Safety Enhancements in Boiling Water Reactor (BWR) Tarapur Atomic Power Station (TAPS-1&2)

Abstract

The primary means of preventing and mitigating the consequences of accidents is through ‘defence in depth’, which is fundamental to the safety of nuclear installations. Defence in depth provides a hierarchical deployment of different independent levels of equipment and procedures in order to maintain effectiveness of physical barriers placed between radioactive materials, the workers, public and the environment, during normal operation and potential accident conditions. The design basis accidents, when postulated unmitigated by engineered safety systems, lead to beyond design basis accidents situations, where core may either degrade or melt due to inadequate core cooling. During these postulated accident scenarios in boiling water reactors if sufficient water is lost from the reactor coolant system (RCS), there could be uncovery and overheating of the core leading to fuel pin cladding oxidation occurs. After accident at Fukushima NPPs, safety review of the design features to handle postulated design extension conditions (DEC) was done for Indian nuclear reactor including TAPS-1&2, and the following safety improvements have been retrofitted. Automatic reactor shutdown initiation on sensing seismic activity.Pre-inerting of TAPS-1&2 containment.Provisions for hookup arrangements for adding cooling water into reactor pressure vessel (RPV) and emergency condenser (EC) system.Containment filtered venting system (CFVS) to maintain the containment integrity. The above enhanced measures will be used in implementing accident management guidelines to mitigate design extension scenarios. This paper discusses the basis and details of various systems, arrangements and management actions to ensure the effective incorporation of above features. © 2020, Springer Nature Singapore Pte Ltd.