Smaller nuclear power plants

[Rod Adams]

One of the common misconceptions about nuclear power is that the plants only come in extra large sizes. I think it might be worth some time to talk about all of the various projects underway in the world to build fission power plants that are focused on providing reliable, emission free power in smaller chunks to areas that are currently either power deprived or dependent on tenuous lifelines of fossil fuel.

Any takers on this topic?

Rod Adams
Publisher, Atomic Insights
Host and producer, The Atomic Show Podcast
Founder, Adams Atomic Engines, Inc.

(Yes, I have a vested interest in finding out what people all over the world think about the idea of smaller nuclear power plants.)

[Lantzelot]

Hi Rod,

I think Sulphur-Johan will cheer about this, he is probably the one of us who knows the most about it. But please share with us your knowledge in the subject!
In Sweden I do not think I ever heard anyone except Johan speak about it as an option, it is certainly not on the political agenda...yet!

[Michael]

Hiya Rod!

Personaly I'm ambivalent of dotting small nuclear reactors all over the place. The advantages are obvious: reliable power, both electricity and heat, for industry, small towns, suburbs etc... with decreased dependence on long distance power transmission. There are some downsides though. One of the reasons I'm for nuclear power is that today's nuclear plants allow concentrating competence to a few select spots. You also get easier inspections and reviews of the sites. Review and keeping an eye on things is one of the things that make nuclear power safe. In short: keep it tight and neat. I'm kind of worried that dotting mini-reactors all over the place might erode that.

Then again... I may be jumping to conclusions. First of all they must get mini-reactors, like Hyperion up and running! Then we can toss it all at the NRC or whatever regulatory bodies are out there and hear what they have to say. In any case it is worth looking deeper into the concept, but I'm not yet entirely sure that we will be dropping nuclear batteries all over the place.

/Michael

P.S: In case you're wondering about "Sulphur-Johan... we have two Johans in NPYP at the moment, Johan Simu and Johan Kilberg. In order to keep them apart, we gave Johan S the nickname "Sulphur-Johan" while the other, Johan K is "Potassium-Johan". Simu is the reactor physicist among us so he's the one with the biggest fetish for new reactor designs.

[Rod Adams]

I'll start with a brief word about my background in reactors - I learned my trade on relatively small reactor heated power plants used to push submarines. Though certainly not tiny, these machines operated on a very human scale that made sense to me. They were small enough to be operated and maintained by a small crew (I had less than 30 nukes working for me when I was the Engineer Officer) and also small enough so that I could do a reasonably thorough inspection of the facility in just a few hours. Even with my liberal arts undergraduate education (I was an English major in college), I managed to learn enough about the details of the technology and all of the pieces and parts that made it work so that I was always comfortable that the plant was well under control.

Somehow, I managed to step back a bit from the daily grind of trying to operate this facility under the stringent, human imposed rules and paperwork and realized that it was a very simple machine with a core that was a thing of almost poetic beauty. Simply by adjusting the position of neutron absorbers, we were able to start up from any temperature, establish a steady rate of heating, and then level off the reactor at the desired temperature. After that process was complete, the reactor pretty much took care of itself as we operated the steam plant to produce whatever power level the ship drivers desired. (Because of the way we were trained in the US Navy, I was also a ship driver, not just an engineer.)

In the early 1990s, I had the opportunity to do some library research and realized that most of the world thought that nuclear power inherently meant enormous machines that produced 50-100 times more power than the reactors I learned on. As a guy who has done a little traveling and visited some power plants in smaller towns, I kept wondering why, especially as I learned more about pollution. I kept thinking back to our closed systems on submarines.

I found out about the German AVR project, and about the investigations that had been going on almost since the very beginning of nuclear fission power to try to combine the simple machinery of Brayton cycle gas turbines with reactors that could produce suitable gas temperatures. Those made so much sense to me (several of my Navy buddies have been engineers on gas turbine powered ships and have demonstrated to me that their engines were much simpler than steam plants).

One of the challenges that seemed to be in the way of success of previous attempts to bring high temperature reactors together with gas turbines is that the researchers wanted to take several giant technology steps at one time. They not only wanted to use a closed cycle gas turbine, but they wanted to operate it at high pressure and to use helium as the working fluid. Both of those are problematic in that they require completely new machinery and a full development path for that machinery that had to be completed before they could put it together with the high temperature reactors - which also needed some time and money to complete their development to allow them to operate at an even higher temperature (desired so that the overall system would produce the most thermally efficient nuclear plant ever.) The quest for the ultimate in high efficiency also led the researchers to propose several "improvements" to the simple Brayton cycle including intercooling and recuperation. All of these enhancements worked fine as long as they remained on paper, but practical challenges impeded progress in every project that attempted to develop the ideas using real metal.

