Japan's government announced that it will turn over a large stockpile of highly enriched uranium and plutonium to the US for "elimination." Tokyo made the announcement on the eve of a nuclear disarmament conference at The Hague.

Reuters:

Japan will turn over hundreds of kilograms of sensitive atomic material of potential use in bombs to the United States to be downgraded and disposed of, the two countries' leaders said ahead of a nuclear security summit on Monday.

China had voiced concern earlier this year about Japan's holding of plutonium but Washington and the United Nations nuclear agency in Vienna have made it clear they are not worried about the way Tokyo is handling the issue.

U.S. President Barack Obama and Japanese Prime Minister Shinzo Abe said in a joint statement that all highly enriched uranium (HEU) and separated plutonium would be removed from the Fast Critical Assembly at the Japan Atomic Energy Agency.

Like uranium, plutonium is used to fuel nuclear power plants and for research purposes, but can also provide material for nuclear weapons. A Fast Critical Assembly is used for studying the nuclear physics of so-called fast reactors.

"This effort involves the elimination of hundreds of kilograms of nuclear material, furthering our mutual goal of minimizing stocks of HEU and separated plutonium worldwide, which will help prevent unauthorized actors, criminals, or terrorists from acquiring such materials," said the joint statement released by the White House.

"This material, once securely transported to the United States, will be sent to a secure facility and fully converted into less sensitive forms."

The announcement was made in The Hague shortly before leaders from 53 countries, including Obama and Abe, were due to hold a two-day summit aimed at preventing al Qaeda-style militant groups from acquiring nuclear bombs.

Japan is what arms control people call a "threshold" nuclear power. It is thought that in the past, they carried out some experiments with nuclear bomb design and may even have a delivery system. In a crisis, it is believed that Japan could construct a few bombs in a matter of weeks.

China has been raising a stink in advance of the summit about Japanese plans to construct a $21 billion reprocessing plant for spent nuclear fuel. They also claim that Japan has far more nuclear matrerial than they need for research and to run their nuclear plants.

The hundreds of kilos of nuclear material Japan is turning over to the US represents only a fraction of the plutonium they possess. It is not likely they will leave themselves totally defenseless while tensions with China remain high.