Abstract: In this paper, based on the spent fuel assembly from the third generation passive nuclear power plant, a comparative study on the decay heat calculation based on ANS 5.1—2005 and ORIGEN-S was carried out. The variation of decay heat of fission products and actinide nuclides under different cooling times is analyzed in detail. The results show that the contribution of actinide nuclides to the total decay heat of spent fuel with cooling time of more than 5 years is close to 20% or even higher, and the main contributions of actinide nuclides are from Cm-244, Pu-238 and Am-241. ANS 5.1—2005 only considers U-239 and Np-239 for actinide nuclides. For the spent fuel storage system with long cooling time, the calculation of decay heat by ANS 5.1—2005 is not conservative. It is suggested that special programs such as ORIGEN-S should be used to calculate the decay heat for the third generation passive NPP spent fuel storage and transportation system.

Key words: decay heat, fission products, actinide nuclides