To Peoria by Atom

Those Magnificent Men and their Atomic Machines

To Peoria by Atom: Atomic-Powered Locomotives

It was 1954, nine years since the birth of the Atomic Age, three years since the first electricity was generated by atomic energy. The US Navy would launch the world's first atomic submarine next year, and the US Air Force would soon test the first atomic turbojet for aircraft propulsion. Other programs aimed to build atomic-powered aircraft carriers, cargo ships, rockets – and trains.

In the early years of the atomic age, atomic energy was seen as a technology analogous to the steam engine or the internal combustion engine, a new source of power that would naturally make its predecessors obsolete. Shielding requirements might make atomic-powered cars or kitchen appliances impractical, but it undoubtedly could and would be used for propulsion. First there would be ships and submarines, where size and weight was less of an issue. Then there would be planes and trains. This was simply the natural progression of technological development. Safety was a solvable problem, and cost would go down as more experience was gained and atomic reactors began to be mass-produced. The future was bright, lit by the atom's friendly glow.

Dr. Lyle Borst's X-12

Speculation about atomic powered locomotives began at least as early as 1946. But the real beginning of the atomic locomotive was in 1954 with Prof. Lyle Borst's X-12.

The X-12 began as a graduate student project at the University of Utah, but went on to be patented and presented in the popular press and at academic and industrial meetings. Prof. Lyle Borst, the project's leader, had been involved with Fermi in Chicago during the early days of the Manhattan Project. He helped design Brookhaven National Laboratory's Graphite Research Reactor before becoming professor of physics at the University of Utah. He had extensive experience with reactor design, and had been part of early efforts with the Federation of Atomic Scientists to lobby congress to keep control of nuclear weapons in civilian rather than military hands.

Figure 1: Prof. Lyle Borst

(Public Domain)

When Prof. Borst began teaching the Physics 280 Nuclear Technology course at the University of Utah, he made the centerpiece of the course designing an actual nuclear system. In 1952, the first year the course was taught, the class helped design the University's research reactor. The atomic locomotive project, or X-12, was the second year's project. Prof. Borst later said he chose it because “A) It was generally considered impossible; B) No known classified investigation was under way.”

In addition to these benefits, an atomic locomotive would be smaller and therefore much cheaper than a commercial electricity reactor. At the time, nuclear reactors for electrical power were having difficulty finding financing; they could only be cost-effective if they were big, requiring large amounts of capital to build. Prof. Borst hoped that an atomic locomotive would be a way to bring nuclear energy into the private sector with a lower upfront cost.

None of the graduate students in the course had any engineering experience, so technical advice was obtained from a number of railway operators and locomotive manufacturers, including GM, Commonwealth Edison, Babcock & Wilcox, Trane, GE, Westinghouse, and McQuay, Inc. The intent was to conduct a basic feasibility study, leaving a great many engineering details to future efforts.

Building a reactor small enough to fit on a locomotive, but powerful enough to provide useful horsepower, was a difficult challenge. The primary constraint would be volume, and in particular width and height. Weight was a comparatively minor issue, and length could be dealt with by daisy-chaining cars together, but the dimensions of rail tracks and tunnels put hard constraints on the shape of the reactor and associated systems.

The Locomotive

The X-12 atomic locomotive would consist of two cars. One would carry the reactor, turbine, condenser, and generators, while the second would carry a system of radiators and fans to dispose of waste heat. The X-12 would essentially be a gigantic version of a diesel-electric locomotive with the diesel engine replaced by the reactor and turbine: the reactor would generate steam, which the turbine would convert to mechanical power, which would turn generators, which would power the motors. The engine car would be 100 feet long, the radiator car another 60 feet; together, they would weigh 720,000 lbs., over half of which would be radiation shielding. By comparison, the EMD F7, a typical diesel-electric locomotive of the time, was only 50 feet long and achieved 1,500 horsepower. The X-12 would not have been the biggest locomotive ever built, but, at the time, it would have been the third most powerful that had ever been built, and the fifth biggest by mass.

