Photo/Illutration Suttsu, Hokkaido (Asahi Shimbun file photo)

The ongoing assessment of areas to host a final disposal facility for high-level radioactive waste from nuclear power plants raises many questions about whether it can really identify suitable locations.

An advisory panel of experts on the matter for the ministry of economy, trade and industry has approved a draft report on the first stage of the process.

The report, called “bunken chosa” (literature survey), or reviews of geological maps and research papers concerning local volcanic and seismic hazards and other related factors, was done for the town of Suttsu and the village of Kamoenai in Hokkaido.

Although the proposal from the Nuclear Waste Management Organization of Japan (NUMO) was partially revised, the ministry intends to proceed, as planned, to the second phase, called “gaiyo chosa” (preliminary investigation).

This phase will include a geophysical exploration, geological reconnaissance surveys and drilling surveys. The ministry claims there is a possibility of finding candidate sites.

There is, however, a known fault zone, a cluster of closely spaced, parallel faults, lying beneath Suttsu and a volcano near Kamoenai.

In addition, brittle and easily crumbled rocks are distributed in that area, and some experts point out that it is “basically unsuitable” for building a nuclear waste repository.

The discussions at the expert panel have shown that NUMO and the ministry have a policy of proceeding to the preliminary investigation unless there is a “high” or “clear” possibility that there may be an active fault, the primary source of earthquakes.

However, there is no established set of criteria for determining whether such a possibility is “high” or “clear.” This means there is a risk that locations unsuitable for nuclear waste disposal might remain candidate sites until the end.

While we understand the need for drilling and other geological surveys to gather information about such factors as stress, pressure and seismic activity to assess seismic risks, there will always remain some uncertainty, no matter how many such surveys are done.

If there is a certain degree of possibility that an area is unsuitable for disposal, it makes sense to eliminate it early. This approach will also help ease the concern among local communities that the process, once started, cannot be stopped even if the local community opposes it.

In the 2017 Nationwide Map of “Scientific Features” Relevant for Geological Disposal, the ministry colored more than 60 percent of the Japanese archipelago green, indicating “favorable features.”

Many people must have thought that the process of selecting candidate sites would focus on these areas.

According to the map, however, the three municipalities where the initial survey has actually started are not “green” areas, with Suttsu and Kamoenai having “unfavorable features” such as faults and a volcano.

In Genkai, a town in Saga Prefecture, where the survey started in June this year, there is a possibility of underground coal, so the entire town falls outside the green classification. It's difficult to say that the map's color coding is being utilized effectively.

On the other hand, being green does not necessarily mean it's safe. The Noto Peninsula, which was hit by a devastating earthquake in January, belongs almost entirely to the green area, yet it experienced a kind of massive uplift of the ground that only occurs once every few thousand years.

Considering that it takes tens of thousands of years for radioactivity to decrease to safe levels, scientists and policymakers must consider this phenomenon.

Editorials in The Asahi Shimbun have been critical of the current plans by NUMO and the ministry, which are largely based on the premise of dependence on nuclear power generation and nuclear fuel recycling.

In addition, new problems and flaws in the current method of selecting candidate sites are emerging.

--The Asahi Shimbun, Aug. 20

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