Nuclear: the answer?

Modern life, unlike that in the middle of the 18th century, is totally reliant upon a high-quality, reliably available supply of electricity.

This includes the whole of our transport system, for refineries would not refine without electricity. And the pumps on the forecourt would not pump, so not dispensing any petrol. The grip of electricity on our society today is complete.

Today, about 80% of our electricity is currently obtained by burning coal, oil and natural gas, much of which we import from countries like Russia and from the Middle East. Our own gas and oil supplies are at their peak or declining. We are, therefore, becoming more and more dependent on imported fuel, unfortunately from the less politically stable areas of the world.

To keep our economies functioning meanwhile, we are producing large quantities of carbon dioxide, the greenhouse gas which, it is generally agreed, threatens us with climate change.

To address this position, the government has launched a programme to promote renewable energy, derived from wind, wave, tidal and solar power, and has supported it with generous subsidies. The purpose is to give us independence and so security of supply.

These green sources of power have made little progress as major producers of reliable supplies. They all rely upon energy sources which, however powerful, they may seem on a human scale, are in fact weak, dilute sources, and which, inevitably, occupy large areas of land or sea. Additionally, they are either chaotic in their production, or can only generate at given times. In fact they are take-it-when-you-get-it sources of power. And, at those times when the wind is not blowing or the tide not turning, they are not productive – so there have to be standby power stations, burning fossil fuel.

Clearly, renewable energy is only a small part of an answer to our problems.

So what is the answer? Ultimately, the only source of safe, dependable, economic and minimal carbon energy lies in nuclear power. The fission reactors progressively developed since the 1950s are, compared with conventional and renewable generation, sources of enormous amounts of power for a small input of fuel. The fissioning of one atom of uranium yields 60 million times as much energy as the burning of one atom of carbon. The nuclear power station needs only a small amount of uranium, which comes from friendly countries such as Canada and Australia. And the fuel lasts a long time, so there are no sudden crises of supply. Power stations are built to generate for some 60 years, making possible the long-term planning of reliable supplies; giving us energy security.

It is the enormous amount of energy available from a small amount of uranium that gives rise to the very small carbon footprint of nuclear energy. The energy, which at the moment is carbon based, used in the production of the steel, concrete, the fuel itself, and indeed the eventual dismantling of the reactor, is dwarfed by the amount of energy produced over the life of the reactor. The new generation of reactors have a design life of 60 years.

Uranium as mined, contains only about 0.75% of the type of uranium which is burned directly. But, in the future, fast-breeder reactors will also be able to convert the rest of the uranium into fuel, expanding the use of the fuel by 60 times. This process has been well demonstrated on a smaller scale and the reactors have produced electricity for many years.

To expand the usefulness of nuclear power, a promising new pebble bed reactor is the answer. This reactor type operates at a high temperature, 900˚C, and uses uranium fuel as tiny pellets encased in a hard carbon coating. These are further encased to make billiard-ball-sized spheres, which are resistant to very high temperatures. The cooling gas is used directly to power turbines, so avoiding the use of steam, which has been an essential step in all power stations.

The high temperature of the coolant gas may also be used to drive chemical processes, the most important being envisaged is hydrogen production. This would be on a very large scale and enable hydrogen to be used as a transport fuel. These reactors, factory-made as modular units, may also be small enough as generators to be used in communities in the less developed areas of the world, given that they are extremely safe.

These are, however, reactors, like the fast-breeder reactors, of the future. They have been demonstrated, but await full commercial development. Given the fluctuating oil and gas prices and current political situation it may now be time for nuclear energy to realise its full potential and for this clean and low-carbon fuel to be exploited on a commercial scale in areas at present absolutely dominated by fossil fuels.

On the safety side, while it is true these reactors produce an ash, and also the materials produced by the fission of the uranium atom are radioactive, this high level waste can be disposed of in a safe and secure fashion. It is all contained within the fuel which, when burned up, is taken from the reactor core, to be replaced by new. This fiercely radioactive part, is only a small part of the fuel.

The fuel is kept for a year to allow the most radioactive part to decay, and during this time it is cooled. This is necessary as the radioactivity is sufficiently intense to be heat-generating. All radioactive materials decay over time, in such a way that for each type there is a time span during which half of the radioactivity disappears. It is different for all materials, and varies from fractions of a second, to millions of years. The longer this half-life, the less radiation it emits.

After a year, the fuel is ready for disposal. This may mean converting the whole of it into a glass-like material, which may be melted into stainless-steel containers ready for disposal. The containers are sealed underground in suitable rocks, where they will remain completely away from any possibility of human contact. Because of this deep disposal, it is impossible for their radiation to reach the surface, and careful selection of the site precludes any chance of the container contents being released into water sources.

An even deeper disposal is possible, in deep granite beds several kilometres below the surface, where the rocks themselves soften under the heating by the containers which then become part of the granite.

Recovery
This method of disposal, however, of the whole of the fuel, throws away valuable uranium and plutonium, which may be recovered by chemical processing and used to make new fuel. Again, after separation, the fission products are converted into glass and buried securely. The adoption of this reprocessing route for used fuel would fit well into the general desirability recycling, promoted by the government for waste materials in general.

The common myth that these wastes “last for tens of thousands of years and form a hazard for generations to come” is completely false. Since the half-life of the fission products in the fuel is only about 35 years, it decays to insignificant levels after three to four centuries underground, and is then no more radioactive that the uranium ore dug from the ground.

Unlike industrial wastes from factories in general, the amount of waste is extremely small. Over the past 50 years, the amount of high-level waste produced from a power programme which supplied at its peak, some 25% of our electricity, would fill the volume about two four-bedroomed houses.

There are other lower-level wastes and these present less harm and can be easily dealt with by compression, sealing and packing into containers, sealed from water penetration. These areas are prohibited to the public, to whom they present no hazard.

Nuclear energy presents a safe, clean, economic and secure source of power. There is no shortage of uranium, which is about as abundant as tungsten, and thorium about ten times as abundant as uranium, is a potential fuel for the fast reactors. Is it time now to emulate the French, who have demonstrated that almost compete replacement of fossil fuel for electricity production is indeed a reality?