Analysis of a partial scram event in a typical BWR/4

A study has been made of core thermal-hydraulic conditions and containment suppression pool water temperature following a partial failure to scram in a BWR 4. This was motivated by the occurrence of such an incident in the Browns Ferry Unit 3. If suppression pool temperature should rise too much, the effectiveness of the suppression pool can be impaired. However, the pool temperature in the present case rose no more than 58 degrees (F), which is considered to be acceptable. In this study the transient is initiated by closure of the main steam isolation valves (MSIV) from 104.5% of normal operating power. The calculations were carried out using RELAP3B code and a plant model based on the Peach Bottom 2 power plant.