Read more: 鈥�Special report: Rescuing nuclear power鈥�
THERE鈥橲 nothing quite like watching reactor buildings explode on live TV to destroy your faith in nuclear power. But the explosions and radiation spills at the Fukushima Daiichi power station in Japan may give an unfair impression of the risks associated with modern nuclear energy generation.
The Fukushima reactors are a 40-year-old design. A new generation of reactors, with more comprehensive safety features and power backups, would likely have fared much better. Alexis Marincic, chief technical officer of French reactor-maker Areva, claims that most of the failures that led to Fukushima鈥檚 radiation leaks would probably not have happened with the latest designs.
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Problems began at Fukushima when it lost electrical power to its reactor cooling systems after the earthquake damaged power lines to the plant and the tsunami engulfed its backup diesel generators. Areva鈥檚 (EPR) has six backup diesel generators in two seismically damped, waterproof concrete buildings sited 50 metres either side of the containment. 鈥淓ven if an aircraft crashes into the reactor building we will still have backup power for cooling,鈥� says Marincic.
The EPR also has four separate backup circuits for the electronics, pumps, valves and pipework that keep the core cool in an emergency.
Lacking cooling, some reactors at Fukushima overheated, splitting water molecules to produce hydrogen, which then ignited. This blew the roofs off the containment buildings and released steam contaminated with radioactive isotopes.
To avoid this, the EPR has a catalytic hydrogen recombiner that ensures any hydrogen generated reacts with oxygen to reform water. The reactor is kept in a double-walled, leakproof containment to stop gases escaping. An inner steel-lined prestressed concrete shell 0.8 metres thick is surrounded by a 1-metre-thick reinforced concrete shell.
We still don鈥檛 know if there was a core meltdown at Fukushima but the EPR guards against this too, says Marincic. The design includes a water-cooled concrete 鈥渃ore catcher鈥� that stops a melting core from exploding. Two EPRs are now being built, one in Finland and one in France.
Areva鈥檚 rival, Westinghouse Electric, owned by Toshiba of Japan, is building a third-generation reactor of its own, the , at a site in China. Like the EPR, it has stronger doubled-up containment and multiple cooling system backups.
鈥淭he first of Areva鈥檚 third-generation EPR nuclear plants is being built at Olkiluoto, Finland鈥�
It also has a passive safety feature: an enormous tank of water in the roof that is automatically released in the event of a cooling system loss. Effectively, this would do what the Fukushima workers did with pumped seawater, says John Gittus, former safety director at the UK Atomic Energy Authority, but without requiring pumps. 鈥淎 flap opens and out it pours,鈥� he says.
鈥淲e鈥檝e calculated that a tank of water that can flood the pit that the reactor sits in can cool it for 72 hours, giving operators a good three days to work out how to deal with the situation,鈥� says Westinghouse spokesman Adrian Bull.
Both reactor designs impress , director of the Dalton Nuclear Institute at the University of Manchester, UK. 鈥淭hese new reactors would have managed the core residual decay heat in a Fukushima situation 鈥� and once you have managed that your reactor would be in a safe shutdown mode.鈥�
Complex safety systems won鈥檛 come cheap. 鈥淏ut cost is not such an issue,鈥� says Gittus. 鈥淩egulators won鈥檛 let people buy reactors that might go wrong.鈥�
