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EUROTRANS – DM1 Preliminary Transient Analysis for EFIT with RELAP5 and RELAP/PARCS Codes PowerPoint Presentation
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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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slide1

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

slide2

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

slide3

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

slide4

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

slide5

Nominal Conditions: RELAP5 Steady-State

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

slide6

List of Transients to be Analyzed by ENEA (1)

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

slide7

List of Transients to be Analyzed by ENEA (2)

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

slide8

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

slide9

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

slide10

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

slide11

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

slide12

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

slide13

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

slide14

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

slide15

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

slide16

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

slide17

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

slide18

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

slide19

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

slide20

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

slide21

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

slide22

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

slide23

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

slide24

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

slide25

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

slide26

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

slide27

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

slide28

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

slide29

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

slide30

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

slide31

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