Investigative study of radiotoxicity of spent nuclear fuel assembly of some commercial nuclear power plants

The European Pressurized Water Reactor (EPR) and Hualong One Pressurized Water Reactor (HPR) are two of the reactors under consideration by the Ghana Nuclear Power Programme. Radiotoxicity analysis of Spent Nuclear Fuel (SNF) assembly was carried out with these commercial Pressurized Water Reactor (PWR) nuclear power technology as case study. This will help determine which one is less radiotoxic on the environment between the two reactor technologies, in the long run. Burnup depletion calculation for the Uranium Oxide (UOX) fuel of these reactor technologies was simulated, using Monte Carlo Neutron Particle Extended (MCNPX), a code used in nuclear fuel management analysis, being a well validated code and also due to its versatile nuclei reactions cross section library. Determination of radiotoxicity for EPR and HPR SNF is the main objective of this study. The radiotoxicity was achieved taking into consideration the radioactive decay rate of the radionuclides and the Dose Factor of each radionuclide present in the SNF using the International Commission on Radiological Protection (ICRP) compendium of Dose Factors due to ingestion. The radiotoxicity for the two reactor's SNF were compared. The initial radiotoxicity for HPR SNF was higher in the duration below one hundred years but at about a hundred years and above, the radiotoxicity was higher for EPR SNF. The radiotoxicity was tremendously reduced for the reprocessed spent UOX fuel (with the Pu and U extracted) to be used as mixed oxide (MOX) fuel. The main finding is that Pu isotopes are the major contributors to the radiotoxicity of the SNF for the two reactors systems due to their very high radioactivity, long half-lifes and high dose factors as compared to other actinides and fission products present in the SNF. •The EPR and HPR fuel assemblies are both designed to have a square lattice containing 265 fuel pins.•It is observed that the initial high radiotoxicity of the SNF is from the fisssion products.•Thorium exhibited high radiotoxicity for the SNF of the two reactors considered.•The radiotoxicity of the Th-UOX fuel cycle being considered as fuel for future similar reactors be further investigated.