New capabilities of computational tools, recent demands from the industry, including nuclear power plant power uprating, and advancement in the understanding of safety concepts may require innovative solutions and approaches for safety analyses. In the framework of such activities, the purpose of the present paper is to streamline the results related to DH (Decay Heat) and the γ (gamma) – DH distribution, two of the relevant issues. Concerning the DH to be introducing in the calculations, a study is presented on the values of the possibility offered by present knowledge and RELAP 5 options; suggested also made on the assumptions to be used in the RELAP5 analysis. The second issue, that is dealt with in this paper, is the DH γ distribution. The short study presents the effect of considering the real absorbed γ distribution in the core. The importance of taking into account this effect is apparent when the influence on important calculation results is considered: e.g. PCT (Peak Clad Temperature) could be affected by more than 100 K.