Hello iroseland,
The video was quite informative. According to the video, it would appear that the pencil pushers and bureaucrats have stood in the way of development of safer alternatives despite many engineer's and nuclear physicist's alternatives. One must have funding to see anything accomplished and the tried and true is winning. In this field we are still using old technology... If computer and phone tech, developed in this fashion we would all be still using floppy discs and rotary phones...
Regards,
O.A.

Thanks interesting.

Thanks interesting.

In some cases (not all), that would be true. I should point out that the coolants used in most of these concepts are not perfect in every area but usually do have superior properties in the areas of greatest intended benefit to that specific reactor type.

Gas coolants such as helium in VHTRs do not have flammability or corrosivity concerns, but gases have inferior heat capacity to liquids for use as coolants. The biggest benefit for reactors using certain gases is that higher temperatures and operating thermal efficiencies (and electrical generation efficiency) for the overall power plant can be achieved. The associated downside is the high temperature material property limitations of materials used by parts of the system and, in some cases, the cooling challenges during emergency shutdowns.

Fluoride salts in MSRs are highly corrosive, which is beneficial for dissolving used nuclear fuel into the mixture but more challenging for long-term corrosion of structural materials in the rest of the system.

Sodium has superior (near zero) neutron scattering and absorption cross-sections for use in a fast energy spectrum, breeder reactor. This makes achieving criticality easier and contributes to better nuclear fuel utilization. It is also a superior coolant. The annoying downsides for sodium are the safety risk of a sodium/air or sodium/water exothermic reaction (fire) in the event of a leak into a non-inert atmosphere. Thus, the design and operation of an SFR is more complicated in order to avoid or mitigate that issue. The melting point (206-208 F) is also just above typical ambient temperatures, which creates a risk of solidification of sodium in pipes for a system that is shut down long enough to cool down. That design challenge is addressed with pipe heaters, etc...

In the normal evolution of product designs in other industries, every successive generation of the product addresses or improves on the problems of the previous one. So, through steady learning and innovation, better designs are matured. The DOE has funded a significant amount of basic nuclear research and demonstrated concept viability for many reactor design concepts, as a result of testing in the 50s, 60s, 70s, and to a lesser extent afterwards. But due to various factors (like NRC regulations) mentioned previously, the pace of U.S. nuclear power plant innovation has been depressingly slow, since the normal evolutionary design maturation process occurs in fits and starts, or not at all...

My thought was that an ionic liquid would not be flammable and not be corrosive.

By lithium salt I mean lithium. The bonds that hold lithium salt together make it quite stable.

There is a version of it specifically made for lithium salt.

It would depend on the specific liquid and the type of reactor it's being used in as coolant. I don't think the "ionic" characteristic would provide a specific advantage but other characteristics potentially could.

Good coolant characteristics include high heat capacity, low pumping power requirements at the operational flowrate, good thermal conductivity, etc...

There are important neutronics characteristics required, as well, of the coolant. In a typical light water reactor, which requires fission neutrons to be slowed (moderated) to lower speeds and energies to fission the most U-235 fuel, the coolant needs low to zero neutron absorption cross-section and high neutron scattering cross-section (so collisions transfer energy and slow down the neutron).

In most advanced reactors that have the best nuclear fuel utilization, most operate with a fast (high energy) neutron spectrum. In that case, any coolant needs low neutron absorption and low scattering characteristics, so that the neutrons maintain high energies.

There are other design considerations tied to the coolant choice -- cost, corrosivity, flammability, safety features needed to mitigate or avoid accident scenarios, etc... Like any design choice, there are tradeoffs made.

All Gen III and IV reactor designs feature passive safety features and redundancies to avoid the safety deficiencies of past reactor failures. And any commercial power plant design is required to operate safely, reliably, and economically for usually 60 years.

I should probably clarify why I specifically pointed to VHTRs and SFRs as most likely Gen IV reactors the U.S. may use in the future (when?). I always gravitate to an "all of the above" policy both for types of energy sources and for technology R&D.

If MSRs, which have a lot of good features, ultimately can be developed and result in a superior combination of life cycle cost, safety, fuel utilization, etc., than it should be the preferred reactor design. I personally was excited to learn more about MSRs when first introduced to them.

There are a few reasons I specifically highlighted VHTRs and SFRs as most likely. First, they have received the most R&D funding in the U.S., and to varying extents, the most test reactor experience (especially EBR-I and EBR-II). So, they are closest to full development with better characterization of design issues, etc. for use either in commercial power plants or in a DOE-operated facility (in the case of SFRs).

Secondly, politics and bureaucracy have stifled innovation and progress in the U.S. commercial nuclear industry for years (due to varying extents to the NRC, environmental activists, DOE, politicians, etc...). If I had to bet money on any Gen IV reactor concept being built in the next 15 years, I would not given all of those impediments to innovation (especially the NRC). Keep in mind it is "illegal" in the U.S. to build and operate any nuclear reactor without mountains of licensing paperwork to/from the NRC. The DOE national labs and the NAVY nuclear program (subs, ships) do not fall under NRC's jurisdiction and are the only areas where innovation has very slowly occurred over the past 60 years. So, as wrong as it is, possible advanced reactor concepts like the MSR have to not only overcome the many technical design challenges, but also DOE R&D funding bias against the concept, NRC ignorance and licensing bias, environmentalist lawsuits, politicians abusing power, etc...

