Abstract
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 that could measure the parameters in severe accident conditions. This paper discusses the GLS electro-chemical type hydrogen monitor and the multi-phase, multi-year evaluations performed for this hydrogen monitoring system. The testing was a comprehensive test program lasting almost 3 years. In the testing, the performance during SA was demonstrated. Since the conditions in SA scenarios are very severe in terms of temperature, pressure and radiation, it was necessary to ensure that the GLS hydrogen monitor utilized measurement methods and materials that could operate in these severe environments. The GLS hydrogen sensors are a chemi-resistive sensor that is intrinsically smart and tuned to hydrogen. Hydrogen measurement is rapid at typically less than one minute. The GLS hydrogen sensor was confirmed to operate at the extremely high radiation dose of 5 MGy, very high pressure of 1MPa, and extreme SA temperature of 700℃. The GLS hydrogen monitor deploys Gas Monitoring Units which measure hydrogen, temperature, pressure and oxygen present during SA conditions. The GLS hydrogen monitor has several benefits during SA, such as confirmation of hydrogen occurrence and variation of hydrogen concentration under extreme conditions. This study is a part of the results of the collaborative project by Japanese electric power companies and plant manufacturers that is carried out as the Safety Enhancement for LWRs program by Agency for Natural Resources and Energy.
