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Energy: a nuclear surprise?

Energy: a nuclear surprise?

Trade journals are increasingly filling with articles which read something as follows: global warming - CO2 - renewables - capital expenditure and costs - reliability - oh dear! - but how about nuclear power?

Hydrogen and nuclear power

This trend is particularly evident in Britain, where the secretary of state responsible for energy and industry policy announced that the UK was to build vast, expensive offshore wind farms. We have already decided to decommission many nuclear plants, and there are no plans to build new ones. This despite over a quarter of our electricity coming from these flawlessly operating, cheap plant, our gas fields coming to the ends of their lives and coal looking an unhappy options. There may be a "coal surprise", as the possibility of the 'zero emission' plant looks technically and economically feasible. However, the chances of a nuclear astonishment seem much higher.

Paul Grant of EPRI has just written about the "hydrogen economy", focusing on vehicle needs in the US. Many companies are involved in the equivalent FreedomFuel program. He notes that the US uses 12 mbd oil for vehicle fuels, which is equivalent to 3 mbd at fuel cell, full-train efficiencies, which he estimates at 64%. That translates into around quarter of a million tonnes of hydrogen per day, which would require a capability to deliver a permanently available 400 GW of electricity generation capacity.

Ignoring duty cycles, this requires 800 x 0.5 GW of CCGT capacity, or 200 Hoover dams, or 100 nuclear clusters of 4 x 1 GW. New installed capacity costs around USD 0.8-1.5 million per MW, so the investment to produce this would come in at something around 250-600 billion dollars, with maintenance charges of 30-90 billion annually. In fact, duty cycles would push this sum rather higher.

There are, however, two reasons to contemplate doing this. One is supply independence. The other is environmental, breaking into the two separate subjects of CO2 release and focused urban pollution. Concentrating on the CO2 argument only, the project has to generate the electricity for the hydrogen with no net release of it, implying sequestration or a non-carbon process. To get the required electricity with the likely duty cycles of sun and wind power would require 130,000 square kilometres for wind and 20,000 square kilometres for sun - half of New York state, or half of Denmark, respectively. Biomass would take an area the size of Nevada, were marginal land in the US to be as productive as its current farm land. It is not.

Investment costs would be very much higher than those for conventional power, as would maintenance; but set against this is the free nature of the motive fuel. Most guess that the all-in cost of this class of renewable installed on a massive scale and with state-mandated land acquisition prices would be 3-4 times that of CCGT best practice at present-day gas prices.

What is the answer to this conundrum, save a completely new technology? I have written about some of these, ranging from new fuels such as sea bed hydrates to new technologies, such as third generation fusion based on accelerator technologies, or ocean-thermal driven Aluminium or Magnesium fuel cycles. All of these are unproven, and represent triumphs of hope over experience.

However, there is a perfectly good, cheap and proven technology available right now, with a defined fuel supply that will meet foreseeable needs for at least a century: nuclear fission. The ultra-safe HTGR pebble bed technology is officially estimated to deliver all-in costs of 3.4 c / kwh, versus the very best US CCGT at 3.8-4.2 c / kwh. The entire net waste production of the US in the history of its nuclear industry would fit in a few London buses. The issues of vitrification and storage in geologically-stable structures has been studied and studied again.

This is not to minimize the issues that are involved. The question of fuel security and weapons proliferation need to be managed, but technologies exist that already go a great way to solving this. Nevertheless, the case for a nuclear re-think, and perhaps a revival, are compelling to all but the most knee-jerk activist.

The costs of emission control

Emission control comes at a price. Hydrogen would remove many emissions (although it would itself leak, with affects already discussed.) It would, however, cost around US$1 million to eliminate one tonne of NOx emission through this route, versus EPA's more conventional scheme which costs US$2000/tonne, its inspection program US$4000/tonne and even its withdrawal program, in which it buys old vehicles, would cost US$10,000/tonne.

However, readers may think that NOx is a poor guide: what of carbon? The cost of capturing CO2 from conventional electricity plants is estimated to add around 30% to the cost of electricity. Schemes such as the revolutionary mineral absorption system that I discussed some weeks ago are likely to be far cheaper. How much would it cost to eliminate emissions of carbon that are equivalent to those from the vehicle fleet?

Vehicle emissions are equivalent to half the emissions of carbon from US power plants. (Cars 10%, other transport 14%, electricity 41%, rest 35%.) It can be shown that reducing the vehicle component directly through a hydrogen infrastructure is unlikely to cost less that US$1000/ tonne. BY contrast, cutting equivalent emissions from existing power plants would cost US$75-150/tonne.

On its own, this is not persuasive. If one is serious about CO2 abatement, why not cut both? However, the US National Academy of Sciences suggested that current technology could cut vehicle emissions from conventionally-fuelled and -engined cars by up to 40%. It could do this without increasing the vehicle's cost. It might even make it cheaper.

Less conventional vehicles - hybrids which, for example, use a low power sterling engine or a mini-turbine and an on-board momentum storage system - have been extensively investigated by GM and Rolls Royce. The resulting design was light, cheap to maintain and - due to the elimination of the power train and all but four major bearings, extremely efficient. Emissions could be significantly better than the USNAS estimate.

