Higher irradiation temperature results in less embrittlement. This effect occurs due to the in-reactor annealing out of many radiation-produced defects before they can become stable defects.

According to Cottrell-Petch theory of radiation embrittlement [11],

where Ao; is the change in friction stress, oy is the yield stress, ky is the unpinning parameter, dky/dT is the change in the unpinning parameter as a function of tem­perature, and doy/dT is the yield stress as a function of temperature. Thus, the change in DBTT can be estimated by knowing these various parameters and their changes with temperature and fluence (Figure 6.34).