Figure 2: X-12 Schematic

There wouldn't be enough room for a heat exchanger and secondary coolant loop, so the turbine would run on steam direct from the reactor, contaminating it with radioactivity. It would take months or years for the turbine's radioactivity to decline enough to be touched, so it would have to be designed to be literally maintenance-free. Since such turbines did not yet exist, they would have to be developed before the X-12 could be built.

Figure 3: X-12 Concept Art

The turbine would connect to four generators. Space constraints meant each generator could only be two feet wide, and each would have to deliver about 1.3 MWe of energy. At the time, generators simultaneously that powerful and that small did not yet exist, and would also have to be developed.

The electric motors, at least, would be fairly standard. The locomotive would be driven by nine powered axels on the engine car, and three on the radiator car; together they would give 7000 horsepower in normal operations, with the ability to reach 10,000 horsepower for short bursts.

As a class project for physicists, the focus of the X-12 design work was naturally the reactor. The X-12 used an aqueous homogenous reactor (AHR), primarily because there was plenty of unclassified information available about AHRs at the time, which was not the case for other reactor types. This proved to be a fortuitous coincidence.

Reactor System

Unlike a conventional Light Water Reactor, such as is used in most nuclear power stations, the fuel in the X-12's AHR would be a liquid. Uranyl sulfate would be dissolved in water, and used as a fuel “soup.” AHRs were one of the earliest types of reactors developed, and the first one was operating at Los Alamos Scientific Laboratory before the bomb was dropped on Hiroshima.

AHR designs have a number of advantages. They are extremely simple, and have strong negative temperature and void neutron coefficients, meaning that an increase in temperature will rapidly reduce the rate of reaction. Thus, if the reactor started to overheat and boil, the chain reaction would quickly stop. AHRs also have excellent neutron economy and reactivity, meaning they can be made extremely small and their power output can be changed very rapidly without danger.

However, AHRs also tend to have severe corrosion issues. They were nick-named “Water Boilers” because gamma rays from the fission process split water molecules in the soup, releasing hydrogen and oxygen, which makes the water look like it's boiling. The hydrogen, oxygen, sulfuric acid produced by sulfur released from fissioned uranium, and intense radioactivity combine to eat away at the reactor vessel. Furthermore, unlike a conventional Light Water Reactor where a coolant leak carries a relatively small amount of radioactivity with it, a leak in an AHR would spill ferociously radioactive fission fragments. These corrosion issues were one of the reasons AHRs never came into widespread use, but in 1954 they weren't yet widely appreciated.

The X-12's AHR would be a hexagonal prism, 3 feet wide, 3 feet tall, and 1 foot long, lying on its side.   There would also be an additional space above the chamber to allow room for expansion and moisture separation.

Figure 4: X-12 Reactor Cross-Sections

Water reflectors would be placed fore and aft, and the whole system surrounded by 4 feet of radiation shielding weighing 200 tons. The reactor vessel would contain 19.8 lbs. of uranium dissolved in 357 lbs. of water. The uranium fuel would have to be weapons-grade, almost entirely uranium-235, to sustain a chain reaction in such a small space. The fuel soup would reach a temperature of 460 F in normal operations, producing 30 megawatts of thermal power. Sheet baffles and rods of cadmium or boron steel could be inserted to control the reaction. Pumps would keep the fuel soup circulating, to maintain an even temperature and prevent settling.

10,000 small tubes would pierce the reactor vessel horizontally to extract heat. Water would pass from one of the reflectors, through these tubes, and into the other reflector, flashing into 250 psi steam in the process. It might even be possible to superheat the steam using the energy from gamma radiation or from recombining the dissociated hydrogen and oxygen. The steam would be used to drive a 6,000 rpm turbine, and then converted back into liquid in a condenser and returned to the reflector. The turbine would drive the electrical generators, producing 6 megawatts of electricity, which would in turn power the 12 driving axles. A second water loop would cool the condenser, carrying waste heat to the radiator car.

Pumps would extract the hydrogen and oxygen split from the water by the fission process. They would be carried to a catalytic combustion chamber above the reactor vessel where they would be recombined.   An inert gas trap in the same section would extract xenon-135 from the gasses. Xenon-135 is a product of the fission reaction and tends to suck up neutrons. By extracting xenon while the reactor was operating, the system fuel could be more efficient.

