Solidified nuclear waste mixed with glass is placed in canisters at a reprocessing plant in Rokkasho, Aomori Prefecture, in 2012
The government has set the criteria for a map meant to identify potential final disposal sites for high-level radioactive nuclear waste, paving the way for its release as early as this summer.
The process of finding a host for nuclear waste could face challenges amid public concerns over safety.
Based on the map, the government will approach select municipalities to allow research to be conducted for suitable sites to store waste from nuclear power generation.
For permanent disposal, high-level nuclear waste needs to be stored at a final depository more than 300 meters underground for up to about 100,000 years until radiation levels fall and there is no longer potential harm to humans and the environment.
The government plans to create a permanent underground repository somewhere in stable bedrock so the canisters can be stored for tens of thousands of years.
The map is likely to classify which areas are geologically suitable for such a structure to be built deep enough underground. This would rule out areas near active faults and volcanoes as well as oil and coal fields.
Based on waste transport criteria, the map is likely to show that zones within 20 km of the coastline are favorable to host final disposal sites.
The government hopes other municipalities — not just the ones located near nuclear power plants — may also become interested in hosting the disposal facilities. It also wants to show that a variety of places nationwide are suitable for nuclear waste management.
The map was originally planned for a 2016 release but the publication date was later postponed, as some local governments were wary that disposal sites would be imposed on them.
About 18,000 tons of spent fuel currently exist in Japan. Including spent fuel that has already been reprocessed, the country’s total jumps to about 25,000 canisters of vitrified high-level waste, all of which needs to be managed.
The process to find local governments willing to host final storage started in 2002, but little progress was made due mainly to opposition from local residents.
In May 2015, the central government introduced a plan announcing that final depository site selection would be based on scientific grounds, rather than waiting for municipalities to volunteer.
Before presenting the map, the government will hold symposiums between mid-May and June at nine cities to explain the map criteria to the public. The cities include Tokyo, Nagoya and Fukuoka.
Radioactive waste is classified into two categories: The high-level type is generated from reprocessing spent fuel by separating the plutonium and uranium for recycling, while the low level type refers to all other waste.
High-level waste is a byproduct of fission in the reactor core, which is very hot and dangerous. It is mixed with glass and solidified before being placed in robust heat-resistant stainless steel canisters that are 130 cm high, 40 cm in diameter and weigh 500 kg each.
A full canister emits about 1,500 sieverts per hour — an extremely lethal biological level — and has a surface temperature in excess of 200 degrees.
Its radioactivity starts at 20,000 trillion becquerels. It will take about 1,000 years to fall to one-thousandth of that level, and tens of thousands of years to weaken to the same intensity as natural uranium ore, the Natural Resources and Energy Agency says.
Worldwide, only Finland and Sweden have been able to successfully decide on a final depository site for nuclear waste, while many other countries with nuclear plants face difficulties in doing so.
The United States decided in 2009 to call off a plan to build a site to dispose spent fuel in Nevada’s Yucca Mountain due to local opposition, but President Donald Trump earmarked funds to revive the plan in the budget proposal for fiscal 2018 unveiled in March.
In Japan, the selection process is also a touchy issue and has triggered conflicts in the communities around which prospective depository sites have been considered.
In one example, Minamiosumi Mayor Toshihiko Morita in Kagoshima Prefecture filed a criminal complaint against a 65-year-old resident for libel, claiming that his allegations that the rural town office had been actively inviting such a facility was not only groundless but also defamation.
The resident handed out flyers to about 500 households in the town in January which said Morita went to Tokai, Ibaraki Prefecture, and Horonobe in Hokkaido at the invitation of the private sector involved in the construction of nuclear waste disposal facilities. Both municipalities host nuclear-related facilities.
Morita flatly denied the allegations, telling Kyodo News in writing that he has heard “rumors” that there have been moves aimed at hosting a nuclear waste disposal facility but “I myself haven’t gone anywhere and been treated to anything.”
“I would reject any request from the central government” to host one, Morita said. The town approved an ordinance to reject a plan to host a nuclear waste disposal facility the year after the 2011 nuclear crisis at the Fukushima No. 1 plant.
A supporter of the mayor, however, did visit nuclear-related facilities in locations including Rokkasho, Aomori Prefecture, several years ago, according to the supporter’s admission, and a Tokyo company covered the expenses of the trip.