The Czech power company CEZ said on 4 April that it will load an experimental batch of six fuel assemblies made by Westinghouse Electric Sweden into unit 1 of the Temelin NPP. The Russian-designed VVER-1000 unit was stopped for a routine maintenance and refuelling outage on 1 March and is scheduled to restart on 30 April. “This does not mean that we are switching to American fuel. It’s just to verify the fuel’s properties and gain know-how from both sides before choosing a supplier for the next contract,” said Bohdan Zronek, member of the CEZ board of directors. At present, the fuel at the Temelin NPP is supplied by the Russian company Tvel. Zronek recalled that the contract with the Russians provides for the supply of fuel until 2023, and that the contract allows an option for further refuelling if necessary.
During the two-month outage, technicians will change almost a third of the fuel (163 assemblies including the six from Westinghouse), examine the safety systems and the turbine and will test a container for used fuel from a new supplier, Škoda JS. The work will comprise more than 12,000 activities including 70 investment actions, and, including suppliers, approximately 1,000 people will take part in the work. The outage for unit 2 is scheduled for the second half of June.
Although the fuel from Westinghouse will constitute only 3% of the total number of fuel assemblies in the reactor, its loading was preceded by a demanding licensing process. “The absolute priority is, of course, safety. Therefore, the licensing process took nearly three years, over 70 technical reports, analyses and assessments have been elaborated, that put together comprising 7,000 pages," said Jan Kruml, Director of the Temelin NPP.
Tvel has been supplying fuel to Temelin since 2010, and in 2018 48 modernised fuel assemblies from Tvel were loaded into unit 2 supplementing the original fuel. Tvel says the new fuel is mechanically more resistant, the fuel pellets have a different design and there are also modifications to the fuel cladding. Previously Westinghouse fuel was used at Temelin from 2002 to 2009. However there were a series of technical problems including fuel deformation and incomplete rod insertion and in May 2006, Tvel Corporation won a tender for a 10-year fuel supply contract with delivery to start in 2009. The plan was to phase in the Tvel fuel gradually but in 2009 CEZ announced that it would immediately switch Tvel fuel in 2010 and the remaining Westinghouse fuel was removed. Westinghouse has since redesigned its VVER fuel following similar problems in Ukraine.
The European Union (EU) has been pressing east European states with VVER reactors to diversify their fuel suppliers to reduce dependence on Russia. Bulgaria’s Kozloduy NPP is also preparing to test Westinghouse fuel at units 5 and 6 in order to satisfy EU requirements, and has commissioned a feasibility study from Westinghouse.