The radiation shielding would consist of layered steel and an unspecified “hydrogenous material,” such as water, paraffin, or plaster. Steel would deal with gamma rays while the hydrogen in the eponymous material would handle neutrons. To save mass, the generators would be used as part of the shielding.

No details were provided on reactor instrumentation or controls. Since it was intended to be operated by only two crewmen with little special training, the reactor would presumably have to be highly automated, operating as a “black box.” How this was to be achieved was left unspecified.

Economics

Borst's group estimated that, ignoring research and development, the production cost of an X-12 would be about $1.2 million, half of which would be the reactor. This was roughly double the cost of an equivalent horsepower of diesel-electric locomotives. However, this would be made up for by lower operating costs.

Maintenance of the reactor or turbine would be almost impossible due to radioactivity. As such, the physicists concluded that, since the reactor shield could never be opened, the engine must be designed so that it would never need to be opened, and therefore maintenance costs would be lower than in a conventional locomotive. Borst's team was made up of physicists, not engineers. The fact that a “maintenance-free” turbine had never been built, despite its obvious advantages even in less exotic vehicles, did not deter them. However, as a concession to reality, they assumed overall maintenance would be roughly equivalent to a four unit diesel group of equivalent horsepower, an estimate they considered “liberal.”

Starting the reactor would take considerable time and highly skilled personnel, but once it was running Borst's team believed it could be safely managed by a normal railway crew. The reactor would only be shut down when the locomotive was put into storage or otherwise had to be left unattended; otherwise it would be reduced to 1% power but kept running.

Since the coolant loops were hermetically sealed, water losses should be minimal. The X-12 would not need the elaborate system of water supply used in steam locomotives.

System availability would probably equal or exceed diesels. Refueling operations would take several days, but would take place only once every two or three months at a central location. Since the capital cost would be high and maintenance costs equivalent, savings would have to come from fuel costs – and here, difficulties arose. The X-12 would burn a pound of weapons-grade uranium each month. But the cost of uranium-235 was a state secret.

If the capital cost was amortized over 10 years, Prof. Borst and his students calculated the atomic locomotive could be competitive over long-distance, high-speed routes at $11,400 per pound of highly-enriched uranium. It could compete under ordinary conditions at $3,200 per pound. Based on an article in the New York Times, Prof. Borst estimated the actual cost of uranium-235 at $20 per gram, or about $9,000 per pound. The cost of 90% enriched uranium today is estimated at about $30,000 per pound, or the equivalent of $4,500 per pound in 1954. The price in 1954 would have been higher, since the technology of uranium enrichment was not yet as advanced. But on the face of it, the engine Borst's team proposed is not obviously uncompetitive, at least for long-haul, high-speed freight...

Except that the capital cost estimates were a fantasy. $600,000 for a mobile nuclear reactor of 6 MWe capacity is $800,000 per MWe in today's money. The capital cost of a fixed coal-fired power plant today is more than $1.5 million per MWe. Prof. Borst's atomic locomotive, if it had existed, could have been more profitably used by plugging it into an electric main. Professional railroad engineers also pointed out that he had overestimated the fuel consumption of comparable diesel locomotives by a factor of two. A more accurate estimate of the costs of diesel locomotives made the project seem even less practical.

Safety

Borst's team considered safety a fairly minor concern. The aqueous homogenous reactor would be intrinsically stable in normal operation, and the reactor vessel would be double-walled in case of leaks. Air would be kept blown through the space between the vessel walls, and then past a radiation detector, ensuring quick discovery of any leak.

The only real danger would be in a crash, and Borst's team believed they could design the reactor to survive almost anything. First, the radiator car would precede the engine car, to absorb the brunt of a head-on collision. Second, the steel shells used as gamma ray shielding would also function as a crash absorber. These two measures would prevent a physical breach of the reactor vessel in any circumstances Borst's team could foresee.

Third, shear pins would be incorporated into the control rods. Any sudden change in velocity – such as a crash – would automatically drop the rods and scram the reactor. Fourth, special auxiliary water tanks and coolant lines would provide emergency cooling to the reactor if the main coolant system was damaged. There would be enough water to keep decay heat from melting the reactor vessel until a cleanup crew could arrive.

