Stored energy recovery of irradiated copper

Abstract

The stored energy released in Stage I recovery of reactor neutron irradiated copper was measured by differential thermal analysis calorimetry for three fluences up to a maximum of 3.5 × 10¹⁸ n/cm² (E>0.1 MeV) after irradiation at temperatures of less than 10 K. The stored energy dependence upon fluence, and a tendency toward saturation, were observed. Theoretical reaction rate processes were compared directly to the experimental rates of stored energy release, and the parameters associated with the theory were compared with results from previous resistivity measurements. Good agreement was found in several parameters, but major differences with previous D + E substage results lead to the conclusion that the point defect model may not describe materials experiencing severe neutron damage. Computer studies of warmup rates were made for first and second order and for correlated recovery processes as a function of defect concentration and of external power input. First and second order processes show definite distortion in their recovery rate curves for high defect concentrations; the correlated recovery process shows a much less pronounced effect.

This investigation of stored energy used several new approaches. The use of one sample in both experimental and control roles was not unique, but the use of induced radioactivity within the sample as the heating source, and the use of computer generated theoretical stored energy release curves to analyze the data were unique.