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IMA Main Findings

Any Plutonium is Potential Primary Bomb Ingredient

The Group's analysis has clearly established that: Plutonium of almost any isotopic composition, and in particular plutonium separated from spent fuel of any nuclear reactor currently operating in Japan, can be used for the manufacturing of a nuclear explosive device. Reactor grade plutonium in the form of oxide crystals in spherical shape has a critical mass of about 35 kg. The radius of this sphere would be about 9 cm, the size of a cantaloupe.

Safeguards: Not up to the Challenge

Independent experts have calculated that, in the case of a large reprocessing plant (capacity of 800 tons of spent fuel per year), even if the error margin in the operator's computer calculation is as low as 1%, the minimum amount of diverted plutonium which could be detected with a probability of 95% and a false alarm probability of 5% is about 220 kg, enough to produce 6 to 10 crude nuclear bombs.

Nuclear Terrorism: An Increasing Threat

Increasing availability of plutonium and the existence of highly trained terrorist organizations make the escalation to nuclear terrorism more likely than ever. Some of these organizations have shown an unprecedented level of cruelty and the use of means of mass destruction. There can be no doubt that some of these groups would be in a position to manufacture a crude nuclear device or to deliver a credible equivalent threat.

Safety of MOX Use in LWR Questionable: MOX Use Would Make a Severe Accident Even Worse

In case of a severe reactor accident with containment failure, the dose at a given distance would generally be 2.3 to 2.5 higher in the case of the MOX fuelled reactor as compared to a UO2 loaded reactor. A major accident would threat the lives of hundred to several hundreds of people, depending upon conditions.

MOX Increases Fuel Costs Significantly

The Group's own economic analysis shows that the introduction of MOX to a third of core will raise the fuel costs of LWRs by a factor of about 2.5. Annual reactor fuel cost of a 1,000MW reactor with one third MOX core is about 11 billion yen as compared to 4.4 billion yen for UO2 core. If Japan's MOX program to use MOX in 16 reactors is implemented, the additional cost will be over 100 billion yen.

Cask Dry Storage Best Available Interim Storage Option: Direct Fuel Disposal Preferable Option for an Optimum Backend Policy

The direct spent fuel storage option is the preferable path if compared to reprocessing for a large number of reasons, and in particular according to the following criteria:

- Waste volumes: The reprocessing path generates at least six times more waste than the direct disposal path, probably even significantly more.

- Radioactive discharges: Reprocessing facilities release very large quantities of liquid and gaseous discharges, the Direct Disposal option virtually none.

- Transports of radioactive materials: More than 200 waste shipments between Europe and Japan associated with the reprocessing option are expected to be carried out in the coming decade.

- Interim storage: Reprocessing is certainly not a credible path to combat insufficient interim storage capacity; technically it can be increased without difficulty.

- Waste heat management: The thermal output of spent MOX fuel is by a factor of two to more than three higher than that of UO2 spent fuel.

Cancellation of Japanese Overseas Reprocessing Contracts Recommended

Reprocessing contracts between Japanese utilities and European reprocessors can be and should be canceled. The reprocessing wastes corresponding to the throughput already carried out under Japanese contracts have to be shipped back from Europe to Japan. Prior to any further shipments there should be an in depth impact assessment and potential adaptation of the shipment mode. Separated plutonium existing in Europe should be treated as waste and be disposed of by a proliferation-resistant measure such as immobilization together with high level radioactive waste.

Plutonium and MOX Transports - Security and Safety at Stake

The case of the planned MOX program for Fukushima I-3 illustrates well a typical case of transport scheme. Nuclear materials and wastes go several times back and forth between Europe and Japan. Even if one considers only one transport per type of shipment, the distance to be traveled by nuclear materials totals some 100,000 km or more than twice around the world: a nightmare for security officials and insurance companies.


The Co-Researchers of the IMA-Project conclude that the disadvantages of the Plutonium-MOX path versus the Direct Fuel Disposal option are overwhelming whether on the level of industrial, economic, security, safety, waste management and societal implications. In other words, there is no reasonable justification or identifiable social benefit in the continuation of plutonium separation and the launch of a MOX fuel program for light water reactors.


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