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Sun May 20, 2018, 09:43 PM

Brief Comments on the Moltex Reactor Concept and Nuclear Creativity...

Light water nuclear reactors and, albeit not on the same scale, heavy water reactors, have been spectacularly successful devices that have saved, according to Pushker Karecha and Jim Hansen's calculations - which I cite often - close to two million lives that otherwise would have been lost to air pollution.

Prevented Mortality and Greenhouse Gas Emissions from Historical and Projected Nuclear Power (Pushker A. Kharecha* and James E. Hansen Environ. Sci. Technol., 2013, 47 (9), pp 48894895)

None of this is meant to imply that nuclear technology is risk free; clearly it isn't. However, nuclear technology need not be risk free to be vastly superior to all other forms of energy, all of which, in terms of risk, when compared to nuclear energy have vastly - and I do mean vastly - greater risks than nuclear energy, despite the extremely ignorant selective attention paid by the awful and mindless anti-nuke mentality that goes around killing human beings continuously and entirely unnecessarily by the use - and regrettably publicly accepted - of incredibly poor logic.

Of course, these reactors, light and heavy water reactors, might have saved more lives were it not for the fear and ignorance of anti-nukes, a group of people for whom I openly hold in intellectual and moral contempt.

The huge success of light and heavy water reactors in saving human lives notwithstanding, these reactor types represent only a tiny subset of possible nuclear reactors. Early in what Alvin Weinberg - once the head of the Oak Ridge Laboratory - described as the "first nuclear era," a number of other types of reactors, generally as prototypes, were built and operated with varying degrees of success. Some very interesting and potentially superior forms of nuclear reactors (to the spectacularly successful light and heavy water versions) were built and operated on a pilot scale.

Weinberg, pictured below with John F. Kennedy and Al Gore's father (then US senator Al Gore Sr.) in the control room of an Oak Ridge Reactor wrote a book with the title evoked above, The First Nuclear Era, Life and Times of a Nuclear Fixer



A few other reactor types have also been commercialized, for example, the British commercialized two novel reactor types, Magnox reactors, and AGCR, the Advanced Gas Cooled Reactor. (An American Gas Cooled Reactor which used helium rather than the carbon dioxide coolant in the AGCR was an economic failure.)

The first Magnox reactor, Calder Hall I, was commissioned in 1956 - making it the western world's first commercial nuclear reactor - and operated until 2003. Although they were developed using 1950's technology, they were rather successful devices. Calder Hall I shut after 47 years, the record for this primitive technology, and 18 of the 26 examples of this type of reactor operated for 40 years or more before being decommissioned, the last one, Wyfa 12 being shut down in 2012 after 41 years of operation.


In the last decade or so, many people have been focused on the LTMSR, Liquid Thorium Molten Salt Reactor, based on an experiment supervised by Alan Weinberg, the MSRE, which involved a solution phase reactor consisting of a molten salt, a eutectic mixture of lithium fluoride and beryllium fluoride - a mixture called "FLIBE" - in which thorium tetrafluoride and uranium tetrafluoride are dissolved. The uranium in this case is a synthetic isotope, U-233 formed from the capture of a neutron in thorium followed by two beta decays. (The very first commercial nuclear reactor operated in the United States, the Shippingport reactor, ran for one fuel cycle on thorium/U-233 fuel.) U-233 (unlike U-235) is, under the thermal neutron spectra resulting from interaction of fast neutrons with moderating lithium and beryllium, a breeder fuel, and therefore can be used to accumulate fissionable fuel.

For a while I was personally intrigued by this idea, and dreamed up several modifications, some of which other people had also thought of before I did, and a few that might have been purely original.

Ultimately though, I changed my mind about this reactor, sometimes advertised as "off the shelf," mostly because I cannot endorse a reactor utilizing beryllium, which is an extremely toxic element, and which, although in its natural form is monoisotopic beryllium-9, can absorb a neutron to make the long lived radioisotope beryllium-10. (Also one isotope of lithium, Li-6, generates tritium in a neutron flux. This would be fine in a world in which fusion reactors were a reality, but might otherwise prove problematic, even though the decay product of tritium (half life 12.23 years) is the valuable and rare helium-3 isotope.

To avoid tritium accumulation, it might prove necessary to separate out lithium-6, an expensive process, although one with considerable industrial experience owing to the use of lithium-6 in the manufacture of thermonuclear ("hydrogen" ) bombs.

Other people have noted some of the problems with the lithium/beryllium reactors and have come up with some inventive ways of avoiding its problems.

I was recently directed in this space to another modification of this type of reactor, which apparently is designed to avoid some of the problems with FLIBE reactors, the "MOLTEX" reactor.

The post directing me there, in response to my comments about my favorite reactor type du jour, the LAMPRE is here:

MOLTEX

My LAMPRE comment, to which the above was a response is here: My hope is that in a future time, this plutonium will have real value. Bomb cores based...

The MOLTEX company website is here: Moltex Energy

I've spent some time going through the MOLTEX concept. (The document is rather long, well written, well thought out and nicely illustrated.) From my perspective, it's not the type of reactor I would find to be ideal for various reasons I have no time to discuss, but what is beautiful, absolutely beautiful, is the return of nuclear creativity that was described in Alvin Weinberg's wonderful book about the early days of nuclear creativity.

