Greens doubt nuclear plant design

BNFL defended the AP1000's safety system

Safety concerns have been expressed over a new nuclear power station which is being considered to replace a plant in Scotland.

Hunterston B in Ayrshire is scheduled to close within the next decade.

The Scottish Green Party and Greenpeace have raised concerns about the simplified pressurised water reactor (PWR) which is among the options being considered as a replacement.

Environmental groups say the Westinghouse AP1000 is the front runner to replace the current station because detailed costings have been drawn up.

I actually find this quite terrifying, the idea of America exporting kit form reactors designed to be as cheap as possible

Robin Harper, Scottish Greens

However, British Energy, which runs Hunterston, said it was looking at a number of proposals and would make its decision in the spring.

It is considering a new reactor being developed by the American subsidiary of British Nuclear Fuels Ltd (BNFL).

The Westinghouse AP1000's selling point is that it requires far fewer valves, pumps and piping than existing reactors and is cheaper and quicker to build.

It can be made in modular form and shipped for on-site assembly.

Scottish Green Party MSP Robin Harper said: "I actually find this quite terrifying, the idea of America exporting kit form reactors designed to be as cheap as possible.

Passive safety system

"That means, not necessarily cutting corners but taking it as close to the line as possible in terms of all the safety factors that you have to build into them. I find this deeply worrying."

The party has also questioned the design, which depends on giant water tanks on the roof to douse the reactor if it overheats, known as a "passive safety system".

The concern was shared by nuclear consultant John Large who said: "If you have an entirely passive system, it means you have no or very limited opportunity to manage events, post the incident. You won't be able to turn valves off remotely.

A number of plant designs are being considered

"Whereas on the present generation of PWRs, you have a potential to intervene on the system to do some post-accident management."

However, BNFL said the design was robust and relying on gravity was safer than pumps and valves.

Richard Mayson, director of reactor systems, said: "It is actually safer. If you think about it, what would you rely on gravity, or on electrically driven pumps and valves?

"I know I'd be inclined to trust gravity more than pumps and valves but there are back-up systems available so it's not as if we're totally reliant on them."

Elements analysis

Mr Harper expressed concern about US certification of the AP1000, which is an upgrade of the smaller and never-introduced AP600.

He said: "Materials that might be appropriate for a smaller design may not be appropriate for a larger design.

"I would have thought they should really start the design, particularly with a nuclear power station, from the beginning again.

"You can't play about with these things, just scaling something that's been made to fit for one design into a bigger design."

That was disputed by Mr Mayson, who said: "For example the building structure is exactly the same as for the AP600.

"So all the analysis that we've done that proves that it's safe against earthquakes, that it's safe against tornados, is all still valid."