Small Nuclear Reactor proposal - Size of a large spruce tree

clark · 2003-10-21 12:19:58

go here: http://www.adn.com/front/story/4214182p-4226215c.html

A Japanese corporation wants to thrust the Interior community of Galena into international limelight by donating a new, unconventional electricity-generating plant that would light and heat the Yukon River village pollution-free for 30 years

The Galena design is part of a new generation of small nuclear reactors that can be built in a factory and transported by barge, truck or helicopter. A federal study, funded at Stevens' request and published in May 2001, found they are inherently safe and easy to operate, resistant to sabotage or theft, cost effective and transportable.
Toshiba Corp., the Japanese electronics giant, calls its reactor the 4S system: super-safe, small and simple.
Washington, D.C., attorney Doug Rosinski, who represents Toshiba, calls the reactor a "nuclear battery," although it has nothing in common with the typical AA cell. The power comes from a core of non-weapons-grade uranium about 30 inches in diameter and 6 feet tall. It would put out a steady stream of 932-degree heat for three decades but can be removed and replaced like a flashlight battery when the power is depleted, he said.
The reactor core would be constructed and sealed at a factory, then shipped to the site. There it is connected with the other, nonnuclear parts of the power plant to form a steel tube about 70 feet long with the nuclear core welded into the bottom like the eraser in a pencil, Rosinski said. The assembly is then lowered into a concrete housing buried in the ground, making it as immune to attack or theft as a missile in its silo.
The reactor has almost no moving parts and doesn't need an operator. The nuclear reaction is controlled by a reflector that slowly slides over the uranium core and keeps the nuclear fission "critical." If the reflector stops moving, the reactor loses power. If the shield moves too fast, the core "burns" more quickly, yielding the same amount of power but reducing the reactor's life, Rosinski said.
Because of its design and small size, the Toshiba reactor can't overheat or melt down, he said, unlike what happened in the 1986 accident at Chernobyl that killed 30 people and spewed radiation across northern Europe.
The nuclear reaction heats liquid sodium in the upper portion of the reactor assembly. It circulates by convection, eliminating pumps and valves that need maintenance and can cause problems, Rosinski said. The liquid is contained in a separate chamber so it isn't radioactive. Because the reactor assembly is enclosed in a thick steel tube, it will withstand earthquakes and floods, Rosinski said.
"What comes out (of the ground) are two pipes with steam that power a turbine," he said. "You wouldn't even know it's there," except for the steam generator building above it.

Could the more scientifically literate comment on this?

When I saw this, it just screamed Mars. :laugh:

dicktice · 2003-10-21 19:52:00

Clark: The Toshiba 4S System sounds like "next generation" nuclear plant design and engineering is finally at hand. (Next thing you know, intercontinental high tension transmission lines will start to become obsolete.) Of course, the prototype reactor should be built and tested--say, in Hokaido. (They loved me in Hokaido--just don't tell them where I am!) I particularly liked the buried "pencil-eraser" security aspect. Geothermal power plant facility operators, having already developed the steam side of things, they could have the demo up and running as soon as proven entirely failsafe, nuclear-wise. Simultaneously, adapt the design for space so as to be ready for the first Mars expedition. Great post!

Bill White · 2003-10-21 22:05:34

This link is to a 20 page PDF technical paper on the Toshiba 4S.

Now for a business question. Suppose Toshiba can sell these things for $25 million each to small towns and villages world wide. Couldn't someone persuade them to give a few reactors, for free, to a Mars settlement in exchange for the publicity?

Maybe even pay the cost to ship the reactors to Mars?

Shaun Barrett · 2003-10-22 00:41:02

I agree with Dicktice, this is a very interesting post from Clark.

The core of the device sounds small and portable enough for a Mars colony but what about the steel tubing, concrete and sodium?
Without going through the 20 page report (yet), what would the whole thing mass and would it fit within the parameters laid down for the Mars Direct reactor's mass, as outlined by Dr. Zubrin?
From memory, the Mars Direct reactor is supposed to be ready to rock 'n' roll as soon as it trundles off the lander. All it has to do is transport itself a hundred metres away into a small crater, trailing a cable, and start cranking out the kilowatts! Can this new design be adapted to do the same?
???

