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Conference Article: Monitoring experiment of gaseous fission products in the primary coolant helium of OGL-1

Terada, H.; Saruta, T.; Suzuki, K.; Wakayama, N.; Aoyama, I. (Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki-ken (Japan))

Abstract

The experiments were carried out to develop a monitoring method of fission products in the primary coolant helium of the experimental VHTR (Very High Temperature Reactor). In the experiments, the high-temperature in-pile gas loop OGL-1 (Oarai Gas Loop-1) was used to simulate a primary circuit condition of the VHTR. The monitoring system consists of a conventional wire-driving precipitator and a Ge gamma-ray spectrometer. The gross counts due to fission products in the primary circuit are measured by the precipitator, and the gamma-ray spectra of the fission products are monitored by the Ge spectrometer for identification of the fission product nuclides. It was observed that gross counts due to fission products released from coated particle fuel samples change significantly depending on the reactor power and the irradiation temperature in the manner of 10 cps (12 MW, 350 deg. C), 150 cps (50 MW, 1100 deg. C) and 325 cps (50 MW, 1350 deg. C). Individual contributions of each fission-product nuclide to the gross count were monitored in detail by the Ge gamma-ray spectrometer. It was determined that the gross inventory of the fission-product activities was 3.4x1011 Bq (9.2 Ci) referred to the primary coolant of the experimental VHTR, and the sensitivity of the experimental monitoring system was 9.6x10-10 cps/Bq (35 cps/Ci) as the equivalent activity to Kr-88. Also, it was shown that the relation between the gamma-ray peak-counts of the individual nuclides and the fuel temperature can be represented by exponential functions in the range of the fuel temperature from 350 deg. C to 1350 deg. C.

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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:351-362