Energy From Thorium Discussion Forum

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PostPosted: Jun 13, 2011 7:21 pm 

Joined: Apr 03, 2011 7:50 pm
Posts: 99
Location: Rhinebeck, NY
Here is an article on an accelerator driven thorium reactor proposal in the UK. It is also one of the most confusing newspapers articles I have ever read. ... world.html

PostPosted: Jun 14, 2011 8:18 am 

Joined: Jul 28, 2008 5:01 am
Posts: 461
Location: Teesside, UK
Well, it is the Daily Wail

Never known to let an awkward fact get in the way of a good story. The most misleading passage here is
Daily Mail wrote:
{An accelerator-driven reactor} would also, as mentioned, be incapable of undergoing a Chernobyl-style meltdown, as a thorium reactor would be ‘subcritical’. There’d be no ‘critical mass’ of unstable, radioactive material liable to produce a runaway chain reaction if its control mechanisms failed.....
And if hit by an earthquake, {Professor Bob Cywinski} adds, even one as powerful as the one that wrecked Fukushima, a thorium plant would be ‘intrinsically safer’.

‘There’d be some residual radioactivity heating the core, but sustained nuclear fission would simply stop. Everything would cool much faster. You’d be left not with potential catastrophe, but just a heap of molten metal and metal oxides.’
That, of course, is just what did happen at Fukushima - fission was shut down within a few seconds of the earthquake being detected, failure to remove decay heat caused all the problems.

The goal of radically reducing accelerator size and cost to enable widespread deployment for cancer therapy should be sufficient reason for doing the project, and a cheaper synchrotron X-ray source would soon aquire a customer waiting list as well, but for reactors it is an expensive solution to the wrong problem.

PostPosted: Jun 14, 2011 8:50 am 

Joined: Jul 14, 2008 3:12 pm
Posts: 5045
The criticality stuff is nonsense of course, but there is truth to thorium being more resilient in a severe accident. ThO2 has a melting point about 500 Celcius higher than UO2, and does not oxidise, swell or dissolve when the cladding fails and water/steam goes in. This is detrimental for UO2 fuels, as the UO2 oxidises to UO3 and U3O8, which causes swelling, exagerbating the problem, as more fission products are released from the crumbled fuel pellets and the crumbled mess blocks emergency coolant flow. With ThO2 the fuel pellets themselves should remain intact, and with the insolubility of ThO2 in water, the fission product release is at least one order of magnitude less. With the pellets keeping their gross shape, emergency coolant can still be injected. I'm pretty sure radiation release would have been many times lower if Fukushima reactors had used ThO2 fuel, just with a different fuel.

Similarly Th metal has a much higher melting point than U metal.

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