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LEADER Project

LEADER Project. Analysis of Representative DEC Events of the ETDR with RELAP5 and CATHARE . Giacomino Bandini - ENEA/Bologna Genevieve Geffraye – CEA/Grenoble LEADER 4 th WP5 Meeting Karlsruhe, 22 November 2012. Outline. Analyzed DEC Transients at EOC ALFRED Modeling

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LEADER Project

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  1. LEADER Project Analysis of Representative DEC Events of the ETDR with RELAP5 and CATHARE GiacominoBandini - ENEA/Bologna Genevieve Geffraye – CEA/Grenoble LEADER 4th WP5 Meeting Karlsruhe, 22 November 2012

  2. Outline • Analyzed DEC Transients at EOC • ALFRED Modeling • Transient Results • Conclusions

  3. Analyzed DEC Transients Main events and reactor scram threshold

  4. ALFRED Nodalization scheme with RELAP5 851 851 851 - - - - - - - - - - - - - - - - - - - - - 8 8 8 441 441 441 - - - 8 8 8 Feedwater Feedwater Feedwater Feedwater 731 731 731 731 731 731 731 731 731 731 731 731 731 731 731 731 731 731 731 731 - - - - - - - - - - - - - - - - - - - - 8 8 8 521 521 521 521 - - - - 8 8 8 8 841 841 841 841 841 841 841 841 841 841 841 841 841 841 841 841 841 841 841 841 841 - - - - - - - - - - - - - - - - - - - - - 4 4 4 4 4 4 4 8 4 4 4 8 4 8 4 020 020 020 Steam Steam Steam Steam 741 741 741 741 741 741 741 741 741 741 741 741 741 741 741 741 741 741 741 741 - - - - - - - - - - - - - - - - - - - - 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 8 8 531 531 531 531 - - - - 8 8 8 8 411 815 815 815 815 815 815 815 815 815 411 815 411 815 815 815 815 815 815 815 815 - - - 8 8 8 8 IC 050 050 050 loops 831 831 831 831 831 831 831 831 831 831 831 831 831 831 831 831 831 831 831 831 831 - - - - - - - - - - - - - - - - - - - - - 8 4 4 8 4 4 4 4 4 8 4 4 4 4 4 4 4 4 811 811 811 811 811 811 811 811 811 811 811 811 811 811 811 811 811 811 811 811 811 - - - - - - - - - - - - - - - - - - - - - 4 4 4 4 4 8 4 4 4 4 4 8 4 4 4 4 8 4 070 070 070 061 061 061 - - - 8 8 8 060 060 060 751 751 751 751 751 751 751 751 751 751 751 751 751 751 751 751 751 751 751 751 - - - - - - - - - - - - - - - - - - - - 8 8 8 401 401 401 - - - 8 8 8 141 141 141 - - - 8 8 8 711 711 711 711 711 711 711 711 711 711 711 711 711 711 711 711 711 711 711 711 - - - - - - - - - - - - - - - - - - - - 8 8 8 761 761 761 761 761 761 761 761 761 761 761 761 761 761 761 761 761 761 761 761 - - - - - - - - - - - - - - - - - - - - 4 4 4 8 4 4 4 4 4 4 4 4 4 4 8 4 4 4 4 4 801 801 801 801 801 801 801 801 801 801 801 801 801 801 801 801 801 801 801 801 801 - - - - - - - - - - - - - - - - - - - - - 4 4 4 4 4 4 4 8 4 4 4 8 4 4 4 4 4 8 771 771 771 771 771 771 771 771 771 771 771 771 771 771 771 771 771 771 - - - - - - - - - - - - 8 8 8 551 551 551 551 - - - - 8 8 8 8 561 561 561 561 - - - - 8 8 8 8 115 180 115 781 781 781 781 781 781 781 781 781 781 781 781 781 781 781 781 781 781 - - - - - - - - - - - - 8 8 8 131 131 131 - - - 8 8 8 8 MHXs 8 8 8 8 - - - - 151 151 151 - - - 8 8 8 200 200 200 151 151 151 151 Steam line 121 121 121 - - - 8 8 8 210 210 210 110 110 110 661 661 661 661 661 661 661 661 661 661 661 - - - - - - - - - - - 4 4 4 4 8 4 4 4 4 4 8 641 641 641 641 641 641 641 641 641 641 641 641 641 641 641 641 641 641 641 641 - - - - - - - - - - - - - - - - - - - - 4 4 4 4 4 4 8 4 4 4 4 4 4 4 4 4 4 4 4 8 Feedwater line 601 601 601 601 601 601 601 601 601 601 601 - - - - - - - - - - - 8 4 4 4 4 4 4 4 4 8 4 621 621 621 621 621 621 621 621 621 621 621 621 621 621 621 621 621 621 621 621 - - - - - - - - - - - - - - - - - - - - 4 4 4 4 4 4 4 4 8 4 4 4 4 4 4 4 4 4 4 8 109 109 109 102 102 102 101 101 101 611 611 611 611 611 611 611 611 611 611 611 611 611 611 611 611 611 611 611 611 - - - - - - - - - - - - - - - - - - - - 8 8 8 220 220 220 Primary 8 Secondary loops 230 230 230 100 100 100 circuit RELAP5 Modeling

