There has never been such an agreement.
What there has been is the NPT's Article I prohibition on the provision of nuclear weapons or nuclear explosive devices to non-weapons-states (which are all but the 5 weapons states, USA, Russia, France, UK, China). It also prohibits assistance / inducement in developing weapons.
The "(or nuclear powered)" bit has never been a thing.
There is also the Nuclear Suppliers Group, which is a group of nuclear-technology-exporting countries that agree not to export to NPT non-weapons-states a much longer list of dual-use nuclear technologies, unless IAEA comprehensive safeguards agreements are in place. Australia is a member of the NSG, and has safeguards agreements with the IAEA.
The IAEA has been informed by all three states of this new proposal.: https://www.iaea.org/newscenter/pressreleases/iaea-on-trilat...