Adaptive collocation method for simultaneous heat and mass diffusion with phase change

Conference · Sat Jan 01 04:00:00 EST 1983

OSTI ID:6120435

Chawla, T C; Pedersen, D R; Leaf, G; Minkowycz, W J; Shouman, A R

In post-accident heat removal applications the use of a lead slab is being considered for protecting a porous bed of steel shot in ex-vessel cavity from direct impingement of molten steel or fuel as released from reactor vessel following a hypothetical core disassembly accident in an LMFBR. The porous bed is provided to increase the coolability of the fuel debris by the sodium coolant. The present study is carried out to determine melting rates of a lead slab of various thicknesses by contact with sodium coolant and to evaluate the extent of penetration and the mixing rates of molten lead into liquid sodium by molecular diffusion alone. The study shows that these two calculations cannot be performed simultaneous without the use of adaptive coordinates which cause considerable stretching of the physical coordinates for mass diffusion. Because of the large difference in densities of these two liquid metals, the traditional constant density approximation for the calculation of mass diffusion cannot be used for studying their interdiffusion. The use of orthogonal collocation method along with adaptive coordinates produces extremely accurate results which are ascertained by comparing with the existing analytical solutions for concentration distribution for the case of constant density approximation and for melting rates for the case of infinite lead slab. The analysis further shows that the melting rate progressively increases as the thickness of lead slab decreases.

• Research Organization: Argonne National Lab., IL (USA); Illinois Univ., Chicago (USA). Dept. of Mechanical Engineering; New Mexico State Univ., Las Cruces (USA). Dept. of Mechanical Engineering
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6120435
• Report Number(s): CONF-830702-30; ON: DE85004816
• Country of Publication: United States
• Language: English

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