Borst's group thought the locomotive reactor could survive almost all accidents without leaking radioactive material. If a leak did occur, the nuclear fuel would contaminate the surrounding area, but would not go through uncontrolled criticality or cause the sort of explosion that could make a large area dangerous.

One can doubt if these measures would be enough, and railway engineers of the time did doubt, and loudly. But the doubters always ended their statements with the caveat that, with technology progressing rapidly, these problems would no doubt ultimately be overcome – although suggestions as to how were somewhat lacking.

Publicity

Although it began life as a class project, Prof. Borst was sufficiently pleased with the X-12 to market it to industry. The project was published as a pamphlet in January of 1954. Prof. Borst was an effective publicist, and Life, Popular Science, and other popular magazines published articles on the project that spring. Articles also appeared in industry journals such as Power and Railway Age. Borst presented the paper to a railway conference in April of 1954, and to the Atomic Industrial Forum in May.

Borst filed a patent on an improved version of the locomotive reactor in April of 1955. The patented design was mostly the same as the original, but the reactor was now cylindrical instead of hexagonal, and the use of gamma rays for superheat was now definite rather than merely a possibility.

Figure 5: Reactor Design from Borst Patent

At one point, Prof. Borst claimed the Babcock and Wilcox company was interested in developing the X-12 to a fully functional locomotive. But this interest evidently never made the jump to intent, and the last we hear of the X-12 is the patent filing in 1955. But, while the X-12 never made it beyond paper, it triggered a wave of interest in the concept of the atomic locomotive.

Bruce Gunnel

The first to follow the X-12 was Bruce Gunnel, who had been the Association of American Railroads' liaison to the Atomic Energy Commission since 1948, and had attended the Atomic Industrial Forum when Prof. Borst presented the X-12. Unlike Borst and his graduate students, Bruce Gunnel was a railway engineer, not a physicist. Like them, he was intrigued by the possibility of atomic propulsion, although rather less sanguine about its short-term prospects.

At the request of the AAR, Gunnel presented his own proposal at the next Atomic Industrial Forum meeting in 1955. This was far less detailed than Borst's plan – hardly a surprise, since it was the work of one man.

Gunnel did not begin with the reactor, but rather with the engine. In the X-12, the choice of a condensing steam turbine-electric design was never discussed, it was simply presented. Gunnel examined existing fossil fuel engines, and concluded that, since both condensing and non-condensing steam turbine-electric engines had never been satisfactory with fossil fuels, they were a poor choice to use with nuclear fuel. Reciprocating steam engines were worse, and there seemed no obvious way to build an atomic equivalent of an internal combustion engine.

That left a gas-turbine-electric approach. There were a number of possible variations on this approach: the reactor could be solid or liquid fueled, it could use a direct air cycle or an indirect liquid-metal cycle with a heat exchanger. As an illustration, Gunnel set forth a design for a solid-fuel, direct air cycle gas-turbine-electric locomotive.

Figure 6: Gunnel's Gas-Turbine-Electric Locomotive with Direct Air Cycle

Gunnel's locomotive would have a reactor with 11.2 MW of thermal power, which would be cooled by air. The air would drive a turbine before being exhausted, and the turbine would drive generator. The generator would, in turn, drive two three-axle trucks on the engine car at 3,000 horsepower, less than half the X-12. No details of the reactor were provided except for its power output and the fact it would be air-cooled; even the moderator is unspecified.

Gunnel's locomotive would be a compact unit, unlike the X-12 with it's dedicated radiator car. The locomotive would mass 384,000 lbs., of which 85,000 lbs. would be shielding, and would be 68 feet long. This would be a positive midget compared to Borst's 160-foot-long, 7,000-horsepower, 720,000-lb. X-12.

Another area where Gunnel differed from Borst was his economic analysis. He estimated a $1,000,000 production cost for each locomotive, in addition to a $20,000,000 development program. This was slightly less than Borst's $1.2 million, but Gunnel's locomotive gave less than half of the horsepower. He also estimated maintenance costs would, at minimum, be double that of a diesel, given the difficulty of working with radioactive components. Adding everything together, he concluded an atomic locomotive would cost 2.58 times an equivalent diesel locomotive to build and operate.