Free Spirit · 2003-10-22 00:59:27

Can't wait until every town on Earth has it's own poorly guarded reactor that runs without supervision. Terrorists must be rubbing their hands together in anticipation of all those dirty bombs they could build and what to do with all that additional nuclear waste. :angry:

Shaun Barrett · 2003-10-22 02:02:50

No problem.
Install it in a corner of the police station car park. Automatic surveillance, 24/7/52.

TJohn · 2003-10-22 06:54:48

This reactor needs to be tested fully for terrestrial and space use immediately. All you guys have mentioned great ideas. We need to get to Mars and the rest of the solar system NOW!

Bill White · 2003-10-22 11:00:19

This reactor needs to be tested fully for terrestrial and space use immediately. All you guys have mentioned great ideas. We need to get to Mars and the rest of the solar system NOW!

Maybe Representative Lampson can introduce a bill into Congress. . .

clark · 2003-10-22 11:04:12

Thanks for the pdf Bill!

The reactor core comes in at about 60 tons, and about 70 feet in length. It looks like each core can produce about 50 megawatts each (the design allow for modular approach, so this can be ramped up with the addition of more reactor core modules). The whole design needs a site space of 20 meters

The diameter of the reactor vessel is only 2.5 meters.

So were looking at about 8-9 feet round, and 70 feet long for the core, weighing in at 60 tons.

Can you say hevy lift rocket (doubt the shuttle could fit this thing in it's bays, or lift it)!

The thing needs to be refuled every ten years or so, and the pdf gives examples of how the 4S can be used to green deserts and desalinate water.

The whole design is supposed to passive saftey, which means there is no need for complex auxillary control systems or human oversight (other than on start-up).

If this could be made to work in space, then you might be able to cold launch this (make those greenies happy) and then start it up after you are beyond GEO, and promptly forget about watching it. However, the passive features are designed around a natural 'air-cooling' system, so I'm, not sure what would have to be changed for the space environment.

It also looks like that what they are proposing has never been tried with nuclear technology, but has been tried in other fields- so they need, what they term, reliability tests to make sure the reflector (the thing that controls the reactivity in the the core) works like they want and need it to.

They also haven't had much experience with core slugs that last this many years (10 years), so they need to ensure that creep deformation of the metallic fuel (which is also seems to be a new item) is within allowable values.

Bill White · 2003-10-22 11:09:19

Thanks for the pdf Bill!

No problem. I stayed up all night writing it, though.

More seriously, google "David Poston" and "SAFE 400" to find links to proposed space rated reactors.

Its my understanding that the reactor Zubrin discusses in Case for Mars is purely hypothetical. In other words, MarsDirect depends on a nuclear reactor that has not yet been developed.

clark · 2003-10-22 11:30:24

No problem. I stayed up all night writing it, though.

It shows.

I am taking you up on your suggestion and i see I have a lot of reading to do... [ugh] :laugh:

http://content.aip.org/APCPCS/v654/i1/339_1.html

NEPTranS; A Shuttle-Tended NEP Interplanetary Transportation System

John O. Elliott, Roy Y. Nakagawa

Recently, a study was performed by a team from JPL and the DOE to develop a mission architecture for a reusable NEP Interplanetary Transfer Vehicle, a "Space Truck". This vehicle is designed to be used for delivery of payloads from Earth to a variety of destinations, including Mars and Venus, dependent on mission needs. In addition to delivering payloads to the target bodies, the vehicle is designed to perform autonomous rendezvous and capture of sample return capsules at the destination for return to Earth. In order to maximize the utility of the vehicle, its design is optimized for servicing between missions with the Space Shuttle. Fuel tanks, ion thrusters, and Power Management and Distribution electronics are all on-orbit replaceable units, located at the payload interface end of the spacecraft to ensure a minimal radiation dose to the Shuttle and crew during maintenance and resupply operations.

