A Simplification of Existing Methods of Calculating Decay Heat Following Reactor Shutdown and an Investigation of the Effects of Power History Upon Decay Heat

A meLhod of calculating decay hea't, is seii which is a simp!ifieation of existing calcultional met'nod spm!aation krAhod in particular. The method involves the assumption that One physical process, neutron capture, is neglighle in order to simplil- the governing physical equations. A Greens function is derived anh the decay heat is defined by quadratur2 of this function with power over time. A discussion of the size of the corer induced by the assuwtion that neutron capture is ner,iligible is oresenteri.. The results show good agreement with the summation method and indicate that the capture process accounts for less than I % of the total decay heat. A discussion of power history effects upon decay heat is presented. The importance of various irradiation intervals is ascertained. The importance of power intervals close to shutdown is recognized. From this work a graphical method of calculating decay heat is described as an aid to understanding the importance played by various irradiation intervals