Passive safety in the news

I posted very quickly on the importance of passive safety designs for future nuclear after the Fukushima accident, and now I see there is a fair bit of media talk on the subject (including about my old interest – pebble bed reactors.) Here are some articles:

* the New York Times talks about China pressing ahead with pebble bed. Lots of good points in a straight forward explanation. (It notes that the South Africans got stuck on using turbines that were to use the helium coolant directly. China is using the helium to boil water for less sophisticated steam turbines.)

I see that the Chinese program director is quoted as saying that pebble bed is yet to prove itself as cost effective as old style nuclear:

“The safety is no question,” Dr. Xu said, “but the economics are not so clear.”

Um, I think nuclear has to give safety the absolute priority at the moment, if its to go anywhere at all.

* Bloomberg had a longer article looking at passive safety generally. Pebble beds get a good mention too. It notes the passive safety in the new Westinghouse model:

The new Westinghouse AP1000 (the AP stands for Advanced Passive), for example, has a huge emergency water reservoir above the reactor vessel that’s held back by valves.

If the cooling system fails, the valves open and a highly reliable force takes over: gravity. Water pours down to cool the outside of the containment vessel. Then another highly reliable force, convection, kicks in. As the water turns to steam, it rises. Then it cools under the roof, turns back into a liquid, and pours down again.

Westinghouse estimates that the pool contains enough water to last three days, after which pumps operated by diesel generators are supposed to kick in and add water from an on-site lake.

Hmm. Doesn’t sound anywhere near as good as a pebble bed to me: get a crack in the vessel, and there goes your passive safety in a long stream of steam. Still, better than the older models, of course.

* Some in South Africa seem to be regretting that they gave up on pebble bed, just at a time it suddenly looks very attractive again:

Analysts have said the pebble-bed option is one the state and industry should reconsider on safety and other grounds.

"The reactor would not need any external cooling. It would cool itself. It's walk-away safe," said Kelvin Kemm, a Pretoria-based nuclear physicist.

But he said the programme may need to be industry-led, after South Africa invested nearly 10 billion rand in developing it over a decade before putting it on ice as it lacked a clear business case.

"There is lots of merit for the technology, specifically for building power plants away from places where you could potentially have tsunamis," said Cornelis van der Waal, an analyst at consultancy Frost & Sullivan.

Pebble-bed reactors are modular in nature and as they do not need a lot of water can be built away from coastal areas.

This modular nature, and the ability to not site them near major water bodies, seems to me to be a very important feature for Australia, where every bit of coast line any where near population centres is loved and used by someone.

Ah well, I’m feeling some vindication for saying for years that they sound like a good idea. (And cue music for “If I Ruled the World”.)