Energy From Thorium Discussion Forum

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PostPosted: Sep 07, 2012 3:30 am 
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Joined: Dec 17, 2011 3:13 pm
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Greetings, this is my first post on this forum, although I have been following proceedings for about a year – I have found the experience both informative and occasionally entertaining, for which many thanks. I am not an engineer or a nuclear expert – my background includes physics (education) and IT systems design, including several years and projects in the nuclear industry.

I am fairly active, with others in the UK, generally advocating MSR, and preparing and using relevant presentation material. The initial focus was on thorium, however, there does now seem (to me) to be some logic in David LeBlanc’s tactical preference for DMSR, perhaps as a twin-track with LFTR. Incidentally, I would have thought that DMSR would be particularly attractive in counties which perceive themselves to have a significant nuclear waste problem, and the Blue Ribbon Commission’s report suggests that the US is high on that list. But either way, the key technology ‘breakthrough’ does look like molten-salt reactors, possibly with a variety of fuel mixtures.

I am seeking some advice. We have recently been presented with some questions / challenges which go back to the engineering outcomes and reviews from the MSRE work at Oak Ridge. The suggestion is that we are, in effect, still left with ‘major technical problems’ particularly in the areas of intergranular cracking of the reactor vessel, thermal creep and fatigue related failure of some key components, as well as the distortion of graphite core elements, likely due to excessive neutron bombardment.

I am aware that some (at least) of these issues are now seen in retrospect as business-as-usual engineering matters which came out of the Oak Ridge work in the 60s & 70s, and were in effect dealt with during or since, and even those which may have not been fully resolved may not necessarily be seen (now or even then) as show-stoppers. I have browsed some of the ORNL papers, particularly the 76 review, but it would be helpful to know, and to be able to justify, quite where we really are now, on the engineering spectrum, somewhere between business-as-usual (problem solving) and show-stoppers.

I am conscious that the moderator question is, to some extent a trade-off. Graphite can be seen as a consumable, and its replacement frequency depends on the setup, and how hard you choose to drive the reactor. By contrast, it is more of a credibility problem if the materials of the vessel and plumbing are seen as vulnerable. Clearly this would be an issue for both LFTR and DMSR.

It has also been suggested (to us) that a better way to study the thorium fuel cycle might be via the IAEA's proposed Gen-IV VHTR (Very High Temperature reactor) or GFR (Gas-cooled Fast Reactor) or pebble bed reactors, following on from the German experiments with pebble-bed reactors in the 70's and 80's, and the original work at Shippingport.

This looks to me a bit like a red herring, avoiding the key technology transition from solid-fuel to molten-salt, and focussing instead on the thorium fuel-cycle. Whilst no doubt this does need further study, especially when promoting LFTR, but presumably India, for instance, will be making some further progress on the thorium fuel-cycle, albeit in the solid-fuel context.

What would be useful to us, however, would be any advice or references (to relevant documents) clarifying the current position, particularly on the question of damage to components (and moderator?), in any molten-salt reactor. Clearly, the relative merits of VHTR & GFR versus molten-salt is a much more general question, but any advice or references on that would also be helpful.

40 years on, we feel that we need to understand and contrast (at least the scale of) problems that have in effect already been solved versus expectations of what is still left to do or prove. Industry professionals would naturally seek quantitative answers, like timescales and budgets, but first we would like to be able to paint a sensible general picture of where we think we are now, in presenting the prospects for molten-salt technology to the wider public.

Sorry if this turned out to be less like a couple of brief questions, and more like a short essay, but any guidance would be much appreciated.


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