Japan submitted to IAEA its annual declaration of holdings of civilian plutonium as of December 31, 2011 - INFCIRC/549/Add.1/15.
According to the document, at the end of 2011 Japan had 4.4 tonnes of separated unirradiated plutonium at the reprocessing facilities, 2.9 tonnes in fuel manufacturing process, and 1.6 tonnes in unirradiated MOX fuel. Additional 0.4 tonnes of unirradiated plutonium is "held elsewhere." In the 2010 declaration, these numbers, reported in kilograms, were 4,400 kg, 2,900 kg, and 2,200 kg respectively.
In addition, Japan has 35.0 tonnes of unirradiated plutonium outside of its territory - the same amount as in 2010.
Japan also declared 133 tonnes of plutonium contained in spent fuel held at reactors sites (up from 127 in 2010) and 26 tonnes - in spent fuel at reprocessing facilities (25 tonnes in 2010). Some material, less than 500 kg, is declared as held at other sites.
UPDATE: In an annual report on the plutonium management policies, Japan described the use of its plutonium in more detail. Although the 2011 report has not been published on the Japan Atomic Energy Commission web site, the key data was published at AtomInfo.ru and the Council for Nuclear Fuel Cycle site. [UPDATE 07/19/2013: The 2011 report has been published on the JAEC website (pdf). The numbers below are updated to reflect the official declaration.] According to that information, as of 31 December 2011, Japan had
44,253 44,254 kg of separated unirradiated plutonium, of which 9,294 9,295 kg was stored in Japan and 34,959 kg was stored abroad.
Below is the breakdown of
9,294 9,295 kg of separated plutonium in Japan: 4,3634,364 kg at reprocessing facilities (3,612 kg at Rokkasho and 752 kg at Tokai). Of this amount, 952 kg is in nitrate and 3,411 kg in oxide form. Note that the numbers don't add, probably due to rounding.). This amount is reported as 4.4 tonnes in INFCIRC/549,
- 4,487 kg in unirradiated MOX fuel. 3,363 kg at MOX fabrication facilities (both in oxide and in fresh assemblies), 959 kg in fresh MOX fuel at power plants, and 165 kg at two research reactors - Monju and Joyo. In INFCIRC/549 this plutonium is reported in two categories - as 2.9 tonnes in fuel fabrication process and 1.6 tonnes in fresh MOX (for the total of 4.5 tonnes), and
- 444 kg at R&D facilties (critical assemblies). This amount is reported as 0.4 tonnes "held elsewhere" in the INFCIRC/549 submission.
34,263 34,959 kg of separated plutonium outside of Japan were located in two countries:
- 17,028 kg in the United Kingdom, and
- 17,931 kg in France.
In addition to unirradiated plutonium, JAEC reported that 2,528 kg of plutonium was contained in MOX fuel loaded to four power reactors - Genkai-3 (1,317 kg), Ikata-3 (633 kg), Takahama-3 (368 kg), and Fukusima Daichi-3 (210 kg). Also, 1,533 kg was contained in the Monju reactor core and 251 kg - in the core of the Joyo reactor.