4 May 2017

Closing Japan’s Monju fast breeder reactor: The possible implications

Masa Takubo

Masa Takubo is an independent analyst on nuclear issues and the operator of the nuclear information website Kakujoho.net. He is a member of the International Panel on Fissile...


After spending more than 1 trillion yen ($9 billion) on its Monju prototype fast-neutron breeder reactor, Japan’s government finally decided in December 2016 to decommission it entirely. Even though the facility had operated only 250 days during its 22-year existence, government ministers still declared that the official policy of developing a fast reactor “has not changed at all” – and even announced a plan to draw up a “strategic roadmap” for fast-reactor development by 2018. The current idea is for Japan to join, as a junior partner, with the French program to design and build a fast reactor called the Advanced Sodium Technological Reactor for Industrial Demonstration on French soil. Just as important, Japan’s government also declared that it would continue its reprocessing policy. This means that there has been no change in the plan to start up the commercial operation of its Rokkasho reprocessing plant – the first industrial-scale reprocessing plant in a non-nuclear weapons state – in 2018. The plant is designed to separate up to 8 tons of plutonium, enough to make 1000 bombs, per year. (And Japan has already accumulated 48 tons of separated plutonium.) This is a long way from the original purpose of civilian reprocessing – to supply plutonium for the start-up cores of fast breeder reactors, which were touted as ways to produce more plutonium than the amount they consume as fuel, thereby achieving a near-eternal source of energy. What does the closing of this one reactor, the continuation of Japan’s research into fast reactors, and the continuation of reprocessing spent fuel mean for the Far East Asia region, the United States, and the rest of the world? Isn’t Japan’s government simply unwilling to admit that its dream of an endless plutonium-fueled future has turned into a costly nightmare? These are legitimate questions for the international community to ask.