Proposals for a new type of nuclear reactor have prompted varied interpretations, not all positive
The nuclear industry has an unfortunate record of making claims that it cannot substantiate – from its original contention in the late 1950s that the technology would provide `power too cheap to meter’.
Professor Carlo Rubbia’s proposal for a reactor that would use thorium rather than uranium as a fuel, initiated by an external neutron source rather than an internal chain reaction, and be able to `destroy’ the most dangerous radioactive waste will strike the cynic as having all the hallmarks of this tradition.
The impression has been reinforced by some of the publicity that has greeted the efforts of Rubbia and his team which has been widely premature and optimistic.
The response of the UK industry which, given its difficulties in recent years might be expected to pounce on any genuine good news, is perhaps more indicative of the true position.
British Nuclear Fuels, the largest producer of radioactive waste in the country, acknowledged that Rubbia’s proposal deserved examination but warned that his system had drawbacks that `might undermine its technical or commercial feasibility’.
A spokesman at British Energy was even more non-committal. `We’re not making any comment on whether or not it’s a good idea, practical or even feasible.’
The proposal has serious backers in the shape of the Spanish nuclear waste company Endesa, Electricite de France and Italy’s Ansaldo. There is also a plan to build a 100MW prototype reactor, probably in Spain, at a cost of around Ecu200m (£140m) within five years.
Much of the technology remains experimental, however, and even if it proves technically feasible there is good reason to be cautious about its future impact on the industry.
A recent assessment by Foratom, the European nuclear forum, drew attention to the uncertainties involved – not least on the engineering front. `One has to demonstrate the industrial feasibility of coupling an accelerator beam (the external energy source) to a reactor. This is not straightforward.’
It also notes that the use of 10,000 tonnes of molten lead as the reactor coolant (the proton beam strikes this to produce fast neutrons for the reaction) would not appeal to any engineer.
Foratom also suggests that the cost of a commercial-scale plant would be around $6bn. `The complete system is not going to generate electricity cheaply.’
But it is the claimed ability of the system to render radioactive waste harmles that has excited most interest – given the turmoil currently surrounding the industry’s plans to bury this lethal legacy of its operations deep underground.
Even if the Rubbia reactor meets all expectations, it will not be a panacea for this most intractable nuclear problem.
Experiments at the Cern particle physics laboratory in Geneva have succeeded in breaking down 1mg samples of the two longest-lived radioactive isotopes in the high-level waste arising from reprocessing – technetium and iodine-129 – into harmless isotopes of the same element.
To apply this on a commercial scale would mean separating the technetium and iodine from the highly radioactive shorter-lived isotopes in reprocessing waste, strontium and caesium – an operation that may not prove feasible on cost or safety grounds. It will also depend on the continued reprocessing spent fuel – by no means a certainty.
The technology would be counter-productive on untreated spent fuel as bombarding its unburnt uranium with neutrons would turn it into plutonium.
And the hundreds of thousands of cubic metres of intermediate-level waste that the industry has stockpiled would have to be separated, concentrated and repackaged before the Rubbia reactor could deal with it – again a proposition of dubious feasibility.
While it would be churlish to dismiss the professor’s initiative at such an early stage, it should be recognised for what it is – a research project that may have a commercial application many years in the future – rather than promoted as the answer to all the problems of a beleaguered industry.
By Andrew Cavenagh