World's First Fast Spectrum Molten Salt Nuclear Reactor To Be Built at Idaho National Laboratory.

[NNadir]

Our government is getting very serious about climate change:

Fast-spectrum salt reactor to be built at INL

Southern Company and the US Department of Energy (DOE) have signed an agreement to design, construct and operate the Molten Chloride Reactor Experiment (MCRE) - a proof-of-concept critical fast-spectrum salt reactor. Southern will lead a collaborative effort to build the MCRE - which it says will be the world's first fast-spectrum salt reactor to achieve criticality - at Idaho National Laboratory (INL)...

...Mark Berry, Southern Company's vice president of R&D described the MCRE as "groundbreaking". Advancing next-generation nuclear is part of Southern's comprehensive strategy to deliver clean, safe, reliable, affordable energy, he said, adding: "The Molten Chloride Reactor Experiment will support the commercialisation of a revolutionary technology on a timescale that addresses climate change benchmarks and delivers on Southern Company's goal of net-zero greenhouse gas emissions by 2050."

TerraPower's MCFR technology uses molten chloride salt as both reactor coolant and fuel, allowing for so-called fast spectrum operation which the company says makes the fission reaction more efficient. It operates at higher temperatures than conventional reactors, generating electricity more efficiently, and also offers potential for process heat applications and thermal storage...

Chloride is definitely not an anion I would have chosen for a fast MSR, but look, I'm sure it will work. The extent to which Terrapower moves away from sodium metal, the better the reactors will be in my opinion.

This is excellent news from my perspective; albeit not so much for uranium mining, since it offers the possibility of conversion all the depleted uranium in the world into fuel, thus rendering all fuel mining unnecessary for many centuries.

Molten systems offer the prospect of in line fuel processing, a very powerful component for sustainable nuclear energy.

[Hokie]

1. Yes, most of the proposed reactors use fluoride molten salts

I have watched hours of videos on LFTR's and other molten salt reactors with a very critical eye and the MSR technology in general looks promising. I am putting my money on FLIBE Energy as the best technology. They propose to use thorium fuel and mixture of lithium fluoride and beryllium fluoride molten salts.

[NNadir]

3. I changed my mind about FLIBE; I see it as a poor choice for a number of reasons.

It's very popular of course, but it is also a thermal spectrum reactor.

Alvin Weinberg was a great and creative man, and the MSRE was innovative in many ways. But these days there are better ideas. I know Kirk Sorensen, although we haven't communicated for a number of years; he's a great guy and he's served the nuclear community well by popularizing the idea of MSRs when they were almost forgotten.

I just loaned my son my copy of Weinberg's The first nuclear era: The life and times of a technological fixer. It's fascinating about how open they were to new ideas then; inspiring, something we need to bring back to the US.

But FLIBE is so 1960's.

People forget that thorium may be more available in terrestrial ores, it is not available indefinitely. Uranium is, since a uranium cycle exists in seawater.

The thorium cycle in my view is not superior to the uranium plutonium cycle. I have nothing against thorium, and mined thorium is readily available from lanthanide ores that have been mined to make magnets for wind turbines and electric cars, but I can easily imagine it being unavailable in a few thousand years.

This said, I am advising my son to take a serious look at other 1960's technologies with a fresh eye. But I'm a plutonium/transuranium kind of guy.

[Hokie]

5. Are you follwoing the Chinese MSR project?

It sounds like we are falling behind on advanced reactor technology. If we can buy a thousand years from thorium I will take that. Who knows what we will develop by then? It boggles my mind that MSR technology was left to lie dormant from the 1060's until the last decade or so. I hope someone smart has Joe Biden's ear to get behind advanced nuclear technology. Renewables are great but I think safe nuclear is best way to go.

[StevieM]

6. William the Conqueror definitely dropped the ball on this one.

Ever since 1066 we have let Molten Salt technology go dormant.

I agree that we should have been working on this for years, and I also think that nuclear energy is our best way of combating climate change.

