AVERAGE IRRADIATION TEMPERATURE FOR THE ANALYSIS OF IN-PILE INTEGRAL MEASUREMENTS

Integral parameters of reactor fuel pins are usually measured after lo ng periods of irradiation, where each period can extend over a number of irradiation cycles. Examples of these parameters include cladding d iametral strain and parameters involved in the evaluation of fuel/clad ding chemical interaction and fuel restructuring. Analysis of these pa rameters requires knowledge of calculated irradiation parameters, whic h can vary between irradiation cycles and within the cycles. Irradiati on temperature is one such parameter. A calculated weighted average te mperature that takes into account the fluctuations in temperature betw een irradiation cycles is introduced. The work discusses the justifica tion for using this temperature and a methodology for its validation. The methodology is based on comparing calculated average temperatures with temperatures inferred from the postirradiation examination of res tructured binary metallic fuel pins in the Experimental Breeder Reacto r II. The analysis shows reasonable agreement between the two temperat ures. The peak irradiation temperatures, which are usually used in the analysis, were out of the range of the temperatures inferred from the experimental observations, showing the importance of using the averag e temperature.