  5. CATHARE Modeling ALFRED Nodalization scheme with CATHARE 2 IC loops (weight 4) Primary circuit 2Secondary loops (weight 4)

  6. TR-4: Reactivity insertion (1/3) (RELAP5 – CATHARE Comparison) • ASSUMPTIONS: • Insertion of 250 pcm in 10 s • No feedwater control on secondary side • Different fuel rod gap dynamic model in RELAP5 and CATHARE • Fuel-clad linked effect  fuel expansion according to clad temperature (closed gap) Core and MHX powers Core and MHX powers 6

  7. TR-4: Reactivity insertion (2/3) (RELAP5 – CATHARE Comparison) Total reactivity and feedbacks Total reactivity and feedbacks Core temperatures Core temperatures 7

  8. TR-4: Reactivity insertion (3/3) (RELAP5 – CATHARE Comparison) Core temperatures Core temperatures • MAIN RESULTS: • Initial core power peak around 700 MW • Maximum clad temperature remains below 650 °C • Maximum fuel temperature (hottest FA, middle core plane, pellet centre) exceeds the MOX melting point of about 2760 °C  only local fuel melting  no extended core melting 8

  9. T-DEC1: ULOF (1/3) (RELAP5 – CATHARE Comparison) Active core flowrate Active core flowrate Core and MHX powers Core and MHX powers 9

  10. T-DEC1: ULOF (2/3) (RELAP5 – CATHARE Comparison) Core temperatures Core temperatures Core temperatures Core temperatures 10

  11. T-DEC1: ULOF (3/3) (RELAP5 – CATHARE Comparison) Total reactivity and feedbacks Total reactivity and feedbacks • ASSUMPTIONS: • No feedwater control on secondary side • Fuel-clad not-linked effect  fuel expansion according to fuel temperature • MAIN RESULTS: • Natural circulation in primary around 23% of nominal value • Core power reduces down to about 200 MW • Initial clad peak temperature at 750 °C; max clad temperature stabilizes around 650 °C 11

  12. T-DEC3: ULOHS (1/3) (RELAP5 – CATHARE Comparison) Core and MHX powers Core and MHX powers Core temperatures Core temperatures 12

  13. T-DEC3: ULOHS (2/3) (RELAP5 – CATHARE Comparison) Core and vessel temperatures Core and vessel temperatures Total reactivity and feedbacks Total reactivity and feedbacks 13

  14. T-DEC3: ULOHS (3/3) (RELAP5 – CATHARE Comparison) • ASSUMPTIONS: • 3 out of 4 IC loops of DHR-1 system in service • No heat losses from the vessel external surface • MAIN RESULTS: • Core power progressively reduces down towards decay level • Maximum clad temperature rises up to about 700 °C after 30 minutes • Maximum vessel temperature rises up to about 650 °C after 30 minutes 14

  15. T-DEC4: ULOHS + ULOF (1/3) (RELAP5 – CATHARE Comparison) Active core flowrate Active core flowrate Core and MHX powers Core and MHX powers 15

