With reference to the nuclear energy research in India, MOX fuels or Mixed Oxide fuels have been of great importance. With this respect, consider the following statements:
1. MOX fuel has the mix of uranium-235 and plutonium-239
2. The usage of MOX fuel eliminates the need of enriched Uranium
Which among the above statements is / are correct?
(Excerpt from “The Power of Promise” by M V Ramana; Penguin UK)
In the 1970s, the DAE started experimenting with using fuel assemblies that were made of MOX (Mixed Oxide, or a mixture of plutonium and uranium oxides). According to the DAE, investigations on refueling TAPS with plutonium were completed in 1972. In 1979, soon after the US decided not to supply fuel to the reactor, AEC Chairman Homi Sethna announced that, within three years, the DAE would develop MOX fuel as a substitute for enriched uranium .
By November 1982, however, an agreement for fuel supply was signed with France, and the first consignment arrived in May 1983. But the promise of MOX was to persist and in 2001, the AEC chairman reportedly claimed: ‘Should there be any difficulty, we can still run the reactors using our MOX technology’. The DAE’s assertions notwithstanding, MOX can only be a partial solution for fuelling Tarapur. Technically, it can be used because plutonium-239 has properties somewhat similar to uranium-235. So, instead of the increased uranium-235 content of LEU, MOX fuel will have an increased amount of plutonium-239. But plutonium-239 is not identical to uranium-235 and there are some important differences.
Two kinds of neutrons are released when an element like uranium-235 or plutonium-239 undergoes fission: those that are released immediately—prompt neutrons—and those that are released after a little while—delayed neutrons. The delayed neutrons are very important for safety and allow the reactor to remain under control in the event of small fluctuations in power level or temperature. When there are fewer delayed neutrons, there is less time for the reactor to be shut down in case of an accident. Compared to uranium-235, plutonium-239 gives out fewer delayed neutrons. Because of this key difference in the neutronic properties of uranium and plutonium, those reactors around the world that use MOX fuel typically—though not always—allow only a maximum of a third of their core to be loaded with MOX. Thus, unless it is decided to compromise on safety requirements and increase the risk of accidents getting out of control, the use of MOX will only reduce the enriched uranium requirements, not eliminate it altogether The substitution of enriched uranium fuel with MOX might not only increase the probability of a severe accident, but also the hazard to public health.
Should there be a catastrophic accident, resulting in the release of large quantities of radioactive materials into the atmosphere, the consequences would be worse for the inhabitants of the regions that experience radioactive contamination. This is primarily because greater quantities of plutonium—which is far more radioactive and injurious to health than uranium—would be released. MOX-fuelled reactors also have higher chances of fuel elements failing and releasing radioactive fission products into the water that cools the reactor because they typically operate at higher temperatures. The DAE’s publications on MOX pay no attention to the dangers to public health and environment that might result from utilizing MOX fuel in reactors.
This question is a part of GKToday's Integrated IAS General Studies Module