ermsar 2012, cologne march 21 – 23, 2012 in-vessel retention as retrofitting measure for existing...
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ERMSAR 2012, Cologne March 21 – 23, 2012
In-vessel retention as retrofitting measure for existing nuclear power plants
M. Bauer, Westinghouse Electric Germany GmbH
K. Knebel, European Commission, Joint Research Centre, Institute for Transuranium Elements
D. Freis, Westinghouse Electric Germany GmbH
ERMSAR 2012, Cologne March 21 – 23, 2012
Introduction
In-vessel melt retention (IVMR) concept : e.g. AP1000
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Principle: 1: oxidic melt layer, 2: metallic melt layer, 3: channel for cooling water, 4: reactor pit, 5: rising two-phase mixture, 6: separation of liquid phase and steam at the height of the primary coolant lines
Source: Westinghouse Electric Company, AP1000 European Design Control Document, Chapter 39, Pittsburgh, 2009
ERMSAR 2012, Cologne March 21 – 23, 2012
ULPU tests
Determination of Critical Heat Flux (CHF) for AP600 (ULPU-III, -IV) and AP1000 (ULPU-V) geometries
ULPU-III: simple flow duct, ULPU-IV: improved flow duct
ULPU-V: improved flow duct + optimized flow cross section
Results: CHF in dependence of surface inclination of RPV
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ERMSAR 2012, Cologne March 21 – 23, 2012
ULPU setups (left: -III, right: -IV)
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ERMSAR 2012, Cologne March 21 – 23, 2012
ULPU results: Critical heat flux (CHF)
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0 10 20 30 40 50 60 70 80 900
500
1000
1500
2000
CHF ULPU V
CHF ULPU IV
CHF ULPU III
surface inclination [°]
he
at f
lux
[kW
/m²]
ERMSAR 2012, Cologne March 21 – 23, 2012
CHF and corresponding thermal power
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ERMSAR 2012, Cologne March 21 – 23, 2012
Possible realization as retrofitting measure
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ERMSAR 2012, Cologne March 21 – 23, 2012
MELCOR simulations
Large PWR (~ 3750 MW)
Adapted to simulate the IVMR-system
Modified correlation for CHF
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0 10 20 30 40 50 60 70 80 900
500
1000
1500
2000
CHF ULPU IIICHF ULPU IVCHF ULPU VCHF MELCOR
surface inclination [°]
he
at f
lux
[kW
/m²]
ERMSAR 2012, Cologne March 21 – 23, 2012
MELCOR simulations: Scenarios
Base case: 10 cm2 SBLOCA, with depressurization of primary side, flow rate 38.4 kg/s
Variations:
– Reduced flow rate
– Without depressurization of primary side
– Increased decay heat
– 200 cm2 LOCA
– LBLOCA (2A-break)
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ERMSAR 2012, Cologne March 21 – 23, 2012
Results: Base case – containment pressure
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1 10 100 1000 10000 100000 10000000
1
2
3
4
t [s]
p [b
ar]
ERMSAR 2012, Cologne March 21 – 23, 2012
Results: Base case – number of layers of RPV wall below melt temperature
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0 100000 200000 300000 400000 500000 6000000
4
8
12
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Segment 1 Segment 2 Segment 3 Segment 4
Segment 5 Segment 6 Segment 7 Segment 8
t [s]
no. o
f nod
es
ERMSAR 2012, Cologne March 21 – 23, 2012
Results: Base case – experimental CHF compared to calculated maximum heat flux
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0 10 20 30 40 50 60 70 80 900
500
1000
1500
2000
CHF ULPU III CHF ULPU IV
CHF ULPU V CHF MELCOR
Lokale Wärmestromdichte
surface inclination [°]
he
at f
lux
[kW
/m²]
ERMSAR 2012, Cologne March 21 – 23, 2012
MELCOR simulations: Results
In all simulated scenarios:
– IVMR worked well:
No RPV failure
No venting of containment necessary
Details of modelling and results of simulations can be seen in paper to this presentation.
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ERMSAR 2012, Cologne March 21 – 23, 2012
Summary
– The feasibility of retrofitting IVMR in large PWRs was analyzed, based on the results of the ULPU experiments.
– A MELCOR model of a German plant was modified to model an IVMR based on gravity driven flow from the spent fuel pool and pump driven injection to the RPV cavity. CHF correlations of MELCOR were modified to reflect the results of the ULPU experiments.
– MELCOR simulations of several severe accident scenarios were performed: In all simulations the melt could successfully be retained in the RPV.
– “Take home” message: The simulations showed the usefulness and feasibility of such a retrofit.
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ERMSAR 2012, Cologne March 21 – 23, 2012
Further work:
Physical:Further work should investigate the effect on CHF of forced convection as proposed for the retrofitting in contrast to natural convection as used in the ULPU experiments.
Technical:From a practical point of view the possibilities of installing a suitable flow duct in the reactor pit have to be examined, along with the development of appropriate installation procedures and tools (manipulators).
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