The International Panel on Fissile Materials has released a new research report, Alternatives to MOX: Direct-disposal Options for Stockpiles of Separated Plutonium, by Frank von Hippel and Gordon MacKerron (pdf file).
The report reviews programs in France, Japan, the United Kingdom and the United States to dispose of large stocks of separated plutonium in nuclear power reactor mixed-oxide (MOX) fuel. Most of these efforts have suffered long delays and large cost increases and all have failed to reduce plutonium stockpiles. This has led some of these countries to consider alternatives.
A less costly and more effective approach may be to treat plutonium as a waste to be processed into a stable form and deeply buried. These alternative approaches include disposal with radioactive waste or spent fuel or disposal down a 3-mile (5-kilometer) deep borehole.
The report recommends that more than one direct-disposal approach be pursued. It also recommends that the countries that share the problem of plutonium disposal collaborate on exploring direct-disposal options. Finally, it recommends that the quantities of plutonium disposed by the weapon states be verified by the IAEA.
UPDATE: The report is also available in Japanese