Uranium transiting through New Zealand ports will only be used for "peaceful purposes", says the Environment Minister, despite one of the firms receiving the material being involved in making nuclear weapons.

Energy Resources has been granted permission to ship Australian yellowcake uranium ore through New Zealand. The destination of the uranium is listed as Honeywell's plant in Metropolis, Illinois.

That plant enriches raw uranium for nuclear fuel and electric power stations. A byproduct of the process is depleted uranium, which has uses ranging from medical equipment to weapons and armour.

Honeywell told TV3 this week that all of its processed uranium was used in the production of nuclear power for civilian use and there was no military usage.

However, the US Environmental Protection Agency lists two Honeywell plants (both in Minnesota) as "depleted uranium manufacturing and testing facilities".

A new Honeywell nuclear weapon parts plant is being built in Kansas City, reports the Kansas Star.

Environment Minister Nick Smith told Parliament last night during question time that he has had assurances from the Australian Government that shipping companies must meet strict criteria before shipping uranium.

"Furthermore, my colleague Georgina Te Heuheu has just this week been part of a conference that is to establish very clear reporting requirements to ensure that such radioactive substances are used only for peaceful purposes," Mr Smith said.

Mr Smith and Labour leader Phil Goff have only recently become aware of the shipments but both have played down the shipments in subsequent television interviews.

Mr Goff, who was Minister of Foreign Affairs, Trade and Defence in the last Government, said he was confident that once processed, the ore would be used for peaceful purposes, although he acknowledged that he could not be sure.

Mr Smith told Parliament last night that he had been advised that uranium had been shipped through New Zealand waters since the 1970s.

Last night Mr Smith was asked by Green Party MP Gareth Hughes if allowing uranium through New Zealand ports compromised the country's nuclear free position.

"No; in fact, if we took that sort of silly position on radioactive substances we would destine hundreds of New Zealanders to a painful death, because many of those radioactive imports are used to treat cancer," Mr Smith replied.

Mr Smith was asked by National MP Chester Burrows about the potential radiation exposure from the shipping containers.

Mr Smith said the National Radiation Laboratory has said that if a person stood next to a drum of the uranium for 130 hours then they would be exposed to the equivalent of a year's natural radiation.

"The Environmental Risk Management Authority actually advises me that the high level of risk is from the toxicity, not the radiation, and then it is a risk only if someone ingests - that is, eats - large quantities. Given that the substance is only to be in the hulls of ships, I do not think the risk of that is high," Mr Smith said.