RobertDyck · 2003-10-22 11:53:45

To adapt this for space the first concern is eliminating heat. You don't have air to take the heat away, in space you have to radiate it. Radiators that do not have air flowing across them produce infrared radiant heat. That is best produced at a high temperature, much higher than boiling water. You would be better off using a secondary coolant with a much higher boiling temperature. In fact, to keep mass down you should consider running using just a single coolant, not sodium for the primary coolant which heats water or some other secondary coolant. The two stage coolant system provides greater safety for a reactor on Earth; if the primary coolant system ruptures it is not radioactive. But that environmental concern is not a problem in space. If you do use a primary coolant that changes phase to power a turbine, then you have to worry about wear. By "phase change" I mean change from liquid to gas. Toshiba avoided the problem of wear of the primary coolant system by not using any valves. You certainly don't want to use pumps for the primary coolant, the whole point is to drive the coolant by heat from the reactor. A space nuclear reactor would have to be a complete system as a single unit: reactor, turbine, generator, and radiator. The Toshiba reactor does not include the steam generator portion of the power plant. These are starting to sound like significant changes. Although the entire heat exchanger will have to be changed, the reactor itself may be a good start for a space reactor.

clark · 2003-10-22 12:22:14

To adapt this for space the first concern is eliminating heat. You don't have air to take the heat away, in space you have to radiate it.

Would it be possible to develop a passive cooling system that radiates the heat using the actual water used in the steam turbine? So as the steam drives the turbine, we condense it, run it past the reactor core to cool it, then back to to the turbine? Or am I just pointing out the phase change problem of a primary coolant?

A space nuclear reactor would have to be a complete system as a single unit: reactor, turbine, generator, and radiator. The Toshiba reactor does not include the steam generator portion of the power plant.

Yet if you look at the schematics, it is based on a vertical intersection of the reactor with the horizontal postioning of the steam turbine. I didn't see any reason we couldn't realign the steam turbine portion in a vertical manner (in effect making the whole thing longer than 70 feet). However, i would imagine that we would need access to the steam turbine portion because of wear and tear (there are moving parts here!).

I also would imagine that the effect of supercritical fluids in space need to be studied a little more before we could sign off on this.

RobertDyck · 2003-10-22 13:52:50

Yes, you are talking about the phase change cycle of the secondary coolant. Normally, the primary coolant will cool the reactor core. The hot primary coolant then circulates via convection to the heat exchanger. Once cooled, the primary coolant circulates back to the reactor core. Sodium makes a better primary coolant because it remains liquid at the temperature the reactor operates. The secondary coolant (usually water) is boiled at the heat exchanger. The steam is contained so it builds pressure. The pressure is released through a turbine. As steam expands it cools, leaving steam that has cooled to just above the condensation temperature of water. You don't want the steam condensing to water inside the turbine because that would lose pressure. Then the steam is run through a large volume radiator to condense it back to water. The hot water is then run back to the heat exchanger to continue the cycle.

This means the radiator must operate at the boiling/condensing temperature of water. Metal will not give off much radiant heat at that temperature. You want to replace the water with something that will boil at the temperature of the heat exchanger (roughly the temperature of the reactor), but will condense at a temperature that heats the radiator so it literally glows in infrared (maybe not red hot, just infrared hot). Actually, the heat exchanger should not just boil the secondary coolant; it should heat the steam (or coolant gas) so that it can expand through the turbine without condensing.

clark · 2003-10-22 14:07:21

Thanks for walking slowly with me on this...

so the primary coolant gets heated, which then is carried to the heat exchanger (this takes the heat away from the reactor so it can cool), this 'heat' is then transferred via the heat exchanger, and the secondary coolant (water) is then turned into steam to drive the turbine...

I'm restating what you have said to have you make sure I'm not in left field here.

Would using liquid CO2 be an option as either the primary or secondary collant? I know that research is going on at NASA looking at super-critical CO2 fluids, and considering Mars has the CO2 to spare, it would make a pretty viable alternative...

