Hydro-Electric locomotive??

Just my luck. I found this news story: Mini nuclear plants to power 20,000 homes: £13m shed-size reactors will be delivered by lorry

Nuclear power plants smaller than a garden shed and able to power 20,000 homes will be on sale within five years, say scientists at Los Alamos, the US government laboratory which developed the first atomic bomb.

The miniature reactors will be factory-sealed, contain no weapons-grade material, have no moving parts and will be nearly impossible to steal because they will be encased in concrete and buried underground.

The company is Hyperion Power Generation, its reactor's size is about 3 m, and its power generation is 70 megawatts of heat and 25 megawatts of electricity. The reactor has some fail-safety built in; uranium in it is combined with hydrogen, making uranium hydride. The hydrogen acts as a "moderator", which slows down the neutrons so that they will react more easily. If the reactor overheats, the uranium hydride decomposes, and the hydrogen departs from the uranium, letting the neutrons through and slowing down the reaction. When the reactor cools down again, the hydrogen and uranium recombine, making uranium hydride again.

It seems like the reactor will function as long as it is cooled, so it needs a good coolant system. It can heat 167 kg of water each second by 100 C, something that Hyperion's site leaves out. Scaling down to a 3-megawatt locomotive requires 8 megawatts of heat rejection, or heating 20 kg of water per second by 100 C. This would require a sizable radiator, complete with fans capable of sending a similar mass of air past it each second.

Boiling water requires a heat-energy input of 5.5 times the amount necessary to heat that water from 0 C to 100 C, so the full-size reactor would boil 30 kg of water per second and a locomotive-sized one 3.6 kg/s, a little less than 1 gallon/s. So if the water is allowed to boil, it will reduce the necessary water flux, though not the air flux.

An alternative to using a radiator is to release the steam without trying to recover it, which is what most steam locomotives are designed to do. A nuclear-powered locomotive would thus need an onboard water tank, or else get its water from a water-tank railcar.

I could find nothing in Hyperion's site about how that reactor's electricity is generated, but "no moving parts" suggests that it generates electricity with thermocouples or some similar system. Also, that reactor only needs refueling every 7 to 10 years if in continual use, and it would be sent back to the factory for refueling.

ETA: the Hyperion reactor's design is much like the TRIGA research-reactor design; TRIGA reactors have been used for years, and they have had a good safety record.

I went to the Press Releases section of Hyperion's site, and read them; I found out that Hyperion's nuclear reactors will generate electricity by running steam turbines.

This means that a nuclear-powered locomotive will be a steam locomotive. The most familiar kind is the side-piston, direct-drive kind, but there have been experiments in building steam-turbine locomotives with both mechanical and electrical transmission, none of which has been very successful. The latter kind is like a diesel-electric locomotive, but with a steam turbine instead of the diesel engine powering the generator.

Like the Southern Pacific's oil-fired steam locomotives and most diesel and electric locomotives, a nuclear-steam locomotive will likely be a cab-forward one, for better viewing of the tracks ahead.

As for recovering water, some steam locomotives had been equipped with water condensers; these were mainly used in desert areas.

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Turning from nuclear fission to nuclear fusion, it gets worse. Much, much worse. Controlled nuclear fusion has yet to be produced in the lab with enough energy produced to run the reactor, though fusion-reactor designers are gradually improving their reactors' performance. The problem is that nuclear fusion involves ramming charged particles together fast enough to overcome their electric repulsion; nuclear fission involves neutrons, which are free of that problem.

Pons-Fleischmann cold fusion? It has been hard to duplicate the positive results that some have claimed, and its occurrence would be theoretically awkward: using known physics, it is hard to push atomic nuclei close enough to fuse with Pons-Fleischmann-type apparatus, and there is no noticeable neutron flux. I remember going to a talk by someone who tried to duplicate Pons and Fleischmann's results -- and failed. No unaccounted-for neutrons, and no heat that could not plausibly be accounted for by chemical reactions and the like.

