Diapositiva 1

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
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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
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Nominal Conditions RELAP5 Steady-State
Parameter Inner zone Middle zone Outer zone Reflector by-pass Target Total
Thermal power (MW) 96 142.3 140.5 5.2 11.2 395.2
Lead mass flow rate (kg/s) 7707 11548 11345 1120 1512 33232
Maximum temperature (C) Inner zone (Fax 1.14) Inner zone (Fax 1.14) Middle zone (Fax 1.16) Middle zone (Fax 1.16) Outer zone (Fax 1.17) Outer zone (Fax 1.17)
Maximum temperature (C) 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 fuel 1251 1150 1328 1213 1285 1094
Surface fuel 869 818 857 804 816 735
Internal clad 538 523 534 519 535 509
External clad 527 513 524 509 526 501
Lead 494 484 494 483 503 483
By-pass outlet Target outlet
- -
- -
- -
- -
431 450
Empresarios Agrupados Madrid, November 13-14,
2007, EUROTRANS DM1 WP1.5 Progress Meeting
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List of Transients to be Analyzed by ENEA (1)
TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN
Number Transient Description BOC EOC ENEA ENEA
Number Transient Description BOC EOC RELAP5 (X-S) RELAP/PARCS (X-C) SIMMER
PROTECTED TRANSIENTS PROTECTED TRANSIENTS PROTECTED TRANSIENTS PROTECTED TRANSIENTS PROTECTED TRANSIENTS PROTECTED TRANSIENTS PROTECTED TRANSIENTS
P-1 PLOF Total loss of forced circulation in primary system (4 pumps) x x X-S (reactor trip on core outlet temp. threshold)
P-1.1 PLOF-1 Loss of 1 out of 4 primary pumps (pump rotor seizure) x x X-S (reactor trip on core outlet temp. threshold)
P-4 PLOH Total loss of secondary loops (4 loops) x x X-S (reactor trip on core outlet temp. threshold)
P-4.1 PLOH-1 loss of 1 out of 4 secondary loops x x X-S (reactor trip on core outlet temp. threshold)
P-5 PLOF PLOH (station blackout) Total loss of forced circulation and secondary loops x x 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 x x X-C
P-11 SGTR Steam generator tube rupture (1 to 5 tubes) x X (reactor trip at 0 s)
Empresarios Agrupados Madrid, November 13-14,
2007, EUROTRANS DM1 WP1.5 Progress Meeting
7
List of Transients to be Analyzed by ENEA (2)
TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN
Number Transient Description BOC EOC ENEA ENEA
Number Transient Description BOC EOC RELAP5 (X-S) RELAP/PARCS (X-C) SIMMER
UNPROTECTED TRANSIENTS UNPROTECTED TRANSIENTS UNPROTECTED TRANSIENTS UNPROTECTED TRANSIENTS UNPROTECTED TRANSIENTS UNPROTECTED TRANSIENTS UNPROTECTED TRANSIENTS
U-1 ULOF Total loss of forced circulation in primary system (4 pumps) x x X-C X
U-2 UTOP (?) pcm jump in reactivity at HFP x x X-C
U-4 DEC ULOH Total loss of secondary loops (4 loops) x x X-C
U-5 DEC ULOF ULOH Total loss of forced circulation and secondary loops x x X-C
U-11 Beam Overpower to (?) at HFP x x X-C
U-12 Beam Power Jump to 100 at HZP x x X-C
Empresarios Agrupados Madrid, November 13-14,
2007, EUROTRANS DM1 WP1.5 Progress Meeting
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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 gt Threshold set-point
  (primary pump trip??, actions on secondary
  side??)

Empresarios Agrupados Madrid, November 13-14,
2007, EUROTRANS DM1 WP1.5 Progress Meeting
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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 kgm2

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 kgm2

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 gt
  773 K

Empresarios Agrupados Madrid, November 13-14,
2007, EUROTRANS DM1 WP1.5 Progress Meeting
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Actions Following Beam Trip (Short Term)
Action Primary pump trip Turbine and feedwater trip
1 Never Never
2 At proton beam trip Never
3 30 s after beam trip Never
4 30 s after beam trip 30 s after beam trip
Loss of 1 Secondary Loop
Maximum Clad Temperature
Inlet Core Temperature
Empresarios Agrupados Madrid, November 13-14,
2007, EUROTRANS DM1 WP1.5 Progress Meeting
15
Actions Following Beam Trip (Long Term)
Action Primary pump trip Turbine and feedwater trip
1 Never Never
2 At proton beam trip Never
3 30 s after beam trip Never
4 30 s after beam trip 30 s after beam trip
Loss of 1 Secondary Loop
Maximum Clad Temperature
Inlet Core 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 gt 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 gt 773 K)

• Reactor trip 10 s after pump 1 stop (T gt 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 Fuel Temperature
Maximum Clad 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
Pump 2,3,4 stop (30 s after reactor trip)
Beam 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 gt 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 gt 773 K)
Core and SG Power

• Reactor trip at 120 s (T lead gt 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 gt 773 K)

• Reactor trip (proton beam switch-off and pump
  stop) after 43 s (T lead gt 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)
Lower and Upper Plenum Temperature
Core 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

Empresarios Agrupados Madrid, November 13-14,
2007, EUROTRANS DM1 WP1.5 Progress Meeting
28
PLOH Loss of All Secondary Loops (3)
Maximum Vessel Temperature
Maximum Clad 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
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