Analysis in support of operator guidelines for severe accidents using TRAC-PWR

The Nuclear Regulatory Commission initiated the Severe Accident Sequence Analysis (SASA) program to further understand both of reactor accident phenomena and of the human-machine interface during a spectrum of accidents. Efforts as Los Alamos for the SASA program have focused on (1) identification of potential accidents involving multiple equipment failures, (2) computer simulations of postulated accident sequences including equipment malfunctions and operator actions and (3) evaluation of critical safety equipment and operator responses. Recent analyses at Los Alamos have used the Transient Reactor Analysis Code (TRAC), version PFl, to investigate the movement of hydrogen in pressurized water reactors following a small-break loss-of-coolant accident. Also, TRAC is being used to study severe accidents in Babcock and Wilcox (B and W) plants. The results of the hydrogen-movement investigations, along with the ongoing B and W severe accident analyses will be discussed