We face some major energy policy choices, and a need to move away from
fossil fuels, with nuclear energy and renewables often being presented as
solutions, but also as polar opposites.
Assuming energy demand can be managed appropriately, it seems likely
that renewables can supply all human energy needs. So why is there still
support for nuclear power?
The simple answer is that it is well established with powerful
supporters, and it does deliver energy, about 11% of global electricity, with
relatively low carbon emissions and relatively reliably. These ‘relative’
qualifications are however important in making comparisons with renewables. The
load factors for UK nuclear plants have been rather poor in recent year, around
60%, due in part to unplanned shut downs, so that wind turbines, with load
factors of 30-40%, depending on location, do not look look too bad by
comparison. Higher nuclear load factors
are now more common in the UK and elsewhere, and new plants may be able to get
to 90%, but wind technology is also improving, with offshore load factors being
higher.
Nuclear will no doubt always win on this measure, but the comparison
turns in favour of wind when we look at the embedded energy and the Energy
Return on Energy Invested ratio. It is around 15:1 for nuclear plants and up to
80:1 for wind turbines on good sites: www.routledge.com/books/details/9781849710732/. The figures for wind and other renewables are likely
to improve, while those for nuclear are likely to get worse as reserves of high
grade uranium ore deplete. More energy is then needed to mine and process the
ore to make reactor fuel. Renewables like wind and solar do not need any fuel.
Given that most of the energy used for the nuclear fuel production still comes
from fossil sources (e.g. diesel for strip mining bulldozers and trucks in
remote areas), emissions will rise as ore quality drops. At present carbon
emissions for the nuclear cycle are said to be similar to those for some
renewables (though views differ), but, unless nuclear and/or renewable energy
can be used for fuel processing, they will rise to be much more, with, in any
case, ever diminishing energy returns on energy investment: www.wiseinternational.org/nuclear-energy/studies-reports
The economics of nuclear suffer not just from the need to supply fuel
but also due to the need to deal with wastes, as well as the cost of
maintaining safety and security, problems which are either absent or relatively
small for most renewables. At present, in the UK, on shore wind projects are
going ahead with strike prices much lower than proposed new nuclear projects.
Some PV solar projects are also cheaper and both are likely to be substantially
cheaper in the years ahead as they move down their learning curves. By contrast
nuclear costs appear to be continually rising, with in effect negative learning
curves, at least in the US and France: www.sciencedirect.com/science/article/pii/S0301421513011440
That
may not always be the case everywhere, as was claimed recently: www.sciencedirect.com/science/article/pii/S0301421516300106
Though that study has
been challenged as unrepresentative and flawed: www.sciencedirect.com/science/article/pii/S0301421516301690 www.sciencedirect.com/science/article/pii/S0301421516301549
It may be that new nuclear technology will emerge that improves on this
situation, but that is far from certain. Some want to look again at fast
breeder reactors and the use of molten fluoride/thorium systems, but there are
many unknowns. Certainly early breeder and experimental thorium reactors proved
to have problems: http://thebulletin.org/thorium-wonder-fuel-wasnt7156 . New
technology may limit some of the problems, but the economics are unclear, and,
even if prototypes prove to be viable, commercial-scale projects are likely to
be decades away. Some also look to the idea of developing new types of small
reactors. In the past attempts have been made to improve the economics of
nuclear plants by going for larger scale units, with little success. There
would seem to be no reason why going for smaller scale units would be any more
successful: http://ieer.org/wp/wp-content/uploads/2013/08/SmallModularReactors.RevisedSept2013.pdf www.sciencedirect.com/science/article/pii/S0301421513011440
Fusion remains the ultimate dream. If it can be successfully developed,
it would avoid the fuel resource limits of fission: without breeders, there is
not enough uranium to run fission plants for more than a few decades, depending
on the number of plants in operation. However, despite very large scale
funding, there is some way to go to viable fusion technology, and, although
break-through are always possible, at present it seems that, even if all goes
well with experimental tests, workable commercial-scale fusion reactors will
not be available until the second half of this century.
Moreover, even if it can be developed successfully, fusion may have
limits. Quite apart from the unknown cost, there would be safety and security
issues. Plasma based fusion plants would contain radioactive tritium gas at
very high temperatures, and there is a risk of leaks or even explosive loss of
containment. They may not generate very
long lived radioactive wastes, but activated components would have to be
stripped out regularly and stored somewhere. Fusion reactors are likely to need
lithium, to make tritium, and reserves of that are finite, and are already in
demand for the batteries of electric vehicles. Looking far ahead, it may be
possible to find fuel for fusion plants on the asteroids or elsewhere in the
solar system. That is fortunate since, if we are to engage in extensive
interplanetary travel, we may need fusion energy for propulsion. For the nearer
future however, on earth, fusion seems almost totally irrelevant. Unlike
renewables, which are available now, for the foreseeable future it can make no
contribution to dealing with the urgent problem of climate change.
Why not both?
While that may be true, couldn’t nuclear fission support renewables, at
least in the interim while fusion and/or more renewables are developed longer
term? This seem unlikely on any significant scale for a range of practical
reasons. Nuclear plants are usually run 24/7 to recoup their high capital
costs, although their output can be varied to some extent, so in theory they
might be able to balance the variable output from renewables. In practice however
this would be difficult for the regular short variations associated with
renewables: there are operational and safety constraints limiting nuclear
plants to relative slow, infrequent ramping up and down. Some of them can
follow the slow daily cycles in demand, but they could not balance the rapid
and frequent, minute by minute, variations in wind and solar availability. Basically, they are inflexible. So rather
than complementing renewables, they can play no real role in flexible energy
system that will be needed.
Maintaining costly nuclear plants to provide back up when wind and solar
were low for long periods would clearly not make sense since there are other
much cheaper options for that occasional standby role. Moreover, if there was a
large nuclear element on the grid, then at times of low demand (at night in
summer), its input to the grid would conflict with any renewable energy input
that was available. One or other, or both, would have to give way, dumping
power wastefully. It is conceivable that storage and exports could compensate
for this and that smaller more variable nuclear plants may emerge, possible
feeding waste heat to nearby users, although there would be safety and security
issues with locating mini-nuclear plants in or near cites, as has been proposed.
For the present, the current generation of large inflexible, usually remotely
sited, nuclear plants and widely distributed variable renewables do not fit
well together on the same grid. The two options are not compatible at large
scale.
