Thanks to sustained diplomatic efforts, starting with Secretary of State Henry A. Kissinger, and to the high cost of reprocessing, Japan is the only non-nuclear state that continues to reprocess its nuclear fuel. South Korea is insisting, however, in its negotiation of a new Agreement of Nuclear Cooperation with the United States, that it should have the same right to reprocess as Japan.

South Korea isn’t alone. South Africa’s energy minister recently reasserted her country’s interest in reprocessing. When asked why the country would want to embark on such a costly venture, a South African nuclear official once responded, “Reprocessing is the currency of power in the modern world!” Meanwhile, Iran insists that it has the same rights as Japan and is building a reactor similar to the one India used to produce the plutonium for its first nuclear bombs.

Despite the added cost of reprocessing — about $2.5 billion a year for the new facility — Japan insists it is the only viable option for the spent nuclear fuel which is filling up the cooling pools at its reactors. But there are easier alternatives.

When nuclear power plants in most other countries need space in their pools, they remove some of the older, cooler fuel and place it in air-cooled casks within the plant’s security perimeter. That costs 5 percent as much as reprocessing does. Eventually, the spent fuel is to be shipped to an underground repository, as is to be done with the high-level radioactive waste from reprocessing.

Reprocessing advocates in Japan and South Korea say that communities around the nuclear power plants will not allow dry-cask storage and that, when the spent fuel pools fill up, the power plants will have to shut down.

But in both countries those local governments receive large subsidies and taxes — typically 50 percent of a municipality’s revenue in Japan — for playing host to nuclear power plants. They are unlikely to force permanent shutdowns just because they don’t like extra spent fuel kept at the reactor site, especially if the safety advantages of dry-cask storage are explained to them.

The Obama administration should make it emphatically clear to Japan’s government that the separation of more plutonium is in no one’s interest. The two countries should instead jointly lead a global effort to reduce existing stocks of separated plutonium by discouraging reprocessing and encouraging safe disposal of already separated stocks, which could be done, for example, by immobilizing the plutonium and placing it in three-mile-deep boreholes.

The waste of trillions of taxpayers’ yen is Japan’s problem. The risk it presents, however, is the whole world’s concern.