United Kingdom / Japan The arrival of the two ships in Japan carrying mixed oxide (MOX) fuel produced at the Sellafield and La Hague reprocessing facilities has been overshadowed by an admission by British Nuclear Fuels that employees at Sellafield have falsified MOX safety data. None of the MOX fuel in the shipment from Sellafield, destined for the 870 MWe PWR Takahama units 3 and 4, operated by the Kansai Electricity Power Company (KEPCO), is affected. The problem is with fuel pellets produced at the MOX Demonstration Facility which were to be part of a later shipment.

The UK Nuclear Installations Inspectorate, Japanese regulators and KEPCO representatives are investigating the incident.

“The fuel pellets are all subjected to automated diameter checks, where any out of specification pellets are rejected,” says a BNFL statement. “Later in the process, a small sample of these pellets is taken and a manual diameter check is performed. The data in question relates to the secondary manual checks on the diameter of fuel pellets.” Through procedural checks BNFL realised some of the secondary checks had not taken place and false data had been logged. BNFL has suspended a number of employees and has halted MOX production.

“No fuel made up from these falsified lots has left the MOX Demonstration Facility, where they are manufactured,” continues the statement. “In spite of these problems with this specific quality check, BNFL is confident that the pellets fully meet the specification and there are no safety issues involved.” If pellets used in a reactor did not meet the dimensional requirements, there could be safety problems.

Despite BNFL’s attempts to downplay the importance of the incident, the implications may be very serious. Japan is planning to burn MOX fuel in as many as 18 reactors and the MOX programme is a key part of the global strategy to deal with the stockpile of plutonium built up as a result of nuclear disarmament and fuel reprocessing. Reprocessing and the production of MOX is a key part of BNFL’s business strategy as it moves towards partial privatisation and the company is currently waiting on a government decision to start up its £300 million MOX production facility.

“The matter does not raise safety concerns at Sellafield, the safety concerns would be at the reactor where the fuel is burned,” said a NII representative. “NII’s concern is whether the quality control problems are symptomatic of failure on a wider management level.”

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What appears to be a criticality incident occurred at the uranium conversion plant at Tokai, Japan, on 30 September. Three workers were irradiated, two seriously.

The incident took place in a building where enriched UF6 is reacted with nitric acid as part of the process of converting it to uranium oxide. Local monitors registered radiation levels 7 to 10 times normal and nearby residents were evacuated.