Nuclear Power Plant MSIV Room Temperature Control

During summer months (June-October), multiple units at two nuclear power plants repeatedly exceeded the Main Steam Isolation Valve (MSIV) room design temperature limits of 10–40°C (50–104°F), raising concerns over electrical equipment reliability and long‑term performance. Uncontrolled heat accumulation inside the MSIV rooms posed a risk of equipment malfunction and accelerated degradation. Temperature data showed that while each of the MSIV rooms at the two nuclear power plants commonly experienced elevated conditions—ranging from 38°C to over 50°C—1 MSIV room consistently maintained significantly lower temperatures, operating 7°C cooler at minimum and up to 11°C cooler at maximum compared to the other MSIV rooms. Notably, this was the only MSIV room utilizing RAPID, contributing to its improved thermal stability throughout the high‑temperature season.