[ RadSafe ] Molten Salt Reactor

[Brennan, Mike (DOH)]

This isn't my part of the nuke biz, but I've done a little reading on it, and I think I know what they would be saying, if the reporter actually understood what they were told.

The molten salt reactor designs I've read about use a salt like thorium fluoride as fuel/thermal carrier.  The salt, either solid or molten, is not critical, and can't become critical without the right geometry and a moderator.  The reactor provides this with a vessel that has rods of moderators in it.  As the molten salt is pumped through the reactor, fission occurs, and heats the salt to even higher temperatures (but no where near the vaporization temperature of the salt).  Someplace downstream some of the heat is removed to heat something and spin turbines, and the salt goes back into the reactor to be heated some more.

In the event of a loss of power in which the salt can't be pumped, valves are opened and the salt is dumped to tanks, where it solidifies, because the decay heat from the fission fragments isn't enough to keep the salt molten.  Even if it didn't get dumped, if the moderators are pulled from the reactor the reaction stops, and at worst the salt solidifies in the reactor.  This is bad, because recovering the reactor will be annoying, but not tragic.  Even if the moderators aren't removed and the salt just sits in the reactor there is no real problem, because reactivity goes down as temperature goes up and it can never reach the boiling point of the salt, nor the melting point of reactor components, so there is no pathway to the environment.

There are some non-trivial challenges with molten salt reactors, but I accept the claim that they cannot fail as catastrophically as BWRs, or even PWRs.  

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Dahlskog, Leif
Sent: Sunday, August 17, 2014 6:59 PM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: Re: [ RadSafe ] Molten Salt Reactor

I don't get this sentence in the article.
  
"Since salt's melting point is higher than the core temperature, even if power is lost and no one is around to fix things, the reaction will eventually stop on its own."

I though the salt was meant to be in a molten state. Anyone able to help me understand this ?

Leif Dahlskog
Radiation Health Branch 

Grace Vaughan House|227 Stubbs Terrace|Shenton Park WA 6008 


-----Original Message-----
From: radsafe-bounces at agni.phys.iit.edu [mailto:radsafe-bounces at agni.phys.iit.edu] On Behalf Of Sander Perle
Sent: Sunday, 17 August 2014 10:49 PM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: [ RadSafe ] Molten Salt Reactor

Here is a link I posted on LinkedIn last night:
http://www.extremetech.com/extreme/187917-startup-gets-funding-for-its-molte
n-salt-nuclear-reactor-that-eats-radioactive-waste

This morning CNN¹s Fareed Zakaria GPS TV interviewed Dr. Leslie Dewan, CEO, Transatomic Power Corporation. She graduated from MIT with a Ph.D. in nuclear engineering, with a research focus on computational nuclear materials. She also holds S.B. degrees from MIT in mechanical engineering and nuclear engineering. Before starting her Ph.D., she worked for a robotics company in Cambridge, MA, where she designed search-and-rescue robots and equipment for in-field identification of biological, chemical, and nuclear weapons. Leslie has been awarded a Department of Energy Computational Science Graduate Fellowship and an MIT Presidential Fellowship. She was named a TIME Magazine "30 People Under 30 Changing the World" in December 2013, an MIT Technology Review "Innovator Under 35" in September 2013, and a Forbes "30 Under 30" in Energy in December 2012.

I recommend that if you have the time, you should review the article as well as the interview.

Regards,

Sandy Perle
Retired, Consultant


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