Mr Marles revealed the detail as he answered questions about Australia's landmark deal with the United Kingdom and the United States to acquire up to eight nuclear-powered submarines by 2054.

The cost of the entire deal is projected to be between $268 billion and $368 billion.

The nuclear reactors will not be built on Australian soil.

"We are making a commitment that we will dispose of the nuclear reactor. That is a significant commitment to make," Mr Marles told journalists.

"This is going to require a facility to be built in order to do that disposal.

"Obviously that facility will be remote from populations and today we are announcing that that facility will be on defence land, current or future."

The Department of Defence has stewardship of more than 3 million hectares of land.

The defence minister said the government would "announce a process by which this facility will be identified" within a year.

The first reactors will not need to be disposed of until the 2050s, Mr Marles said.

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He reiterated Australia's commitment to the Treaty of Rarotonga, which commits Australia not to operate nuclear weapons.

"Now it's been said a number of times today that this is a conventionally armed nuclear-powered submarine, so Australia has no intention of operating nuclear weapons on our soil," the defence minister said.

"But we reiterate, reaffirm today that in every part of this arrangement, Australia will be maintaining its obligations under the Treaty of Rarotonga."