And that's without including safety and liability. Unlike Borst, Gunnel was very concerned about the safety of an atomic locomotive, and described the aftermath of a head-on collision between two such locomotives vividly, warning of lawsuit-induced bankruptcy and contamination “several hundred feet” in radius in the event of a crash.

Given all this, one would expect that Gunnel would conclude the atomic locomotive should not be built, at least for the foreseeable future. But this was not so.

Gunnel concluded that the atomic engine had no role in civilian transport in the near future, but said that it would nonetheless eventually be necessary given the limited supply of fossil fuels. In the short term, he advocated its development by the military for use in remote areas, probably as a way to develop the technology without worrying about short-term economics. In the long run, he was very confident that the present problems of safety and economics would be worked out.

The Big Boys

Gunnel wasn't the only person to follow in Borst's footsteps, just the first. Ray McBrian of the Denver & Rio Grande Western Railroad had been quietly researching atomic-powered engines since 1952. In January 1955 the Baldwin-Lima-Hamilton Corporation and the D&RGW began a study of an atomic-powered reciprocating engine under the Atomic Energy Commission's industrial participation program, giving them access to classified AEC data on power reactors. At least $100,000 were spent on the project over several years.

Unfortunately, details of the program are scarce. The engine would consist of a cylinder made out of a moderating material such as beryllium or graphite. Uranium hexafluoride gas, UF6, would be contained in the cylinder and compressed by a piston. The compression would cause the gas to go critical, generating heat and pushing the piston in reverse, a sort of nuclear internal combustion engine. Possibly both ends of the piston would be linked to reactors, each going critical in turn and pushing the piston back to compress the other. The motion of the piston would be turned into electricity using electromagnets, and used to drive the train.

This approach would not be as thermally efficient as a conventional design. However, it could be much more compact since it would not require turbomachinery or a condensor – team members suggested it might even be suitable for use in the perennial atomic dream, a nuclear-powered automobile. The design would be theoretically capable of 20,000 horsepower, and one optimist on the team suggested it could be ready for sale by 1970.

However, at high temperature uranium hexafluoride breaks down into UF4, a green powder, and fluorine gas. Fluorine is extremely corrosive and extremely toxic, and uranium does anyone little good sitting on the floor of the reactor chamber or clogging the piston. And, although it was not addressed in the materials that have survived, in the event of a leak in the reactor – such as might occur in a crash – the fuel gas could escape.

In a conventional, solid-fueled reactor, a leak in the core is dangerous but not catastrophic; most of the dangerous radioactive material remains locked up in the fuel rods. Even if the fuel rods melt, generally only the volatile and gaseous fission fragments will escape, while most of the remaining radioactive material will remain in or close to the core. Even in Lyle Borst's Aqueous Homogenous Reactor, most of the non-volatile, non-gaseous radioactive material would either remain in the core or sink into the ground, where it might hopefully be retrievable through excavation.

By contrast, in the atomic reciprocating reactor, a leak would likely result in the escape of the entire contents of the core, which would then be blown hither and yon as a corrosive, toxic, radioactive gas.

BLH and D&RGWR continued their efforts after AEC involvement ended. The Walter Kidde Nuclear Laboratory, a subsidiary of a company that made fire extinguishers, joined the project in 1956, and the project continued until at least 1960. However, by this time research had been refocused on radioisotope-powered headlamps, and the use of gamma rays to powder coal as an additive to diesel fuel. The exact reasons for the change in focus are not known.

Meanwhile, in October 1955, Senator John Butler (D-MD) announced he would introduce legislation authorizing the Atomic Energy Commission to develop a miniature atomic reactor suitable for a locomotive. This was probably at the instigation of Patrick McGinnis, CEO of the New Haven Railroad, who never met a new technology he didn't like. Sen. Butler suggested the AEC build an atomic-powered “Freedom Train” that would “tour the United States and give our people a firsthand view of the progress made in the 'atoms for peace' program.”

