A Survey of Nuclear Microreactors Designed to Produce Thermochemical Hydrogen.

[NNadir]

Last edited Sun Dec 1, 2024, 12:06 PM - Edit history (1)

Hydrogen, because of its very poor physical and chemical properties, along with incompatibility with many materials, notably metals like iron, is a very dangerous material, even when handled by highly trained and highly educated chemical engineers.

The hype about making hydrogen a consumer product should disgust knowledgeable people in my view; nevertheless, every decade or so, dangerous and disingenuous "hydrogen economy" garbage rears its ugly head, usually promoted by the fossil fuel industry in an effort to secure its position, which it has successfully done, albeit at great cost to humanity.

Nevertheless, as a captive chemical intermediate, hydrogen is an extremely important industrial compound, primarily for the production of ammonia, on which the world food supply depends. It is overwhelmingly made from the reformation of dangerous fossil fuels for this (and other) purposes, and its production is a significant contributor to the extreme global heating we now experience world wide. Nevertheless, itt can also, in theory, though not in practice, contribute to closing the carbon cycle if made in a sustainable fashion, which is decidedly not how it is made now.

Anthropogenic Chemical Carbon Cycle for a Sustainable Future George A. Olah, G. K. Surya Prakash, and Alain Goeppert Journal of the American Chemical Society 2011 133 (33), 12881-12898

In particular, it may be used to hydrogenate carbon dioxide to make fluid fuels such as methanol and DME (dimethyl ether) as discussed in the paper from Nobel Laureate George Olah above, shortly before his death.

The hydrogenation of carbon dioxide to make methanol is already an industrial process, and is often discussed in the primary scientific literature. Just yesterday, in my general reading, I came across a paper (hundreds if not thousands are published each year) discussing this topic:

Analysis of Dynamic Characteristics of Reconfigurable Modular Reactor Systems for Renewable Methanol Synthesis Xin Gao, Xinshan Kong, Lixia Kang, and Yongzhong Liu Industrial & Engineering Chemistry Research 2024 63 (43), 18479-18496

The paper refers to hydrogen sources from so called "renewable energy" which is not sustainable, but nevertheless, might be approached as a drop in for sustainable and clean energy, of which there is one, and only one, form, nuclear energy.

The paper I will briefly discuss in this post refers to approaches to making industrial hydrogen for captive use, by using nuclear heat, whereupon the traditional use of nuclear energy, to make electricity, a useful but thermodynamically degraded form of energy, will become a side product.

The paper is this one: Anshuman Chaube, Zayed Ahmed, Broderick Sieh, Caleb S. Brooks, Hitesh Bindra, Nuclear microreactors and thermal integration with hydrogen generation processes, Nuclear Engineering and Design, Volume 419, 2024, 112968.

From the introduction:

In an effort to mitigate climate change, low carbon energy solutions are being explored. One source of clean baseload energy is nuclear power, which is safe and reliable, has no direct emissions, and has median life cycle emissions (for instance, from plant construction; nuclear fuel mining, milling, and processing) lower than both solar photovoltaic and wind power sources (Markandya and Wilkinson, 2007, Qvist and Brook, 2015, U.S. Energy Information Administration (EIA), 2021, IPCC, 2014). The significance of nuclear power is also evidenced by its inclusion in near- and long-term emission reduction goals of nations such as the United States, China, France, and Japan (The White House, 2021, Yang et al., 2013, AP News, 2021, Electricity Review Japan, 2019). However, nuclear power plants have seen an increase in construction costs and construction times in the United States, and building a conventional, large-scale nuclear power station is perceived as a high risk endeavor (Lovering et al., 2016, Saunders and Townsend, 2018, Kessides, 2010, Davis, 2012). Therefore, there is renewed interest in smaller nuclear power plants that require lower capital costs (Testoni et al., 2021).

One such nuclear power technology is microreactors, which can typically generate up to 20 MW (Zohuri, 2020). They are being developed for applications such as integration with remote microgrids, supporting key military infrastructure and disaster relief efforts, and for process heat (Macdonald and Parsons, 2021, Gabbar et al., 2020, Nuclear Energy Institute, 2018, Ross and Bindra, 2021, Ross et al., 2023). Due to their smaller size, microreactors are uniquely positioned to act as a dependable distributed energy source. Additionally, the reduced footprint allows them to be deployed at remote locations or locations which have accessibility limitations for larger nuclear power plants...

