Development of instrumentation systems for severe accidents. 1. R and D in Hitachi-GE

The accident at Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Plant (TF-1 accident) caused severe situations and resulted in a difficulty in measuring important parameters for monitoring plant conditions. Therefore, we have studied the TF-1 accident to select the important parameters that should be monitored at the severe accident (SA parameters) and are developing the Severe Accident Instrumentations and Monitoring Systems (SA-keisou) that could measure the parameters in severe accident conditions. Hitachi-GE has also been developing some instrumentation systems for use under severe environmental conditions during a severe accident including a fiber optic radiation monitor and a fiber optic water level monitoring system. The fiber optic radiation monitor uses a neodymium doped radiation luminescence element which emits infrared wavelength light when irradiated by gamma-rays. We confirmed that the monitor has a capability for measuring dose rates from 10 mGy/h to 100 kGy/h. The fiber optic water level monitoring system consists of a pressure sensor which is set on the tip of the optical fiber and a fiber optic temperature sensor. We are presently confirming that it can measure the water level properly under severe accident conditions. (author)