Fourth generation nuclear power may not be the clean energy silver bullet UPDATED

New models for nuclear reactors have been attracting a lot of interest recently, with all sorts of ideas touted as the solution to the problems of the standard designs in use today.

The huge cost, and delays and budget over-runs in construction, of third generation reactors such as Areva’s EPR, along with concerns about their safety, has inspired a search for new smaller designs, including some that are only the size of a garden shed.

There is also renewed excitement over fourth-generation reactor technology that can use spent uranium fuel as its feed-stock.

Bill Gates has been advocating one version of that technology, the “travelling wave reactor”, and has invested in a company developing it.

The promise is great: cheap power without the waste problems that have still not yet been solved. Gates says we need an “energy miracle”, and fourth generation nuclear power is it. But there are also some nuclear experts who warn that the promise is a snare and a delusion.

The International Panel on Fissile Materials, which campaigns against nuclear proliferation, has released a report on “fast” reactors, one version of fourth generation technology that is decades old, but is earning a new lease of life as a potential solution to the problem of dealing with nuclear fuel waste.

GE Hitachi, the US-Japanese joint venture, has proposed its fourth generation reactor, the PRISM, for that purpose in the US.

Some of the commentary about the technology has been breathlessly excited. The IPFM, however, is sceptical. The report argues that the use of these reactors as a global solution to the problem of nuclear waste, suggested as part of the Bush administration’s Global Nuclear Energy Partnership in 2006, had already been shown to be ineffective. The report argues:

A [1996] National Academy of Sciences assessment commissioned by the U.S. Department of Energy, had concluded that such an effort would have very high costs and marginal benefits and would take hundreds of years of recycling to reduce the global inventory of transuranic isotopes by 99 percent. The Obama Administration and the U.S. Congress share this skepticism
and propose a new research and development program to investigate alternative
strategies for managing U.S. spent fuel.

One of the big issues is the reactor coolant: liquid sodium. The advantage of that is that sodium melts at about 98°C, and vapourises at 883°C, so you are highly unlikely to get a vapour blow-out. The disadvantage, as anyone who studied chemistry at school will remember, is that sodium is highly reactive, exploding on contact with water and burning in air.

The IPFM report details the instances of the problems this has caused with prototype sodium-cooled reactors in the past.

As the country studies detail, a large fraction of the liquid-sodium-cooled reactors
that have been built have been shut down for long periods by sodium fires. Russia’s BN-350 had a huge sodium fire. The follow-on BN-600 reactor was designed with its steam generators in separate bunkers to contain sodium-water fires and with an extra steam generator so a fire-damaged steam generator can be repaired while the reactor continues to operate using the extra steam generator. Between 1980 and 1997, the BN-600 had 27 sodium leaks, 14 of which resulted in sodium fires (see chapter 5). Leaks from pipes into the air have also resulted in serious fires. In 1995, Japan’s prototype fast reactor, Monju, experienced a major sodium-air fire. Restart has been repeatedly delayed, and, as of the end of 2009, the reactor was still shut down. France’s Rapsodie, Phénix and Superphénix breeder reactors and the UK’s Dounreay Fast Reactor (DFR) and Prototype Fast Reactor (PFR) all suffered significant sodium leaks, some of which resulted in serious fires.

Regulators will take a lot of convincing that those incidents can be avoided in the future before they will give the go-ahead for sodium-cooled reactors in the US.

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