LMFBR fuel analysis. Task B: Post-accident heat removal. Final technical report 1 October 1977-15 November 1978

This report presents a review of post-accident heat removal problems and views upon areas that include debris bed phenomena, molten pool growth, gas film boundaries and crusts, and the influence of basemat conduction upon pool formation and evolution. It introduces plausible circumstances for the formation of non-coolable debris beds, and so leads to crude estimates of the initial dimensions of core debris distributions for pool growth problems. The GROWS code is reviewed and examples given using initial conditions derived from those estimates. Gas film boundaries with crusting and freezing phenomena are qualitatively discussed as potentially significant factors in defining heat split and pool evolution. Research on density gradient mixing in dense pools overlying light sacrificial materials is reviewed. The conductive transport of heat in the solid basemat surrounding the pool is discussed as a factor that might influence the initial spreading of a molten mass upon a basemat, may influence the shape of a pool when strong top surface cooling is present, and is a dominant factor in defining the cessation of penetration