I hate to sound pessimistic about future nuclear progress in the U.S., but it is the most heavily regulated industry (commercial power) and doesn't fit the political agenda of most environmentalists (despite having virtually no carbon emissions that they focus so much on)...

This might be a stupid question, but could you use an ionic liquid instead of Sodium?

Here's a fun document describing various isotopes that just happen to be fission products and what they get used for: https://www.idph.state.ia.us/eh/common/p...

PBMR is actually quite different both in physics, lifespan, etc. The big thing different with PBMR was that a) the fuel pellets were not ceramic, b) the pebbles were coated in their own sintered moderator (graphite); and c) they were meant to be HTGR (high temp gas rxr), using something like CO2 or another gas for the primary coolant.

As for fusion, the old joke joke about fusion always being 50 years off is quite descriptive. At least with tokamak type designs you could envision a heat transfer mechanism to deliver power out of it. The only fusion mechanism enjoying success at the moment is the laser compression, and how do you make a power plant in that configuration???

True enough, but Kirk Sorensen has done a remarkable job of raising this technology from the apparent dead for the last decade plus. You'll find videos galore, TED talks, Google Talks, etc all over the internet. http://energyfromthorium.com is a good start, and I saw someone else with a link to one of the conglomeration videos that Gordon McDowell keeps putting together.

As a nuclear engineer - although granted with only a year of experience before the industry really went dark (pardon the pun) in the early-mid 90's - I was a big fan of the Integral Fast Reactor concept, an SFR (to use robertmbeard's terms) using liquid sodium first and second loops, metal fuel (vice ceramic) and on-site reprocessing via pyroprocessing concept. LFTR is a better concept by far, with most of the corrosion questions not looking nearly as insurmountable as 60 years ago.

iroseland,
The video looks very interesting. I am going to try and view it in its entirety tomorrow morning.
Thank you.
O.A.

actually.. one better..
http://www.haynesintl.com/pdf/h2052.pdf

The corsion problems with lithium salts at high temperature are pretty much just engineering
problems.

It seems that the biggest problems they need to do a bunch of solving for involve chemically separating the reaction products from the lithium salt and the remaining actinides. Some of the *waste* products from these reactors include some really useful rare earth elements. Also, it there will be some medically useful isotopes. The rest of the actinides should probably remain in the reactor till they are consumed.

This video is worth taking a look at..

https://www.youtube.com/watch?v=8Pyq8kCe...

Hello iroseland,
Yes, Hastalloy is very tough. It is used in Wheelabrators in the foundries I support for shot blast/peening, finishing and ceramic removal. In the past, I produced several molds to produce patterns for casting of Hastelloy Wheelabrator parts (Blades/vanes, impellers). It does have mechanical properties that suggest possible application. It is very abrasion resistant, but I am unfamiliar with its salt/corrosion resistance characteristics.
Regards,
O.A.

Hastalloy X or one of the Haynes Alloys.
http://www.haynesintl.com/historypage/hi...

There have actually been a number of newer better superalloys invented since the LFTR at Oak ridge was shut down. If they could operate walk away safe back in the 60's and 70's with material science from 40+ years ago it should not be hard to blow that success away..

Hello robertmbeard,
Yes, an alloy of stainless steel would be my first choice, although I am always hearing about new plating/coatings that can be applied including diamond. I'm sure there are many factors to consider including conduction, convection, etc. If a particular alloy of stainless will do the job economically, I would design with a redundant system for emergencies as well as maintenance so components could be changed out at necessary intervals. Certainly cost is a factor to be considered... unless it is our government spending tax dollars of course. :(
Excellent exchange.
Regards,
O.A.

There are always problems but the proof of concept is done. It ran for thousands of hours in Oak Ridge. Its time to build a power plant and work the production issues. From what I've read corrosion is not a major stumbling block.
It seems to me that if we wish to remain competitive in wold power generation it's time we turn loose the productivity and imagination of Americas industry.

It reminds me of the Pebble Bed Modular Reactor design from South Africa. For its forty-year span, you load it in advance with all the fuel it will ever need. And when its fuel is spent it is SPENT. You then pour concrete on top and bury the whole thing in place.

But the real goal--and let's not kid ourselves--is fusion.

Chief, I am a graduate of K-25, the manhattan
project UF6 plant (6.5 years there), where the
gas solidified when shut down. now, this does not
result in a wall-to-wall solid, I admit, but preparation
for this is not impossible. 208F is the melting point
of Na,, so you engineer in heated chambers for
the piping --- and crank up robots to do the
maintenance! cubic $$, yes. I wouldn't think it
smart to think of this for a sub.

maybe I'm missing something. -- j

p.s. Yes, the primary obstacles are politics, the
media, and the lawyers.

And in the infinite wisdom (sarc) of the US, we'll end up paying royalties, licenses and fees to use THEIR technology. Ironic, eh?

Shutting down a liquid metal plant is very difficult. It becomes a solid. That is why any emergency shutdown is almost permanent. The USS Seawolf from the 50's started out with one, and the problems withit made the design prohibitive. The Russians had one in the Alpha, but they had most of them go bad too. I would be nice for innovation and creativity to surface and make a breakthrough, any problem can be solved, if there are no politicians or lawyers nearby.

sounds similar to the breeder reactor of the Jimmy Carter era, the problem will be that the granola chomping nutbags that always file lawsuits and cause costs to rise to such a level that the projects die...are all a bunch of Luddites that want us all living in grass huts.