Japan’s Ministry of Economy, Trade and Industry (Meti) has begun work on identifying the technical challenges of constructing a disposal facility for high level waste (HLW) under the seabed. A Meti study group is expected to finish the work by summer.

The government would avoid potentially difficult negotiations with landowners by building a disposal facility under the seabed but the facility would have to overcome many technical hurdles. At a meeting of the expert study group on 26 January, a Meti official stressed that nothing has been decided.

The storage would have to be connected to an onshore facility through a tunnel in order to comply with international law that restricts dumping nuclear waste at sea. Candidate sites are expected to be 10-15km off the coast, an official from the Nuclear Waste Management Organization (NUMO) told the meeting. Meti also plans to take into account nearby volcanos and active faults in assessing candidate sites.

A Meti panel last month compiled an interim report on conditions for disposal sites for liquid HLW arising from the reprocessing of used fuel. The report suggested areas within 20km of coasts would be appropriate disposal sites, adding that a proximity to ports would ensure the safety of nuclear waste transport. Meti set up the team to carry out a geological survey of coastal areas.

At the meeting NUMO officials showed a picture of how tunnels from coastal areas or a nearby island would connect disposal sites built under the seabed. They said groundwater flows slowly beneath the seabed, adding that such disposal sites are unaffected by sea level changes and have security advantages.