Bill White · 2003-10-22 14:12:48

RobertDyck writes:

To adapt this for space the first concern is eliminating heat.

This may go off on a tangent, yet I have been thinking that for any permanent Mars settlement eliminating waste heat may be more of a challenge than keeping warm. Especially if the settlement structure is wrapped with an aerogel thermopane (layers of aerogel with vacuum in between) and buried under a few meters of regolith.

Could you generate additional electricty by channeling the waste heat through a geothermal heat pump system into the regolith? If your settlement is built near regolith with large ice content, perhaps run the pipes far away before discharging the heat, or you might melt your foundation.

RobertDyck · 2003-10-22 14:13:22

Would using liquid CO2 be an option as either the primary or secondary collant? I know that research is going on at NASA looking at super-critical CO2 fluids, and considering Mars has the CO2 to spare, it would make a pretty viable alternative...

The only problem with CO2 is that the condensation temperature is not high enough to make steel radiate heat in infrared, at least not significant amounts of heat. You could consider another material for the radiator other than steel, but any metal I know of will require significant temperature to glow in IR.

clark · 2003-10-22 14:17:53

What about a wrapped multi-alloy compositite then?

Think of it like a layer, each layer contains a different metal alloy, each with slightly different temp/radiating capabilities.

So the first layer absorbs the heat, then passes it off onto the next layer of metal, and so on and so on (not sure how many layers are needed.

Probably way off on this, just thinking off the cuff...

OR, install studs- in radiating heat, it's all about surface area, right- so think of little studs (hollow on the inside) sticking out from the heat source- the heat flows into these small empty chambers, and then have more surface area to be excreted from...

Bill White · 2003-10-22 14:22:43

The only problem with CO2 is that the condensation temperature is not high enough to make steel radiate heat in infrared, at least not significant amounts of heat. You could consider another material for the radiator other than steel, but any metal I know of will require significant temperature to glow in IR.

Can you walk me through another amateur pipe dream?

Suppose the night-time ambient air temperature is below a key level for super-critical C02 while the daytime sun-heated temperature is above that level? Could you generate electricity by storing supercritical C02 cooled by the overnight ambient air temperature and then heat it by running it through sun heated black pipes during daylight hours?

By playing with the pressure could we tune a super-crit CO2 reactor so that a phase change occurs between night time lows and day time highs?

Or is that just crazy?

RobertDyck · 2003-10-22 15:33:55

Suppose the night-time ambient air temperature is below a key level for super-critical C02 while the daytime sun-heated temperature is above that level? Could you generate electricity by storing supercritical C02 cooled by the overnight ambient air temperature and then heat it by running it through sun heated black pipes during daylight hours?
By playing with the pressure could we tune a super-crit CO2 reactor so that a phase change occurs between night time lows and day time highs?

Hmm. This reminds me of a tide harness on Earth. A tide harness forces ocean water to run though a turbine when the tide rises, and back through the same turbine when the tide falls. It generates electricity each way.

This CO2 idea could work. I don't see how to generate electricity when CO2 condenses, but you could generate electricity by expanding CO2 gas. However, you have to pressurize CO2 to get it to liquefy. At Mars ambient pressure (or Earth pressure) CO2 will solidify directly to dry ice or sublimate to CO2 gas. The triple point is 517.3kPa at -56.6?C (75.1 psi at -69.9?F). Below the triple point CO2 will not become liquid. If you want to run it on just daily temperature change then you must maintain a sealed system. That requires a large vessel to hold the gaseous CO2 during the day.

RobertDyck · 2003-10-22 16:03:10

What about a wrapped multi-alloy compositite then?
Think of it like a layer, each layer contains a different metal alloy, each with slightly different temp/radiating capabilities.
So the first layer absorbs the heat, then passes it off onto the next layer of metal, and so on and so on (not sure how many layers are needed.
Probably way off on this, just thinking off the cuff...
OR, install studs- in radiating heat, it's all about surface area, right- so think of little studs (hollow on the inside) sticking out from the heat source- the heat flows into these small empty chambers, and then have more surface area to be excreted from...