The paper has a nice table of thermochemical processes for producing hydrogen:



Not all of these thermochemical approaches are desirable. Much of the world's hydrogen is currently made, as it happens, from the steam reforming of coal (coal gasification), particularly in China, with the combustion of coal providing the heat to do so. Nuclear heat would reduce the climate impact, but not to zero, thus, is unacceptable, since coal is a dangerous fossil fuel for which, in my view, the use should be banned. This is also true of the SMR process, steam methane reforming, which currently dominates the production of hydrogen worldwide, as well as POX (partial oxidation of methane), ATR, a combined methane oxidation scheme,

Also included in the table are three electrolysis methods, as well as an electrochemical modification of the SI (sulfur iodine) process, the HyS process. These may be acceptable only in the case where excess electricity is produced as a side product of thermochemical industrial processes, i.e. the case where electricity prices on the grid are so low that it is more profitable to utilize it in industrial processes like electrolysis, aluminum manufacture, and the FFC process for titanium and other metals. Of the electrolysis methods, the least destructive of exergy is the SOEC process, which is high temperature electrolysis using a solid oxide medium.

Note that the efficiency given for all these processes are for the processes themselves, but the rejected heat can be captured to generate electricity, this being the essential factor in process intensification, integrated heat flows.

Nor should this list be considered comprehensive; I note missing processes, and a few processes I can personally imagine that have not yet shown up in the literature to my knowledge. The table that follows refers to various kinds of small nuclear reactors that the authors consider as fitting the bill. Not all of these reactors will proceed to full development; many will fall by the wayside. Nevertheless a few designs, perhaps partially, or even greatly modified, may come through for use by a more sensible (and almost certainly more desperate) generation than the one that screwed the future, ours.

This should not be taken as soothsaying indicating that they will succeed; obviously bad ideas often prevail over good ideas, bad people over good people, and so on. This is, in fact, why we are where we are. It is merely to say it is feasible that these ideas, many generated in the United States, a country about to fall into intellectual and moral irrelevance because of public stupidity, public stupidity that is even worse than the idea of consumer hydrogen, consumer hydrogen being a very, very, very bad idea.

A table of reactor types:




There are some interesting graphics in the paper, notably relating to heat transfer properties, something I often discuss with my son to whom I am working to leave at least my best ideas. (He appreciated that I added thermal conductivity as a vector component in his goals in combinatorial optimization of nuclear material development.)



The caption:

Fig. 2. Figures of merits of various coolants (Air, Helium and H₂O at 7 MPa and others at 0.1 MPa).

A brief general description of both process reactions for thermochemical processes to produce hydrogen are given, as well as an overview of reactor designs.

It's a nice paper overall.

I trust you had a pleasant Thanksgiving holiday, the last probably for a long time in the old and dying American Democracy about to abandon its more than two century old Constitution to become an oligarchy run by venal and ignorant men. (There will be hell to pay.)

May there again be a future where ignorance does not prevail.

[ramapo]

1. Thanks

I've been reading your posts for 20-some years now and I still struggle to understand what the hell you're talking about most of the time. But I always get the general idea and appreciate your knowledgeable insights. I even, many years ago, saw the wisdom in your position on nuclear power. If only...

While I will never have a full grasp of the technical material you present (and I like to think of myself as fairly intelligent), we do share the sad knowledge that it is our generation that screwed the future. To make matters worse, we somehow also made sure that succeeding generations are just as stupid if not even more stupid. To think that I hoped that the younger generation might save us from ourselves....

We are going to have front row seats to the greatest disaster movie of all time which we will get to watch in real time no less.

Your last line is particularly apt and poignant. If you don't mind, I might use it from time to time.

"May there again be a future where ignorance does not prevail."

[NNadir]

2. Thank you for your kind words. Nothing makes me happier than to recognize that I changed a mind, having...

...done so myself, decades ago, with respect to nuclear energy after it became clear about the fact that the effects of Chernobyl were trivial compared to the destruction of the planetary atmosphere.

The topic is obviously now a passion of mine, since I do see it as the last, best hope of the world.

Feel free to appropriate the line you liked.