But I remember once contemplating the design of a "Fleischmann Flyer" locomotive; it required heavy shielding for the fusion reactors, because of the neutrons that they would produce. But my discussion of fission-reactor shielding could be carried over into fusion-reactor shielding, since both reactions produce similar amounts of neutrons per unit energy released. Fusion turns out to be somewhat worse than fission, because the energy released per individual reaction is less, while the neutrons released per reaction is similar. The numbers:

Nuclear fission typically releases around 200 MeV and 2.5 neutrons per reaction, and one neutron gets consumed as part of keeping the reaction going. So the energy per escaping neutron is about 130 MeV or so. 1 MeV = 1 million electron volts, a common energy unit in nuclear and particle phyusics.

Nuclear fusion depends on the reaction. To find out what possible reactions, we must consider the most plausible fusion fuels. The short list is deuterium (hydrogen-2), tritium (hydrogen-3) and helium-3. Of these, deuterium and helium-3 are stable, while tritium has a half-life of about 17 years. And deuterium is about 0.015% of the hydrogen on the Earth's surface, while atmospheric helium-3 is 1.4 parts per million of total atmospheric helium, itself with very low concentration. In fact, it's easier to collect helium-3 by letting tritium decay than by separating it out from the atmosphere.

This leaves deuterium, and the main deuterium-deuterium fusion reactions are
H-2 + H-2 -> H-3 + p + 4 MeV
H-2 + H-2 -> He-3 + n + 3.5 MeV
with approximately equal probability. Thus, the energy per escaping neutron is about 7.5 MeV -- about 20 times less than for fission. Thus, some amount of energy released by fusion will involve releasing 20 times as many neutrons as by fission.

Oh, my goodness.

One note: I spent years as a nuclear engineer in US Navy submarines. I am intimately familiar with the design, construction, operation and administration of REAL nuclear power plants that WORK, not those of fantasy.

You will never see a self-contained, internally nuclear-powered rail vehicle. Many many years ago the Navy tried to develop a varied range of powerplants in terms of size and weight, ranging from the Combustion Engineering plant for hunter-killer boats (S1C, eventually S2C on USS TULLIBEE) all the way to massive dual-reactor dual-engine room plants for fast nuclear radar picket submarines (S3G, eventually S4G on USS TRITON) and beyond of course to cruiser and destroyer plants. One thing fouled the whole scaling program: Shielding. Neutron energies are independent of reactor output in megawatts and the shielding weight required for the S1C/S2C plant was appalling. This ended the Navy's attempt at small nuclear plants (except of course for NR-1, which has not been duplicated) since weight skyrocketed out of control.

In US Navy subs, the hull can be considered as a layer of containment as well but in a civil construction you have to provide layered protection. This would further drive up weight.

Further, our laws and regulations barely allow shipping of waste material, let alone motion of an operational nuclear power plant. Can you imagine the CFR regs that would accompany a moving atomic powerplant? I can - and it would be a deal killer. For example, you not only have to develop and prove the efficacy of tiered physical protection for the reactor complex itself (in terms of physical structure, which we call "containment" which must not only contain but protect) but you also have to provide for emergency power generation, plant makeup water, chemical control and monitoring and removal of decay heat. Once again -- you will NEVER see a mobile nuclear powerplant in the US.

All programs at developing mobile fission powerplants in the United States were abandoned as impractical. This includes the US Air Force nuclear-powered bomber project (which culminated in the HTRE series of test reactors and a 3 MW flying test core but no more) and the US Army's wide range of mobile powerplants and portable powerplants (essentially cut short by the SL-1 disaster, although the Panama Canal powerplant project continued secretly for many years.) Remember that these programs initially had great MILITARY funding but were abandoned. Further, a project initiated in the 60's jointly by Walter Kidde laboratories, Baldwin-Lima-Hamilton and the Denver & Rio Grande Western to explore an atomic powered locomotive was quickly abandoned.

Also: Cold fusion is a lark. It's the perpetual motion machine of the 90's. It's snake oil. Forget it.

BTW, I would really love to see some of the core figures on that tiny little 70 MWt / 20 MWe reactor. I would especially like to see the expected Peak Centerline Temperatures required to develop that much power in that small of a size envelope.

-Will Davis

Thanx for your perspective on this question.

It's been difficult for me to find good numbers for what thickness of shielding is considered adequate for a nuclear reactor. Do you have any numbers on that? But if the necessary thickness is more than 1 - 1.5 m, then there is no way for a reactor to fit inside a typical locomotive loading gauge.

