRID core behaviour under design-extension conditions (KIT-IKET) KIT, CEA, JRC and EDF will perform calculations with the SIMMER code, but employing different modelling assumption to evaluate the possible transient scenarios. 22

23 IAEA Technical Meeting on Priorities in Modelling and Simulation for Fast Neutron Systems Modelling and simulation of severe accidents in GEN IV reactors, research tools used in the Institute for Energy and Transport at the European Commission s Joint Research Centre. A. Flores y Flores, V. Matuzas, L. Ammirabile, H. Tsige Tamirat, K. Tuček, A. Lazaro Chueca European Commission Joint Research Centre Institute for Energy and Transport Alain.Flores-y-Flores@ec.europa.eu 23