Multy-cascade enrichment schemes for reprocessed uranium recycling

Abstract

This paper deals with the problem of reprocessed uranium (RepU) enrichment in cascades of gas centrifuges with simultaneous fulfillment of requirements on concentrations of isotopes 232,234,236U. These harmful isotopes bred by nuclear chain reaction are responsible for an increase in radioactivity level and neutron poisoning of fresh nuclear fuel. The study examines the cascade schemes that aim at closing the nuclear fuel cycle by satisfying the formal condition of the complete uranium reclaim. The prospective VVER fuel cycle strategy of multiple uranium recycling is considered. Schemes under consideration are multi-cascade ones. Such configurations are necessary to fulfill both a series of requirements on concentrations of even-numbered isotopes in commercial low-enriched uranium and condition of ‘full return’ of uranium extracted from spent nuclear fuel from particular reactor to produce fresh fuel load for the same reactor. The research provides a basis for comparison between three various multi-cascade schemes designed to re-enrich RepU under mentioned above conditions. The unified metrics (related to ordinary cascade and normalized to LEU product) of natural uranium savings, separative work, and depleted uranium consumption and their derivative, we used. The calculations take into account the necessity of RepU dilution to compensate for the adverse effects of 232,234,236U isotopes. As the reference cascade scheme, a simple modification of a single triple-flow cascade for RepU enrichment was considered. It is demonstrated that some modern cascade schemes could provide repetitious recycling of uranium.

On the problems of reusing reprocessed uranium by enrichment in schemes based on ordinary cascades

“…In other words, the article investigates mass transfer in cascades based on ordinary cascade designed for enrichment of reprocessed uranium in order to assess if they are capable to solve the problem of returning the whole amount of reprocessed uranium to the nuclear fuel cycle in the regime of multiple recycling when the isotope composition is degrading each cycle. These schemes have additional input of natural uranium to dilute unwanted 232 U to meet standard fresh LEU requirements [15]. At the same time, the reasons for the emergence of difficulties with the enrichment of reprocessed uranium with the simultaneous fulfillment of the conditions for even-numbered isotopes and the 1:1 use of the RepU using such schemes are revealed.…”