The Irish Government is bringing legal action in an attempt to close the Sellafield nuclear reprocessing plant.
The UK says Sellafield does not generate radioactive discharges
Irish ministers are concerned about claims that radioactive discharge from the Cumbrian plant is polluting the Irish Sea.
The government will start legal action under the UN Convention on the Law of the Sea (UNCLOS) at an international tribunal in The Hague on Tuesday.
But marine minister Dermot Ahern said they faced an uphill battle.
"It is going to be difficult. I have spoken to the attorney general no later than the weekend and he knows that the might of the British Empire is against them on this," he said.
Environment minister Martin Cullen said he regretted such a step was necessary, but said action was essential to protect the Irish Republic's interests.
The fact is that the Sellafield Mox plant has virtually no impact on
UK energy minister
He said: "These cases are among the most significant legal actions ever taken by Ireland.
"They represent the Irish Government's absolute commitment to ensuring that Ireland's rights under these international conventions in relation to Sellafield and its operations are fully vindicated.
"I know the team, led by the attorney general, will make the strongest possible arguments in support of our concerns."
He said there were several worrying issues, including claims of pollution from the discharge of radioactive waste from the Mox plant into the Irish Sea.
Mr Cullen also expressed concern at the "inadequacy" of the environmental assessment undertaken by the UK in relation to the facility and the failure to properly assess the risk of terrorist attack on the site.
International movements of radioactive materials associated with the site were also a cause for concern.
The hearings will take place before a five-member tribunal.
They will proceed for around three weeks and will be open to the public with some exceptions where material being referred to is of a confidential nature.
Attorney General Rory Brady will lead the Irish legal team and will make the opening statement to the tribunal.
The UK team is expected to argue that the court does not have jurisdiction over Sellafield.
UK energy minister Brian Wilson said:
"The fact is that the Sellafield Mox plant does not generate any significant radioactive waste and has virtually no impact on
"The European Commission has made clear that the operation of the plant would not lead to any detrimental environmental impact on Ireland, or indeed on any other member state of the European Union."
He said the UK and Ireland were "very much in agreement" on the
issues faced in maintaining safety and security at nuclear sites.