The following articles are from the Japanese CNIC, the Citizen's Nuclear Information Center.
Reprocessed plutonium from nuclear weapons has only been used in Japanese reactors since 2009. Now there's 1,345 kg of plutonium being used throughout Japan.
Fukushima 1-3 Begins Operating with MOX Fuel
On September 18, 2010 Tokyo Electric Power Company (TEPCO) started up its Fukushima I-3 Nuclear Power Plant (BWR, 784MW) using MOX fuel. It loaded MOX fuel into the reactor on August 21 and plans to begin generating electricity on the 23rd.
Over 10 years had passed since this fuel was fabricated. It was fabricated between 1997 and 1998 and arrived at the nuclear power station in 1999, but it was never loaded. Falsification of fuel quality control data for MOX fuel for Kansai Electric Power Company's Takahama-3&4 nuclear power plants was discovered and troubles and cover-ups were discovered at TEPCO nuclear power plants. In response, the prefectural government revoked its agreement with TEPCO. On January 20 2010, TEPCO applied again for permission to use MOX fuel and on August 6 the governor gave his consent.
The Impact of a Possible MOX Fuel Accident at Fukushima I-3
The legal case against TEPCO's use of MOX
On 9 August 2000, over 850 plaintiffs from across the country, including 138 from Fukushima Prefecture, took Tokyo Electric Power Co. (TEPCO) to the Fukushima District Court asking for a suspension of the use of MOX fuel at Fukushima I. The first hearing was held on the next day, when the plaintiffs explained their case to the court. Their main argument is that there is a strong possibility of falsification of the quality-control data for the 32 MOX fuel assemblies already on site at Fukushima I-3.
The danger of using MOX Fuel with dubious data
When MOX fuel is burned in nuclear plants designed for burning uranium fuel, many safety problems arise. For example, the control rods worth are reduced, the emission of radioactive gasses increase, and difficulties arise due to the lower delayed neutron ratio. (See International MOX Assessment report published by CNIC.) Using MOX fuel which is of a low quality, or which exceeds the reactor's design criteria, further increases the likelihood of accidents. Damage to fuel rods and malfunctions in the cooling system are particularly likely in such circumstances. Large amounts of radioactivity may be released and diffused due to the functional failure of reactor vessels and filters.
If there is an accident at Fukushima I-3
Exposure doses for residents resulting from a diffusion of radioactivity caused by a severe accident at Fukushima I-3 were calculated by applying the same method used in the disaster assessment in 'WASH-1400', an accident analysis report produced by the U.S. Atomic Energy Commission.
The plan to burn MOX fuel in light water reactors is called the pluthermal program in Japan. In the core of a pluthermal reactor, there are ten times more actinides such as plutonium, americium, and curium than the core of a uranium reactor. Actinides cause serious internal exposure in human bodies and thus pose a very serious threat to human health.
In short, exposure doses resulting from an accident at a pluthermal reactor would be twice those produced by an accident at a uranium reactor. A given exposure dose would be received by residents over twice the distance. The overall affected area would be four times larger. When fatalities by cancer from an accident at a pluthermal reactor is calculated with an assumption that Tokyo was downwind, the number of cancer fatalities would increase from 0.4 million in the case of an accident at a uranium reactor to 10.6 million. In view of such risks, MOX utilization is simply too dangerous.
Japan's inventory of separated plutonium at the end of 2009 was published on September 7, 2010 by the Japan Atomic Energy Commission. The end of year inventory has been published for each year since 1993. A shipment from France of 1,508 kgHM of plutonium oxide arrived in Japan in January 1993. The shipment caused an international uproar. Japan responded by publishing its plutonium inventory in an attempt to increase transparency. The figures published were for "total plutonium", but since 2006 the figures for Japanese plutonium held in France and the UK have only been published for "fissile plutonium", making precise calculation of Japan's total plutonium holdings difficult.
Japan's pluthermal program (using MOX fuel) began in 2009, ten years later than planned. Plutonium shipped and loaded into reactors is reflected in the figures in these tables. The 1,458 tons of plutonium held as "Unirradiated new fuel at reactor sites etc." includes 210 kg at Fukushima I-3 (TEPCO), 205 kg at Kashiwazaki-Kariwa-3 (TEPCO), 213 kg at Hamaoka-4 (Chubu) and 831 kg at Ikata-3 (Shikoku). (The figures don't add up due to rounding.) The plutonium held at Tokyo Electric Power Company's (TEPCO) reactors was shipped there in MOX fuel over ten years ago. The plutonium held at Chubu Electric's and Shikoku Electric's reactors arrived in MOX fuel from France in May 2009. MOX fuel for Kyushu Electric's Genkai-3 plant (677 kg) also arrived in May 2009, but it was loaded in the same year, so it is included in "Plutonium loaded in nuclear reactors" under "Separated Plutonium in Use". The remaining 669 kg of the total 1,345 kg plutonium loaded in nuclear reactors was loaded in Monju last year. (Monju started up in May this year.)