Ambrose Evans-Pritchard tells the Financial World about Thorium

Hi, In Th-based reactors, who is ahead of who? I read India has very good Th based experimental reactor/s and has been active in Th based nuclear reactors for sometime. Now China has said to invest in Th based reactors. Why one cannot see much news from India related to Th reactors? Is it because their tech is inferior to Chinese? Thanks

@ ET: all fission reactors produce about the same fission products like cesium etc. LFTR are better for the long lived transuranics like plutonium and that stuff. And David L. knows what he´s talking about :-)

Chris Crowe, it IS more complicated than that. Light water reactor fuel is mostly U238. The 238 is transmuted into heavy isotopes with long decay chains inside the reactor. LFTRs have almost no transuranics, so almost no decay heat from them. The fission decay products accumulate in a light water reactor for about three years before the fuel is moved to a spent fuel pool. The decay products are continuously removed from the LFTR fuel. It is not that the energy is not released, it is that the decay energy is not left in the reactor. In summary, there is much less radioactive decay heat in a LFTR upon shutdown.

A couple quick points. Dr. Cywinski's mistaken comment was regarding their solid thorium fueled, accelerator driven design. Their decay heat post shutdown will be virtually identical to a solid fueled reactor consuming uranium. I'll give him the benefit of doubt that the reporter misquoted him. He may have been trying to explain that their design is better at dealing with decay heat than LWRs which is probably true. For MSR i.e. LFTR we do have less initial decay heat in the salt, but not so much because of fission product removal, more from Xenon and other volatiles coming out continuously (but their decay heat must be then taken care of elsewhere, usually our same dump tanks so it actually gets combined). In the salt it is the short lived decay products of hours or days half life that give the vast majority of the initial decay heat which needs to be safely removed. We don't remove fission products fast enough to really effect those elements (except in one proposed design that hoped to pull out fission products on a 6 hour timescale! Unworkable in my opinion). David LeBlanc

Please correct me if I misunderstand anything. The dominant safety risk of all nuclear reactor installations is dispersion of fissile products (FPs). This is by three primary means: A. Uncontrolled reactivity increase leading to reactor damage. B. Decay heat after fission criticality is shutdown leading to reactor damage. C. External containment breach exposes reactor to air or water. My understanding is that with LFTR designs this is greatly limited by the following (additional to conventional) main factors: 1. High negative temperature coefficient of reactivity in the core -> A. 2. Unpressurized core -> A+B+C. 3. Operational removal of FPs, even continuous removal -> B. 4. Passive emergency systems and cooling geometry changes -> B+C. 5. Low chemical reactivity of molten salts -> B+C. My other understanding is that while from a prototype design and lab perspective point 4 is straightforward, it may be a significant engineering challenge as the reactor is scaled up in size or to comply with regulations. However, with point 3, it may be possible (and cost effective?) to remove FPs so often prior to an abnormal shutdown that the decay heat from the FPs can never result in the molten salt boiling which I assume may lead to reactor or containment damage. Finally, what is not clear is the presence of moderators and the part they play in both abnormal shutdowns and controlled startups in modern LFTR designs since the speed of shutting down fission can greatly impact the amount of decay heat being managed and therefore safety. This seems to be one of the notable hallmarks of both TMI and Fukushima whereby very speedy fission emergency shutdowns/SCRAM did actually occur and all problems were subsequent to that. @Chris Crowe, I imagine the reason why you may find it tricky to obtain realistic figures for LFTR decay heat is for a given rated power plant it will depend on thermal to electrical efficiency not observed in conventional reactors and how often FPs are removed from the core. Though this post from jaro may help: http://energyfromthorium.com/forum/viewtopic.php?f=3&t=2565