The ratio between the decay heat output and activity content of discharged magnox fuel

Values of the ratio between activity and heat production rate have been calculated for magnox fuel irradiated to 3500 and 8000 MWd.Te-1 and for cooling times of 100, 200 and 500 days. Results are expressed in terms of both MeV.decay-1 and MCi.KW-1. The results indicate that: for these irradiation and cooling conditions 21 nuclides account for over 99% of the total activity; the calculated values show only small variations with burn-up and cooling time, although the mean energy per decay does fall slightly at 500 days cooling: so for many purposes a median value of 0.63 MeV.decay-1 (0.27 MCi.MW-1) may be used; the calculated values have standard deviations ranging from 2.6% at 100 days cooling to 9% at 500 days cooling. (author)