U.S. Department of Energy and Canadian utility Ontario Power Generation will work together to produce Pu-238 for use in space missions. The isotope will be produced at the Darlington nuclear station near Toronto. Target rods for irradiation will be supplied by the Pacific Northwest National Laboratories (PNNL) in Washington State.

Although Pu-238 is not considered a direct use nuclear material and plutonium containing more than 80% Pu-238 is normally exempt from IAEA safeguards, this isotope is produced by irradiating Np-237 targets:

Np-237 is believed to be a material that can be used to manufacture nuclear weapons. It is not, however, defined by the IAEA as source material or special fissionable material and therefore is not covered by the IAEA safeguards. According to the IAEA Safeguards Glossary "separated neptunium is monitored by the IAEA under voluntary arrangements with relevant States" (4.19). It is likely that the neptunium shipped to Canada for Pu-238 production will be subject to safeguards, but the nature of these safeguards is not clear.