Unit 3 at the South Ukraine NPP suffered an emergency shutdown on 27 November. The Ministry of Energy said it had been disconnected from the grid to identify and eliminate the causes of the reactor scram. Emissions and discharges of radioactive substances into the environment did not exceed the permissible values and there were no safety violations, it noted.

While the cause of the scram was not revealed, Russian experts noted that unit 3 was one of the Ukrainian reactor currently using Westinghouse-manufactured nuclear fuel and that the unit had a long history of problems resulting from this. In 1998 Ukraine signed a nuclear co-operation agreement with the US under which Washington undertook to consider upgrading Ukraine’s nuclear fuel industry, including promises of US capital for fuel supply to Ukrainian NPPs. The next year, Westinghouse was selected to supply the first batch of Western-made fuel assemblies to Ukraine, and in 2000 the US Department of Energy (DOE) launched the Ukraine Nuclear Fuel Qualification Project (UNFQP) aimed at qualification of Westinghouse fuel for use in Ukrainian reactors.

The first six TVS-W fuel assemblies were delivered to the South Ukraine NPP in 2005 “as humanitarian aid, free of charge”. The assemblies were placed into the core of the VVER-1000 reactor together with Russian fuel for a period of “pilot operation”. They were the lead test assemblies for a larger batch of 42 expected for delivery in 2009. However, Energoatom complained about the quality of the US fuel, and after prolonged negotiations Westinghouse agreed to improve the first six assemblies. DOE announced in 2007 that it would supply the other 42, which would be made at Westinghouse’s Swedish facility, and a commercial deal was agreed in 2008 for Westinghouse to supply 630 assemblies for three units at South Ukraine.

However, in late June 2012 Energoatom reported technical problems at South Ukraine units 2 and 3, where the assemblies were on test after a routine inspection revealed that they had suffered structural damage. They were removed and replaced with Russian-made fuel assemblies at an estimated cost of over $170m, which Energoatom sought to reclaim through legal action. Westinghouse submitted a proposal to Ukrainian State Nuclear Regulatory Inspectorate (SNRI) to redesign the assemblies, but inspectors later found further defects and SNRI then banned the use of Westinghouse assemblies pending a damage assessment investigation.

With the change of regime in Kiev, however, Ukraine in April 2014 renewed the 2008 contract with Westinghouse, after dismissing the top management in both Energoatom and SNRI. The contract was extended to 2020 with the aim of replacing 25% of the Russian fuel. Westinghouse fuel was reloaded into South Ukraine unit 3 in 2015 with plans to extend its use to other reactors. The Westinghouse BEACON Core Monitoring System is now being used at South Ukraine. The software is designed to prevent problems which may arise from the use of Westinghouse fuel in Russian designed VVER reactors and has also been installed at unit 5 of the Zaporozhye NPP where Westinghouse fuel is in use.