I thought back to the simple combustion turbine machines that my buddies had showed me on Navy ships. They have an air intake, a compressor, a burner, a turbine and an exhaust stack. I also thought back to the "heater" on my boat and imagined using the pebble bed technology for a similar heater that would simply stay at a predictable temperature (because of the negative temperature coefficient of reactivity). (My concept for a pebble bed gets rid of the on line refueling system and the notion of moving the pebbles around during operation.)

I learned a bit about the challenge that combustion gas turbine designers have in regards to maintaining temperature and thought that the nuclear version would actually simplify some design considerations. I also thought about the temperatures and pressures used for combustion gas turbines and realized they allowed reasonably compact machinery without requiring thick boundary walls or extraordinary effort to seal between the stages of the compressor and turbine.

The real aha moment came when I tried to work my way past the helium challenges. I tried to explain to a combustion turbine engineer that I wanted to find a shelf model compressor turbine set that would operate reasonably well with helium; the man almost laughed at my ignorance. He explained the differences in Reynolds numbers, specific heat, specific mass, and sonic velocity and told me that I would have to start all over with blade design, interstage sealing, and even rotational bearings. Then I remembered that N2 is a lot like air and that it behaves reasonably well in a neutron flux. I went back to that engineer and asked which existing compressor turbine sets would work with N2 and he gave me a simple answer - all of them.

So, that is a long winded explanation for just one of the possibilities that I see for much smaller reactor power plants. Use a fixed pebble bed reactor as the heat source. In early models, operate that heat source to produce easily achievable and well proven temperatures of 700-900 C. Use a compressor/turbine combination with demonstrated industrial capacity and reliability. Use N2 as the working fluid with compressor inlet pressure at standard atmospheric pressure, a pressure ratio selected using standard Brayton cycle analysis based on the available reactor gas temperature, and then cool the outlet of the turbine with air or water to remove the waste heat and complete the cycle. Control the power output the same way you control the power output of a steam turbine - adjust the gas flow through the turbine.

As one of my non engineer, but watch officer qualified ship driver friends describes it, that system is understandable with the following mantra - suck, bang, blow, go. (In the Navy, we try to teach people simple ways to remember what are occasionally complex concepts. In this case, the Brayton cycle is simple compress gas, heat gas, expand gas, cool gas - repeat.)

Of course, there are enhancements to this system that can be attached AFTER we have built and operated machines, trained a cadre of operators, and built a market in all of those wonderful places in the world where affordable power is not currently available and where cleaner power is a desirable goal that allows us to charge early adopter rates to pay off the development and bureaucratic overhead that has been imposed by people who LIKE selling coal, oil and natural gas.

I personally like the idea of expansion of this knowledge and power to as many people as possible, I am not a big fan of concentrated power or wealth.

Hope this story generates some thought and discussion. (Of course, the Adams Engines also just exist on paper, but we are working hard to change that and seem to be making some progress toward that goal without any physical or technical hurdles in the way. Those bureaucratic hurdles are a challenge, but it is easier to overcome human rules than natural rules.)

Rod Adams
President, Adams Atomic Engines, Inc.
Publisher, Atomic Insights
Host and producer, The Atomic Show Podcast

[Michael]

That's a very interresting read Rod! Thank you.

I think we all agree that switching to reactors that allow using the Brayton cycle is something to strive for, no matter if we are talking small or large reactors. The thermal efficiency of today's uranium samovars, with LWR's and PWR's being the most common types around the world, is shamefully low. In Sweden alone, we throw away 130 TWh of thermal energy yearly from nuclear power, with a mere 65 TWh becoming useful energy. In engineering speak: this is not an elegant solution.

This however is also one of nuclear power's greatest strengths today: it has <b>huge</b> potential for improvements. Switching to higher temperature reactors allows better thermal efficiency, and switching to closed fuel cycles or once-through fuel cycles that burn up more than a measly 2-5% of the fissile material, can give improvements in fuel efficiency that is in the range of 2500-5000%, a nearly unbelievable figure! This is while renewables such and wind and solar are at nearing their ceiling. Wind power is at 50% of 59% possible. That's a mere 20% increase left. Photo-voltiacs are at about 20-30% for the economically viable cells... which gives at best a 500% increase in efficiency, although on a cloudy day 100% of 0W is still 0W.

The question about small reactors though... I think that the biggest use of small modular reactors we'll see will be for nuclear plants. Cluster 50 Hyperons together and you'll get a near uninterruptable power plant, save for getting disconnected from the grid.

/Michael

[Rod Adams]

Michael - there is little doubt that clusters of smaller nukes will capture some of the market - in many ways the concept is not unlike the way that Google puts together what are effectively super computers based on clusters of essentially PC's.

However, I still believe there is a much larger market for distributed power plants that most urbanites recognize. The world is a big place full of people that do not have any access to reliable, clean power at an affordable price, but those people have the same needs and desires as the rest of us.

