Analysis of Feasibility and Spent Fuel Characteristics of REMIX Fuel

Abstract

A new fuel technology named REMIX (REgenerated MIXture of uranium and plutonium oxides) based on the spent nuclear fuel of light water reactors and fast reactors has come into being in the pursuit of closed fuel cycle in many countries. It was first raised in Russia as a possible way to reduce spent nuclear fuel storage. In traditional spent nuclear fuel reprocessing progress, uranium and plutonium are separated after the codecontamination cycle. For REMIX fuel, the uranium and plutonium nuclides from spent nuclear fuel can be used together without a further separation, which brings the benefits in natural uranium consumption reduction and nuclear non-proliferation. This article aims at validating the feasibility of 5 recycles and analyzing the radiation and decay heat characteristics of spent REMIX fuel. The CMS code package was used in core calculation, and the spent nuclear fuel characteristics were calculated through the SNF program in the package. A typical M310 reactor core was chosen as the target reactor in this article, 30% REMIX FA (fuel assembly) loading fuel management for 5 REMIX recycles was primarily researched, in which enriched uranium was added to the reprocessed fuel of uranium and plutonium. The REMIX core, which contains 30% (48 of 157) REMIX FA, meets equilibrium after three cycles while the REMIX FA from the former recycles can be completely replaced by the new REMIX FA manufactured in the next recycles at the same time. The spent REMIX fuel was gathered and mixed with fresh fuel after a 5-year cooling. The radiation and decay heat characteristics of the cooled spent nuclear fuel were analyzed, which helps the design of radiation shielding during separating the dissolved fuel rods and manufacturing new FA. The results show that the 30% REMIX FA loading fuel management plan can be used in the M310 core without changing the basic neutronics and safety design of the reactor. The feasibility of 5 recycles was proved. Although the spent nuclear fuel may be recycled more than 5 times, the nuclides in the spent nuclear fuel of 5th recycle has already made it hard to be reprocessed and used. The radioactivity and heat release rate of the spent nuclear fuel increase with the recycling times, which contributes to the cost increasing of the spent nuclear fuel reprocessing and FA manufacturing. It is also a factor that decreases the economy of further recycling. The gamma power of the spent nuclear fuel reduces due to the reduction of 134Cs and 137Bam in the spent nuclear fuel, which means that the existing MOX FA manufacturing progress can handle the spent REMIX fuel without extra gamma shielding. The results of this article can help the further research of REMIX fuel on the M310 reactor core.

Keywords

• remix fuel
• fuel management
• spent nuclear fuel
• natural uranium consumption reduction
• closed fuel cycle