The Association of American Railroads' Committee on Locomotives also issued a series of reports between 1955 and 1959 on atomic-powered locomotives. In January 1956 they hired a nuclear physicist and engineer, Boris Cimberlis from the Armour Research Foundation, to work half-time on a study of applying atomic energy to railroads, including atomic-powered locomotives as well as more mundane applications such as food sterilization. The ALCO company also funded a study to design an atomic-powered locomotive, called the “A-100,” which got as far as commissioning railway artist Howard Fogg to paint a picture of it. Unfortunately, little information on either project has surfaced.

Figure 7: Schematic of Atomic Locomotive from AAR

The Russians are Coming

Other countries were also starting to get interested. In late 1956 the West German government made plans for an eight-axle, 35m-long, 175-ton, 5916-horsepower atomic locomotive using a helium-cooled reactor costing $500,000. Few details have surfaced, however.

More information is available on a Russian program, carried out at the Baumann Institute in Moscow beginning in 1956. It's unclear if this was a serious study, or just speculation, but a paper published by the Institute describes a 430-ton, 50-meter-long, 5,500-horsepower steam turbine-electric locomotive. The locomotive would consist of two cars: a fore car carrying the reactor and heat exchanger, and an aft car carrying the turbine and condenser, linked by flexible pipes.

The Baumann locomotive featured probably the most impressive reactor ever proposed for locomotive use, a cylinder 6 feet tall and 4.5 feet wide. It used metallic uranium rods contained in a matrix of graphite moderator. Liquid sodium coolant, propelled by electromagnetic pumps, would pass through the space between the fuel rods and the moderator. This primary coolant loop would heat a second liquid sodium coolant loop through a heat exchanger, which would in turn boil water to use in a turbine. Generators would then power twelve driving axles. This would be a giant compared to Borst's reactor, carrying one and a half tons of uranium compared to the X-12's 19.8 lbs. This gigantism was made necessary by the use of low-enriched uranium as fuel instead of Borst's weapons-grade fuel.

The Baumann locomotive's fuel would reach a temperature of 500 C, producing steam of 400 C at 80 atmosphere pressure. The shielding would be layered concrete and steel, and would be focused towards the front of the locomotive, where the engineer's cab would be located.

The locomotive would have 1,000 kilometers endurance, this limit being imposed by the water supply, not the fuel. The Russians claimed the engine could go for 300 days between fuel replenishments.

Figure 8: Comparison of Atomic Locomotives

(Author)

Conclusion

The atomic locomotive faded away after 1960, and it's not hard to see why. After Borst, almost all of the studies ended with the conclusion that an atomic locomotive would probably be unsafe, and would certainly be uneconomical. Even such a perennial booster of atomic energy as Edward Teller was pessimistic; in 1957 he described the nuclear locomotive as “a most ingenious solution of the question how to combine minimum utility with maximum danger,” adding that the trains of the atomic age would be powered electrically. Although many saw these as solvable problems, the solutions were not yet available, and seemed unlikely to be available in the near future.

The most enthusiastic boosters of the atomic locomotive, such as Prof. Borst and Senator Butler, were never really interested in an atomic locomotive per se. They were interested in atomic power, and a locomotive offered a conveniently compact way to use it. More sedate railway engineers like Bruce Gunnel were interested, but their view was longer-term; the atomic locomotive might be useful one day, but the point was the locomotive, not the reactor it carried. And while the railroad offered advantages to the budding atomic power industry, atomic power had nothing to offer in return. So research petered out in the early 60s. In 1963 Ray McBrian, who had led the Denver & Rio Grande Western's atomic reciprocating engine program, proposed adapting the Air Force's SNAP miniature satellite reactors for locomotives, but this was the last proposal outside of the popular press for decades.

However, in recent years there has been a revival of interest in the atomic locomotive. A group of Japanese researchers patented a locomotive reactor in 2007, an American inventor patented a concept for a maglev train powered by an onboard nuclear reactor in 2008, and the Russian companies Rosatom and Russian Railways have announced plans to build a locomotive powered by a small liquid-metal-cooled fast reactor.

Few details are available, and it's impossible to tell if this is a serious program or a publicity stunt – although the latter seems more likely. But this is not the only mobile nuclear power plant the Russians are building – a floating reactor for use in remote regions is under construction in St. Petersburg, currently scheduled to be finished in 2012. Only time will tell if this is vaporware, a disaster in the making, or perhaps the final realization of one of the dreams of the atomic age.

