Get rid of transuranians in Liquid Fluoride Thorium Reactors?

[Astronuc]

Well, you can always deport them back to Transurania or force them to stop cross dressing and remain uranium-atoms...
[Sorry, could not help it...please don't ban me!?]

Molten salt reactors would have issues with the release of volatile fission products (Xe, Kr, I, Cs and so fourth). In todays' solid fuel the leakage is quite small and does not cause serious concern as most fission products are locked in the oxide matrix. For MSR's the solution around this would require some form of double cotainment to stop significant leakage of fission products outside the plant.

Well, in theory, the primary system would be sealed so that the fission products are extracted from the coolant. The gases and volatiles would certainly have to be collected and held up to decay, and then that stream would have to be processed.

 

[Matte Patte]

Well, yes but you also have no secondary containment (fuel cladding). The primary circuit is (considered) the tertiary barrier in LWR's...

 

[Astronuc]

Well, yes but you also have no secondary containment (fuel cladding). The primary circuit is (considered) the tertiary barrier in LWR's...

I don't think we consider the fuel material a primary containment, since it doesn't necessarily retain all fission products, especially the Xe, Kr radioisotopes, or the volatiles, Cs, I, Te, etc. Fast reactor fuel allows for centerline void due to restructuring. In LWR and FR fuel, the primary containment is the cladding, the secondary containment is the primary or coolant circuit, and the tertiary containment is the containment building and ancillary buildings where coolant treatment system collect any fission products and activated corrosion products from the core.

In a liquid fuel system, the primary containment is the core and piping related to the liquid fuel transport and processing system. The benefit should be relatively low equilibrium activity in the core and primary circuit, except where the fission products accumulate.

 

[mheslep]

Well, you can always deport them back to Transurania or force them to stop cross dressing and remain uranium-atoms...
[Sorry, could not help it...please don't ban me!?]

Molten salt reactors would have issues with the release of volatile fission products (Xe, Kr, I, Cs and so fourth). In todays' solid fuel the leakage is quite small and does not cause serious concern as most fission products are locked in the oxide matrix. For MSR's the solution around this would require some form of double cotainment to stop significant leakage of fission products outside the plant.

Since MSRs would run at atmospheric pressure without water around the core which can flash to steam, some designers are arguing for no confinement.

 

[Astronuc]

Since MSRs would run at atmospheric pressure without water around the core which can flash to steam, some designers are arguing for no confinement.

Atmospheric pressure at the top of the highest point in the primary system, but going down to the bottom of the core under a few meters of the liquid fuel, the pressure will be greater by ρgh, so the bottom of the core will be several atmospheres. I imagine there will be some kind of containment to collect the radioactive gases and volatiles in the event of the break in the primary system, and particularly where the steam generator is located, since the steam pressure is likely to be on the order of 900 to 1000 psi. A steam-fluorine reaction would be problematic with respect to HF gas.

Note that a commercial scale has not yet been constructed let alone designed. As far as I know, none of the promoters/advocates in the US have designed or constructed any type of nuclear plant.

 

[mesa]

Atmospheric pressure at the top of the highest point in the primary system, but going down to the bottom of the core under a few meters of the liquid fuel, the pressure will be greater by ρgh, so the bottom of the core will be several atmospheres. I imagine there will be some kind of containment to collect the radioactive gases and volatiles in the event of the break in the primary system, and particularly where the steam generator is located, since the steam pressure is likely to be on the order of 900 to 1000 psi. A steam-fluorine reaction would be problematic with respect to HF gas.

Note that a commercial scale has not yet been constructed let alone designed. As far as I know, none of the promoters/advocates in the US have designed or constructed any type of nuclear plant.

Didn't Rusty Holden came up with a design? As I recall it was by no means a complete work of engineering but it seemed a like a reasonable start. Perhaps a few well placed emails will give a more clear answer on this.

 

[Astronuc]

Didn't Rusty Holden came up with a design? As I recall it was by no means a complete work of engineering but it seemed a like a reasonable start. Perhaps a few well placed emails will give a more clear answer on this.

I should probably qualify that statement further by saying a 'licensed and approved design'. Lots of folks can claim to have a design, but I'd want to see some details, particularly with respect to the nuclear design and core neutronics.

