Over the next few days, lawyers acting for the environmental campaigners, Greenpeace and Friends of the Earth, will closely examine the detail of the British government's decision to give the green light to mixed oxide fuel production at Sellafield.
The MOX plant was completed in 1996, but it has never carried out the purpose for which it was designed - mixing plutonium and uranium to produce fuel for nuclear reactors.
The British government held five public consultations before yesterday's decision to allow British Nuclear Fuels Ltd (BNFL) to bring the plant into service. But as the executive director of Greenpeace, Mr Stephen Tindale, hinted at the possibility of a legal challenge, he said the British government's decision was not the end of the MOX controversy, "in reality it is just the beginning".
His words may be pre-emptive, for some observers believe the British government has been very careful in the wording of its decision, with the aim being to see off any legal challenge by the environmentalists.
The Irish Government is also considering its legal options - it has already launched a challenge to the Mox plant, which is in arbitration under the OSPAR convention - an agreement between 14 North Atlantic states relating to pollution and discharges into the marine environment. The Government is now considering other legal options under EU or UN law - with a challenge before the European Court seen as the most likely option.
As the lawyers on both sides of the Irish Sea consider their next move, BNFL will be hoping that any legal challenge comes to nothing and that it can finally begin fuel production securing lucrative oversees contracts, principally from Japan and Europe. It would also raise the company's profile - it reported pre-tax losses of more £210 million sterling in its 2001 annual report - and help it overcome the damaging publicity generated by its admission in 1999 that workers fabricated safety data for a demonstration batch of mixed oxide fuel destined for Japan.
Greenpeace and Friends of the Earth believe the case for opening the mixed oxide fuel plant at Sellafield is far from conclusive. Apart from environmental concerns, which are shared in Ireland, it believes that in the light of the terrorist attacks in the US, shipping large consignments of plutonium-based fuel around the world is highly dangerous.
Greenpeace insists it is not just the fact of the terrorist attacks on the World Trade Centre and the Pentagon that have helped its case - plutonium is already used around the world - but the increased potential for environmental accidents and terrorist incidents presented by mixed oxide fuel shipments. Irish concern will focus on the movement of these shipments through the Irish Sea and the risk that they could face terrorist attack. Irish politicians and environmentalists also warned of the risk of accident or attack on the plant itself and pointed to the likelihood of increased discharges into the Irish Sea.
Environmentalists also point out that at a conference of the watchdog on atomic energy (the International Atomic Energy Agency) in Vienna last month, industry analysts warned that Sellafield and the nuclear reprocessing plant at Cap de la Hague, in France, could be terrorist targets.
"What are very big risks are the huge tanks of very, very radioactive liquid stored in reprocessing plants," said Dr Frank Barnaby, a nuclear physicist working for the Oxford Research Group.
"They contain a huge amount of radioactivity and are less well protected than reactors." For its part, BNFL says its reactors and reprocessing plants are "extremely robust" and can withstand accidents, including plane crashes. It also says that any mixed oxide fuel shipments must comply with maritime and Nuclear Installations Inspectorate rules before they can leave the Cumbrian plant.
Among the many arguments for and against the Sellafield plant, about 300 jobs at the plant will be safeguarded. But in reality the jobs are not guaranteed until legal action, or possibly a European review of the decision, has been played out.