[eppur_se_muova]

2. What disadvantages of Cl do you know of ?

Will it produce radioactive isotopes of S ? Ar ? Others ? Or just lead to neutron losses ?

(I'm a little surprised to see Southern Co involved -- thought they had a pretty bad record re fossil fuel plant investment. This would be a notable change for them, IIRC.)

[NNadir]

4. Chlorine 36 as an induced species from Cl-35.

In theory one could avoid this problem by separating Cl-37, but I don't like the expense of isotope separations and I think they are best avoided, except for simpler separations like deuterium/protium. (My favorite thermal reactor, by far, is the HWR reactor.)

I grant that the capture cross section of Cl-35 is fairly low, so this isn't going to be a big problem, except for stupid people, but where nuclear issues are concerned, stupid people have ruled the day for a very long time. The resonances in the fast region seldom exceed one barn, but they can be substantial, 10 to 50 barn in the thermal region. Some neutrons will always thermalize before absorption.

Also bromine is a fission product (albeit only bromine 81) and why place the need to separate bromine from chlorine?

(Br-81 has fairly strong absorption resonances in the epithermal region, not good for neutron efficiency, but a cheap way to make Krypton.)

Fluoride has more moderating capability than chlorine to be sure, but it's not a particularly better moderator than sodium, and sodium is widely used in fast reactors. It is, to my mind, the best anion among the halogens.

(I-127 and I-129, both fission products are strong absorbers and have a special place in my heart for shielding and reactivity control, but they are not counterions for fission salts.)

There are, of course, many anionic fluoride complexes of transition metals and p-block metals as well, and - no one ever talks about this - phosphate species - and last but certainly not least, zintl salts.

Overall though, although I am very fond of molten salts as heat transfer tools, I'm a liquid metal kind of guy, just not sodium.

[StevieM]

7. This is exciting and seems to have a lot of potential.

I appreciate your posting it, especially since I know that you are not a molten salt kind of guy.

[Hokie]

8. Until I started looking into MSRs I had not clue how inefficient water cooled conventional ...

... reactors were. Inefficient from the standpoint that only 1% of the fuel is consumed before refueling is required.

[NNadir]

9. This 1% figure is very, very, very misleading, and frankly, wrong.

The current fleet of nuclear plants run continuously and are refueled, typically one third of the fuel is replaced, after a period of about 2 years. The very high energy density of uranium, which accounts for the environmental superiority of nuclear power, means that at 3000 MWth plant run on plutonium - my favorite nuclear fuel - would consume about 3 kg of fuel a day, since the energy density of plutonium is approximately 80 TJ/kg.

There are no commercial energy systems in the world other than nuclear plants themselves, that can match this mass efficiency. A 3000 MWth coal plant requires trainloads of fuel per day.

At the end of fuel life, used nuclear fuel typically contains about 4% fission products, meaning that about 4% of the actinides have been consumed. This means that the actinides are available for recovery and reuse after removal of the fission products, or with minor mechanical reprocessing as in the DUPIC fuel cycle.

Unfortunately the current fleet of nuclear reactors, dominated, albeit not completely, by PWR and BWR operate at low thermal efficiency, as they are largely Rankine type steam plants. These typically operate at 33% thermal efficiency. This is unfortunate, because nuclear fuel is extremely hot during plant operation. In theory this allows for very high thermal efficiency. Modern materials science has developed options for exploiting high temperatures to increase efficiency, notably with thermal barrier coatings developed for jet engines (Brayton cycle devices) and combined cycle devices.

I have convinced myself that heat networks can be built using nuclear fuels which may reach, even exceed, 70% thermal efficiency, exceeding the best thermal efficiencies achieved by dangerous natural gas fueled combined cycle plants, which can approach 60%. Some of the 70% thermal efficiency would involve the direct conversion of heat into chemical energy, captive hydrogen to make fuels, but the thermodynamic penalty normally associated with storing energy, would not matter since it would represent energy normally rejected to the environment as waste heat.