You could use a radiator that uses one material to contain the coolant and a coating of another to radiate heat. You really only need the two. Radiator fins could get rid of more heat, just like the heat sink on the CPU in your computer. I'm not sure of the details, that requires thermodynamics and it isn't something I can quickly google.

Bill White's suggestion raises another possibility. I have been thinking of interplanetary space but on Mars you do have the ground. Mars air is thin but the ground is solid. High efficiency heating/cooling systems on Earth use a heat pump. That uses a coil buried in the ground below the frost line. In winter it collects heat from warm ground (above freezing), and in summer it eliminates heat into cool ground. It does take a large area of land so it can only be installed in houses with a large yard. This takes advantage of the fact that 4 feet below the surface the ground remains a relatively average temperature year round. On Mars the average temperature will be way below freezing. If the daily surface high is -8?C and the low is -77?C then the ground would be somewhere around -42?C. A large ground loop could get rid of a lot of heat.

clark · 2003-10-22 16:39:47

I have been thinking of interplanetary space but on Mars you do have the ground. Mars air is thin but the ground is solid. High efficiency heating/cooling systems on Earth use a heat pump. That uses a coil buried in the ground below the frost line. I

Hmmm, and here I thought it might make for a novel passive means to drill through Europa's crust...

Bill White · 2003-10-22 22:08:51

Suppose the night-time ambient air temperature is below a key level for super-critical C02 while the daytime sun-heated temperature is above that level? Could you generate electricity by storing supercritical C02 cooled by the overnight ambient air temperature and then heat it by running it through sun heated black pipes during daylight hours?
By playing with the pressure could we tune a super-crit CO2 reactor so that a phase change occurs between night time lows and day time highs?
Hmm. This reminds me of a tide harness on Earth. A tide harness forces ocean water to run though a turbine when the tide rises, and back through the same turbine when the tide falls. It generates electricity each way.
This CO2 idea could work. I don't see how to generate electricity when CO2 condenses, but you could generate electricity by expanding CO2 gas. However, you have to pressurize CO2 to get it to liquefy. At Mars ambient pressure (or Earth pressure) CO2 will solidify directly to dry ice or sublimate to CO2 gas. The triple point is 517.3kPa at -56.6?C (75.1 psi at -69.9?F). Below the triple point CO2 will not become liquid. If you want to run it on just daily temperature change then you must maintain a sealed system. That requires a large vessel to hold the gaseous CO2 during the day.

Okay - suppose a fully sealed two phase system. Solid CO2 (dry ice) and gaseous CO2. I imagine 2 compartments with two passages between them. Each passage can be sealed air-tight and the entire system is enclosed.

Step #1

One compartment is packed with dry ice. It is positioned so sunlight can heat it and pipes are run through it to dissipate waste heat from the settlement or the nuclear reactors.

As the dry ice heats it phase shifts to gas to create pressure. The gas passes through a valve into compartment #2 turning a turbine.

Step #2

The second compartment is much, much larger, perhaps a dome made of kevlar, etc. . .

The gaseous CO2 is allowed to cool (overnight?) and condenses (precipitates?) as dry ice snow. Through gravity it falls to the floor of compartment #2 which is shaped like a funnel (perhaps lined with Teflon for slickness). The dry ice snow slides down the funnel to a gate which when opened leads back into compartment #1.

The funnel gate is closed airtight while the dry ice is heated by sunlight or waste heat. Dry ice transforms into gaseous CO2 and spins a turbine.

At the appropriate time, the heat source is removed and the turbine gate/valve closes. Once the temperature inside the dome compartment #2 falls to a point where dry ice forms, the funnel gate opens allowing the dry ice snow fall to re-enter the first compartment transported by gravity.

Thoughts?

= = = Variation = = =

Suppose you have a station at one of the poles. Dry ice lies in huge mounds and drifts all around your station.

Modify a solar chimney, see this link for one example.

