By Renfrey Clarke

April 8, 2010 -- “When the facts change, I change my mind. What do you do, sir?” Attributed to economist J.M. Keynes, that retort has always been good advice. Now that carrying on with “business as usual” greenhouse gas emissions has been revealed as a road to disaster, should environmentalists change their minds on nuclear power?

To be sure, the dangers of the nuclear industry have not gone away. A major nuclear war, by creating “nuclear winter” conditions, would end most life on Earth. Humanity, however, has managed the threat of nuclear war in the past, and the chances are that we will continue to do so.

If thousands of nuclear power reactors were in operation, reactor accidents would be frequent enough that they would almost stop being news. But deaths would probably be few, and other losses would be relatively minor compared to the dead oceans and scorched grainlands of the greenhouse future.

Consequently, it is not surprising that some prominent climate scientists have called for massive investment in nuclear power as a practical way to replace fossil-fuelled energy generation. “Going nuclear” is a key recommendation of renowned US climatologist James Hansen, head of NASA’s climate change research unit, who toured Australia in March. Among Australian climate scientists, an outspoken nuclear advocate is Adelaide University’s Professor Barry Brook.

Characteristically nuanced in his approach, Hansen poses nuclear power as one element in a policy triad that also includes economising in energy use and developing renewable energy sources. Nuclear power is indispensable, he argues, because the combination of economising and renewables will simply not meet energy demand, especially considering the need for rapid expansion of supply in developing countries.

Voicing no particular support for the current “second-generation” nuclear technology, Hansen instead calls for a combination of the (inherently safer) generations three and four. Third-generation reactors are in essence evolved versions of the pressurised-water installations that provide almost all of today’s nuclear energy. Now being built for the first time, “third-generation” plants are arguably still at the pre-commercial stage.

The technology of fourth-generation plants is very different, and these installations exist only in concept. Various experimental reactors, however, have provided insights into problems that the “fourth generation” will likely encounter.

With a variety of “passive” safety features, designed to make them shut down without human intervention in the event of accidents, third- and fourth-generation reactors should in theory have an incidence of contained core meltdown in the one-in-millions-of-years range. But in third-generation installations, at least, other dangers and drawbacks of second-generation plants will persist.

Like their forebears, third-generation reactors require energy-hungry enrichment of their uranium fuel, and induce fission in only about 1 per cent of it. As the world’s limited reserves of high-grade uranium ores are used up, these inefficiencies will make the greenhouse abatement advantages of third-generation plants increasingly unimpressive. Again like their precursors, third-generation reactors produce fiercely radioactive wastes that must be locked away from the environment for more than 100,000 years. Scores of thousands of tonnes of high-level waste are now in limited-term storage at reactor sites around the world.

Plutonium in the waste from third-generation reactors can be extracted and used to create nuclear weapons. A further danger is the possibility that ill-guarded waste could be stolen and used to make so-called dirty bombs, from which high explosives would disperse radioactive material.

Immature technology

When a technology is immature – as is the case with third-generation nuclear power generation – the time needed to make it fully operational is always an important question. And when the task is to replace fossil-fuelled energy generation, the timeframes for perfecting the new equipment and building it out are critically short.

Just how short emerges from work performed by James Hansen himself. If a basically recognisable natural world is to survive, the US climatologist has concluded, atmospheric carbon dioxide must be cut by the end of the century to a level below 350 parts per million (ppm). This will require ending net human-induced CO2 emissions by 2050.

How much CO2 can be emitted during this period, if the eventual concentration of 350 ppm is to be achieved? Other scientists have calculated the allowable “carbon budget” for the years until 2050 at a total of 420 gigatonnes (billion tonnes) of CO2, with other greenhouse gases in proportion. At present emission rates, this budget will be exhausted around 2021.

How might third- and fourth-generation nuclear plants fit these requirements? Highly complex, and still unproven, third-generation plants would not be operating in significant numbers before 2020, and probably for rather longer. This is indicated by experience with the plant now being built at Olkiluoto in Finland. Construction at the site is at least three and a half years behind schedule, and is plagued by cost overruns of some 60 per cent.

Compared to earlier installations, the projected fourth-generation plants – specifically, the “integral fast reactor” (IFR) designs that have drawn most attention – promise important advantages. Passive safety features would make the chance of core meltdown ultra-remote. Unlike most reactor designs, IFRs would use “fast” or high-energy neutrons, allowing them to create more fissile material – in this case, plutonium – than they consume. This would be achieved through the irradiating of depleted uranium, of which large stockpiles exist. Fresh mining of uranium would not be needed for hundreds of years.

Along with plutonium, the reactor products from IFRs would contain highly radioactive isotopes of minor transuranic elements. The “integral” reactor complexes would include facilities for extracting the plutonium from the reactor products for use as fuel, with long half-life transuranics also removed and included in the fuel mix. In this form, the fuel would be unsuitable for nuclear bomb-making without elaborate and easily detected reprocessing. Its attractiveness as a basis for weapons proliferation would arguably be slight.

High-level wastes from other reactors could also be incorporated into the IFR fuel, to be “burned” and transmuted into relatively manageable materials. The wastes left behind after the fuel extraction would initially be dangerous – and quite usable for dirty bombs – but within 200 years would be no more radioactive than natural uranium ores.

Energy bonanza?

Through the use of IFRs, proponents like Hansen maintain, huge quantities of energy could be created without major emissions of greenhouse gases. Meanwhile, the costs and dangers of uranium mining and enrichment would be avoided. With plutonium and highly radioactive wastes never leaving the reactor sites, security would be easier to manage. From being a massive obstacle, end-product waste storage would become quite feasible.

