The continuous release of fission-gas from ceramic fuel was measured during irradiation in the Hitachi Training Reactor. Two different types of in-core assemblies were devised. In these assemblies, UO2 specimens were heated up to 2, 000°C by a heater rod, or else cylinder of tungsten. These assemblies can usefully serve in the study of fission-gas release rate at tem-peratures conducive to grain growth.In these assemblies, the fission-gases are purged by continuously flowing Ar or else He, and led out of the reactor, where the radioactivity was measured with γ-ray spectrometer. The radioactivity of Ar and fission-gas was left to decay in a radioactivity decay tank and a fission product collection train submerged in the reactor pool.
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