Reprocessing and the Pluthermal program, using MOX fuel are little more than a makeshift solution for Japan's nuclear waste disposal problems.

(Source) Aileen Mioko Smith Green Action-Japan
"Pluthermal" is a Japanese word which combines two English words, "plutonium" and "thermal". Pluthermal refers to the utilization of 'plutonium' fuel in commercial ('thermal') nuclear power plants. The fuel is commonly referred to as plutonium uranium mixed oxide fuel, or MOX fuel.
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A decade ago, the pluthermal program was called an interim program, a 'bridge' to consume plutonium until fast breeder reactors were developed for full-scale plutonium utilization. However, since the 1995 accident at the prototype fast breeder reactor Monju, Japan's fast-breeder reactor development program has come to a standstill, and there are no concrete plans to build a commercial fast-breeder reactor in sight.
Over the last several years the government and electric utilities have argued that the pluthermal program is a method of recycling precious resources. 
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What is Wrong with the Pluthermal Program?
The use of MOX fuel increases the risk and severity of a nuclear accident. When using MOX fuel, the control rods' capacity to function is reduced and power output is less stable and harder to control. The Japanese government claims that there has been many years of MOX fuel utilization experience in Europe, but fails to inform the Japanese public that experience with MOX fuel is minimal when compared to uranium fuel. Importantly, the government fails to inform the public that the scale of MOX fuel use in Japan will be unprecedented. There will be a higher concentration of plutonium in the fuel, a higher burn-up rate ---experimentation has shown that there are serious safety concerns with high burn-ups, and no reactor adaptations such as increasing the number of control rods.



The real need for the Pluthermal Program
Then why have the Pluthermal Program? Although plutonium is a major liability for electric utilities, the pluthermal program remains in place because at present reprocessing facilities are the only place for Japanese electric utilities to send their spent nuclear fuel. Failing to carry out the pluthermal program would imply that there is no need for plutonium, thereby making the Rokkasho Reprocessing Plant now being constructed in Aomori Prefecture unnecessary.
This would then leave the utilities with no place to send their spent nuclear fuel. If this were to happen, some of the reactors at nuclear power plant sites would have to be shut down since there would be no space to store the used fuel coming out of them.
Clearly, reprocessing and the pluthermal program are little more than a makeshift solution for Japan's nuclear waste disposal problems.