The Morality of Energy Efficiency

 In the ongoing debate on the future of the UK’s energy supplies the idea of energy efficiency and its implementation is often framed in moral, as well as economic, terms. The idea being that since there are inherent externalities in energy consumption, such as land use and various types of pollution, that result from the production of energy and its consumption that energy should be used far more sparingly than simple economic analysis should allow.

This argument holds well for most fossil fuels that tend to produce large quantities of pollutants in the form of carbon dioxide, nitrogen oxides and particulates; It even holds relatively well for renewable energy sources such as solar power and wind turbines that have a large aesthetic and land use impact even if they do not produce large quantities of greenhouse gases directly.

However there is a form of energy production that has far lower externalities than almost any other – that being nuclear fission.

The externalities of nuclear power

A nuclear power station is a surprisingly compact machine – it uses relatively little concrete and steel in its manufacture considering its enormous energy production, is physically small compared to other generation systems such as wind turbines and consumes relatively little land compared to systems such as biomass generators and solar panels.

Waste

Waste that is produced can be stored extremely compactly for long periods in various dry storage systems such as the Modular Vault Dry Store concept – an operational unit at the Pacs pressurised water reactor plant in Hungary is pictured. Other, similar, units have also experienced decades of service at the Wylfa Magnox plant in Wales and at the Torness AGR plant in Scotland - the former actually being loaded with fuel directly from the reactor.

MVDS store at Pacs NPS in Hungary

Despite numerous attempts it seems unlikely that reprocessing of relatively young spent fuel will ever be economic, the cheapest solution simply being to store the fuel for at least one hundred years before making any attempt to permanently dispose of it by any of the available methods. The drastically lower heat generation [~75% cut between 10 years and 100 years of aging] of such aged fuel significantly reduces the cost of either reprocessing or deep geological disposal due to higher allowable fuel densities in the final repository.

Storage in a dry facility has been estimated based on previous experience in Japan to be as low as $0.80/kgHM per year.[1]

Whilst people may remark that long term storage is simply transferring the cost of dealing with the waste into the future it could be argued that if an investment fund is established to cover the ongoing costs of storage and of final disposal then there is no real externality – the cost has been internalised.

It seems likely that $800/kgHM is sufficient, even if reprocessing century old waste is not significantly cheaper than decade old waste the storage could continue for an entire millennium – assuming the management of the fund kept pace with inflation, which is historically conservative. After 1000 years the fuel would have a surface radiation dose below those known to cause health effects even with prolonged contact with the assembly.[2]

Considering that an ESBWR might expect to produce nearly 420MWh of electricity from a single kilogramme of fuel. [3] It is also the case that advances in technology over the next century or more could drastically change the economics of reprocessing and as such it would be beneficial to ensure the fuel is easily accessible.

Land use

A nuclear power station is an incredibly compact machine – for example the Gravelines nuclear power station in France covers an area of less than one square kilometre and produced nearly 35TWh in 2014 [4]. That is 35 times more than the total insolation [assuming every joule that reached the ground was collected] of a typical square kilometre of the United Kingdom, and it could be expected that this power intensity would improve with the development of newer, more compact reactors such as the ESBWR. Indeed using a more reasonable set of assumptions for the solar option would increase the factor of advantage to something approaching 200.

Waste storage does however consume land, however it does so in very small quantities – it could be estimated that if the entire current energy supply in the UK was provided in the form of nuclear generated electricity that it would take a hundred years for dry storage casks to fill one of the runway aprons at Heathrow.

If the average Briton was to use electricity as prodigiously as the average Quebecois (the highest use region in the world by some margin]) and consume 20MWh per year [5] then the entire population of the UK [using 1.2 Petawatt hours per year] could be supported by nuclear plants covering less than 35km² – less than three times the area of Heathrow Airport and negligible in comparison with the size of other energy infrastructure.

Uranium mining

The other great externality associated with modern nuclear power technology is that of uranium mining – which certainly generates the greatest ecological impacts of the entire fuel cycle. However the amount of material removed from mines is relatively small and new emergent technologies such as ‘In-situ Leach’ and the fabled uranium extraction from seawater seem likely to further reduce this.

Utilising fairly conservative assumptions and optimising in an attempt to conserve uranium the kilogramme of fuel mentioned above (producing 420MWh-electric) would require enrichment to 4.2% ²³⁵U and consume roughly seven kilogrammes of natural uranium in its production.

That implies that the Quebec style ‘electric economy’ mentioned above would consume roughly 20,000t of natural uranium per year. This is a large quantity – however its production does not have a large impact on the environment compared to other power generation arrangements.

MacArthur River Uranium mine in Sasketchewan

 For example, the MacArthur River Uranium mine in Sasketchewan, Canada produces 8500t of uranium per year and covers a very small area of land due to its use of subservice mining techniques. It also represents a form of uranium deposit that is exceedingly rich and was totally unknown prior to the discovery of the resource. This bodes well for future searches for uranium.

Additionally, ‘In-Situ Leach’ is a technology that uses scattered wellheads to inject fluids into a uranium deposit and extract a liquor containing a soluble uranium salt – this avoids the need to disturb the land at all beyond that necessary to dig the requisite boreholes. This technology is used extensively in Kazakhstan and Australia and is now responsible for a large fraction of world production.

Finally there is the often attempted process of extracting uranium from seawater – which promises negligible environmental impacts, even by the high standards of the relatively no invasive ISL production scheme. Whilst it is not currently economic it is believed feasible at a price of only $660/kgU [6], which would add less than a US cent to the price of a unit of electricity and this is almost certain to fall with further technological improvements.

Conclusion

In summary, nuclear power has no significant externalities that cannot be easily and affordably priced in to the cost of the generated electricity. Thefore there is little reason not to encourage as much electricity to be consumed as possible as long as it is sold at the price for which the electricity can be generated. There is no moral reason to restrict electricity consumption beyond the reasons offered by simple economics.

Of course the question becomes - just how cheaply can you generate nuclear electricity and what sort of things can you do with an unlimited supply of cheap electricity providing you can provide it? I will investigate this in another blog post(s) at a later date

References

[1] 'Interim storage of spent nuclear fuel' Harvard University Press, 2001. [$60/kgHM, estimate of 75-100 year lifespan and negligible operating costs].
[2] Canadian Nuclear Waste Management Organisation - document TR-2012-16
[3] 50 Gigawatt-days/tonne (thermal) @ 35% efficiency yields 420MWh-electric/kg
[4] IAEA Reactor database 'PRIS'
[5] "Fragmented Markets: Canadian Energy Sectors under performance" - Pierre-Olivier Pineau, 2013
[6] New Scientist, 22/08/12