Continuous Monitoring of Fission Gas Release During Irradiation of Nuclear Fuel Specimens PDF Download

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Languages : en
Pages : 15

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Book Description
A program is in progress at Battelle-Columbus which is aimed at developing a basic understanding of the mechanisms and processes which contribute to the phenomenology of swelling and fission gas release in nuclear fuel materials during irradiation. As part of this program, neutron radiography has been used to obtain data on the dimensional changes of fuel specimens periodically during irradiation. This data is used to develop plots of fuel swelling as a function of burnup for the specimens under irradiation. These data show a decided nonlinearity of swelling with accumulated burnup for many specimens, and it has been postulated that the shape of the curves is due, at least in part, to the gas release characteristics of the specimens. Accordingly, it was considered advantageous to develop a system to continuously monitor fission gas release from the fuel during irradiation. The system developed consists of a null-balance pressure transducer attached directly to a clad fuel specimen in the capsule. Fission gases escaping from the fuel collect within the cladding and exert pressure on a diaphragm in the transducer. A balancing pressure is introduced on the other side of the diaphragm and the null-balance position of the diaphragm is detected by an electrical contact which is part of a detection circuit. Instrumentation is provided to monitor the balance pressure, and the fission gas temperature and pressure is correlated with the known fission gas generation rate to calculate the fractional release from the fuel. In addition to monitoring fission gas release, the system also provides information on cladding integrity. Cladding failure is detected as a large reduction in pressure while operating at essentially constant temperature. This system has been used successfully in two irradiation experiments at fuel and cladding temperatures in excess of 1700 C. The data it provides on fission gas release has been used in conjunction with swelling data from neutron radiography to provide considerable insight into the phenomenology of the behavior of nuclear fuels during irradiation.