Scientists at the MIT Nuclear Reactor Laboratory have devised an unconventional plan for accelerating the development of a small, safe, cheap nuclear reactor: they want to build a prototype that piggybacks on their existing facility.
Since the planned one-megawatt demonstration reactor would be incapable of sustaining a fission reaction on its own, the researchers believe they could avoid building a standalone experimental prototype, which the Nuclear Regulatory Commission generally requires. That site selection and licensing process can take a decade or longer, so the hope is that this approach could cost hundreds of millions of dollars less and take half as much time to build.
[...] The researchers specifically want to test designs for a small, transportable molten-salt-cooled reactor, intended for off-grid purposes such as generating electricity for remote villages or worksites. Molten-salt reactors, first researched in the 1950s, are a subject of growing interest in the field because of the potential they offer for greater safety and lower costs compared with traditional nuclear power plants.
http://www.nextbigfuture.com/2017/03/mit-wants-to-build-add-on-1-mw-sub.html
(Score: 5, Insightful) by Aiwendil on Monday April 03 2017, @01:01PM (2 children)
Subcritical is the fancy way of saying "can't sustain a chain reaction".
'Requires [externally sourced] neutrons to activate' just means it is subcritical.
No need for it to be thoruim - it can simply be kept below critical mass (ie, neutron absorbtion and leakage is too high), unmoderated (will make most neutrons miss), without reflector (standard hack to nudge to critical), too low enrichment (increased critical mass needed), no reprocessing/removing bred fuel (too few new neutrons internally), subcritical configuration (ie - neutrons miss due to fuel alignment)...
I actually see this as a great way to test a burner (keep it at .99% or critical), reprocessing, fueltesting, material testing, testing moderators - in short, as a highly flexible research reactor to validate molten-salt technologies
(Score: 0) by Anonymous Coward on Monday April 03 2017, @06:30PM (1 child)
"keep at 99% of critical"
seems risky if it makes them think they don't need control measures.
everything has error bars
What if something changes in the configuration and it gains 2%?
I'd be more happy with 80+-5%, or moving to someplace less populated, even if it is a blue state.
So, if you have a working reactor radiating neutrons to activate a nearby sub-critical reactor,
does the now activated reactor radiate neutrons back to the first reactor?
Is this a one-way sort of thing, or does the additional reactor affect the controlling of the first?
(Score: 3, Informative) by Aiwendil on Monday April 03 2017, @08:50PM
Then you'd get a system that heats up, and it will cause the fuel to become less dense and thereby increase the requirement for critical mass, this kinda is how molten-salt (and AHR) self-regulates. Also, you could pump in more of a known low-reactivity salt, or get a nobel prize for discovering how to make the neutron poisons (unwanted absorbers) vanish, the problem actually is to reach criticality.
The normal way to irradiate an external target is to simply have an unshielded part that allows the neutrons to escape the source to reach the target, in this case the target will be a circulating fluid and also one with less excess. And any feedback will be kept below what the source can deal with (ie - should be less of an issue than fresh fuel in the source reactor)