Unfortunately, IFRs do not offer a solution to global warming. The catch, above all, is in the time lines. There is simply no way that IFRs can be designed, brought to practical operating status and built in massive numbers during the few years – barely a decade, if something like today’s natural world is to survive – that the greenhouse emissions budget allows us.

Developing workable IFRs would not be straightforward or quick, even if massive resources were assigned to the task. Since the 1950s nuclear engineers have acquired considerable experience of fast-neutron reactors. Mostly, this experience has been with so-called “fast breeder” reactors, designed to maximise plutonium output for bomb making and reactor fuel, rather than with “burner” reactors like IFRs. But the message is the same for both types: fast-neutron reactors are particularly complex, have a high rate of accidents and breakdowns, and are fiendishly difficult and time consuming to service and repair.

Needing to maintain high neutron energy levels, fast reactors cannot use water as a coolant, since this would slow the neutrons down. The coolant of choice is molten sodium metal. Sodium is highly reactive, burning readily in air and exploding on contact with water. If leaks are not to result in sodium-air fires, the reactor vessel and coolant pipes must be surrounded with inert argon gas, adding to complexity and costs. At a certain point, the sodium coolant must be used for steam generation; here, it is separated from high-pressure water by only a thin barrier of pipe metal, any flaw in which can have drastic consequences.

The sodium that passes through the reactor core becomes highly radioactive. This means that an extra coolant loop must be incorporated, isolating the reactor coolant from the steam-generating equipment so that an explosion cannot disperse radioactive sodium; again, the additional complexity raises capital costs. For various repair and maintenance procedures, the sodium must be drained and the pipes flushed. This has to be done with regard for the radioactivity, while taking care to prevent fires. Even minor malfunctions can result in months of down time.

Sodium fires

Between 1980 and 1997, Russia’s BN-600 fast reactor experienced 27 leaks, 14 of which resulted in sodium fires. Japan’s Monju reactor suffered a major sodium-air fire in 1995, and was still out of action at the end of 2009. The only attempt so far at a commercial-scale fast reactor, the French Superphénix plant, was shut down after a decade in 1996; it had a lifetime capacity factor – that is, actual as compared to designed output – of just 7 per cent.

The development of IFRs, if it goes ahead, will be expensive, difficult and prolonged. Wikipedia predicts a commercialisation date for fourth-generation nuclear plants of 2030. But we cannot wait that long before drastically curtailing greenhouse emissions.

With both third- and fourth-generation nuclear plants outside the time bracket, what is left for environmentalists who hanker after nuclear power? The only option for them is the one embraced by the French and Chinese governments, and now, it seems, by the Obama administration in the US: an accelerated roll-out of second-generation nuclear plants, built to standardised designs following rushed or non-existent consultation with the plants’ future neighbours.

There are no guarantees, however, that major savings of carbon emissions would result. The power-generating operations of nuclear plants emit virtually no greenhouse gases, but other parts of the nuclear cycle – uranium mining, milling and enrichment, and the construction of power plants – are fossil fuel-intensive. Estimates of the all-up carbon footprints of today’s nuclear plants are controversial, but whatever the actual emissions might be, they are considered certain to increase dramatically over time. High-grade deposits of uranium are few, and likely to be quickly exhausted. “If nuclear energy were to be expanded to contribute (say) half of the world’s electricity”, researchers Mark Diesendorf and Peter Christoff calculated in 2006, “high-grade (uranium) reserves would last less than a decade”.

Once these reserves are gone, second- and third-generation nuclear plants will depend for their fuel on low-grade ores some 10-20 times less concentrated than those which now grace the supply picture. The cost in carbon emissions will mount accordingly.

The renewable alternative

The only responsible course for human society is to cut its greenhouse gas emissions through combining stringent energy economies with accelerated roll out of the renewable energy technologies which are available now. These technologies are wind, solar, hydropower, biomass and conventional geothermal. To them may be added several others that are at the demonstration-plant stage, and which concerted development could make fully practical within a few years. In this category are wave and tidal power, and “hot dry rock” geothermal.

Hansen’s argument that renewables can never meet humanity’s demand for energy is contested by a growing list of studies. His view would not carry weight with the group Beyond Zero Emissions, which in February began releasing a program for meeting all of Australia’s stationary energy needs with renewables by 2020. Nor would it impress the Duke University researchers in the US who in March reported that 94 per cent of the electrical energy needs of their state of North Carolina could be met from in-state renewable sources. Equally unmoved would be people from the organisation Desertec, which proposes using low-loss direct current electrical transmission to link solar thermal energy plants in supply grids tracking the sun across and between continents.

A renewably powered future requires a good deal of “thinking outside the square”, along with a willingness to radically re-order social and fiscal priorities. But with renewables, the technologies required are mature, or quickly maturing. The obstacles are not of the same order as those which confront IFR nuclear plants.

If governments and electricity authorities around the world nonetheless swallow the nuclear industry’s lobbying, there is little chance of projections such as Desertec’s ever being realised. Typical prices cited for new nuclear plants in the US are in the region of US$3-5 billion each, and Stanford University’s Mark Jacobson puts the number of plants required for nuclear to meet all the world’s present electricity needs at 17,000. The opportunity costs of building even a fraction of these would surely smother any possibility of financing the parallel development of renewables.

In cases such as this, where spin threatens to outsell substance, influential scientists can play a big role in restoring rationality to government decision-making. Or, if they fail to inform themselves properly before pronouncing on topics outside their core expertise, they can add substantially to the problems.

Hansen is a formidable climatologist, and there is no doubting his intellectual courage. But on nuclear power, he is simply wrong. It would be a tragedy if his errors on this topic were to undo much of his contribution to the fight against global warming.

[Renfrey Clarke is a climate change activist and member of the Socialist Alliance in Adelaide, South Australia.]