Russia loads REMIX fuel into MIR research reactor

Russia has started testing its new type of nuclear fuel, REMIX, at the MIR research reactor at the Research Institute of Atomic Reactors in Dimitrovgrad, which is in the Ulyanovsk region. Development of REMIX (from Regenerated Mixture) fuel is part of state nuclear corporation Rosatom's strategy to enable better use of recycled uranium and plutonium on an industrial scale in pressurized water reactors.

Rostaom said on 3 November that REMIX fuel rods manufactured in July had been "immersed in the active zone" of MIR. A loop-type research reactor, MIR is designed mainly for testing fuel elements, fuel assemblies and other core components of different types of operating and promising nuclear power reactors.

Loading of the REMIX fuel into MIR followed "lengthy and painstaking work" on preparing documentation for, and the production of, the fuel and fuel rods, Rosatom said.

The first data from testing the fuel in MIR will include the "swelling, gassing and distribution of fission products and, of course, the isotopic composition of the used fuel rods," the head of innovation at the Khlopin Radium Institute, Andrey Belozub, said in the Rosatom statement.

Use of the MIR research reactor is an "extremely important step", Rosatom said, towards full implementation of the project to introduce REMIX into the Russian fuel cycle.

Rosatom announced in July that it had started pilot testing of REMIX at unit 3 of the Balakovo nuclear power plant, saying that the use of REMIX will increase the efficiency of uranium use in the nuclear industry.

REMIX fuel is produced directly from a non-separated mix of recycled uranium and plutonium from reprocessing used fuel, with a low-enriched uranium (LEU, up to 17% U-235) make-up comprising about 20% of the mix. This gives fuel initially with about 1% Pu-239 and 4% U-235 which can sustain burn-up of 50 GWd/t over four years.

The used REMIX fuel is then reprocessed and recycled again, after low-enriched uranium top up. The wastes (fission products and minor actinides) are vitrified, as today from reprocessing for mixed-oxide (MOX) fuel, and stored for geological disposal. REMIX fuel can be repeatedly recycled with 100% core load in current VVER-1000 reactors, and correspondingly reprocessed many times - up to five times according to Russian nuclear fuel manufacturer Tenex, so that with less than three fuel loads in circulation a reactor could run for 60 years using the same fuel, with LEU recharge and waste removal on each cycle.

Researched and written
by World Nuclear News