The Government has said it is receiving insufficient information from companies and other governments on shipments of nuclear material that pass close to Irish waters.
It comes as an armed shipment of plutonium from decommissioning United States nuclear weapons is due to pass within 150 miles of the Cork coast towards the end of this month, on its way for reprocessing into nuclear fuel in France.
This is the first known transport of weapons-grade material to be shipped to a commercial site in recent years, and could be one of many transports as a result of a stockpile of weapons-related plutonium in the US, left over from the Cold War.
As part of the US non-proliferation pact the material will be manufactured into nuclear fuel.
Anti-nuclear activists yesterday claimed the shipments posed a serious security threat, especially because of current terrorist activities, and were against best safety practice.
The current shipment of plutonium oxide is being transported in an armed convoy of two ships from Virginia in the US to Cherbourg in France, and is facing protests on both sides of the Atlantic. The resulting nuclear fuel will be transported back to the US next year.
The ships, the Pacific Teal and the Pacific Pintail, are owned by PNTL, a subsidiary of BNFL, which specialises in the shipment of nuclear materials.
The boats are armed with naval guns and carry armed guards. In a statement this weekend, Areva, the French energy company behind the reprocessing, said that PNTL had "safely transported nuclear material four million nautical miles without a single incident involving the release of radioactivity."
The ships left their home port of Barrow-on-Furness near Sellafield reprocessing plant on Friday, and are due to arrive at Charleston, Virginia, in 10 days.
In a statement to The Irish Times yesterday, the Minister for the Environment, Mr Cullen, said the Irish Government was "aware of contracts that exist between French and American companies that can include shipments of nuclear material across the Atlantic."
He said that Ireland, under international agreements, is now advised of all shipments of nuclear materials passing through Irish waters, but that that the level of information was insufficient.
The Government has also signed a resolution, to be tabled in a fortnight at a meeting of the International Atomic Energy Agency in Vienna, on the issue.
If passed, the resolution will require nuclear states and nuclear companies to provide much more detailed information to coastal states such as Ireland about nuclear shipments.
Greenpeace International is organising a flotilla of protest vessels at Charleston, and another near Cherbourg, later this month, when the convoy is due to arrive there.