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LEADER Project
Analysis of Representative DEC Events of the ETDR with RELAP5 and CATHARE
Giacomino Bandini - ENEA/BolognaGenevieve Geffraye – CEA/Grenoble
LEADER 4th WP5 MeetingKarlsruhe, 22 November 2012
2
Outline
Analyzed DEC Transients at EOC ALFRED Modeling Transient Results Conclusions
3
Analyzed DEC Transients
TRANSIENT Initiating Event (t = 0 s) Reactor scram and threshold
Primary pump trip
MHX FW trip
MSIV closure DHR startup
TR-4: Reactivity insertion (UTOP)
Insertion of 250 pcm in 10 s No No No No No
TO-3: Reduction of FW temp. + all pumps stop
FW temp. from 335 °C down to 300 °C in 1 s
2 s, low pump speed 0 s 2 s 2 s DHR-1 at 3 s
(4 IC loops)
TO-6: Increase of FW flowr. + all pumps stop
20% increase in FW flowrate in 25 s
2 s, low pump speed 0 s 2 s 2 s DHR-1 at 3 s
(4 IC loops)
TDEC-1: Total ULOF All primary pump coastdown No 0 s 1 s 1 s DHR-1 at 2 s
(3 IC loops)
TDEC-3: ULOHS All MHX feedwater trip No No 1 s 1 s DHR-1 at 2 s (3 IC loops)
T-DEC4: ULOHS + ULOF
All primary pumps and MHX feedwater trip No 0 s 0 s 0 s DHR-1 at 2 s
(3 IC loops)
T-DEC5: Partial block. in the hottest FA
10% to 97.5 % blockage at hottest FA inlet No No No No No
T-DEC6: SCS failure Depressurization of all secondary circuits
2 s, low second. pressure No 2 s No No
Main events and reactor scram threshold
4
RELAP5 Modeling
Feedwater
Steam
521- 8
531- 8
551- 8 561-8
151-
8
Feedwater
Steam
521- 8
531- 8
551- 8 561-8
151-
8
841 - 4
851 - 8441 -8
801 - 4
811-4831 - 4
815
401 - 8
841 - 4
-
801 - 4
811-4831 - 4
815
841 - 4
-
801 - 4
811-4831 - 4
815
611 - 8
841 - 4
-
801 - 4
811-4831 - 4
815
611 -
711-
731-
741- 4
751 - 8
761- 4
621- 4
641 - 4
771
781 - 8
601- 4
661 - 4
611 -
711- 8
731- 8
741- 4
751 -
761- 4
621- 4
641 - 4
771 -8
781 -
601- 4
661 - 4
611 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781
601- 4
661 - 4
841 - 8
-
801 - 4
811-4831 - 4
815
841 -
-
801 - 8
811-8831 - 8
815
611 -
841 -
-
801 -
811-831 -
411 -8
611 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771
781
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781 -
601- 8
661 - 8
611 -
711-
731-
741- 8
751 -
761- 8
621- 8
641 - 8
841 - 4
851 - 8441 -8
801 - 4
811-4831 - 4
815
401 - 8
841 - 4
-
801 - 4
811-4831 - 4
815
841 - 4
-
801 - 4
811-4831 - 4
815
611 - 8
841 - 4
-
801 - 4
811-4831 - 4
815
611 -
711-
731-
741- 4
751 - 8
761- 4
621- 4
641 - 4
771
781 - 8
601- 4
661 - 4
611 -
711- 8
731- 8
741- 4
751 -
761- 4
621- 4
641 - 4
771 -8
781 -
601- 4
661 - 4
611 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781
601- 4
661 - 4
841 - 8
-
801 - 4
811-4831 - 4
815
841 -
-
801 - 8
811-8831 - 8
815
611 -
841 -
-
801 -
811-831 -
411 -8
611 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771
781
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781 -
601- 8
661 - 8
611 -
711-
731-
741- 8
751 -
761- 8
621- 8
641 - 8
ALFRED Nodalization scheme with RELAP5
8 MHXs
8 Secondary loops Primary circuit
8 IC loops
Steam line
Feedwater line
100
101102109
110
115
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
100
101102109
110
115
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
100
101102109
110
180
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
Feedwater
Steam
521- 8
531- 8
551- 8 561-8
151-
8
Feedwater
Steam
521- 8
531- 8
551- 8 561-8
151-
8
841 - 4
851 - 8441 -8
801 - 4
811-4831 - 4
815
401 - 8
841 - 4
-
801 - 4
811-4831 - 4
815
841 - 4
-
801 - 4
811-4831 - 4
815
611 - 8
