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Conference Article: Fission product plate-out measurement of Oarai helium gas loop OGL-1

Tsuyuzaki, N.; Sasajima, H.; Endo, Y.; Itami, H. (Department of JMTR Project, Japan Atomic Energy Research Institute, Oarai Research Establishment (Japan)); Matsumoto, M. (Nuclear Engineering Co., Omika-cho, Hitachi-shi (Japan))

Abstract

Fission Products (FP), released from the UO2 fuel kernels, circulate in the primary circuits of the VHTR reactor and deposit on the surface of circulation components during operation. An in-pile helium gas loop OGL-1 which simulates the VHTR coolant condition is installed in the JMTR reactor. The distribution of the FP plate-out had been measured by a non-destructive method using germanium detectors. The reactor coolant removes the FP from the reactor core and deposits 137Cs at temperature area of 400 deg. C and 131I at 300 deg. C. In the case when the OGL-1 fuel was replaced to a new specimen which has lower FP release ratio, it was found that the deposited nuclide of 137Cs constantly removes from the inner surface of high-temperature pipes of 600 deg. C and redeposits to the temperature area of 400 deg. C. Furthermore, this non-destructive method is possible to measure the short half-life noble gas nuclides which a conventional gas sampling method fails to measure. The experiment of dust filter installed in the OGL-1 primary circuit has been continued to study plate-out mechanism. Results have been used for verification of the plate-out analysis code and the design of the experimental VHTR components.

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key words: Gas Cooled Reactor, Nuclear Technology
Reference:
Specialists' meeting on fission product release and transport in gas-cooled reactors Berkeley (United Kingdom) 22-25 Oct 1985
International Atomic Energy Agency, International Working Group on Gas-Cooled Reactors, Vienna (Austria)
IWGGCR--13, pp:363-370