The Republic of Ireland attempted to use the international horror over the Chernobyl nuclear accident in the former Soviet Union to press for a cessation of all discharges from the Sellafield plant in the UK.
Secret documents, released under the 30-year rule, also reveal concerns the Chernobyl fall-out cloud might drift over Ireland.
Weeks after the accident, vegetables from a German embassy garden in Moscow had 10 times the normal levels of radiation.
A secret briefing note for Taoiseach Dr Garret FitzGerald, dated December 4, 1986, warned the outright closure of Sellafield would also be "more complex than it might appear".
"It is clear that the Irish people are being exposed to a potential nuclear hazard from operations outside Irish jurisdiction.
"This makes the problem an international one.
"Sellafield is an activity outside our jurisdiction - we cannot simply insist that a separate sovereign state close down this operation," it read.
But it said the discharge of radioactive waste into the Irish Sea, no matter how small the quantities, was something "the Irish government is totally opposed to".
"The recent accident at the Chernobyl plant in Russia brought home to the entire world the consequences which can result from an accident at a nuclear establishment."