The MOLTEX, is not a breeder, by the way, and from my perspective, I am mostly interested in breeder reactors, since I have convinced myself that depleted uranium and thorium waste from the lanthanide mines used to build stuff like wind turbines and electric cars, can eliminate all energy mining for several generations, if not forever.

Unfortunately most breeder reactors built on this planet have been problematic, although a few have had decent, if not great, performance. Creativity has been lacking in these kinds of reactors, since for reasons that escape me, they have all relied on liquid sodium coolants for the most part.

I'm rather fond of liquid metals, in particular liquid plutonium and liquid plutonium alloys of various types, but liquid sodium is not my cup of tea and I think we need to think anew about liquid metal coolants.

The kind of reactors I dream up all operate at extremely high temperatures, because high temperatures imply high efficiency, and the opportunity to generate electricity as a side product while using nuclear heat for carbon dioxide and/or water splitting as a means of reversing climate change, a very, very, very challenging engineering problem that is just on the edge of "remotely possible."

As for the Moltex, it is nice, very nice, to see the re-emergence of interest in nuclear creativity. If you are interested in nuclear technology, enjoy.





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Reply Brief Comments on the Moltex Reactor Concept and Nuclear Creativity... (Original post)
NNadir May 2018 OP
hunter May 2018 #1
NNadir May 2018 #2
John ONeill May 2018 #3
NNadir May 2018 #4

Response to NNadir (Original post)

Sun May 20, 2018, 10:37 PM

1. The The Moltex pdf throws a bone to renewables on page 9...

This capital cost is actually lower than a comparable Combined Cycle Gas Turbine plant operating at the same, quite typical, capacity factor. MIT and the University of Berkeley carried out a study and the increased value of electricity produced when it is flexible in this manner is 42% in Texas and 67% in California. This need for flexible power will only grow in the future as renewables expand.

http://www.moltexenergy.com/learnmore/An_Introduction_Moltex_Energy_Technology_Portfolio.pdf


One might wonder why the use of renewables would expand if inexpensive nuclear power is available, especially from such a responsive system as this.



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Response to hunter (Reply #1)

Mon May 21, 2018, 06:57 AM

2. One has to sing the national anthem at sporting events.

And it's kind of like that, a rote recitation that has no meaning.

Lots of money is being thrown at renewables to make them "expand."

The problem is that they are financially inefficient and that they are expanding at only a tiny fraction of the rate at which fossil fuel use is expanding.

According to the 2017 World Energy Outlook, in this century dangerous fossil fuels expanded by 130 exajoules; so called "renewables" by less than 7 exajoules.

The Moltex is well thought out from what I can see, but it's not an ideal kind of reactor and most importantly, it's a paper reactor.

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Response to NNadir (Reply #2)

Sat May 26, 2018, 09:16 AM

3. Moltex

Thanks for that Nnadir. Apparently the Moltex team have given up on getting licenced in the United Kingdom in any useful timeframe, and are working on getting a prototype built in Canada. A shame, since the UK will need to replace all its gas-cooled reactors soon.

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Response to John ONeill (Reply #3)

Sat May 26, 2018, 01:37 PM

4. My pleasure John. I spent a little more time looking the Moltex over.

It has certain features that are an improvement of FLIBE type and other salt systems that are FLIBE like, for example, FLINAK.

Nevertheless, I have a number of reservations about this type of reactor, its benefits aside. (Chloride is not an anion I'd chose for a reactor, because I see a necessity for considering isotope separation.).

I'm not sure about the putative ZrCl4 distillation will work. It works in neat solutions, possibly those with enough energy to dissociate the normal hexacoordinate polymer, but it also forms group one hexachlorocomplex ions, particularly with cesium and rubidium, both of which are fission products. I don't know this a problem but I would b

Some hears ago, I was rather enamored of a gas phase separation between plutonium and uranium from fluoride based reactors continuously during operation in a breeder situation only to learn about the interesting stability of cesium and rubidium complexes of the the (V) actinide fluorides. I abandoned this line of thinking not because the problem is necessarily insurmountable, but because I can think of approaches that can be investigated more cheaply experimentally

The temperature of the Moltex is generally too low for use in thermochemical cycles. I regard this technology a key point at phasing out high density fuels based on either dangerous petroleum or dangerous natural gas.

Finally I would be concerned about neutron economy. I believe it is incumbent upon humanity to either eliminate or substantially reduce mining energy materials. We have enough depleted uranium and waste thorium from the wind and electric car industry to fuel humanity - almost all of its energy requirements - for many centuries before we'll even need to consider uranium from seawater. (If however, we choose to process seawater for other purposes, such as desalination, we can collect uranium as a side product; the Indians have such a system already piloted.

I believe that the ultimate reactor to do this will be a "breed and burn" scenario. I've imagined lots of these over the years.

Over the years of considering various breeding ratios of actinides and their compounds, I have found that liquid plutonium is the best such fuel. It produces 1.6 excess neutrons if the literature from the 1960's can be believed.

I have ideas on how to address the tantalum issue that was associated with the LAMPRE, and completely eliminate it.

I've been investigating novel materials that were not even imagined in the 1960s.

Finally, I've convinced myself as well that it is entirely feasible to spontaneously separate the most problematic fission products from the fuel more or less continuously so that they can be put to use to address important environmental and energy uses.

My next dream is to eliminate turbines, but that's far off.






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