Russia’s Siberian Chemical Combine (SCC) in Seversk, part of Rosatom’s TVEL Fuel Company on 3 June began pilot production of uranium-plutonium Remix fuel assemblies (TVS) for VVER-1000 light water reactors. Fabrication of the first Remix-TVS was organised in cooperation with the Mining and Chemical Combine (MCC) in Zheleznogorsk, Krasnoyarsk Territory, where the production of uranium-plutonium fuel pellets was undertaken. The first batch of pellets has already been delivered from Zheleznogorsk to Seversk and has successfully passed incoming inspection procedures at SCC. Experimental fuel rods and fuel assemblies using Remix fuel will be manufactured according to the TVS-2M design – this is one of the basic designs for VVER-1000 fuel.

Remix (regenerated mixture) fuel is an innovative Russian development for light-water thermal reactors. It comprises a mixture of reprocessed uranium and plutonium, which is formed during the reprocessing of used nuclear fuel, with the addition of enriched uranium. Unlike uranium-plutonium fuel for fast reactors (MNUP and Mox-TVS), Remix fuel is characterised by a lower plutonium content (up to 1.5%). Its neutron spectrum does not differ from standard enriched uranium fuel, so the behaviour of the fuel in the reactor core and the amount of plutonium generated from uranium as a result of irradiation are generally identical. For NPP operators, this means that in future, Remix fuel can be introduced without changes in the design of the reactor and additional safety measures. The use of such fuel will make it possible to expand the resource base of the nuclear power industry many times over by closing the nuclear fuel cycle and by reusing irradiated fuel instead of storing it.

Since 2016, the pilot commercial operation of three experimental fuel assemblies has continued in the VVER-1000 reactor at unit 3 of the Balakovo NPP, each containing six experimental fuel elements with Remix fuel (in total, there are 312 fuel elements in one fuel cassette). In 2020, the third 18-month cycle of its irradiation started.

“The production line for fabricating VVER-1000 fuel at SCC was established in record time – the work began in the third quarter of 2020,” said Alexander Ugryumov, vice president for scientific and technical activities and quality at TVEL. “In total, it is planned to manufacture several full-scale TVS-2M with Remix fuel in 2021. The first cycles of irradiation of Remix fuel rods at Balakovo NPP showed good results, while testing of full-scale fuel assemblies is an important stage for the transition to widespread commercial implementation of this technology and, in the case of confirmed market demand, the creation of a full-fledged industrial production of Remix fuel at one of the Rosatom enterprises.” 

The production of fuel rods and fuel assemblies for VVER-1000 reactors at SCC meets all of TVEL’s high standards, the company said. At each stage of the product production, about a dozen of control operations are carried out to confirm, in particular, the quality of welded joints, the tightness of the fuel elements, the parameters of the content and pressure of the gas under the fuel element cladding, the entry of the fuel assembly into the slipway simulating the reactor core cell, the radiation background, etc. SCC staff at the production site for Remix-TVS, completed a refresher course in the fabrication of nuclear fuel at the Novosibirsk Chemical Concentrates Plant.

Image: TVS-2M fuel model (Credit: TVEL/Rosatom)