It is funny how little things can change your life. There I was, a thirty-one year old lieutenant commander with ten years of commissioned service, a wife, and two young daughters. Within a few months of performing that search, I had written a paper on nuclear gas turbine engines, had become addicted to spending as much free time as possible devouring everything I could find on the topic and I was trying to figure out how to turn the paper designs I was doodling into something real. Though I have no intention of dwelling on it during this tale, I have to admit here and now that there were several people in my life, including my lovely and loyal wife, who were not at all pleased with my new obsession.
This blog will not shy from the personal, but it is mainly aimed at trying to share the thoughts and technical decisions that have resulted in the concept I call the Adams Engine™. (By the way, that name itself has a story which I plan to share along the way.)
What's Wrong With Steam?If you have ever done much reading about nuclear power plants or even received an introduction at a visitor's center or in a textbook, you will probably be familiar with the idea that nuclear reactors are a means of producing heat that is used to boil water to create steam that then turns a turbine and produces electricity. Some of the many people that fight against developing nuclear energy generators like to demean this process by saying something like "just another way to boil water". Of course, boiling water is a venerable and useful thing to do with large scale heat sources; technical historians have often pointed to the development of the steam engine as the main driver in the Industrial Revolution that enabled rapid travel and reliable, mass production of many wealth enabling commodities.
However, as a steam plant engineer officer, I had a pretty deep experience base that led me to understand that steam power has its disadvantages that had resulted in the development of several more advanced cycles used to convert heat into useful mechanical power. Steam was fine for locomotives, factories and ships, but steam automobiles were far too bulky and balky for mass consumption and the Wright Brothers would have never gotten off of the ground if they had to carry a boiler and feed water with them. As time moved on, the machines like diesels and jet engines used to power smaller, lighter applications had grown up to compete quite well with steam for the larger scale applications like ship propulsion and were even making large inroads in the electric power generation market.
There is always an advantage in using less material when making a product and in making products that take less effort to operate. Steam plants by their nature require lengthy, thick-walled piping systems, heavy water storage tanks, and very careful chemistry control to reduce corrosion. In their boilers, multi stage heat exchangers and condensers, they also use a multitude of thin walled, small diameter tubes that are in challenging chemical, thermal and physical environments that tend to lead to deterioration over time.
Because of the large temperature variations and high pressures used, there is always a need for great care to prevent material failures that can cause serious injury or death. Steam plant operators are a proud bunch that need excellent training and often extra pay to account for the difficulty and importance of their assigned work. Even with the extra pay, it is often difficult to attract enough people to the field; the nature of steam plants also leads to a rather uncomfortable work environment characterized by high ambient temperatures and elevated humidity.
These characteristics of steam plants can be mitigated with advanced designs and materials along with automated control systems, but they can never be eliminated. I am proud to be a steam engineer, but I recognize that steam is not for everyone, especially if they happen to be accountants. The only places where steam can still be competitive in power markets is where it enables the use of really low cost fuel - like lignite or coal - that has too much "stuff" in it to burn cleanly enough in an internal combustion engine or in Brayton cycle turbine engines. The need for reasonably clean fuels in those systems is not just because of concerns about pollution - the ash and other contaminants in coal, lignite and many biomass fuels would degrade the internal components of pistons and turbines so much that the machinery would fail.
Traditionally, steam has also been applied in nuclear fission power plants, even though the fuel releases its heat very cleanly. A major reason that nuclear power plants are considered more expensive than other alternatives like combustion gas turbines is actually associated with that assumed need for steam as the working fluid.
In the Navy, we had been taught that diesels and gas turbines had replaced steam in most applications because of the reduced complexity of operation, the reduced manning required, and the smaller machinery systems required. Our teachers acknowledge that the choice had required the use of higher quality, more expensive fuel, but the tradeoff was considered to be worth it except in cases like very large, high speed ships that consume enough heat to make fuel costs a large consideration or on submarines where oxygen and exhausts are strictly limited.
Is There An Alternative to Steam For Fission Heat?Before I had served as Engineer Officer, I had attended the Navy Postgraduate School in Monterey, CA. While there, I had a running mate named Mike LeFever who had just finished serving as an engineer officer on a gas turbine ship; we often talked about the difference in his experiences and mine while running along the path between Monterey and Pacific Grove. While struggling with steam generator chemistry, leaky steam valves, and slow plant warm ups during my tour, I often thought back to those conversations. However, I also used to tease Mike about "that underway replenishment thing" and the need for large smokestacks to dump his plant's waste products. I liked having a plant that could run for decades between refuelings and that allowed us to breathe while submerged.
When on shore duty at the Naval Academy, I decided to take a few advanced engineering courses. You see, though the Navy allowed me to serve as an Engineer, my undergraduate degree was in English, so I felt a little disadvantaged at times in groups of my peers and wanted to fill in some gaps in my detailed knowledge. As a member of the staff/faculty, I could take the courses for free. (There are not many people that take advantage of that benefit; I have been stationed at the Academy for 4 academic years and have never seen any other officers in courses with me. I guess I really am kind of a geek - or maybe just a cheapskate who prefers free classes without credit to the same class at another school in the evening.)
The first course I took was Power Conversion and one of the assignments was a paper on an advanced power system. That was the assignment that took me to the library and initiated the search to determine if it was technically possible to combine the mechanical advantages of Brayton Cycle gas turbines with the fuel cleanliness and density of uranium fission reactors. I realized that not only was it possible, but that it had been recognized for years as an almost ideal way to capture and use fission heat.
"The "ultimate" nuclear plant for merchant ship propulsion appears to be some form of direct cycle reactor-turbine, eliminating steam and other forms of intermediate heat exchange. There are indications that such a cycle might be a pressurized gas reactor coupled directly to a gas turbine."Once I figured out that atomic Brayton Cycles were possible, I decided to apply one of the important lessons I had learned as an Engineer in Rickover's part of the Navy. I began "pulling the string" to figure out why this idea had not been pursued to wide scale implementation.
Source: Crouch, Holmes F., Nuclear Ship Propulsion, Cornell Maritime Press, Cambridge MD, 1960 p. 140