TOPICS: Managing nuclear waste through ‘transmutation’

A loose interpretation of the second law of thermodynamics is that “there is no such thing as a free lunch”. And so it is with electrical energy production. If you burn fossil fuels, you generate CO2; if you build dams, you destroy the ecology of entire valleys. Nuclear power is no exception. If you carry out controlled fission in a nuclear power station, you get long-lived radioactive waste, and that poses a long-term hazard to the environment unless it is dealt with properly. This has justifiably caused concern among many who would otherwise welcome nuclear power as a source of clean, carbon-free energy.

The favoured option is to store the treated and vitrified waste in deep geological repositories. Understandably, people don’t want this in their backyard, not least because material such as plutonium remains radioactive for tens of thousands of years. In a democracy, in the throes of deciding its future energy policy, such concerns are a serious issue. I find this a very str-ange concern: here we are trying to figure out how to avert the disaster of climate change now, and yet the long-term problem of nuclear waste still worries us. But what if there was a way to incinerate the nuclear waste, destroying nearly all that plutonium and dramatically reducing the need for long-term storage?

One such strategy is known as accelerator-driven transmutation. The basic idea is to place the radioactive material in a machine and smash it up into much more stable products, with shorter half-lives using a beam of high-energy subatomic particles. The waste would still need to be stored, but would be much less hazardous. At the same time, the process of transmutation would eliminate other biologically toxic products that exist in “normal” nuclear waste. The real beauty of the process is that it could generate more energy than is pumped in. The heat generated by splitting the waste nuclei can be used to generate electricity, part of which is used to run the accelerator and the rest fed into the national grid. This type of plant is known as an “energy amplifier” and the idea has been around since the 1990s.

Many experts argue that while transmutation is a feasible future technology, there are several other options available too. The most widely touted is to use what is a called a fast-breeder reactor that would re-use the nuclear fuel over and over again until all the plutonium is burned up. Another option many nations are looking into is to use thorium as the basic nuclear fuel. It is more abundant in nature than uranium, and much less radioactive material is produced compared with uranium fuel cycles.

With all these possible options for coping with nuclear waste it is disappointing that what little public debate there has been seems to have been aimed at answering the question of “should we” rather than the technological question of “could we”. The answer to the question is only likely to be found in a multidisciplinary effort involving scientists from a wide range of fields. Then the philosopher’s stone will finally be within our grasp. — The Guardian