THE NUCLEAR Installations Inspectorate, the official watchdog on nuclear safety, is to visit Sellafield today after an admission by officials at the plant of serious "irregularities" in the manufacture of highly dangerous nuclear fuel rods destined for export.
The investigation follows claims made to The Independent that safety checks on the fuel rods have been "falsified".
The problem concerns the production of uranium and plutonium mixed-oxide (MOX) fuel rods on an assembly line at British Nuclear Fuels' (BNFL) plant in Cumbria. Each rod contains more than 1,000 cylindrical pellets and about 200 pellets in each rod have to be routinely sampled and measured at three points to check they are the correct size.
However, a source at the plant told The Independent that some of these checks may have been faked. To save time, some employees bypassed quality- control checks by using data sheets from previous samples. Thus some batches of rods were passed as safe when they had not been checked at all.
MOX fuel is a highly dangerous substance. It receives the highest security classification and each consignment is shipped in armoured vehicles with armed escorts.
BNFL insisted yesterday that the irregularities it had found did not affect any of the assemblies now being sent to Japan on board two ships. But at least 10 lots have been found to have been falsified, according to the source. He added: "If the pellets are larger than they should be, they can expand and damage the cladding of the fuel rod. If they are too small, they can vibrate and the pellets can rupture."
The admission could not come at a more sensitive time for BNFL. It is preparing for a pounds 1bn privatisation and has applied for permission to open a new and highly controversial MOX facility costing pounds 300m. The future of the whole industry is dependent on the success of MOX manufacture and shipment to countries such as Japan, which is planning to run up to 18 reactors on the fuel by 2010. BNFL and its French partner, Cogema, are banking on 70 MOX reactors being run worldwide within 11 years.
Ed Lyman, scientific director of the Nuclear Control Institute in Washington DC, said that if true, the allegations would have serious safety implications for reactors loaded with the defective MOX fuel. "Clearly this is very important for Japan," he said. Japan's custom is the key to BNFL's ambitions to expand its activities to the new plant at Sellafield, which is expected to produce more than 100 tons of the fuel each year, Dr Lyman said.
"Any hint that the fuel would be defective would lead to a serious re- evaluation because the shipment would have to be sent back and refabricated at enormous cost," he added.
In a statement to The Independent, BNFL said: "Some irregularities in data have been detected during the quality- control checks on MOX fuel currently being manufactured. Measures have been taken to address the issue." The company said all MOX fuel assemblies on the way to Japan have been fully certified. "Some fuel for additional assemblies is being prepared at this moment, and this fuel has not yet been certified," the spokesman added.
When asked to explain the nature of the irregularities, he said: "It is an irregularity in the data. They are not quite as we would have expected them so we've gone back and had another look to see how they might have arisen, and we are trying to put in place measures to make sure it is dealt with accordingly."
A spokesman for the Nuclear Installations Inspectorate said: "We've been informed of irregularities in the implementation of procedures for checking the size of MOX pellets for export."
Inside the plant, page 3