Japan’s nuclear renaissance dogged by waste challenge Nuclear reprocessing is years late; repository is in limbo By Dennis Normile, in Tokyo

IMAGE: JAPAN NUCLEAR FUEL LTD./ADAPTED BY G. GRULLÓN/SCIENCE

J

apan’s battered nuclear industry is finally getting back on its feet, raising anew a vexed question: what to do with the waste. Nearly 4 years after the Tohoku earthquake and tsunami sparked meltdowns at the Fukushima Daiichi Nuclear Power Station and led to the shutdown of all 48 of the country’s reactors, the central government is expected this spring to approve the restart of two nuclear reactors in Kagoshima Prefecture. But critics charge that uncertainties and wishful thinking are clouding prospects for dealing with the waste. “Japan is totally at a loss about how to resolve the high-level waste disposal problem,” says antinuclear crusader Hideyuki Ban of the Citizens’ Nuclear Information Center here. “The waste issue should be addressed before restarting the reactors.” Prime Minister Shinzo Abe’s administration has acknowledged the challenge. The energy plan of April 2014, which reversed the previous government’s no-nukes policy, noted that delays, accidents, and cover-ups in developing technologies for handling radioactive waste “have generated a feeling of distrust among the people.” When Japan commissioned its first nuclear power plant in 1966, it envisioned reprocessing spent fuel to extract uranium and plutonium for reuse in reactors and to reduce the amount of radioactive waste that would need to be entombed underground. In theory, reprocessing could help ensure a supply of fuel and make it easier to cope with the remaining waste. But a half-century later, none of the reprocessing technologies are ready. Japan now has 17,000 tons of spent nuclear fuel submerged in cooling pools at reactor sites across the country, and a planned reprocessing plant has suffered years of delays. Reprocessing turns out to be the answer to “a very complicated equation,” says Hajimu Yamana, a reprocessing expert at Kyoto University. Japan Nuclear Fuel Ltd. (JNFL), owned by 10 utility companies, broke ground on a reprocessing facility in Rokkasho, a village at the northern tip of Honshu, in 1993 and planned to complete it 4 years later. Two decades later, it is still a work in progress. The new facility will use the Plutonium Uranium

Redox EXtraction (PUREX) method, pioneered in the Manhattan Project, to separate plutonium and uranium from spent fuel. The process greatly reduces the volume of waste but leaves a highly radioactive residue that amounts to about 3% of the original volume. JNFL opted to design its own method for encasing these leftovers in glass, a process known as vitrification. Yamana says Japan chose an experimental liquid-fed ceramic melter vitrification process that promised

to process a planned 800 tons of waste per year. Yamana says this amount would gradually put a dent in the accumulated waste if Japan reduces its reliance on nuclear power in accordance with the latest energy plan. Critics question whether Japan should even be in the business of reprocessing. The original plan was to use the separated uranium in conventional reactors and the plutonium in so-called fast reactors, once thought to be a next-generation nuclear power source. But Japan’s experimental Monju fast reactor in Tsuruga on the Sea of Japan has been largely shuttered since it was commissioned 20 years ago. Most other countries have abandoned fast reactor projects because of technical difficulties, high costs, and concerns about safeguarding plutonium, though China and India are still studying the technology. The 2014 energy strategy calls for using

Recycling radioactive remains Japan’s reprocessing takes spent fuel rods and separates low-level waste for disposal, highlevel waste for vitrification, and purifies uranium and plutonium for reuse. Spent fuel rods Uranium for reuse

High-level waste separation

Uranium and plutonium separation

Uranium purifcation

Initial processing Mixed fuel for reuse

To vitrifcation To disposal

Uranium

Plutonium purifcation Plutonium

High-level waste

to be more durable and provide a higher throughput than the metallic melter-based techniques then in commercial use. But when scaled up, the chemistry involved in mixing the aqueous nitric acid solution containing the waste into the molten glass, he says, proved “extremely complex.” JNFL announced in early 2013 that it had finally worked out the kinks. But tougher seismic and safety requirements that followed the Fukushima disaster led to further delay. The price tag for the Rokkasho facility will end up at about $18.8 billion, according to JFNL, nearly triple the original $6.5 billion budget. The new target date for finally completing the plant is March 2016, after which it will take several years to ramp up capacity

SCIENCE sciencemag.org

Fuel rod debris

Monju to “burn” spent fuel to reduce the volume of high-level waste. But that won’t eliminate the waste issue. Despite more than a decade of trying, the government has been unable to interest any locality in hosting a deep underground repository. In September 2012, the Science Council of Japan recommended abandoning the idea, arguing that it is impractical in seismically active Japan to identify a geological formation that would remain stable for millennia. The council suggested instead that Japan develop secure facilities for temporarily storing nuclear waste until further research hits on a better solution and a public consensus can be reached on an overall nuclear energy policy. That could take a while. ■ 23 JANUARY 2015 • VOL 347 ISSUE 6220

Published by AAAS

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