Well, without giving any guarded information away I can tell you this much; any attempt to use the generally accepted shielding material, Pb, would naturally result in such massive weight (to bring trackside exposure down - remember, putting the powerplant on one end of the train and the crew on the other ONLY PROTECTS THE CREW and the NRC would require protection for persons lineside and persons on passing trains) that the proposed locomotive would be crushingly heavy. Use of lighter, less dense shielding materials like polyethylene or other substances would result in violation of clearances over the line of road due to the thickness required.

Think about this- the well known GE / UP gas turbine electric locomotives were well known to be cost effective only when running loaded over the road. Idle fuel use was high since on average idle speed and load is about 60 percent of full rated for gas turbines. (That figure is accurate for JT8D engines on a Boeing 727 at least.) Take that kind of operating requirement and multiply it by several million and you'll see the economic aspect. Civil nuclear powerplants were funded, built and put online - and then run at full power for YEARS to pay back the enormous construction and insurance costs while conventional powerplants were taken offline and scrapped.

The practical combination of nuclear energy and railroading is lineside power generation with delivery to catenary and the use of straight-electric locomotives.

-Will Davis

PS For those who still think this could work, look into the labor complications for operators and maintainers that you'd have to have in terms of training and cost, and the responsibility that would be placed on the RAILROADS for safety and emergency response. For details on this kind of thing, look deeply into the experiences of the nuclear powered N.S. Savannah (the only US-built nuclear powered merchant ship.)

seen the price of lead lately ???
also , i would imagine stationary nuclear power plants are engineered with the back up of large amounts of water for emergcency cooling . how are you going to provide for that on a locomotive .

When I started this thread, I had already ruled out, in my mind, the possibility of nuclear-powered locomotives. It was safety considerations that made me doubt nuclear locomotives. Trains have a tendency to leave their tracks sometimes. Imagine what a mess it would be if you had nuclear waste all over the place in the aftermath of a derailment! Quite impractical indeed! (Need I explain myself here? I would prefer not to.) It's starting to look like steam fired by propane or methane would be the best non-diesel approach.

Steamal--
There is a companion thread about atomic powered locomotives on the Alco forum (for the moment, though the participants seem nervous about the lack of direct connection to Alco locomotives).
You mentioned methane a while back. Natural gas is largely methane, so this would amount to a natural gas powered locomotive, and there have been such: there are a few LNG-powered switchers, built with Caterpillar engines by, I think, Morrison-Knudsen on the U.P. and the BNSF, which use them in Los Angeles. Burlington Northern experimented for several years with using LNG in modified EMD and (I think) GE freight locomotives.
There have also been Natural Gas powered steam locomotives. A scrap yard in the Chicago area that was famous for using steam locomotives for switching around its plant into the ?? 1970s ?? set up at least one 080 to burn Natural Gas. The modification was quick and dirty: large gas tank in place of coal bunker on tender (which --- ??? perhaps to keep gas tank further from fire box ??? --- was attached to locomotive backwards).

I found a table of neutron flux dose equivalents. It translates from neutrons/cm^2 to rem, an older dose measure (1 sievert = 100 rem).

A 10-megawatt reactor releasing 1 neutron per reaction (about 200 MeV) produces 3.12*10^(17) neutrons/s. At a distance of 1 m and using the inverse square law, the neutron flux is 2.48*10^(12) neutrons/cm^2/s. The best case in the table is thermal neutrons, neutrons slowed down to thermal-equilibrium speeds with the reactor. This is about 970*10^6 neutrons/cm^2/rem. That is a dose of 2560 rem/s or 25.6 sievert/s.

A more likely distance of 3 m / 10 ft pushes it down to 2.84 sievert/s. If all those neutrons escape as fast ones, however, the dose becomes much worse. At about 10 MeV, have a dose equivalent of 24*10^6 neutrons/cm^2/rem, producing 115 sieverts/s. Even if only 1% of the reactor's neutrons escape without getting slowed down, the fast-neutron dose effects would be comparable to the slow-neutron ones.

The "Shielding the Hazard" link claims that 20-MeV neutrons can be attenuated by a factor of about 5000 with about 1 m of concrete (density: 2.3 g/cm^3). This nevertheless allows through a dose of 2000 sieverts/day for all-fast neutron release.