Although I'm not an MSR kind of guy - I don't oppose MSRs, I just think there are better options - the use of heat networks are very possible for MSRs. The Wyoming hybrid reactor being build by Terrapower will apparently store thermal energy in molten salts. I'm OK with that; it's not the best option, but it's certainly a good option. It will however not use molten salt fuels, but molten salt heat transfer, something I regard as a very, very, very, very good option. The options I recommend to my son will involve some salt based heat transfer.

[Hokie]

10. I did not mean to be inaccurate

I have seen some pro-MSR sources that claim PWR only consume 1-2% of the fuel. I think you are implying the fraction of fissile material in the fuel is initially around 8% then. If the 4% fissile material left in spent fuel is mostly recoverable that makes a huge difference. Yes, the energy density of nuclear fuel is amazing.

[NNadir]

11. No problem. In the old days, burn ups were very low, and such a figure in older literature...

...does not surprise me.

This may have been routinely true, say in the 1980's, when many of the reactors that now serve us were relatively new. Burn ups in those days, particularly when run by incompetent operators like SMUD in California or Maine Yankee, could be as low as 20,000 MWd/ton. Properly run by competent people, these reactors might have saved lives and helped prevent climate change. That didn't happen however. They had short operational lives as well as low capacity utilization, leading to much cheering by stupid people who thought so called "renewable energy" would save us. "Renewable energy" didn't save us. We're in a hell of a fix.

As a caveat, in my opinion, the MSR people do overhype their fuel advantages a bit. The big advantage for fluid fuel reactors, not limited to MSRs by any means, is they offer the opportunity for in line processing and, capacity utilization of 100% over a period of many years with no shutdowns excepting those for routine maintenance.

Well run reactors today, which feature the highest capacity utilization of any power system, generally greater than 90%, routinely feature burn ups over 40,000 MWd/ton. Although PWRs and and BWRs in the United States developed on 1950's and 1960s's technology in an age before advanced computer power are in no way the best devices possible, with the exception of Three Mile Island - still a huge bugaboo to rather mindless people 4 decades later - and a few outliers described above, they have been the most successful energy devices ever built in a purely environmental sense. They saved a large number of lives that otherwise would have been lost to air pollution and might have saved more without all the appeals to fear and ignorance they engendered. It is notable that while some assholes still claim nuclear energy is "too expensive" - having a very low understanding of external, and for that matter internal costs - the United States historically built more than 100 reactors while providing the lowest cost electricity in the industrial world and we are still using reactors built well before many now functioning adults were born. They were largely a gift to our generation, but not being too bright, we looked this gift horse in the mouth much to our disadvantage.

Anyway.

My favorite thermal reactor, the HWR (CANDU), has low burn ups, since they run on natural unenriched uranium. (They also can be continuously refueled.) Under these conditions, CANDUs, although they use uranium more efficiently and cheaply by avoiding enrichment, can be significantly less than 20,000 MWd/ton. Theoretically the burn ups in CANDUs can be much, much higher, by incorporating plutonium, depleted uranium and thorium. I've heard figures like 60,000 MWd/ton. Such an approach would require changes to fuel management but in theory could greatly reduce the need for any energy mining anywhere at any time.

The current generation of breed and burn reactors, such as those developed by companies like Terrapower, Nuscale etc also offer extremely high mass efficiency since they are fast spectrum reactors. The press on them is that they are designed to never need refueling in their lifetimes.

Per Peterson's KAIROS reactors are hybrid TRISO/MSR types, but here the molten salts are heat transfer tools. I haven't looked into the details however. At one time he wrote a lot about FLINAK, another molten salt, not necessarily an ideal salt, but one that is clearly superior to FLIBE. I haven't kept up with his work however, and I don't know much about the KAIROS technology, beyond a superficial understanding that they are hybrid pebble bed/MSR types.

I'm a nitride kind of guy, but there are some things about TRISO that strike me as not so bad, quite interesting actually. I'm fond of silicon carbide.