September 16, 2010

This technical position addresses an acceptable approach for evaluating Sr-90 source activities. Sr-90 decays to Y-90 which readily reaches equilibrium. The issue is whether the value in Appendix E of 10 CFR 835 includes both Sr-90 and Y-90 activity or should the Sr-90 activity be accounted for separately. The value given in Appendix E for Sr-90 should be applied to the total activity.