Transmutation of minor actinides in the pressurized water reactors

Abstract

We study the effects of adding MA nuclides to the PWR core and the MA nuclide transmutation rate in the PWRs. Our calculation results show that even 1% homogeneous addition of MA nuclides to the nuclear fuel can reduce keff of the PWRs drastically. The uniform distribution of MA nuclides in the uranium dioxide fuel can also affect the lifetime of a fuel loading. Calculation results also indicate that the uniform distribution of MA nuclides in the uranium dioxide fuel results in a reactivity mismatch and control difficulties in the PWRs. The spatial self-shielding effects of the heterogeneous distributions of MA nuclides in the PWR core can avoid the initial reactivity to drop significantly, and the reactivity mismatch and control difficulties in the PWRs can be also overcome.During 300-day-exposure of MA nuclides in the PWRs 14.8% Pu-238 and 7.7% Pu-239 of the initial MA nuclides are created, this explains at least 22.5% MA nuclides transmute to plutonium isotopes during 300-day-exposure in PWRs by various nuclear processes. We may incinerate plutonium-239 and plutonium-238 isotopes in the subsequent MOX fuel loading of the PWRs. Alternatively, we may also use Pu-238 created in the transmutation of MA nuclides in the PWRs to fabricate the nuclear batteries. Pu-238 mainly transmuted from neptunium-237 in PWRs, neptunium-237 constitutes 56.2% of the total minor actinides in the depleted nuclear fuel of PWRs. The majority of commercial reactors in operation in the world are PWRs, if we get the neptunium-237 transmuted in the PWRs during their power generating, the inventory of high level long-lived radioactive minor actinides in the world will be greatly reduced.Our study show MA nuclides actually can act as the burnable poisons in the PWRs. MA nuclide transmutation materials may be used to partially substitute for the burnable poisons in the PWRs, or reduce the concentration of the boric acid in the coolant of the PWRs and increase the negative temperature coefficient of the PWRs. This is a distinct advantage to transmute MA nuclides in the PWRs. The transmutation characteristics of MA nuclides in PWRs and high flux thermal reactors are also compared in this research.