4 ms·
What you say about U/Pu fast breeders is true, but there are other pertinent differences between those and LFTR: 1. LFTR safety is based on passive cooling. P
by thingification 14y ago
What you say about U/Pu fast breeders is true, but there are other pertinent differences between those and LFTR:
1. LFTR safety is based on passive cooling. Pu breeders do not share this property. Fukushima-style accidents involving loss of active cooling power for decay products are not a failure mode of LFTR.
2. MSR reactors don't suffer from the safety problems introduced by the use of liquid sodium.
3. MSR reactors don't suffer from the control complications introduced by Xe poisoning in solid fuels.
4. MSRs involve a continuous liquid process. Essentially all industrial chemical processes work that way, and that's because liquids are very convenient to work with. There are good reasons to think this will pay off in multiple cost-saving ways.
Another way of looking at the billions spent on Pu breeders is that it might be an indication that other technologies are worth a bet. Orders of magnitude less have been spent on MSR than on U/Pu breeders.
I'd say the big selling points of Th are not fuel efficiency and spent fuel, for exactly the reasons you note. The big selling points are the promise of lower cost and public acceptance (both of these promises come to a large extent from the real safety advantages of MSR over conventional reactors).
The hard one, public acceptance, will only happen if we can figure out how to sell it, but luckily, making that effort is something that those of us who think we need nuclear power have a duty to choose to support, not something that's in the lap of the gods.
Re China: it's possible my memory is playing tricks on me, but I believe that one of the guys at the top of that program, when he came to a North American conference to speak about it, said that MS as coolant was the initial focus simply because that is a natural early step, but MS fuel was very much a long term goal (it's on youtube if somebody wants to check). Edit: I just checked (somebody already linked to it), and my memory was playing tricks: he said that they're developing both in parallel, with the priority initially on MS as coolant, because that is "more technically ready". It still seems that MS as fuel is where they want and intend to go eventually.
- uvdiv 14y agoOh, thank you. I intended only a very narrow point about chloride reactors being untested (not MSRs: just fast-spectrum chloride MSRs). I didn't mean to provoke a debate between molten-salt and liquid metal reactors. I claim neutrality. :) LFTR safety is based on passive cooling. Pu breeders do not share this property. I'm unfamiliar with the details, but I read that liquid-sodium reactors are capable of fully-passive decay heat removal, e.g. [0] (slide 6). Certainly sodium has a much higher boiling point than water. By the way, fast-spectrum MSRs are really Pu breeders -- that's the point of actinide burning! 3. MSR reactors don't suffer from the control complications introduced by Xe poisoning in solid fuels. This is not a relevant issue with fast-spectrum reactors, e.g. [1] (c.f. [2]): "The xenon-135 and samarium-149 mechanisms are dependent on their very large thermal neutron cross sections and only affect thermal reactor systems. In fast reactors, neither these nor any other fission products have a major poisoning influence." 4. MSRs involve a continuous liquid process. Essentially all industrial chemical processes work that way, Pretty sure it's a batch process? [0] http://rpd.ans.org/presentations/DesignFeatures_Economics.pdf http://rpd.ans.org/presentations/DesignFeatures_Economics.pd... [1] http://www.hss.doe.gov/nuclearsafety/techstds/docs/handbook/h1019v2.pdf http://www.hss.doe.gov/nuclearsafety/techstds/docs/handbook/... [2] Xe-135 absorption: http://www.nndc.bnl.gov/sigma/getPlot.jsp?evalid=15174&mf=3&mt=102&nsub=10 http://www.nndc.bnl.gov/sigma/getPlot.jsp?evalid=15174&m...
- thingification 14y agoAh, I did notice you were talking about fast reactors, then hastily slid back to thermal ones! Sorry. I guess my error reflects the fact that I think the thermal LFTR is more important. Re passive cooling in sodium breeder reactors: that's certainly interesting. I'd not heard about this.
- yk 14y agoAbout your first point, this depends on the scale of the reactor, since the capacity of passive cooling scales with the surface area and the energy generation scales with the volume of the reactor. AFAIK submarine reactors can utilize passive cooling, since they are only about 100 MW.