Talk-Polywell.org

Forgive my lack of technical knowledge on this subject.

I see a lot on Liquid Thorium Reactors and how great they would be, but I very rarely see much on the drawbacks and dangers of them. There are obviously some technological and engineering hurtles to be overcome and I have seen/read these discussions.

Mainly, I hear about their safety/etc with recent talk about how there would be no problems with a LFTR in events similar to the earthquake/tsunami in Japan.

But, aren't fluoride salts highly reactive to water? Doesn't that create special concerns? What about the chemical extraction processes that are discussed, like U-233 from the blanket salts and waste from the fissile salts? Doesn't this extraction from high temperature fluoride salts create unique opportunities for accidental leaks/releases of radiation? In general, doesn't dealing with radioactive liquid and necessary regular chemical processing of it create many unique dangers.

I guess what I am saying is that the proponents of LFTR tech are doing a lot of talking, but I rarely hear from the opponents. What are some of the real dangers in exploring this technology if there are any?

Try;

http://www-pub.iaea.org/MTCD/publicatio ... 50_web.pdf

Not read it all myself yet, but maybe it contains what you are looking for.

In respect to the existing nuclear technology is much more safe.
In respect to actual carbon technology is hugely more safe.

There are of course drawbacks and limitations, but that is the same for each technology.

Here you can find all the information you need to get your own point of view:
http://www.energyfromthorium.com/pdf/

Lot of reading, but worth each minute of the time you will spend on it.

chrismb wrote:Try;

http://www-pub.iaea.org/MTCD/publicatio ... 50_web.pdf

Not read it all myself yet, but maybe it contains what you are looking for.

Thanks for the link. Very little discussion of MSRs in there. It did provide reference to this http://www.ornl.gov/~webworks/cppr/y200 ... 115042.pdf which had a little more.

This was something I hadn't heard before:

"Noble metal fission products that do not dissolve as stable fluorides can plate
out on heat-exchanger walls as metal or lower-valence metal-metal bonded fluoride clusters. This is an
operational issue that scales with the power level of the MSR. In the case of loss of heat sink, the decayheat
load from the metal metals could cause significant damage, leading to loss of integrity of the MSR
intermediate heat exchanger. Several methods to address this issue have been proposed but R&D is
required to develop an effective control system."

Too bad they didn't give any number, it would have helped a lot to understand the real dimensions of this issue.

Yet, as we are speaking of the intermediate heat exchanger, the quickest solution is to have a spare one in line. One works, one gets cleaned.

On water reactivity, I found this from the following link:

http://www.energyfromthorium.com/pdf/ICAPP-AHTR.pdf

"Molten salts do not react with helium or nitrogen but will react slowly with water over time.
Experiments have been conducted to determine the impact of injecting molten salt into water, such as
might occur in some types of systems that have water. In the largest experiment, 230 kg of molten salt
at 815°C was injected into a water bath over 45 to 50 seconds with the discharge pipe 1.5 m (5 ft)
under the water level. No steam explosion occurred, only a negligible amount of steam reached the
surface of the water, and no entrainment of water or steam into the air was observed (Mann 1955)."

Doesn't sound so bad:)

Same paper also had this regarding noble metals and the heat exchanger:

"and (7) better management of
noble metal fission products. The fission process generates noble metal fission products. These do not
dissolve as stable fluorides in the molten salt and can plate out on heat-exchanger walls as metal or
lower-valence metal-metal bonded fluoride clusters. Molten salts do not wet carbon, so MSR primary
systems built with advanced carbon composite materials may enable simple recovery and separation of
noble metal fission products using metallic sponge filter materials. Better removal techniques for
these fission produces is desirable and may be possible."

The wikipedia article on MSRs has a reasonably good first cut at the pros and cons.

KitemanSA wrote:The wikipedia article on MSRs has a reasonably good first cut at the pros and cons.

Actually, the discussion of the article more interesting. Wiki article reads as a bit of a PR piece and the discussion points out as much, noting the many pros sections, that in some cases pros are disguised in the con sections and that cons are off-handedly dismissed.