Radiation control and monitoring system on the HTTR

The High Temperature Engineering Test Reactor (HTTR) is a helium-gas-cooled and graphite-moderated reactor with thermal output of 30MW and outlet coolant temperature of 850degC at the rated operation and 950degC at the high temperature test operation. The Japan Atomic Energy Research Institute (JAERI) started the construction of the HTTR facility in March 1991 and the first criticality was attained in November 1998. And the reactor performance test will follow to achieve its full power operation in FY 2000. The radiation control and monitoring system on the HTTR consists of the radiation monitoring system and the computer system. The former is composed of six channels of effluent air monitor, eight channels of room air monitor and fourteen channels of dose rate monitor. And the latter is composed of two server computers and eleven client computers. The design of this system was especially considered measuring for radioactive gaseous substances. For instance, the tritium monitor applied high polymer membrane for selectively separation of tritium from the other gaseous elements and two different types of gas monitor for beta-ray emitters and gamma-ray emitters are used for rare gas monitoring. Besides, tritium and carbon-14 in effluent air and working environment air are absorbed into the liquid absorbent monthly and then measured. The computer system was utilized for improvement of reliance, rapidly data processing and rationalizing of radiation control works. The functions of the computer system are watching unusual data and machine troubles, data processing, calling on urgency, presuming the cause of unusual radiation levels, etc. These computers have connected with LAN in the Oarai Research Establishment. Therefore, the monitoring data and the process information of the facility such as the reactor power of state of the ventilation can be watched at any points in the HTTR building and the central supervising room in the other building. (author)