An inpile loop is described which is capable of continuously measuring the release of fission gas from ceramic fuels during irradiation in the Japan Research Reactor No.3.
The fuel specimen is heated to temperatures of up to 1, 000°C by the combined action of its own fission and a Pt wire heater.
The neutron flux for the specimens is controlled by changing the rod pattern and the reactor power. Specimens of about 22 mm diameter and of lengths up to 40 mm can be accommodated. A continuously flowing sweep gas (He gas) carries the fission gases outside the reactor where the radioactive isotopes are measured by γ-ray spectrometry. The non-radioactive gases released from the specimen during irradiation is determined continuously by an elusion gas chromatograph.