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EUROTRANS – DM1 Preliminary Transient Analysis for EFIT with RELAP5 and RELAP/PARCS Codes

FPN-FISNUC / Bologna. EUROTRANS – DM1 Preliminary Transient Analysis for EFIT with RELAP5 and RELAP/PARCS Codes. G. Bandini, P. Meloni, M. Polidori. WP5.1 Progress Meeting Empresarios Agrupados - Madrid, November 13-14, 2007. OUTLINE.

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EUROTRANS – DM1 Preliminary Transient Analysis for EFIT with RELAP5 and RELAP/PARCS Codes

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  1. FPN-FISNUC / Bologna EUROTRANS – DM1 Preliminary Transient Analysis for EFIT with RELAP5 and RELAP/PARCS Codes G. Bandini, P. Meloni, M. Polidori WP5.1 Progress Meeting Empresarios Agrupados - Madrid, November 13-14, 2007

  2. OUTLINE • RELAP5 Thermal-Hydraulic Model Improvements and EFIT Parameters • List of Transients to be Analyzed by ENEA • Sensitivity Study to Pump Inertia (ULOF) • Definition of Reactor Trip Set-Points • Results of Protected Transients with RELAP5 • Analysis of Unprotected Transients with RELAP/PARCS Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  3. RELAP5 Model Improvements • Update of steam generator model and secondary side boundary conditions • Primary mechanical pump model added  effect of pump inertia in LOF transients • Core pressure drop (grid spacer model added) • Target loop and power removal added • Upper plenum mesh refinement  recirculation flows according to SIMMER-III results RELAP5 Nodalization Scheme Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  4. EFIT Design and Parameters • Primary circuit layout from ANSALDO presentation at the last EUROTRANS - DM4 Technical Review Meeting (March 2007): • Reactor core with 3 fuel zones • 4 primary pumps, 8 steam generators, 4 secondary loops • 4 DHR units (3 out of 4 in operation in transient analysis) • Primary circuit parameters: • Reactor thermal power = 395.2 MW • Lead mass flowrate = 33230 kg/s • Core inlet / outlet temperature = 400 / 480 C • Total primary circuit pressure drop = 1.1 bar (core = 0.45 bar, SG = 0.35 bar, Pump + others = 0.3 bar ) • Secondary circuit parameters: • Total feedwater flow rate (4 SGs) = 244.4 kg/s, Temperature = 335 C • Steam pressure = 140 bar • Steam temperature = 452 C (Superheating of 115 C) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  5. Nominal Conditions: RELAP5 Steady-State Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  6. List of Transients to be Analyzed by ENEA (1) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  7. List of Transients to be Analyzed by ENEA (2) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  8. Preliminary Analysis of Protected Transients • P-1 – PLOF: Total loss of forced circulation in primary system (4 pumps) • P-1.1 – PLOF-1: Loss of 1 out 4 primary pumps (pump rotor seizure) • P-4 – PLOH: Loss of all secondary loops • P-4.1 – PLOH-1: Loss of 1 out of 4 secondary loops • P-5 – PLOF + PLOH (Station blackout): Total loss of forced circulation and secondary loops and beam trip • REACTOR TRIP: Proton beam switch-off if average core outlet temperature > Threshold set-point (primary pump trip??, actions on secondary side??) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  9. Sensitivity Study to Pump Inertia (ULOF) (1) Pump Mass Flow Rate • Unprotected Loss of Flow accident analysis (4 pumps lost) • Pump inertia varying in the range 20 – 200 kg*m2 Pump Velocity • Primary pumps stop in few seconds • High pump reverse flow is induced by free level movements Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  10. Sensitivity Study to Pump Inertia (ULOF) (2) Maximum Clad Temperature • Core mass flow rate oscillations induced by free level movements • Lowest undershoot for pump inertia in the range 50 – 100 kg*m2 Inlet Core Mass Flow Rate • No significant effect of pump inertia on maximum clad temperature peak • Largest value of pump inertia is not favorable Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  11. Definition of Reactor Trip Set-Points (1) • Clad safety limits for categories DBC II – DBC IV (PDS-XADS): • Tclad max ≤ 823 K with • time ≤ 600 s at 823 – 873 K • time ≤ 180 s at 873 – 923 K • Threshold set-point on measured lead temperature (top assembly, upper plenum  average core outlet, pump inlet) ULOH Temperature • Threshold set-point at 773 K on average core outlet temperature limits the maximum clad temperature at 823 K Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  12. Definition of Reactor Trip Set-Points (2) ULOF Temperature • The clad safety limit of 823 K is exceeded by 15 K in case of 1 pump trip event and threshold set-point at 773 K on average core outlet temperature ULOF (1 Pump) Temperature • In case of all primary pumps trip the high clad temperature peak cannot be limited by lead temperature threshold on average core outlet temperature Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  13. Actions Following Proton Beam Trip • Actions on Primary and Secondary sides are in general needed after automatic proton beam trip to bring the plant in safe conditions and avoid lead overcooling ULOH (1 Loop) Temperature • Primary pump trip • Turbine and feedwater trip • The results of different actions and timing have been evaluated for the initiating event of loss of 1 secondary loop • Beam trip at 120 s when core outlet temperature > 773 K Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  14. Actions Following Beam Trip (Short Term) Loss of 1 Secondary Loop Inlet Core Temperature Maximum Clad Temperature Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  15. Actions Following Beam Trip (Long Term) Loss of 1 Secondary Loop Inlet Core Temperature Maximum Clad Temperature Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  16. Preliminary Analysis of Protected Transients INITIATING EVENTS: • PLOF-1: Loss of 1 