Monday, January 14, 2008

British Thumbs-up to Nuclear.

In fulfillment of our protracted anticipation, the UK government has just released a White Paper which indicates it will go ahead with building "new-nuclear" [1]. The report is lengthly, at 185 pages, as befits such a sensitive matter, and airs arguments from all sides. Not surprisingly, various environmental groups are appalled at the idea, but rarely do they offer sums to support any view that present levels of energy use can be maintained through renewable sources, mainly because they can't. When I began this blog, I hoped to prove that renewables were indeed all we needed, and having been in Russia when the Unit 4 reactor at Chernobyl blew-up on April 26th, 1986 (five days after my birthday as it happens), I also wished to prove we could do without nuclear altogether, on numerous grounds.

I am no longer of either ambition, having since learned about the colossal amounts of energy we do get through as a population of 6.5 billion, mainly in the industrialised nations, and my feeling now is we will need all we can get, from any and every kind of source. The debate over nuclear is not just a question of building "new" reactors, in a programme of proliferation, but replacing the existing generation of reactors which will, bar for one, have reached the end of their ca 40 year projected lifetimes by 2023. One third of existing coal and gas-fired power stations will also need to be closed within this timescale and so just to keep the current number of lights on, will require building a new generation of nuclear and fossil fuelled power plants. Any further substitution of fossil fuel by nuclear will necessitate more new build for nuclear.

Incidentally, I am well aware of the savings in electricity that could be achieved by using energy-efficient light bulbs, which would mean us needing about three less 1 GW power stations, and so energy efficiency should be promoted as well as power generation, ignoring the apparent health hazard from the mercury they contain, as we were warned of by the BBC last week. "If you break an energy efficient bulb indoors, open the window for 15 minutes," the soundbite said, which doesn't sound too serious to me, and I think we should continue to buy them.

It takes around 15 years to put-up a nuclear power station from scratch and so the first one might just be up and running by 2016, which is the date for the first one of the current cohort of nuclear reactors to be mothballed. Nuclear power provides about one fifth of the UK's electricity in total, which constitutes about one fifth of the entire energy used by this nation; hence the total nuclear share of our overall energy is about 4%. An interesting comparison can be drawn with the nearer 36% of total energy that is consumed by the transportation sector, mainly in terms of imported oil.

This brings on a related issue, that of imported nuclear fuel. Nuclear power is often given the credits that it is carbon-free and that it helps to break our reliance on fuel imports, neither of which is entirely true. As the paper notes explicitly, there are huge variations in various estimates of the amount of CO2 generated by a nuclear power station during its lifetime, including fabricating the concrete to construct it, and the uranium fuel, which has been predicted to cause a rise in the amount of overall CO2 as the uranium ore becomes poorer (lower in its uranium content), the uranium enrichment and the fabrication of fuel rods.

As the report noted, separating uranium isotopes by centrifugation rather than by gaseous diffusion is less energy intensive and will hence generate less CO2, and so adjustments in technology will improve the figure overall. There is undoubtedly a considerable CO2 saving incurred in installing nuclear over gas and even more over coal-fired plants, whatever the final figure proves to be, which should help us to met our greenhouse gas emissions targets. On the issue of security of uranium supply, there are geological surveys being carried out to look for uranium supplies indigenous to the UK, but it is thought that imports of uranium are quite stable. The report also alludes to using thorium as a nuclear fuel (our friendly neighbour, Norway has plenty of it) and converting existing stockpiles of enriched uranium and plutonium to nuclear fuel. We have around 51,000 tonnes of uranium and 200 tonnes of plutonium, or something like it, which could keep us going for about 60 years.

Reprocessing is not being considered in the immediate term but instead storage of spent fuel in underground bunkers; neither are fast-breeder reactors part of the initial plan. However, should circumstances so necessitate it, I imagine that the "depleted" uranium could be dug-up again and processed into plutonium in a breeder-reactor programme, where the majority isotope uranium-238 (normally thrown away or made into "depleted uranium" for shells and armaments) is converted into plutonium-239 (by capture of fast-neutrons), which is a fissile nuclear fuel. Reactors that use "mixed-oxide" fuel, i.e. a mixture of uranium oxide and plutonium oxide, are anticipated. If we do end up using thorium, this will also require a breeder programme, in which thorium-232 is converted by capture of slow neutrons, to uranium-233, which is another fissile material.

There does of course remain the inevitable issue of what to do with the nuclear waste finally, but given the energy crunch we are facing in the immediate term, I think nuclear has a valuable place, whatever concerns about radioactive materials and terrorism (should it fall into malicious hands) remain with me, as I suspect they always will. The major energy problem that nuclear does not resolve is, how to keep transportation running? But really nothing can, or not on the present scale of personal transport. At least by maintaining the national grid, electric trains might still be run for essential carriage of goods and services, but much else will fall to the remit of local economies, being far less demanding in well-to-wheels miles.


[1] "A White Paper on Nuclear Power," January 2008, H.M.Government. BERR. www.dti.gov.uk/energy/whitepaper/page39534.html.

5 comments:

Anonymous said...

I wonder how they manage with 40 year old nuclear generators? I was involved in designing & building supertankers for a large oil company, about 30 years ago, and we had superheater tube thicknesses of (I think) 4mm, for steam at 60 bar and 600C. We found from experience that the superheater bends eroded after about 10-12 years, so we insisted on boiler manufacturers using 5mm bends, which prolonged things a lot. In any case our whole-life costing calculations included allowing for renewal of tubes after 12 years. My questions are, how long do nuclear superheater tubes last, what are the whole-life renewal assumptions? Why, for instance, in the French programme, with very many very old sets, we do not hear of tube failures?

energybalance said...

We hear a lot about "boiler problems" which have caused the shutting-down of some nuclear reactors during the past few years. Probably these are of the type you allude too.

The French seem to have a very mature nuclear industry, which provides about 80% of their electricity. Maybe they don't push the technology to breaking point. I wonder what the situation is in other parts of the world, e.g. some of the FSU countries?

My understanding is that in the hottest part of the system the tubes are changed after about 15 years but in cooler regions they can last for about 30 years.

So for nuclear the lifetime of the tubes looks to be comparable with those from your own experience.

Regards,

Chris.

energybalance said...

We hear a lot about "boiler problems" which have caused the shutting-down of some nuclear reactors during the past few years. Probably these are of the type you allude too.

The French seem to have a very mature nuclear industry, which provides about 80% of their electricity. Maybe they don't push the technology to breaking point. I wonder what the situation is in other parts of the world, e.g. some of the FSU countries?

My understanding is that in the hottest part of the system the tubes are changed after about 15 years but in cooler regions they can last for about 30 years.

So for nuclear the lifetime of the tubes looks to be comparable with those from your own experience.

Regards,

Chris.

optimader said...

unrelated but intersting
http://news-service.stanford.edu/news/20...

Anonymous said...

Nuclear energy can power transportation, too. Powering ships is quite easy, it has been done before (submarines, aircraft carriers and ice breakers), all that's needed is the commitment to develop and build these smallish (tens of megawatts instead of a thousand) reactors.

Nuclear powered trains and light rail are also available and in use all over France. Okay, technically they are powered by electricity, but that comes from nuclear power plants.

As for personal transportation (read: cars), electricity might cut it for short commutes, but for longer travel you want some sort of chemical fuel. The debate which synthetic fuel is to be used isn't settled, but any number of them can easily be produced from nuclear power.

So please, do not repeat the wrong mantra that nuclear cannot power transportation, okay?