Loss of Pumping Power Scoping Analysis: Fuel Pin Failure Mechanisms Program

摘要

A scoping analysis of walk-thru for a hypothetical, unprotected loss-of-pumping-power accident occurring in a designated reference commercial LMFBR has been completed. The study was carried out with the express intention (and RRD direction) to be independent of any of the current failure analysis models or safety analysis codes. The walk-thru covers the progression of an unprotected loss-of-flow accident, beginning with loss of power to the pumps and continuing to the point where the reactor is subcritical and in a coolable geometry. The purpose of avoiding the current models and codes was to minimize the danger of casual acceptance of conventional failure mechanisms. Instead, basic engineering principles have been employed to outline the sequence of events after the pumps begin to coast down. Steady state operating conditions for the fuel, cladding, coolant and reactor structure were computed with the SAS computer program and formed the starting point for the effort. Perturbation theory (PERT-SN2D) was used for preparing material removal worth tables. Doppler reactivity feedback coefficients were also computed with existing physics tools. The data were later utilized as a reference for estimates of the reactor kinetics influences which result from processes involving material motion and significant temperature changes. From a host of possible accident paths, the sequence believed to be most likely was chosen.