Nuclei in nuclear reactors and stars

To evaluate the characteristic properties of fission products, the fission yield and decay data (decay constant, decay energy and release rate of decayed neutron) of about 1000 kinds of nuclide are necessary. From 1970 to 1980 years, the decay heat and the characteristics of delayed neutrons for the principle fission nuclide such as 235U, 238U and 239Pu were appreciable to use in the general light water reactor. We discussed relation between calculation of the characteristics of fission products and study of unstable nuclide and astronomical physics. Total calculation of decay heat was investigated by formal solution. To increase the evaluation values, the accuracy of fission yield and the decay data of nuclides with short life should be increased by measurements. (S.Y.)