This work has done for an accidental release of radionuclide in case of a research reactor. For human being it is so important to know the harmfulness of radionuclide and also the safety guidelines from these radionuclides. For accidental case of TRIGA Mark-II research reactor, the isotopes of Krypton nucleus plays harmful effect. Four isotopes of krypton considered for research. These are 83mKr, 85mKr, 85Kr, and 88Kr.