Nuclear fission is a form of low-carbon energy which has a resource life sufficiently long to be for all practical purposes considered sustainable. Any country adopting nuclear power can be confident that adequate supplies of uranium fuel will be available to power any reactors it may install.
Is Uranium a sustainable resource?
While it’s too early to fully assess the health and safety impact of the combined calamity of earthquake, tsunami and nuclear emergency in Fukushima, Japan recently or, indeed, its implications for public attitudes, the incident has refocused debate on all aspects of nuclear energy, including its sustainability.
In a post-Fukushima world, Tom O’Flaherty looks at questions surrounding the long-term availability of uranium and argues that nuclear energy derived from uranium supplies will be sustainable long into the future.
It is still too early to say with confidence how this prospective development will be affected by the events at Fukushima.
It is possible that a moratorium of several years will occur in the building of new nuclear plants throughout the world, with many countries deciding to reject nuclear power indefinitely.
It is equally possible that, after a relatively brief period of re-appraisal of safety issues, with particular emphasis on locating in or near earthquake zones, most of the countries that have nuclear power programmes will proceed with them, more or less, as originally planned.
In the latter case, or even if programmes only gather momentum again after a significant delay, the question will arise as to whether supplies of the raw material of nuclear fuel, uranium, will be sufficient to supply an expanding nuclear power industry into the indefinite future.
After peak oil, ‘peak’ uranium?
According to the latest (2010) joint survey of uranium resources by the OECD’s Nuclear Energy Agency and the International Atomic Energy Agency, identified resources amount to 6.3m tonnes. The same source indicates that current annual consumption of uranium by operating reactors is in the region of 59,000 tonnes.
So, by simple calculation, at present consumption rates, the identified reserves would last in the region of 100 years. What is not so simply established is, on the one hand, how much the consumption rate will increase if use of nuclear power expands over coming decades, especially in India and China, and, on the other hand, what amount of further uranium reserves will be discovered as exploration is intensified, under the stimulus of an anticipated rise in price.
Should expansion resume more or less as anticipated pre-Fukushima, it can be envisaged that, over a few decades, the number of operating reactors might increase from the present 440 to possibly 1,500.
These are likely, on average, to be of higher ratings than the existing fleet, but this may be counterbalanced by the somewhat higher efficiencies likely to be achieved by the newer units. It seems reasonable, therefore, to assume that the annual consumption of uranium will increase more or less pro rata with the number of reactors, i.e., by a factor of three or four. If no further uranium resources were to be discovered, this clearly would foreshorten severely the working life of uranium fission reactors.
So, the focus very much turns to the exploration scenario. In this regard, it has to be borne in mind that between the early 1980s and about 2003, uranium exploration virtually ceased. This was due to a slump in price, caused by a combination of stagnant demand and the effect on the market of uranium released from weapons decommissioning. While very recent years have seen a rise in the price of uranium and a corresponding revival of exploration activity, it is still too early to permit any precise estimate of the total reserves that will be recoverable at an economic cost.
The joint Nuclear Energy Agency/International Atomic Energy Agency survey quoted earlier estimates that resources still to be discovered could amount to some 10m tonnes. Taking this figure, in conjunction with the estimated increase in consumption indicated above, yields the conclusion that some 75 to 100 years would be the outer limit of the life of the planet’s uranium reserves, were consumption of uranium, using Generation 3 reactors, to continue unrestrained until reserves are exhausted. Instead, it can be expected that this progression will be interrupted by the introduction to commercial use, at some point in the coming decades, of Generation 4, fast-breeder, reactor technology.
With this technology, the physics of the nuclear chain reaction is such that, from an initial charge of uranium, the reactor can ‘breed’ its own fuel. In net effect, the efficiency of conversion to energy of the original uranium is of the order of 50 times greater than that achievable by the familiar thermal-neutron fission process of Generation 3.
The life of proven and estimated uranium reserves is, therefore, increased from tens, to many hundreds, if not thousands, of years – a scenario that can surely be deemed sustainable, by any reasonable yardstick.
The crucial issue, which at this point is difficult to predict, is when exactly Generation 4 reactors will come into commercial use. The considerations surrounding this are:
• the time needed to bring a reactor of this type to full commerciality;
• which of a number of alternative reactor designs will prove most successful;
• how much this type of reactor will cost; and,
• what rate of depletion of uranium resources results from the expanding deployment of Generation 3 reactors over the next couple of decades.
This is a scenario which can only play itself out over time, and is clearly going to be influenced by the post-Fukushima perception of the safety of nuclear power.
What is broadly foreseeable is that, by mid-century, at least one design of fast-breeder Generation 4 reactors will have come into common commercial use and that several such units will be operating side-by-side with the many hundreds of Generation 3 reactors that will continue to be built between now and, perhaps, 2040. From about then onwards, it can be expected that all new reactors to be constructed will be of Generation 4 type.
As far as adequacy of uranium resources is concerned, this deployment of Generation 4 reactors could continue without difficulty for several centuries.
Dr Tom O’Flaherty Chartered Engineer, FIEI, FIET, is the former CEO of the Radiological Protection Institute of Ireland. He is currently the Irish member of the Scientific and Technical Committee of Euratom, and a member of the committee of the Energy and Environment Division of Engineers Ireland. He is also a member of the voluntary group BENE (Better Environment with Nuclear Energy), which supports the view that nuclear power has a contribution to make to Ireland’s future energy needs. The author is grateful to Frank Turvey Chartered Engineer, FIEI, for reviewing the first draft of this article.