Generation IV: A Hint Of Déjà Vu?

by Bertrand Barré, ENS President-Elect

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Back To The Future

Since 1999, a dynamic multinational¹ effort has been launched to delineate the features of the proposed ‘Generation IV’ reactors, to be put in operation after 2030, and to identify the R&D to conduct in order to make them possible. The Generation IV International Forum, GIF, has focused on six concepts, considered to be the most promising among the 100+ initially considered. This endeavour has attracted a great deal of interest throughout the world, but some critics point out that these concepts are not really ‘new’, and that they are more revisited than invented. Are we going ‘back to the future?’

To answer this question, let us look at the ‘natural history’ of the nuclear reactor, considered as ‘a living species’, and starting not from Oklo² (a bit too far away), but from the first man-made sustained chain reaction on 2 December 1942.

Natural History Of The Nuclear Reactor

The fifties and sixties, following on from the famous ‘Atoms for Peace’ speech whose jubilee we celebrate this year, heralded – mostly in the United States – an era of unbridled creativity, of vital luxuriance we can hardly imagine today. All possible reactors, and again some more, were dreamt of, designed and often built, and most of them were actually operated! Just about all conceivable combinations of fissile and fertile materials and moderators and coolants were tried, in facilities of which the scale was, admittedly, moderate and the safety not up to modern standards. Let us say that respect for the environment was relative.

But all these ‘devices’ did operate, albeit for a few days, and without major accident - with the exception of SL1. Uranium, thorium, plutonium, metals, oxides, carbides or more exotic compounds, air and various gases, light and heavy water, graphite, beryllium, rods, pins, needles, particles, suspensions, fluidised beds, liquid metals and molten salts - everything was tried at least once between 1945 and 1965. And this does include all the Generation IV concepts, at least on paper. As an illustration of this luxuriance, at the Idaho Falls Center alone, more than 50 reactors were built between 1949 and 1974 and none of them was identical! If you add to this the prototypes of Brookhaven, Oak Ridge, Hanford, Savannah River and Los Alamos, you can almost double the figure.

And then, as in the natural history of species, this creative fervour was followed by a selection, which led to the survival of a small number of reactor systems, as illustrated in Figure 1.

Figure 1: World Nuclear Power Plants, 31/12/2001
(Total: 356 GWe)

Various mechanisms led to such a drastic selection and these were helped by the very specific conditions of this ‘pioneer’ (some would say: ‘cowboy’) era, during which the delays were so short from first concept to first concrete that the succession of generations was very fast-paced indeed.

Many branches of the evolutionary phylum did terminate abruptly, sometimes for diriment technical reasons, such as the swelling of graphite by sodium impregnation which killed Hallam, or the bulk of shielding which would have prevented the nuclear powered aircraft from taking off. Safety played its role: the Windscale fire led graphite reactors to forego air cooling, and nobody will order a new RBMK after the Chernobyl accident.

Some models were simply too complex, and, though quite viable, were overtaken by the competitors, like the French Brennilis EL4. For a couple of years, the competition between Molten Salt and Liquid Metal was very heated, and the latter may have won mostly because of the sheer willpower of its proponents. Some designs were simply unlucky, introduced with bad timing: the first series of 8 High Temperature Reactors ordered in the USA disappeared along with a hundred LWRs during the rash of cancellations which affected the whole utility industry after the 1974 oil crisis.³ Sometimes, economic factors were involved, but seen in retrospect, the comparisons of the time appear laughable.

There were also positive forces which boosted some of the designs. First, the technological evolution: without enrichment, there would not be any LWR, and no breeder without reprocessing. Not having to depend on the US monopoly on enrichment was a key factor of success for natural uranium-fuelled reactors, as long as this monopoly lasted. The success of the nuclear-powered US submarines (and the personality of Admiral Rickhover) gave a strong, initial competitive advantage to the PWR versus its BWR cousin, and the overwhelming power of the American industry in the sixties did a lot to spread the LWR technology around the world outside the Soviet Union.

The results are tangible: with 87% of the installed power, the various LWRs occupy the ‘biotope’, leaving a small niche to HWRs, while GCRs and RBMKs, once dominant, are slowly decaying.

Is There Life After The LWR?

When a species completely dominates its biotope, it leaves potential competitors with little chance of coming to the fore. When dinosaurs ruled the earth, mammals had no option but to stay put, until changes in the environment gave them the opportunity to move in. When the automobile was developed at the end of the 19th century, it experienced the same vital luxuriance we have witnessed in nuclear reactors, and the internal combustion engine did not immediately establish its present primacy. The first car to break the 100-km/h barrier, in 1899, was the ‘Jamais Contente’, an electric car, and in 1906, the record speed of 196-km/h was held by a car powered by a steam engine.

Nowadays, steam-powered cars have been forgotten, and electric cars occupy a very small niche. It is even funny to consider that internal combustion engines share their market supremacy between two cousin technologies, explosion and diesel, as do the LWRs between the pressurised and the boiling varieties.

But evolving environmental conditions are now challenging the all-potent internal engine: concerns about urban pollution today and greenhouse gases tomorrow will probably give the electric car a new chance, possibly as a combined hydrogen-electric device. Similarly, some nuclear designs which did not pass the selection, because their specific qualities were not critical according to the criteria of the ‘70s and ‘80s, may find a second chance in today's environment. Let us take two examples from the GIF concepts, shown in Figures 2-7.

Figures 2-7: The 6 GenIV Families

LWRs are sturdy, reliable, economically competitive in many country, and they can operate much more flexibly than was originally thought. EPR, SWR, AP1000 and ABWR are ready to assume overwhelming dominance of the Generation III about to start. Even the latest Candu is now partly LWR! But they have some weaknesses, which did not hamper their success: their thermal efficiency is mediocre, they make rather poor use of fertile materials, their excellent safety relies on sophisticated systems – and sophisticated operators. Up to now, their only use has been ship propulsion and electric power generation.

If nuclear energy is to supply a share of the world's primary energy which is significantly larger than the present 6 or 7%, uranium availability and price will become a concern, and all four breeder systems will attract renewed interest.⁴ If nuclear energy is to help to significantly reduce greenhouse gases emissions, then generating hydrogen in addition to electricity might prove very valuable and could make the VHTR quite attractive.

Conclusion

Nuclear technology is young. Hardly 50 years have elapsed since Queen Elisabeth II inaugurated Calder Hall and the Nautilus completed its undersea cruise around the earth. Its future is very open, and could follow many routes. Yes, there is a hint of déjà vu in the designs selected by the GIF, but they appear promising and well worth revisiting.

Notes

¹ The 10 partners are the USA, which initiated the project, Argentina, Brazil, Canada, France, Japan, Korea, South Africa, Switzerland and the UK, with the Nuclear Energy Agency acting as secretariat for the GIF.

² Slightly less than two billion years ago, the natural enrichment of ²³⁵U was above 3%. In one location in Gabon, where uranium was highly concentrated deep underground in the presence of water, several genuine natural nuclear reactors went critical and ‘operated’ for many thousands of years. This fascinating ‘Oklo phenomenon’ was discovered in 1972.

³ Contrary to popular belief, it is the first oil crisis which maimed the US nuclear industry, but the 1979 TMI-2 accident did nothing to help the recovery.

⁴ In 1976, when SUPERPHENIX was ordered, it was expected – or feared – that the total installed nuclear capacity would reach 1800 GWe by the year 2000. If such had been the case, most reactors on order today would be breeders!