841 - 4
-
801 - 4
811-4831 - 4
815
611 -
711-
731-
741- 4
751 - 8
761- 4
621- 4
641 - 4
771
781 - 8
601- 4
661 - 4
611 -
711- 8
731- 8
741- 4
751 -
761- 4
621- 4
641 - 4
771 -8
781 -
601- 4
661 - 4
611 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781
601- 4
661 - 4
841 - 8
-
801 - 4
811-4831 - 4
815
841 -
-
801 - 8
811-8831 - 8
815
611 -
841 -
-
801 -
811-831 -
411 -8
611 -
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771
781
711-
731-
741- 4
751 -
761- 4
621- 4
641 - 4
771 -
781 -
5
CATHARE Modeling
ALFRED Nodalization scheme with CATHARE
Primary circuit
2 Secondary loops (weight 4)
2 IC loops (weight 4)
TR-4: Reactivity insertion (1/3)(RELAP5 – CATHARE Comparison)
Core and MHX powers Core and MHX powers
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)
6
7
TR-4: Reactivity insertion (2/3) (RELAP5 – CATHARE Comparison)
Core temperatures Core temperatures
Total reactivity and feedbacks Total reactivity and feedbacks
8
TR-4: Reactivity insertion (3/3) (RELAP5 – CATHARE Comparison)
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
Core temperatures Core temperatures
9
T-DEC1: ULOF (1/3) (RELAP5 – CATHARE Comparison)
Active core flowrate Active core flowrate
Core and MHX powers Core and MHX powers
10
T-DEC1: ULOF (2/3) (RELAP5 – CATHARE Comparison)
Core temperatures Core temperatures
Core temperatures Core temperatures
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
12
T-DEC3: ULOHS (1/3) (RELAP5 – CATHARE Comparison)Core and MHX powers Core and MHX powers
Core temperatures Core temperatures
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
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
15
T-DEC4: ULOHS + ULOF (1/3) (RELAP5 – CATHARE Comparison)
Active core flowrate Active core flowrate
Core and MHX powers Core and MHX powers
16
T-DEC4: ULOHS + ULOF (2/3) (RELAP5 – CATHARE Comparison)
Core temperatures Core temperatures
Core temperatures Core temperatures
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 surfaceMAIN 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
18
TO-3: FW temp. reduction + PP stop (1/2) (RELAP5 Results)
Total reactivity and feedbacks Core temperatures
Active core flowrate (short term) Active core flowrate (long term)
19
TO-3: FW temp. reduction + PP stop (2/2) (RELAP5 Results)
Core decay and MHX powers Primary lead temperatures
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 removalMAIN 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)
20
TO-6: FW flowrate + 20% + PP stop (1/2) (RELAP5 Results)
Total reactivity and feedbacks Core temperatures
Active core flowrate (short term) Active core flowrate (long term)
21
TO-6: FW flowrate + 20% + PP (2/2) (RELAP5 Results)
Core decay and MHX powers Primary lead temperatures
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 removalMAIN 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)
22
T-DEC6: SCS failure (1/2) (RELAP5 Results)
Secondary pressure Total reactivity and feedbacks
Core and MHX powers Primary lead temperatures
23
T-DEC6: SCS failure (2/2) (RELAP5 Results)
Core decay and MHX powers Core and vessel temperatures
ASSUMPTIONS: Depressurization of all secondary circuits (no availability of DHR-1 system) reactor
scram at t = 2 s on low secondary pressureMAIN 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
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
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
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