Sunday, March 8, 2009

Nuclear vs. wind

How to make nuclear power even more risky- and kill off wind power

Nuclear plants can’t easily vary their output and are usually run flat out 24/7, which, given that they are very capital intensive, also helps their economics. However this means they can’t be used to back-up variable renewables like wind. Moreover, if we have a lot of nuclear capacity, as is now planned, there would be less room for electricity generated from wind farms , at least during low energy demand periods. For example the UK’s baseload, the low level of energy generation capacity required at night and at other low demand periods, is 20GW, and there is talk of nuclear being expanded to provide much if not all of this. At present it’s only at about10GW. And yet there are also proposals for 25GW of wind power. In the absence of significant storage capacity or export potential, much of this would therefore be in excess of requirements. We only have about 2GW of pumped storage capacity and a 2 GW in cross channel grid links.

In its 2008 consultation document on its renewable energy strategy, the UK government admitted that the UK nuclear fleet was ‘designed to run continuously and is not well suited to short-term response to shifts in the supply-demand balance, for safety as well as economic reasons’. So it says ‘when wind speeds are high and demand is low, for example during the summer or overnight... the system may not be able to absorb all of the output of both wind and nuclear generating plants’

However, they say that ‘nuclear plants can be designed to run flexibly and this has been shown to operate effectively in practice by the experience of the Flamanville 3 plant in France. We therefore believe that the expectation of a greater penetration of intermittent generation is not in itself a barrier to the deployment of new nuclear capacity’.

Unfortunately, they seem to have it wrong. Flamanville 3 hasn’t actually been built yet. Indeed construction work on it was recently stopped when the nuclear inspectorate found faults in the concrete mix being used. Leaving this hiccup
aside, it is true that some of France’s existing plants can and do load follow- the Pressurised Water reactors they use are more capable of that than the UK’s gas cooled reactors. We could presumably build similarly variable plants in the UK.

Sinclair Knight Merz (SKM) consultants, in a report to BERR, agreed. Although they admit that ‘increased amounts of nuclear plant in a system with high penetration of wind would invariably result in higher curtailment,’ they suggest that wind curtailment can be limited by using variable nuclear plants. They report claims that the Flamanville plant should be able to run down to 25% of output. However they add that, while the potential for flexible operation ‘are considerable, it does not necessarily mean that it will be regularly operated in such mode, as other considerations such as life reduction and safety may discourage full use of this capability’

Basically reactors don’t like being cycled through large temperature ranges regularly and running up and down to full power also creates short-lived radioactive by-products which can disrupt efficient operation. These operational problems may well be worsened by the fact that the new reactor designs now being developed seek to increase the fuel burn up ratios- in order to improve the economics of the plants.

However, in addition to the fact that the spent fuel will be much more radioactive since more fission products will be produced, this approach may also involve safety problems related to plant operation - existing fuel cladding materials may not maintain their integrity over the longer period, especially in emergency shut down situations.

New reactor technology is clearly being developed which may make it possible to run nuclear plants in ways which make them more compatible with variable renewables like wind. But this introduces new risks. The issue that arises then is whether we should be relying on potentially risky adjustments nuclear technology to avoid wasting wind energy? As wind expands and other variable renewables are added to the mix, including wave and tidal power, the need to curtail nuclear, so as to make way, will grow. Unless that is, we decide to keep nuclear running at full power and dump increasing amounts of renewable power at low demand times. Or invest in energy storage which is an expensive option.

This crazy competition between sensible sustainable energy options and the dead end option of nuclear power is what we’ve come to expect from the capitalist system, which is obsessed with shoring up the large companies that it has created. Most of the running in the UK will be made by the French company EDF, which now owns British Energy and will presumably build French EPR reactors here. But not take the waste they produce! Just the profits. While seeing off wind power…. and introducing extra risks. Business as usual it seems.