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

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 Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting RELAP5 Nodalization Scheme  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

4. Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting  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) EFIT Design and Parameters

5. Nominal Conditions: RELAP5 Steady-State Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting Maximum temperature (°C) Inner zone (Fax = 1.14) Middle zone (Fax = 1.16) Outer zone (Fax = 1.17) Hot FA 1/42 Fr = 1.12 Average FA 41/42 Hot FA 1/66 Fr = 1.13 Average FA 65/66 Hot FA 1/72 Fr = 1.24 Average FA 71/72 Central fuel125111501328121312851094 Surface fuel869818857804816735 Internal clad538523534519535509 External clad527513524509526501 Lead494484494483503483 ParameterInner zone Middle zone Outer zone Reflector + by-pass TargetTotal Thermal power (MW)96142.3140.55.211.2395.2 Lead mass flow rate (kg/s)770711548113451120151233232 By- pass outlet Target outlet -- -- -- -- 431450

6. List of Transients to be Analyzed by ENEA (1) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN NumberTransientDescriptionBOCEOC ENEA RELAP5 (X-S) RELAP/PARCS (X-C) SIMMER PROTECTED TRANSIENTS P-1PLOF Total loss of forced circulation in primary system (4 pumps) xx X-S (reactor trip on core outlet temp. threshold) P-1.1PLOF-1 Loss of 1 out of 4 primary pumps (pump rotor seizure) xx X-S (reactor trip on core outlet temp. threshold) P-4PLOH Total loss of secondary loops (4 loops) xx X-S (reactor trip on core outlet temp. threshold) P-4.1PLOH-1 loss of 1 out of 4 secondary loops xx X-S (reactor trip on core outlet temp. threshold) P-5 PLOF + PLOH (station blackout) Total loss of forced circulation and secondary loops xx X-S (reactor trip at 0 s) X (reactor trip at 0 s) P-10 Spurious beam trip beam trip for 1,2,3 ….. 10 s intervals xxX-C P-11SGTR Steam generator tube rupture (1 to 5 tubes) x X (reactor trip at 0 s)

7. List of Transients to be Analyzed by ENEA (2) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN NumberTransientDescriptionBOCEOC ENEA RELAP5 (X-S) RELAP/PARCS (X-C) SIMMER UNPROTECTED TRANSIENTS U-1ULOF Total loss of forced circulation in primary system (4 pumps) xxX-CX U-2UTOP (?) pcm jump in reactivity at HFP xxX-C U-4 DECULOH Total loss of secondary loops (4 loops) xxX-C U-5 DEC ULOF + ULOH Total loss of forced circulation and secondary loops xxX-C U-11 Beam Overpower to (?)% at HFP xxX-C U-12 Beam Power Jump to 100% at HZP xxX-C

8. Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting 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??)

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

10. Sensitivity Study to Pump Inertia (ULOF) (2) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting Inlet Core Mass Flow Rate 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  No significant effect of pump inertia on maximum clad temperature peak  Largest value of pump inertia is not favorable

11. Definition of Reactor Trip Set-Points (1) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting  Threshold set-point on measured lead temperature (top assembly, upper plenum  average core outlet, pump inlet) 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 ULOH Temperature  Threshold set-point at 773 K on average core outlet temperature limits the maximum clad temperature at 823 K

12. Definition of Reactor Trip Set-Points (2) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting ULOF Temperature ULOF (1 Pump) 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  In case of all primary pumps trip the high clad temperature peak cannot be limited by lead temperature threshold on average core outlet temperature

13. Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting  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 Actions Following Proton Beam Trip 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

14. Actions Following Beam Trip (Short Term) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting ActionPrimary pump tripTurbine and feedwater trip 1Never 2At proton beam tripNever 330 s after beam tripNever 430 s after beam trip Maximum Clad TemperatureInlet Core Temperature Loss of 1 Secondary Loop

15. Actions Following Beam Trip (Long Term) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting ActionPrimary pump tripTurbine and feedwater trip 1Never 2At proton beam tripNever 330 s after beam tripNever 430 s after beam trip Maximum Clad TemperatureInlet Core Temperature Loss of 1 Secondary Loop

16. Preliminary Analysis of Protected Transients Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting 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

17. PLOF-1: Loss of 1 Primary Pump (1) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting 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

18. PLOF-1: Loss of 1 Primary Pumps (2) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting Lower and Upper Plenum Temperature Maximum Lead Temperature Reactor trip (T > 773 K) T max = 839 K (hot channel of outer core)  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

19. PLOF-1: Loss of 1 Primary Pumps (3) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting T max = 869 K (hot channel of outer core) T max = 1620 K (hot channel of middle core) Maximum Fuel TemperatureMaximum Clad Temperature  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)

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

21. PLOF: Loss of All Primary Pumps (1) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting Primary Pump Mass Flow RateInlet 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

22. PLOF: Loss of All Primary Pumps (2) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting 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) Lower and Upper Plenum TemperatureMaximum Lead Temperature T max = 995 K (hot channel of outer core)

23. PLOF: Loss of All Primary Pumps (3) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting T max = 1700 K (hot channel of middle core) T max = 1080 K (hot channel of inner core) Maximum Fuel Temperature Maximum Clad Temperature  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

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

25. Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting PLOH-1: Loss of 1 Secondary Loop (2) Maximum Fuel Temperature Maximum Clad Temperature Maximum Lead 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 T max = 860 K T max = 865 K

26. PLOH: Loss of All Secondary Loops (1) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting Inlet Core Mass Flow Rate Lower and Upper Plenum Temperature  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 Reactor trip (T > 773 K) Pump trip

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

28. PLOH: Loss of All Secondary Loops (3) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting Maximum Vessel TemperatureMaximum Clad Temperature  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) T max = 877 K (hot channel of outer core) T max = 722 K

29. PLOF + PLOH: Station Blackout (1) Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting Core and DHR Mass Flow Rate Core and DHR Inlet/Outlet Temp. Core and DHR Power  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)

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

31. Empresarios Agrupados – Madrid, November 13-14, 2007, EUROTRANS – DM1 – WP1.5 Progress Meeting PLOF + PLOH: Station Blackout (3) Maximum Clad Temperature Maximum Vessel Temperature Maximum Lead 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