There are also some fantastic places to live where there is plenty of salty water and not enough fresh water. As a former submarine sailor I know very well that taking out the salt is a pretty simple process if you have sufficient supplies of energy.

I must caution you on the quest for ultimate thermal efficiency, however, no matter how "inelegant" it feels to "waste" thermal energy. The first Adams Engines will probably achieve something like 20% efficiency at first, but they will be very simple, low capital cost machines based on fuel that is readily available at about 50 cents per million BTU (compared to coal at $1.50). There will be a lot of heat coming out of our coolers at first.

Of course, we recognize that the heat has some value and should be captured, but that is a later step. One of the nice things about smaller plants is that cogeneration concepts are much easier to develop because there are a lot of industrial customers that need reliable heat as much as they need electricity.

[Michael]

It's not that I don't agree that small reactors don't have their place! Just like wind, solar and similar have their niches to fill, small nuclear reactors will have their place too. Every solution must be concidered for every application and individually judged based on its merits.

The future will tell there the minis will show up (hopefully not in russian light houses again... *shiver*). The next step will be to see the Hyperion through the NRC approval process (see page 8).

/Michael

[Rod Adams]

Michael - on Monday, March 30, I had the opportunity to present some thoughts about small nuclear gas turbines at a local college. I followed Deb Blackwell of Hyperion on the program and spent some time chatting with her during breaks and at lunch.

Their system design efforts are progressing well, they been hiring on a measured and steady pace and they have continued with casual discussions with the NRC. They have not yet asked for formal docketing for several good and logical reasons:

1. Once an applicant gets docketed and engages in formal license reviews, a lot of valuable commercial information suddenly becomes public information.

2. In the US, our process also requires the applicant to pay all government charges for their application review. The current fee structure allows the government to charge $258 per bureaucrat hour for a process that lasts for approximately 42 months and involves a number of public hearings and comment periods. As you might imagine, the process can eat up tens of millions in venture capital without paying a single technician or manufacturing worker.

It is prudent to wait until fully ready to begin the process, even though there is a day for day delay between the time of application and the time of license approval. Hyperion should be filing their manufacturing license application before the end of 2009.

Rod

[Michael]

2. In the US, our process also requires the applicant to pay all government charges for their application review. The current fee structure allows the government to charge $258 per bureaucrat hour for a process that lasts for approximately 42 months and involves a number of public hearings and comment periods. As you might imagine, the process can eat up tens of millions in venture capital without paying a single technician or manufacturing worker.

*picks up jaw from floor*

Jumping neutrons.... that is just unbelievable. That fee is just through the roof! I mean I work as a consultant for an IT company, and even though we've had to slash our prices, not even during boom times did we charge such insane hourly fees! Sweet Isaac Newton's wig...

/Michael

[myatom]

Hi, gentlemen!
I hope you are still interesting in small reactor topic even if it is frozen here for months.
Let me revive the discussion with my question about the market.

I see the renewal of small and medium size reactors issue in the nuclear world. A number of new projects had been proposed or restarted last time. All these names of Hyperion, mPower, 4S, IRIS, Traveling-Wave etc. We got a number of they here in Russia - SVBR (lead-bismuth), ABV (water with natural circulation), VBER-300 (LWR on sub basis). But they all are paper reactors (even if take into account our KLT-40 floating project that is now on some construction stage . Why?

I personally am not involved in small and medium size reactors design, but I am interesting in it because of really elegant ideas behind it. So I wonder why are they all still on paper? I came to the conclusion (intermediate, I hope) that it is because of market situation or, in other word, because of absence of real demand in this reactors.

A month ago Thomas L. Sanders, ANS President, came to visit Russian Nuclear Society annual meeting. He made the presentation about "Right-sized Reactor" the same as he made at ANS meeting. But when he discussed who is going to be the customer of that innovative American reactors he pointed it out quit vaguely - they all are outside US, somewhere in Asia, developing countries with growing demands...
But what is that countries with poor grid infrastructure that could afford a number of reactors 1-300 MWe?

Now in Russian nuclear press there is some kind of discussion about small and medium size reactor for Russian northern and far eastern territories. The discussion was started again of a series of article by Dr. Tschepetina from Kurchatov Inst. She insists there is a great demand (up to 20 GWe) in the reactor of 1-100 MW for supply small towns, ports or mines in Siberia and Russian Far East. But this demand is so unstructured and specific that neither mining companies nor federal government not ready to order that reactors.

The market of small and medium size reactors (if it exists) seems very complex. There are theoretical needs in reactors of very different types - from several MW batteries for distant settlement on Northen Sea Route to the hundreds MW reactor for the town with giant mine of ore. And add here different reactor lifetime needed in different places. So there is no universal reactor would cover all spectra of needs that we can manufacture in some urban places and transfer to the site. And so it is hard to get reasonable economics for each of that reactor projects...

So, can you specify more carefully what do you think is the market for the small reactor?
Or - how to build this market?

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