ANS 5.1

Abstract

This standard sets forth values for the decay heat power from fission products and 239U and 239Np following shutdown of light water reactors (LWRs) containing 235U, 238U, and plutonium. The decay heat power from fission products is presented in tables and equivalent analytical representations. Methods are described that account for the reactor operating history, for the effect of neutron capture in fission products, and for assessing the uncertainty in the resultant decay heat power. <br>Decay heat power from other actinides and activation products in structural materials, and fission power from delayed neutron&#8211;induced fission are not included in this standard and shall be evaluated by the user and appropriately included in any analysis of shutdown power. <br><strong>Purpose and application</strong> <br>This standard provides bases for determining the shutdown decay heat power and its uncertainty following shutdown of LWRs. The information in this standard can be used in the design, performance evaluation, and assessment of the safety of LWRs. This standard can be used as the basis for comparison with the results of alternate methods of determining fission product decay heat power.¹⁾ <br>¹⁾ Examples of the use of the standard methods are presented in Appendix B.