out 4 primary pumps • PLOF: Total loss of forced circulation in primary system • PLOH-1: Loss of 1 out of 4 secondary loops • PLOH: Loss of all secondary loops • PLOF + PLOH (Station blackout): Total loss of forced circulation and secondary loops and beam trip REACTOR TRIP: • Proton beam trip if average core outlet temperature > 773 K • Primary pump trip at beam trip • No actions on secondary side Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  17. PLOF-1: Loss of 1 Primary Pump (1) Primary Pump Mass Flow Rate Inlet Core Mass Flow Rate Pump 2,3,4 stop (Reactor trip) Pump 2,3,4 stop (Reactor trip) Pump 1 lost • Steady-state at 5000 s (primary pump 1 lost with reverse flow) • Pump 2, 3 , 4 stop at reactor trip after about 10 s Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  18. PLOF-1: Loss of 1 Primary Pumps (2) Lower and Upper Plenum Temperature Maximum Lead Temperature T max = 839 K (hot channel of outer core) Reactor trip (T > 773 K) • Reactor trip 10 s after pump 1 stop (T > 773 K) • Maximum lead temperature is 839 K in the hot channel of outer core zone Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  19. PLOF-1: Loss of 1 Primary Pumps (3) Maximum Clad Temperature Maximum Fuel Temperature T max = 869 K (hot channel of outer core) T max = 1620 K (hot channel of middle core) • Maximum clad temperature exceeds the limit of normal conditions (823 K) but is below the clad safety limit for DBC1- 4 transient conditions (923 K) • Limited fuel temperature increase (below 1620 K) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  20. PLOF-1: Loss of 1 Primary Pumps (4) Primary Pump 2, 3, 4 Trip 30 s after Beam Trip Primary Pump Mass Flow Rate Maximum Clad Temperature T max = 838 K Beam trip Pump 2,3,4 stop (30 s after reactor trip) Pump 1 lost • Clad temperature peak is limited by delaying primary pump shutdown (30 s) with respect to proton beam switch-off Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  21. PLOF: Loss of All Primary Pumps (1) Primary Pump Mass Flow Rate Inlet Core Mass Flow Rate • Pump mass flow rate reverses just after stopping (negligible effect of pump inertia) • Initial oscillations of inlet core mass flow rate are due to free level movements and stabilization Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  22. PLOF: Loss of All Primary Pumps (2) Lower and Upper Plenum Temperature Maximum Lead Temperature T max = 995 K (hot channel of outer core) Reactor Trip • Reactor trip about 10 s after pump trip (average lead temp. at core outlet > 773 K) • Large temperature peak due to initial core mass flow rate undershoot • The maximum lead temperature remains well below the boiling point (1476 K) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  23. PLOF: Loss of All Primary Pumps (3) Maximum Fuel Temperature Maximum Clad Temperature T max = 1080 K (hot channel of inner core) T max = 1700 K (hot channel of middle core) • Maximum clad temperature exceeds for few seconds the limit of 923 K for DBC1 – 4 transient conditions • The maximum fuel temperature is 1700 K in the hot channel of middle core zone Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  24. Inlet Core Mass Flow Rate PLOH-1: Loss of 1 Secondary Loop (1) Pump trip at beam trip Upper and Lower Plenum Temp. Reactor trip (T > 773 K) Core and SG Power • Reactor trip at 120 s (T lead > 773 K, beam and pump trip) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  25. Maximum Clad Temperature PLOH-1: Loss of 1 Secondary Loop (2) T max = 865 K Maximum Lead Temperature T max = 860 K Maximum Fuel Temperature • Lead and clad temperature peaks can be avoided with pump trip delay • Maximum clad temperature peak is within the safety limit for DBC1 – 4 transient conditions Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  26. PLOH: Loss of All Secondary Loops (1) Inlet Core Mass Flow Rate Lower and Upper Plenum Temperature Pump trip Reactor trip (T > 773 K) • Reactor trip (proton beam switch-off and pump stop) after 43 s (T lead > 773 K) • Large oscillation of lead mass flow rate at core inlet due to free level movements Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  27. PLOH: Loss of All Secondary Loops (2) Core and DHR Power Lower and Upper Plenum Temperature • Maximum DHR performance (3 units) = 20 MW is attained after about 5000 s • Maximum lead temperature stabilizes after about 5000 s at 723 K Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  28. PLOH: Loss of All Secondary Loops (3) Maximum Clad Temperature Maximum Vessel Temperature T max = 877 K (hot channel of outer core) T max = 722 K • Maximum clad temperature is 877 K in the hot channel of outer core zone (no peak with delayed pump trip) • Vessel temperature (maximum after about 3000 s) remains below the safety limit (723 K) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  29. Core and DHR Power PLOF + PLOH: Station Blackout (1) Core and DHR Mass Flow Rate Core and DHR Inlet/Outlet Temp. • Natural circulation mass flow rate in primary system and DHR power removal confirmed by SIMMER-III 2-D results • DHR mass flow rate in good agreement with ANSALDO specifications at 3600 s (2985 kg/s) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  30. Maximum Clad Temperature T max = 848 K PLOF + PLOH: Station Blackout (2) Maximum Lead Temperature T max = 844 K Maximum Fuel Temperature • Maximum clad temperature is within the safety limit for DBC1 – 4 transient conditions (time ≤ 600 s at 823 – 873 K) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

  31. Maximum Lead Temperature PLOF + PLOH: Station Blackout (3) Maximum Clad Temperature Maximum Vessel Temperature T limit = 723 K T max = 715 K • Maximum lead and clad temperatures stabilize around 730 K • Maximum vessel temperature remains below the safety limit Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting

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