The issue is, therefore, whether Hydrogen is the fuel of the future, or the far future. It is clear that the economics point to a range of easy early winners, and a migration path that could ultimately end up with hydrogen as the primary energy intermediate. However, this choice will be made when science will have advanced very substantially. There are very striking things happening both in energy engineering and in fundamental physics that would suggest to me, at least, that there may be new bets to place in a few decades. Further, it seems likely that social changes are going to have a major impact. The US policy to town planning - termed "access", but elsewhere called "densification" - must have a profound impact. When work, home, shopping, entertainment and schooling are either co-located or served by re-thought public transit, just in time micro-retailing and sub-surface automated delivery systems, one is in a new world. It may be the world of the dream for third world conurbations, but it need not be. There are "appropriate technology" approached to all of these issues which appear to be cheaper to install and to run than is random sprawl. .

Nuclear futures

Marvin Schaffer, writing in Foresight (Vol 5 #3 2003) discusses nuclear power in a refreshingly novel way. For example, nuclear power is considered an energy source driving hydrocarbon reforming, desalinisation and electricity generation alone or in combination.

He focuses on the high temperature gas reactor (HTGR) in its pebble-bed modular form. To dispense quickly with the technology, the "pebble-bed" consists of small (0.5 mm) Uranium oxide pellets, embedded in graphite and shelled by silicon carbide. The carbon in the graphite is the neutron moderator for the reactor. A proportion of pellets do not contain Uranium and these moderate the reaction. The pellet heap is blown with Helium, which carries away heat, and the pellets are turned over continuously. Each pellet is scrutinised separately as the reactor "heap" turns over and defective or discharged pellets are removed from the stream. If the gas flow ceases, the reactor temperature rises to a stable level over a two day period, during which many measures can be taken to stabilise the system. There are many other unique safety features, not least those relating to the safety of the waste and the impossibility of weaponising the fuel.

Costs - including decommissioning - have been assessed by the US Committee on Energy Awareness and the following comparison is striking:

CCGT cents per kWh 3.8-4.2 (current US gas prices)
Current nuclear 3.6-3.8
HTGR 3.4

Build times and footprint for a 1GW plant are comparable to CCGT.

Desalination

Integrated nuclear desalination plants are already in operation in Japan and Kazakhstan, with around a reactor-century of experience. Eight countries have such projects in train, each costing US$200-300m. Water so produced will cost around US$1-1.3 per tonne, comparable with Middle-Eastern urban purified river water, but expensive when compared to Gulf oil charges to current hydrocarbon-driven desalination systems. As the Middle East will have exhausted its fossil water sources within the decade, and as its rivers are already under dispute, the potential for desalination will grow. Carbon emission issues may well tip the balance to nuclear, or perhaps to solar solutions, which cost roughly the same to install and manage.

Steam reforming

The IAEA sees nuclear-powered steam reforming of methane as a primary potential source of hydrogen. Carbon is easily sequestered from such processes, or can be transformed into methanol through further use of energy from a nuclear source. The Japan Energy Research Institute intend to bring a pilot on stream in 2005. Germany and China also have projects with this in mind.

Integrated schemes

A fully-integrated scheme, aimed at the gas-rich countries of the Middle East, uses a HTGR to run a cascaded system, with the high grade heat being used to synthesise methanol, and the waste from this used successively to generate electricity and to desalinate water. A 1.5-2 GW system would generate power to support a city of 3.5 million, a million tonnes per day of fresh water and around 50 tonnes of hydrogen (or of course proportionately more methanol.) However embodied, the fuel would allow around 0.6 million car-miles per day, less than a total solution but nevertheless helpful. Alternative configurations could use the energy in different ways, including gas-station electrolysis and the like.

Security

Considerations of risk have been so heavily built into modern nuclear systems that political controls are of more concern than issues of technical safety or waste disposal. However safe a nuclear system may be, it remains the case that if the owners of it choose to extract irradiated fuel from it, they can make a dirty bomb. Equally, a major pharmaceuticals research laboratory can be subverted and weaponised, or a chemical plant. The issue is one of political stability, transparency and, ultimately, deterrence.

Public attitudes.

Nuclear power is linked in the public mind with the nuclear bomb. Plainly, therefore, the involvement of outside interests in nuclear-based schemes in must wait on local political credibility. This is not to say that nations such as Britain (currently highly dependent on nuclear power, but apparently planning to fill the gap with wind power, or political hot air) will not choose to revive their once-vibrant nuclear industry.

Nuclear power has been the victim of its own early public relations success. It was trumpeted as the face of modernity after WW II. General Atomic, the once sister of General Electric (now GE) spent enormous sums publicising medical possibilities, flying reactors and the like. Then came the cold war, bomb testing and fear of fall-out; and the two ideas became linked in the public mind as an icon of a particular kind of offensive modernity. The USSR spent a great deal on promoting anti-nuclear sentiment during the 1955-75 period, apparently believing that it was paralysing the West by denying it access to a critical economic tool. The terror of the pervasive, invisible threat was given a (literal) concrete face. An activist culture has become established, just as a similar one has since grown around other large civil projects such as dams and highway construction. Despite an extraordinary record of safety, the critics of the industry have managed to suggest that Homer Simpson, and behind him, Mr Burns, are in charge. Chernobyl showed us what happened when this proved to be a fact.

It should be remembered, however, that the consumer antipathy to nuclear power is confined to specific but vocal cadres in particular rich nations, and is far from a universal fact. These nations have anyway operated under a plethora of options, where choices about energy sources were dictated by economics and convenience. Options are now narrowing, and the luxury of deliberate inefficiency or the choice to pollute without consequence are no longer open. Despite the many difficulties that the nuclear industry faces, therefore, it may well be possible to see a new role for it in the future.

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