  16. T-DEC4: ULOHS + ULOF (2/3) (RELAP5 – CATHARE Comparison) Core temperatures Core temperatures Core temperatures Core temperatures 16

  17. T-DEC4: ULOHS + ULOF (3/3) (RELAP5 – CATHARE Comparison) Total reactivity and feedbacks Total reactivity and feedbacks • ASSUMPTIONS: • 3 out of 4 IC loops of DHR-1 system in service • No heat losses from the vessel external surface • MAIN RESULTS: • Natural circulation in primary circuit reduces down to very low value (around 1%) • Core power progressively reduces down towards decay level • Max T-clad rises up to 800 °C after about 15 minutes and stabilizes around 825 °C • Maximum vessel temperature rises up to about 500 °C after 60 minutes 17

  18. TO-3: FW temp. reduction + PP stop (1/2) (RELAP5 Results) Core temperatures Total reactivity and feedbacks Active core flowrate (long term) Active core flowrate (short term) 18

  19. TO-3: FW temp. reduction + PP stop (2/2) (RELAP5 Results) Primary lead temperatures Core decay and MHX powers • ASSUMPTIONS: • Loss of one preheater (FW temperature from 335 °C down to 300 °C in 1 s) + primary pump coastdown  reactor scram at t = 2 s on low pump speed signal • 4 IC loops in service for decay heat removal • MAIN RESULTS: • Power removal by 4 IC loops of DHR-1 system is about 7 MW • No risk of lead freezing after DHR-1 start-up • Lead freezing at MHX outlet is reached after about 2 hours (cold lead at the MHX outlet to the core inlet without significant mixing in the cold pool above MHX outlet) 19

  20. TO-6: FW flowrate + 20% + PP stop (1/2) (RELAP5 Results) Core temperatures Total reactivity and feedbacks Active core flowrate (long term) Active core flowrate (short term) 20

  21. TO-6: FW flowrate + 20% + PP (2/2) (RELAP5 Results) Primary lead temperatures Core decay and MHX powers • ASSUMPTIONS: • FW flowrate increase of 20% + primary pump coastdown  reactor scram at t = 2 s on low pump speed signal • 4 IC loops in service for decay heat removal • MAIN RESULTS: • Power removal by 4 IC loops of DHR-1 system is about 7 MW • No risk of lead freezing after DHR-1 start-up • Lead freezing at MHX outlet is reached after about 2 hours (cold lead at the MHX outlet to the core inlet without significant mixing in the cold pool above MHX outlet) 21

  22. T-DEC6: SCS failure (1/2) (RELAP5 Results) Total reactivity and feedbacks Secondary pressure Primary lead temperatures Core and MHX powers 22

  23. T-DEC6: SCS failure (2/2) (RELAP5 Results) Core and vessel temperatures Core decay and MHX powers • ASSUMPTIONS: • Depressurization of all secondary circuits (no availability of DHR-1 system)  reactor scram at t = 2 s on low secondary pressure • MAIN RESULTS: • Initial MHX power increase up to 800 MW  no risk for lead freezing • Slow primary temperature increase due to large thermal inertia of primary system and efficient hot lead mixing in the cold pool at MHX outlet before to reach the core inlet 23

  24. TDEC-5: Partial FA blockage (RELAP5 Results) • ASSUMPTIONS: • ΔP over total FA = 1.0 bar • ΔP at FA inlet = 0.22 bar • No heat exchange with surrounding FAS • Flow area blockage at FA inlet • MAIN RESULTS: • 75% FA flow area blockage  50% FA flowrate reduction • 85% blockage  T max clad = 700 °C • No clad melting if area blockage < 95% • Fuel melting if area blockage > 97.5% • 50% inlet flow area blockage can be detected by TCs at FA outlet 24

  25. Conclusions • The analysis of DEC transients with RELAP5 and CATHARE codes has highlighted the very good intrinsic safety features of ALFRED design thanks to: • Good natural circulation characteristic, • Large thermal inertia, and • Significant negative reactivity feedbacks • In all analyzed transients there is no risk for significant core damage or risk for lead freezing  large grace time is left to the operator to take the opportune corrective actions to bring the plant in safe conditions in the medium and long term 25

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