Suppression-pool temperature limits for BWR containments

Boiling water reactor (BWR) plants are equipped with safety/relief valves (SRVs) to protect the reactor from overpressurization. Plant operational transients, such as turbine trips, will actuate the SRV. Once the SRV opens, steam released from the reactor is discharged through SRV lines to the suppression pool in the primary containment. Steam is then condensed in the suppression pool in a stable condition. Extended steam blowdown into the pool, however, will heat the pool to a level were the condensation process may become unstable. This instability of steam condensation may cause severe vibratory loads on containment structures. Current practice in dealing with this phenomenon restricts the allowable operating temperature envelope of the pool in the Technical Specifications so that this instability will not occur. This restriction is referred to as the pool temperature limit. Task Action Plan (TAP) A-39, Determination of Safety/Relief Valve (SRV) Pool Dynamic Loads and Temperature Limits for BWR Containment, was established to resolve, among other things, the concern about steam condensation behavior for the Mark I, II, and III containments. This report presents the resolution of this issue and includes: (1) the acceptance criteria related to the suppression pool temperature limits; (2) events for which a suppression pool temperature response analysis is required; (3) assumptions used for the analysis; and (4) requirements for the suppression pool temperature monitoring system. This report completes the subtask related to the suppression pool temperature limit in TAP A-39