The Ministry of Economy, Trade and Industry has started work on identifying the technical challenges of constructing a disposal facility under the seabed for highly radioactive spent nuclear fuel.
A study group set up by the ministry is to finish the work by around summer.
The government would be able to skip potentially tough negotiations with landowners if it decides to build a disposal facility under the seabed.
But construction of such a facility would involve many hurdles.
At a meeting of the study group Tuesday, a ministry official stressed that nothing has been decided.
Such a facility would have to be connected to an onshore facility through a tunnel so as not to violate an international law that restricts dumping nuclear waste at sea.
Candidate sites are expected to be 10 to 15 km off the coast, an official from the Nuclear Waste Management Organization of Japan said at the meeting.
The ministry also plans to take into account nearby volcanos and active faults when it assesses candidate sites.