As we face the twin perils of an energy crisis arising from the ever increasing cost of oil extraction and the serious threat of climate change, nuclear power has again come back onto the agenda.
When the Nuclear Age first came into being in the 1950s, it seemed as though it was going to provide a clean power source that would soon be completely ubiquitous. As the sound-bite went, it would make electricity so cheap there would be no point in metering it. People dreamed up plans of nuclear powered neighbourhoods and even nuclear powered cars. The potential seemed limitless.
Nuclear power advanced much more slowly than was anticipated. Partially this was because oil still provided a cheap and abundant fuel source that didn’t require the large and expensive installations necessary to run a light-water reactor (the type most people immediately imagine in their heads). However, there was also a real popular movement in opposition to nuclear power even before the 1960s. The first such movement in the US occurred between 1958-1964 at Bodega Bay where the first commercially viable nuclear power plant was to be built. Eventually Pacific Gas & Electric had to abandon their attempt. Indeed these grass-roots movements continued through the 60s and 70s in the United States and may have had some hand in reducing the application of nuclear power.
In France on the other hand, things were different. The French embarked on an extensive nuclear power program in 1974, following the first oil shock. By 1985 the majority of their electricity energy production was from nuclear sources. The French standardised their nuclear plant design fairly early on, going for a pressurised water reactor and deploying it nationally. This is sometimes cited as the reason for the relatively low cost of its electricity generation and lack of safety problems. By contrast, reactors in the US are like snowflakes. Every one is unique, itself an experiment in diversity.
In some ways the popular opposition of the anti-nuclear movement was prophetic. It occurred long before any serious accidents. It wasn’t until the Three Mile Island incident in 1979 that any real large scale difficulties were encountered. And it wasn’t until Chernobyl in 1986 that nuclear energy suffered a true disaster.
After Chernobyl, nuclear power was forced to the very bottom of discussions on power generation, and not without reason. The size of the catastrophe was impressive. The west first became aware of the disaster when radiation alarms went off at the Forsmark Nuclear Power Plant in Sweden, which is several hundred miles from Chernobyl. Though 56 direct deaths are attributed, as many as 4000 people may have died due to increased cancer risk from radiation.
After this, nuclear power had to take a back seat. No politician with any sense would touch it. People were frightened of its destructive potential and certainly were not keen on having one in their neighbourhood. The marginal cost difference with oil was too narrow to make it worth the while of big business to pursue a lobbying strategy on its behalf. Its defence has since then largely been up to those companies already operating and a few nuclear scientists and enthusiasts.
Nuclear catastrophes aren’t the only worrying thing about nuclear power, however. Nuclear waste is another key issue in the debate. The waste products of light water nuclear reactors have half-lives that ensure that they are still radioactive after thousands of years. This means that disposal projects have to be commensurately long. Expecting to house nuclear products with integrity over a scale so large that language itself will drift to being unrecognisable raises serious concerns. Reading a maintenance manual two thousand years down the line will be akin to reading Aramaic text. Only a handful of institutions, such as the Catholic Church, have existed for time periods on this scale. Perhaps we would need a church of true nuclear disposal believers, with an army of monks taught the intricacies of the ancient texts. This is not to mention all the intervening opportunities for earth quake, material faults, seepage etc.
However, the objections to nuclear power are in some ways self fulfilling. As it turns out, long lived nuclear waste is not an inevitable consequence of nuclear reactions. It is merely the outcome of one particular type of nuclear reactor. These reactors, sometimes called once through reactors take mined uranium and increase the ratio of the fissionable isotope U235 in an enriching process. The fuel is then allowed to undergo fission resulting in a veritable cornucopia of elemental products including everything from Zirconium to Neodymium. Among these are the particularly nasty isotopes, Strontium 90, Cesium 137 and many others.
Strontium 90 and Caesium 137 have relatively short half lives of around 30 years. While these are potent radioactive sources, they decay relatively rapidly until they are no longer radioactive. The most problematic products are those with life-spans of between 10² an 2×10⁵ years. These products are in a class of being just radioactive enough to present a serious threat to human health, but not so radioactive that they decay to nothingness quickly.
As early as the 1940s it was realised that a particular class of reactors, known as breeder reactors could have a novel way around the problem. Nuclear reactions can provide a source of the radiation needed to convert elements. This means that if a reaction is tuned appropriately we can control the type of products made. If the products are themselves fuel then we are breeding. Of course the process isn’t infinite, our fuel products are still the result of moving down a chain towards Iron. It can, however, result in substantial increases in fuel economy, improving it by as much as 10 or even 100 times.
A light water reactor does in fact breed fuel itself, however the breeding ratio is low. A breeder is often defined as a reactor which aims to produce more new fuel than it consumes of the original fuel source. This is generally achieved by covering the core with a breeder blanket, a covering of material from which we are to breed fuel.
