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Computational study of the mixed cooling effects on the in-vessel retention of a molten pool in a nuclear reactor

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Abstract

The retention of a molten pool vessel cooled by internal vessel reflooding and/or external vessel reactor cavity flooding has been considered as one of severe accident management strategies. The present numerical study investigates the effect of both internal and external vessel mixed cooling on an internally heated molten pool. The molten pool is confined in a hemispherical vessel with reference to the thermal behavior of the vessel wall. In this study, our numerical model used a scaled-down reactor vessel of a KSNP (Korea Standard Nuclear Power) reactor design of 1000 MWe (a Pressurized Water Reactor with a large and dry containment). Well-known temperature-dependent boiling heat transfer curves are applied to the internal and external vessel cooling boundaries. Radiative heat transfer has been considered in the case of dry internal vessel boundary condition. Computational results show that the external cooling vessel boundary conditions have better effectiveness than internal vessel cooling in the retention of the melt pool vessel failure.

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Abbreviations

A:

Surface area of a hemispherical pool (m2)

C:

Morphology constant

c:

Specific heat capacity (J/kg·K)

f:

Lliquid fraction of solidifying melt (0<ΔH/L<1)

g:

Gravity acceleration vector (m/s2)

ΔH:

Nodal latent heat undergoing phase change (0<ΔH<L) (J/kg)

Hl :

Initial depth of molten liquid relocated in lower plenum (m)

h:

Enthalpy (J/kg)

Kp :

Permeability

L:

Latent heat of fusion (J/kg)

Nu:

Nusselt number

p:

Pressure (N/m2)

q”:

Heat flux (W/m2)

\(\bar q^n \) :

Surface-averaged heat flux (W/m2)\(\left( { = \int\limits_s {q^n dA/A} } \right)\)

q m :

Volumetric heat source (W/m2)

R:

Inner radius of the hemispherical cavity (m)

R’:

Ratio of the up-to-down heat fluxes

Ra′:

Modified Rayleigh number based onq′″ (=ρ 2 cgβq′″R 5/κ 2μ)

T:

Temperature (K)

u:

Velocity vector (m/s)

V:

Volume of a hemispherical pool (m3)

ρ:

Liquid density (kg/m3)

β:

Thermal expansion coefficient of liquid (1/K)

ε:

Emissivity

K:

Thermal conductivity (W/mK)

θ:

Angle along the vessel wall

μ:

Dynamic viscosity (kg/m·s)

avg:

Average

b:

Buoyancy

dn:

Downward

e:

Electricity

h:

Latent heat

l:

Liquid

mp:

Molten pool

s:

Surface

th:

Thermal

u:

Velocity

up:

Upward

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Authors and Affiliations

  1. School of Mechanical Engineering, Kyungpook National University, 1370, Sankyuk-dong, 702-701, Daegu, Korea

    Byung Seok Kim

  2. Integrated Safety Assessment, Korea Atomic Energy Research Institute, 150, Dukjin-dong, 305-353, Daejon, Korea

    Kwang Il Ahn

  3. School of Mechanical Engineering, Kyungpook National University, 1370, Sankyuk-dong, 702-701, Daegu, Korea

    Chang Hyun Sohn

Authors
  1. Byung Seok Kim
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  2. Kwang Il Ahn
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  3. Chang Hyun Sohn
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Correspondence to Chang Hyun Sohn.

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Kim, B.S., Ahn, K.I. & Sohn, C.H. Computational study of the mixed cooling effects on the in-vessel retention of a molten pool in a nuclear reactor. KSME International Journal 18, 990–1001 (2004). https://doi.org/10.1007/BF02990871

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