Thermal vs fast MSRs for nuclear wastes destruction

Threads relating to the design of liquid-fluoride reactors.
NNadir
Posts: 241
Joined: Jul 01, 2009 1:13 am

Re: Chloride reactors vs LFTR

Post by NNadir » Sep 26, 2009 2:50 am

Kirk Sorensen wrote:
Alex P wrote:Moreover, can you please explain me why it's so difficult to separate plutonium from uranium, instead thorium ? Which are the typical efficiency separations (in the case of thorium or depleted uranium), if there are some figures, for the other transuranics ?
Thorium has one valence (+4) while uranium has two (+4 and +6). You can "shift" uranium from UF4 (in solution) to UF6 (gaseous) through fluorination. Thorium stays put.

Uranium and plutonium both have multiple valences. Fluorination will preferentially remove uranium, not plutonium, making fluorination as a blanket reprocessing step pretty useless. You'd remove all the blanket before you'd remove the bred fuel (plutonium). That's the inverse of what you want.
Actually uranium has more oxidation states than that.

It has commonly +3, +4, +5 and +6.

There are even examples of lower valence states, although they are somewhat controversial.

The chemistry of uranium is quite rich, although not quite as exciting as the chemistry of plutonium, the latter being fascinating.

jagdish
Posts: 2292
Joined: Apr 19, 2008 1:06 am

Re: Thermal vs fast MSRs for nuclear wastes destruction

Post by jagdish » Sep 26, 2009 5:25 am

From a study on internet, I find that uranium can be oxydised to UCl6 which is volatile like UF6 and sublimates at 75C. Other actinide Chlorides are not volatile. This can reduce the mass of spent fuel to 5%, which amount can be electrorefined. The other volatile chlorides ZrCl4(331C) and TcCl6 can be removed by fractional distillation from uranium. Actinides can be kept together to assuage feelings of anti-proliferation crowd and burnt in fast reactors (or LFTR) after easy conversion to oxides or fluorides..

samy_2111
Posts: 1
Joined: Dec 30, 2009 11:56 pm

Re: Thermal vs fast MSRs for nuclear wastes destruction

Post by samy_2111 » Dec 31, 2009 11:38 am

ORNL did accomplish it using fluoridation and to a level quite sufficient for blanket processing. In blanket processing we don't need to remove 99.9% or even 90%. We just need to remove most of the fissile to keep the fission reactions in the blanket down

jagdish
Posts: 2292
Joined: Apr 19, 2008 1:06 am

Re: Thermal vs fast MSRs for nuclear wastes destruction

Post by jagdish » Jan 01, 2010 9:42 am

Separation of uranium is just one aspect of reprocessing. Sodium fires have created a scare about fast reactors. If a better and safer coolant like a gas or a stable salt can be employed, fast reactors are better as they can destroy actinides and burn uranium or thorium as fuel. unmoderated LFTR is also feasible. Fast MSRs would be optimum.

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