Use a robot bobcat and/or conveyor belts to pile dry ice at the base of the chimney. Heat with sunlight and/or waste heat from the mobile base. Spin turbine. Use electricity.

Another solar chimney link.

Also, look here for an ammonia/water solar thermal power generation project.

RobertDyck · 2003-10-23 07:03:10

CO2 would freeze to form dry ice frost; think of hoar frost. This would be fluffy and stick to the inside surface of your tank. You could add wipers to scrape it off so that it falls down your funnel, but the motors to drive wipers would take power. Would that take more power than the turbine generates? It would be simpler to increase pressure above 75.1 psi so CO2 forms liquid and just drips into the collection compartment. That would require a heavy pressure vessel.

However, this is the way Robert Zubrin wants to separate CO2 from Mars atmosphere for ISPP. I wonder if he was thinking of collecting dry ice frost or increasing pressure to create liquid. At night the temperature doesn't quite reach the freezing temperature for CO2, almost but not quite. Only the winter pole gets cold enough to freeze CO2. Actually, that's what regulates pressure on Mars. So to use night time cold temperature to separate CO2 from Mars atmosphere you do have to increase the pressure somewhat.

RobS · 2003-10-23 19:23:42

I am no expert, but it seems to me one could keep carbon dioxide at a temperature high enough so that daily sunlight would boil it and nighttime temperatures would reliquify it. The big problem with the scheme is the extremely low efficiency that the laws of thermodynamics would require. As I understand it, you can convert a very large percentage of thermal energy into mechanical energy (and thence via turbine and generator to electricity) if the temperature drop is from many hundreds of degrees Kelvin to only one or two hundred Kelvin. Oil and coal-fired plants generate steam at very high temperatures and get 30% efficiency or so as a result. But if this scheme has a delta-t (change of temperature) of only ten or twenty centigrade, its efficiency surely would be under ten percent-probably even less--which is lower than the efficiency of solar panels.

So I think solar panels are better.

Regarding the storage of heat for heating greenhouses and such during dust storms and other occasions, it once occurred to me that water wells could make excellent thermal storage wells also. If one were to drive two shafts fifty meters apart 300 or so meters into frozen regolith, even at the equator there would be some water in the pore spaces, especially at the bottom. Solar thermal panels or a nuclear reactor could be used to generate heat; for example, if one used solar arrays that made electricity from concentrated sunlight, no doubt the reflected light would make the arrays hot as well. One could blow compressed Martian air through pipes on the back of the array to pick up the heat, then pump the heated, compressed Martian air down one of the well shafts. There it would penetrate into the natural pore space in the rock--rock is usually 10 to 30 pore space--heating the rock. Any ice in the rock would melt and probably evaporate. The cooler, wetter air would then come back up the same shaft later or, better, up the parallel shaft continuously. You could let the air expand and cool once it reached the surface, causing the water to condense out of it, and since it came to you as vapor it would not have dissolved salts in it (as the subsurface ice likely does). So you'd get desalted water. As a bonus, after many, many months, you'd also get a blob of heated rock underground between your shafts; rock that has more pore space because the ice filling some of the pores is now gone. After a few years one could easily have several tens of thousands of tonnes of rock heated significantly. If a dust storm then hit and you needed heat, you could pump cold compressed Martian air down one shaft and it would come back up the other warmed by the rock. You could then use a heat pump to heat the greenhouses.

Of course, the heat would constantly leak from the rocks. The compressed air would escape laterally into the pore spaces around the shafts. But the leakage would tend to seal itself off because the heated air would evaporate water from the rock, then carry the water vapor outward into colder rock, where the water would revert to ice and plug the pore spaces. Over time the water well would form an ice ball around it, and as the heat continued to expand outward the ice ball would melt, some of the water coming inward and escaping up shafts where it could be collected, some moving outward to refreeze pores and cracks in the rock.

-- RobS

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#1 2003-10-21 12:19:58

Re: Small Nuclear Reactor proposal - Size of a large spruce tree

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