Testing has begun on VVER-type fuel elements with uranium-plutonium mixed-oxide (MOX) fuel in the MIR research reactor. Based on the results of irradiation and tests, scientists "intend to substantiate the efficiency and safety of MOX fuel operation in VVER reactors".

(Image: Rosatom)

The testing is being carried out in Dimitrovgrad by the Research Institute of Atomic Reactors (JSC RIAR), which is part of Rosatom's science division. MOX fuel is manufactured from plutonium recovered from used reactor fuel, mixed with depleted uranium. It allows the recycling of used nuclear fuel, thus helping to close the fuel cycle.

In Russia, MOX fuel is currently produced for fast neutron reactors. Uranium-plutonium REMIX fuel has been developed for VVER reactors, with the first 18-month pilot operation recently successfully completed at the Balakovo nuclear power plant. Rosatom explains that REMIX fuel "is based on a mixture of 'unburned' regenerated uranium and plutonium formed in the reactor, with plutonium content of up to 1.5%". MOX is a mixture of plutonium oxides and of depleted uranium oxides, Rosatom says, with MOX fuel for VVERs expected to contain approximately 5.5-7.5% plutonium.

The tests in the MIR reactor will involve 21 fuel elements based on MOX pellet fuel, with 12 fuel roads in the experimental fuel assembly, with another nine fuel rods to be gradually added to replace irradiated ones at various stages of the testing.

Alexander Ugryumov, senior vice president for scientific and technical activities at TVEL, said: "In the near future, having confirmed references for uranium-plutonium fuel, we will be able to offer the full range of options for the fuel composition, depending on the requirements of the reactor plant and the fuel cycle strategy. Considering that the basis of nuclear energy is precisely light water thermal reactors, we will be able to expand their resource base many times over, process irradiated fuel instead of storing it, and also significantly reduce the amount of nuclear waste generation."

According to Rosatom, Russia is aiming to create a "two component nuclear power industry with thermal and fast neutron reactors, as well as the introduction of technologies for closing the nuclear fuel cycle based on the fabrication of fresh uranium-plutonium fuel from spent fuel. At the same time, as 'fast' reactors become more widespread, it is expected to achieve a balance in the 'circulation' of nuclear fuel materials between installations operating on fast and thermal neutrons".

Rosatom's fuel division, TVEL, currently supplies fuel for 75 reactors across Russia and in 14 other countries. MIR is a loop-type research reactor designed mainly for testing fuel elements, fuel assemblies and other core components of different types of operating and promising nuclear power reactors.

Researched and written by World Nuclear News

Date: Thursday, 29 June 2023
Original article: world-nuclear-news.org/Articles/MOX-fuel-tests-for-VVER-reactors-begin