ACHIEVEMENTS IN DEVELOPMENT OF

(3) Tritium Management Technology Heavy water, used as the moderator in Fugen, contains deuterium atoms that generate tritium (half-life of 12.3 years) absorbing neutrons. The tritium concentration in the moderator (heavy water) has been rising along with the duration of Fugen's operation. It reached approximately 260MBq/cm3 as of March 2003. Consequently, radiation control has been essential for related tritium works at Fugen. In order to perfect tritium management techniques, the work procedures were examined, and measurement techniques and protection tools for tritium were developed and improved.

Build up of Tritium in Heavy Water

Tritium Measurement/Evaluation Method Simple and high sensitive measuring techniques for tritium have been developed, and the monitoring procedures in the working area have been optimized in Fugen. One such tool, the membrane separation tritium monitor is an original product of the Fugen. The method is that the sample air is blown through a hollow fiber membrane permeable to moisture only, and then the tritium vapor passed through the membrane is measured in an ionization chamber. It is effective in eliminating the influence of natural radioactive nuclides contained in the air, such as radon or thoron, and in measuring the tritium concentration highly sensitively. The monitor is used in several purposes: portable room monitor for work environment measurement, stack tritium monitor in the main stack, the heavy water upgrader building, and the waste treatment building; and area tritium monitor in the heavy water upgrader building.
		Membrane Separation Tritium Monitor