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Consortium for Advanced Simulation of LWRs
CASL-U-2015-0251-000
Study on Two-Phase Fluid and Heat
Transfer Regimes in CRUD
Miaomiao Jin, Michael P. Short
Massachusetts Institute of Technology
July 7, 2015
CASL-U-2015-0251-000
STUDY ON TWO-PHASE FLUID AND HEAT TRANSFERREGIMES IN CRUD
{ MIAOMIAO JIN, MICHAEL P. SHORT }@MASSACHUSETTS INSTITUTE OF TECHNOLOGY
BACKGROUND
Macro Image Micro Image Definition
• Consequences:
– Boron pickup⇑ ⇒ axial offset anomaly– Heat transfer⇓ ⇒ corrosion⇑– Post-process radioactivity
• Details need understanding:
– Heat transfer– Chemistry
METHOD• Overview
– Based on the parallel computingframework, MOOSE (MultiphysicsObject Oriented Simulation Environ-ment).
– MAMBA-2Phase
∗ 3-D symmetric (2-D)∗ Heat & flow & chemistry coupled
– PWR operating parameters
• Features
– Explicitly assume film boiling
– Abandon wick boiling assumption
RESULTS FOR TYPICAL PWRA. Parametric Analysis:
0 10 20 30 40 50CRUD chimney density ( ·108 /m2 )
625
630
635
640
645
650
655
Clad
sur
face
pea
k te
mpe
ratu
re (K
)
Temperature
0
1
2
3
4
5
6
7
8
Vapo
r fil
m fi
lm t
hick
ness
(µm
)
Film thickness
3 4 5 6 7 8 9CRUD maximum pore size ( ·10−1µm)
630
635
640
645
650
Clad
sur
face
pea
k te
mpe
ratu
re (K
)
Temperature
2
3
4
5
6
7
8
Vapo
r fil
m t
hick
ness
(µm
)
Film thickness
0.3 0.4 0.5 0.6 0.7 0.8CRUD porosity
630
635
640
645
650
655
660
Clad
sur
face
pea
k te
mpe
ratu
re (K
)
Temperature
0
2
4
6
8
10
Vapo
r fil
m t
hick
ness
(µm
)
Film thickness
15.0 15.2 15.4 15.6 15.8 16.0System pressure (MPa)
630
635
640
645
650
Clad
sur
face
pea
k te
mpe
ratu
re (K
)
Temperature
2
3
4
5
6
7
8
Vapo
r fil
m t
hick
ness
(µm
)
Film thickness
B. Case study (left fig):Variables across domain hconv : 4.5209× 104 W/m2
Heat flux: 1.0 MW/m2
System pressure: 15.5 MPaCoolant temperature: 600 K
REFERENCES AND FOOTNOTE
[1] Deshon, J et al. Simulated Fuel CRUD Thermal Con-ductivity Measurements Under Pressurized Water Reac-tor Conditions. Technical Report 1022896, 2011
aSingle phase wick boiling model, under low heat flux
FUTURE WORK
1. Simulate CRUD growth.2. One way coupling: add an external layer in
BISON with pre-calculated CRUD thermalconductivity depending on local heat flux.
3. Two-way coupling: neutron depression byboron deposition could be calculated bycode, e.g. MPACT and fed back to BISON.
4. Add water radiolysis.
ACKNOWLEDGEMENTS
This work is funded by CASL (Consortiumfor Advanced Simulation of Light Water Reac-tors). Special thanks also go to my advisor Prof.Michael Short ([email protected]).
DISCUSSION-HEAT TRANSFER REGIMES
From the profile of experimental results [1], we propose a concept of double critical heat flux for porousmedia with boiling chimney, heated and cooled at each end. (1) thin CRUD: the heat transfer may gothrough (a)− (b)− (f) with increasing heat flux(left fig, upper right). These pores can act as nucleationsites, facilitating heat transfer; (2) thick CRUD: (a) to (f) may be expected(left fig, lower right). Underhigh heat flux, film boiling hinders heat transfer.
MODEL CONSTRUCTION
Typical CRUD parametersCRUD porosity 0.6
CRUD tortuosity 1.5CRUD chimney diameter 4 µm
CRUD pore diameter (min) 0.25 µmCRUD pore diameter (max) 0.50 µm
CRUD thickness 25 µmChimney density 2× 109/m2
• Separated two domains• A phase flag on each domain• Tune relative thickness of the two domains
until the solving gets mutually converged.
CRUD ADDED TO BISON
(a) Quarter fuel rod (b) Compare results from BISON and MAMBAa
(c) Schematic big picture of coupling
Single phase MAMBA calculation under low heatflux implies the necessity of coupling BOTH (b).
CASL-U-2015-0251-000