 

[mesa]

I should probably qualify that statement further by saying a 'licensed and approved design'. Lots of folks can claim to have a design, but I'd want to see some details, particularly with respect to the nuclear design and core neutronics.

An excellent point, and I would imagine these would be very difficult steps to complete. How would one go about doing this after coming up with a design?

 

[Matte Patte]

I don't think we consider the fuel material a primary containment, since it doesn't necessarily retain all fission products, especially the Xe, Kr radioisotopes, or the volatiles, Cs, I, Te, etc. Fast reactor fuel allows for centerline void due to restructuring. In LWR and FR fuel, the primary containment is the cladding, the secondary containment is the primary or coolant circuit, and the tertiary containment is the containment building and ancillary buildings where coolant treatment system collect any fission products and activated corrosion products from the core.

In a liquid fuel system, the primary containment is the core and piping related to the liquid fuel transport and processing system. The benefit should be relatively low equilibrium activity in the core and primary circuit, except where the fission products accumulate.

The fuel pellet is considered the first barrier, when the fuel is considered as part of the waste stream, I am pretty sure same goes for during operation but not 100% sure (one of five barriers, fuel pellet, cladding, primary circuit, containment and reactor building). Yes, the barrier is weak for some nuclides (so is the cladding) but it is pretty good at retaining more of the nasty ones.

Today, small cladding defects in a few fuel pins would bring a plant close to their annual release limits for radio-iodine, possibly xenon and krypton as well (PWR). At least in my neck of the woods. Running a complete core with only the primary circuit as containment for volatile fission products would require a pretty neat feat in convincing any regulatory body that those releases would be ok for the public to absorb (dose wise that is).

 

[Astronuc]

An excellent point, and I would imagine these would be very difficult steps to complete. How would one go about doing this after coming up with a design?

One would have to arrange for the NRC to develop a review plan and the regulatory structure with which to license and approve a design. It would likely be similar to the system now in place for current light water reactors, which includes NUREG-0800, Standard Review Plan.

http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0800/

The regulatory structure includes mandatory requirements concerning the design and operation of a nuclear power plant to ensure the safety of plant personnel and the public. Basically, the system must control the disposition of fission products, must ensure control of the reactor (reactivity control, with the requirement that the nuclear chain reaction can be terminated and the reactor maintained in shutdown), and must ensure coolability of the core/fuel in order to ensure that there is no release of fission products outside of the reactor system or damage to the reactor.

Some of the regulations are found in Title 10 of the Code of Federal Regulations, 10 CFR.
http://www.nrc.gov/reading-rm/doc-collections/cfr/

10 CFR 50 addresses Domestic licensing of production and utilization facilities
http://www.nrc.gov/reading-rm/doc-collections/cfr/part050/
Appendix A provides the general design criteria

10 CFR 52 address Licenses, certifications, and approvals for nuclear power plants, which applies to new builds.
http://www.nrc.gov/reading-rm/doc-collections/cfr/part052/

There are also Regulatory Guides
http://www.nrc.gov/reading-rm/doc-collections/reg-guides/power-reactors/rg/

The process starts with a meeting with the US NRC, or corresponding body in another nation.

 

[mheslep]

Atmospheric pressure at the top of the highest point in the primary system, but going down to the bottom of the core under a few meters of the liquid fuel, the pressure will be greater by ρgh, so the bottom of the core will be several atmospheres. I imagine there will be some kind of containment to collect the radioactive gases and volatiles in the event of the break in the primary system, and particularly where the steam generator is located, since the steam pressure is likely to be on the order of 900 to 1000 psi. A steam-fluorine reaction would be problematic with respect to HF gas.

Note that a commercial scale has not yet been constructed let alone designed. As far as I know, none of the promoters/advocates in the US have designed or constructed any type of nuclear plant.

The pgh at the bottom of a salt tank would be on a liquid, which if exposed via a leak would have no phase change flash. A secondary salt loop is usually considered, so that if a Rankine cycle is used eventually involving steam there is no radioactivity involved . Given the high temperatures afforded by a lftr core, a Brayton cycle seems likely. In any case, containment would not have the problem of dealing with high pressure (300atm) gases.