From radiation poisoning, one starts to have noticeable symptoms and 10% or so risk of death at 1 sievert or so of acute dose, and one will almost certainly die in a week after 10 sieverts of acute dose. It can take a few months or even a few years to recover if one survives a large dose, suggesting a maximum long-term survivable dose of 1 sievert/year to 1 sievert/month. A common existing standard is 0.02 sievert/year, suggesting that my calculation is a bit optimistic.

Allen Hazen wrote: There have also been Natural Gas powered steam locomotives. A scrap yard in the Chicago area that was famous for using steam locomotives for switching around its plant into the ?? 1970s ?? set up at least one 080 to burn Natural Gas. The modification was quick and dirty: large gas tank in place of coal bunker on tender (which --- ??? perhaps to keep gas tank further from fire box ??? --- was attached to locomotive backwards).

Perhaps on the order of the "cab-forward" locomotives? (Except they would be gas-fired instead of oil-fired.)

Steamal--
Sorry, my description was ambiguous. Not a cab forward: tender was attached to cab end of locomotive, but water-tank end of tender closer to locomotive. Result was very weird looking! (I ***think*** the photo I saw was in "Trains," some decades ago.)

Allen Hazen wrote:Steamal--
Sorry, my description was ambiguous. Not a cab forward: tender was attached to cab end of locomotive, but water-tank end of tender closer to locomotive. Result was very weird looking! (I ***think*** the photo I saw was in "Trains," some decades ago.)

Well, perhaps "cab-forward" would be the best way to handle it. (I'm assuming, of course, you've seen what cab-forward locomotives looked like.) Attach a combination water and gas tender at the smokebox end of the locomotive while enclosing the cab.

Yes, I suspect a cab-forward configuration would be the best if you were building a new steam locomotive for LNG fuel, Northwestern Steel and Wire, the scrapyard operator I was referring to, wasn't interested in building new steam locomotives (they eventually got new locomotives: SW1001 from EMD), and their gas-burning steam switcher was a minimum-budget modification of a second-hand coal burner.
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Interesting that Southern Pacific only went for the cab-forward configuration on their articulateds, and not on the other oil-burning power they bought. Santa Fe, another big user of oil-fired steam, at least considered a proposal for a cab forward passenger engine: a Baldwin proposal, I think, since it was also supposed to be duplex-drive (like PRR's T-1). Opportunities for creativity suggest themselves, if anyone is into free-lance model railroading!

The answer must be no and yes. On board hydro would reqire a pump to get it back up to the top of the system.
I seem to remember that the electrified sections of the Northern Pacific and Milwaukee Road crossings of the Cascade Mountains here in Washington State bought their power from off line hydro dams to power their conventional electric locomotive. So you could say that electric locomotives could be powered by off line diesel , steam, hydro, wind turbine,and even nuclear. The steam in turn can also burn besides oil and coal, my favorite renewable energy source - garbage!

RickRackstop wrote:The answer must be no and yes. On board hydro would reqire a pump to get it back up to the top of the system.

Such things do exist. They're called 'pumped storage' systems. Basically, you use a low off peak demand as a chance to pump up the reservoir (billions of gallons), then at high demand, you run it down to generate power. It's not a generation source but a storage one. It works pretty darn well, even if it's not 100% efficient (though batteries aren't either, and nothing can be anyway). It's reliable, too - hydro basically kills everything in terms of availability, not to mention ability to start/stop/throttle. You can run a hydro dam for years on end, or turn it on when it's needed and off when it's not. Zero to full power in a few minutes. Nukes can run 18 months full out before an outage, and they can't throttle much. Turbines can throttle and have that instant stop/go, but they can't run all day for years on end. Coal's like nuke with worse availability. Wind happens if you're lucky.

As for on board nukes? No, it's not going to happen. Just do it the French way - electrified RRs with nukes feeding the general system. Economics dictate you build the largest nuke you can get away with at a site - they're huge these days. A license isn't cheap and having inspectors there and everything else isn't either. All the new stuff being proposed is north of 1,000 MW, and some are north of 1,500 MW. That's per reactor, BTW. IIRC, that works out to around 1/2 a million gallons through the core per minute.