MOX is made from a mixture of plutonium and uranium oxides and is used in nuclear reactors in Japan, Switzerland, Germany, Belgium and France. Nuclear reactors normally burn enriched uranium fuel. When MOX is used, about 30 per cent of the enriched uranium is replaced by the MOX fuel.
In October 1999, a British Nuclear Fuel (BNFL) MOX shipment delivered to Japan was found to have falsified quality control documents. Two years ago, a £40 million compensation package was agreed so the fuel could be returned to Britain.
The MOX shipment was transported in fuel pellets contained in two forged steel casks weighing between 80 and 100 tonnes. It was carried aboard the Pacific Pintail, a doubled-hulled vessel designed to withstand a severe collision with a much larger vessel without penetration of the inner hull.
The vessel is equipped with enhanced buoyancy which, according to BNFL, allows it to remain afloat even in extreme circumstances. It has a dual-propulsion system with two engines and two propellers. It has two sets of navigation, communications, cargo monitoring, electrical and cooling systems to provide back-up. It is fitted with satellite navigation, weather routing and tracking equipment, allowing position transmissions and communications. The vessel also carries a naval cannon.
The plutonium which arrived in Sellafield will eventually be recycled and returned to Japan. However the Japanese are not willing to take delivery until the safety measures recommended by Britain's Nuclear Inspectorate have been implemented.