The output products of breeder reactors can be restricted to those which are very short lived, such as Cesium 137 and Strontium 90, and those which are tremendously long lived and so do not constitute a serious threat to human health if diluted. While it would be necessary to store Caesium 137 and Strontium 90 for sustained periods, it turns out that they are also useful as fuel sources for nuclear batteries. They can themselves be used to generate electricity and are the power source for most of our inter-planetary missions.
Not only are breeder reactors more efficient in their fuel economy and more tunable in their waste products, they are also able to use different sources which might not otherwise have been fuel. While once through reactors require that uranium be enriched, no such requirement exists for a breeder reactor. It can simply be added to the breeder blanket and the appropriate fissionable products can be produced from uranium 238 directly. In addition, Thorium becomes a viable fuel if we use breeder reactors. This increases the distribution and quantity of fissionable fuel tremendously.
The use of breeders can also be brought to bear on the question of the proliferation of fissionable products. Since the fuel is reduced to effectively useless products the only remaining danger is dirty bombs using Strontium 90 and Caesium 137. Since the quantity of these products is relatively low, it may be feasible to keep them on site for use in nuclear batteries for additional power until they are effectively inert.
If that weren’t enough already, breeders can also be designed to consume our present nuclear waste. The nuclear products should be consumed until they fit into one of the two classes of either very high half life products or those that are very low. Even if breeder reactors are not explored for the purpose of power generation, their ability to burn waste should be seriously considered as an answer to our four decades of nuclear waste accumulation, the storage of which seems to be infeasible in the long term.
Breeder reactors come in many types and designs. They range from the lead cooled fast breeder reactors that the Soviets used for their submarines to the newly designed salt-cooled thermal breeder reactor programme which India has started in order to make use of its abundant Thorium reserves.
Breeders can also be manufactured to fit very small and local designs. They need not be produced on the massive scales that generally come to mind when we think of nuclear plants. The nuclear submarine designs of the Soviets are currently being modified by the Russian state energy company Rosatom to produce modular nuclear reactors. These can be used to produce heat as well as power, which allows combined heat and power systems which can provide neighborhoods with essentially free heating using the waste heat from electricity generation.
The space of design possibilities is indeed quite large. As we know from the automobile and software industry, new designs are always problematic. It’s best to get the third year of a car model or a late minor version of a software product rather than the cutting edge. Designs have to be honed over time. Any practical nuclear programme should be restricted to only a few designs which should be deployed on a wide scale such that economies of safety and scale can be taken into account.
However, the question still remains: is nuclear power safe to use, or will we be contributing to a serious health hazard by taking it up? While the severity of the Chernobyl disaster cannot be denied, the numbers tell a quite different story than one might expect.
The most usual way to compare the safety of various energy sources is to compare the number of deaths per terrawatt year – essentially how many people are likely to die for the production of a terrawatt year. To get perspective on the size we are talking about, currently the world uses energy at a rate of about 15 terrawatts.
It has been estimated that Hydro power causes 883 deaths per terrawatt year, Coal causes 342 deaths, however Nuclear causes only 8 deaths per terrawatt year and only if you count Chernobyl. If you restrict to the French nuclear programme, this number is closer to zero.
This leads one to wonder not so much about the safety of nuclear power, but the safety of everything else. Clean power sources such as hydro really take their toll in human life. In fact, some of the largest human catastrophes in history are due to dam failure. Coal of course has the added deficit of contributing to a potential global climate catastrophe aside from all the dangers associated with its production.
However, even assuming that nuclear power is safe, is it really worth the effort when we’ll merely be shifting from one finite resource such as oil to another finite resource such as uranium? Is it simply kicking the can down the road and will it be a problem that we have to deal with in 100 years all over again?
Bernard Cohen did an investigation of nuclear power as a sustainable energy source and published his results in the American Journal of Physics. In it, he concluded that, assuming the use of breeder reactors, there were sufficient fissionable products in the ocean which can be reclaimed in an (energetically) economical fashion that they will last more than a billion years. While this is not technically sustainable or renewable, it’s on the order of the lifetime of the sun, so can be considered sustainable for all practical purposes. Beyond that we will have to be worried about the colonisation of new star systems rather than what power sources to use on earth.
From a purely technical perspective it does in fact seem that nuclear power can be used as a safe and sustainable energy source. However, all of this ignores the political and social problems of the research and development, the creation and the maintenance of nuclear power. In the past we’ve seen that the governments and corporations who run nuclear (as well as hydro and others) have not been transparent about plant management and have endangered human lives in pursuit of profit goals or for reasons of political expediency. No technical fix is possible for these problems.
Indeed, our environmental problems are not so much about lack of technical choices as lack of political will and the ever present drive of energy companies to maximise their profits regardless of impact. Unless these social questions can be solved, the question of nuclear power will largely remain theoretical.