Sources

X-12 Sources

Abel, G. K., Borst, L. B., et al. An Atomic Locomotive: A Feasibility Study.

“An Atomic Locomotive Could be Built.” Popular Science, April 1954.

Borst, Lyle. “Atomic Powered Locomotive.” Nuclear Reactor Development: Proceedings of the Atomic Industrial Forum, Washington, D. C., May 24 1954.

“Nuclear-powered Locomotive's Economic Feasibility Questioned by Railroad Men.” Nucleonics, Vol. 12 No. 3, March 1954. Pp. 78, 80.

O'Connor, Anahad. “Lyle Borst, 89, Nuclear Physicist Who Worked on A-Bomb Project.” New York Times, August 12 2002.

US Patent No. 499,867. “Nuclear Reactor for a Railway Vehicle.” Inv. By Lyle B. Borst, assigned to the University of Utah. Filed April 7 1955, pat. March 31 1964.

Waite, Thornton. “Dr. Borst's X-12: The Atomic Locomotive.” Railway History, Bulletin No. 175.

Gunnel Sources

Gunnel, Bruce. “Atomic Powered Railroad Locomotive.” Atomic Energy, a Realistic Appraisal: Proceedings of the Atomic Industrial Forum Meeting, May 23 & 24 1955, New York, New York.

Gunnel, Bruce. “A Progress Report on Development of an Atomic-Powered Locomotive.” American Society of Mechanical Engineers. 56-A--79.

Russia Sources

Perel'Man, R. G. Soviet Nuclear Propulsion. Trans. Yadernyye Dvigateli. Triumph Publishing.

“Подкиньте атома в топку!: Атомные локомотивы.” Popular Mechanics (Russian), December 2008. (Russian).

“Russia Designs Nuclear Train.” Barents Observer, February 24 2011.

BHL and D&RGW Sources

Feasibility of Atomic Energy for Use on American Railroads. Association of American Railroads, 1957. Report No. MR-280.

Garwood, Darrell. “Nuclear-Powered Locomotive Idea Unorthodox.” Bakersfield Californian, March 28 1955, p. 7.

“Is Nuclear Power Practicable?” Railway Age, October 8 1956.

McBrian, Ray. “Atomic Methods Promise New Horizons in RR Research.” Railway Age, February 25 1957, pp. 42-44.

McBrian, Ray. “Nuclear Energy and Future Fuels for Railroads.” Papers of the Fourth Annual Transportation Research Forum, December 28-29, 1963, 98 – 103.

Germany Sources

“Atom Locomotive May be Built in Germany.” Railway Age, December 10 1956.

Imagery Sources

Figure 1: Public domain. Found at link.

Figure 2: Abel, G. K., Borst, Lyle, et al. From An Atomic Locomotive: A Feasibility Study. Copyright expired 1982. Found in “Design for an Atomic Locomotive,” Railway Locomotives and Cars, May 1954, pp. 50-55.

Figure 3: Unknown. Date of composition unknown, but believed prior to 1960; no record of copyright renewal found before 1990. Thumbnail used under Fair Use. Found in “Atomic Locomotive: How Soon?”, Chemical and Engineering News, Vol. 32, No. 9, March 1954, p. 816 – 817.

Figure 4: Abel, G. K., Borst, Lyle, et al. From An Atomic Locomotive: A Feasibility Study. Copyright expired 1982. Cropped and modified by author for legibility.

Figure 5: Borst, Lyle. From US Patent No. 499,867. Copyright expired 1983. Cropped and modified by author for legibility.

Figure 6: Gunnel, Bruce. From “Atomic Powered Railway Locomotive,” Atomic Energy, a Realistic Appraisal: Proceedings of the Atomic Industrial Forum Meeting, May 23 & 24 1955, New York, New York. Copyright expired 1983.

Figure 7: Association of American Railroads. Found in “Congress Hears of Progress on Atom-Power Locomotive,” The Machinist, Vol. 14, No. 19, July 16 1959, p. 4. Copyright expired 1987.

Figure 8: Author. This image is hereby released under a Noncommercial-Attribution-Share Alike 3.0 Creative Commons License on condition that any page showing this image must contain a link to this page.