Why write about a reactor that isn't commercially available?  Molten salt reactors can provide almost free energy.

Current conventional reactor technology is proving to be both unacceptably expensive and apparently has safety issues that cannot be engineered away. 

China has a high-priority formal development program for this reactor.  Molten Salt Reactors (MSRs) have almost nothing in common with conventional reactors, promise to be far cheaper and easier to make and run, go cold when shut down, use an energy metal that requires no expensive enrichment, and produces 1% the nuclear waste of conventional reactors, most of what waste there is is unsafe for less than ten years and none of it has any military value.

Developed by nuclear chemists, molten salt reactors naturally run red-hot at 1,300°F and use unpressurized melted salt carrying dissolved nuclear fuel circulating like blood through the reactor and its heat exchangers, daunting characteristics in the eyes of the typical nuclear engineer trained on 550°F, solid fuel, high pressure conventional reactors.

Unpressurized means it cannot explode.  Radioactive molten salt that leaks out turns solid when it cools and, unlike radioactive water from a nuclear power plant, cannot sink into the environment.

Origins

The applications described here are for a "new" old reactor that was developed at Oak Ridge National Laboratories and then put on the shelf and forgotten.  This reactor was to be the Air Force's equivalent to the Navy's nuclear submarine reactor.  Yes, it was a nuclear reactor designed to power two or more nuclear jet engines in a nuclear bomber.  Several "proof of performance" versions of the airplane reactor were built by Pratt & Whitney and General Electric. 

(Photographs: Above, MSRE reactor on display at Oak Ridge National Laboratories.  Below, Proof-of-performance prototype of Pratt & Whitney jet engine reactor at Idaho National Laboratories.

The "Molten Salt Reactor Experiment" reactor was built and run for 5 years at the ORNL facility that developed the airplane versions.  The MSRE version was 8 megaWatts thermal in power.  While it ran as expected on every rational nuclear fuel including nuclear waste, starting it on uranium and then running it on thorium was an excellent combination providing unbelievable fuel economy with almost zero nuclear waste. 

How cheap?  $300 million dollars worth of coal or $50,000 worth of thorium will produce the same amount of heat.  That's 6,000 times cheaper.  Think of what that would do for your electricity bill.  How can this be?  There is 4 times as much thorium as uranium, unlike uranium, thorium does not need costly enriching - you just use it - and a molten salt reactor gets about 100 times the thorium mileage as a conventional reactor gets uranium mileage.

The MSR on this web site is unpressurized, so it can't explode.  This also means it can be made of much thinner metal than a conventional reactor.  That should make it much cheaper to build and safer to be around.  Also, if it gets into trouble, it goes cold naturally - it is convection air cooled so it doesn't need any shut-down power.  No other type of reactor can make that claim.

The Applications

MSRs appear to be well-suited for the supremely important task of replacing coal, natural gas, and oil. 

Repowering coal burning power plants  Because of it's much higher temperature (1,300°F) than conventional high-pressure water cooled reactors (550°F) and its unpressurized red-hot heat transfer salt cooling system, by simply replacing a power plant's fossil fuel boiler with a thorium boiler, a coal power plant would become 100% environmentally clean at very low cost.

Hydrogen generation  In addition, with a little help from some heat booster Calrods, MSRs can open the doors to the hydrogen economy by powering the sulfur-iodine water splitting process developed about a decade ago by General Atomics.  The hydrogen produced would greatly reduce the cost of refining crude oil into gasoline.

Repowering combined cycle jet turbine power plants  Its jet engine roots also make it a wonderful candidate for Global Warming-free repowering of today's gas turbine generators in combined-cycle power plants.

Oil extraction from shale and oil sands  Shale oil and oil sands bitumen are "Tight Oils" that need to be melted free from the rocks that hold them before they can be pumped.  Combined, the United States and Canada hold over twice the tight oil man has already pumped. 

Synthetic vehicle fuels  Gasoline from garbage and sewage become both environmentally and economically practical feedstocks for vehicle fuel when using a high temperature MSR to power plasma torches to gasify the feedstock, to power a small water splitter to make the needed hydrogen for hydrocracking, and also to power a gas-to-liquids synthesis refinery.  Carbon capture technology can also recycle what used to be the refinery's CO2 emissions into vehicle fuel feedstock if ample hydrogen for hydrocracking is available.

Replacing all stationary fossil fuel fires  The applications cited here are the world's biggest users of fossil fuels and are a good heat, power, and physical match for the 70' in diameter, 50' high EBASCO molten salt reactor, a 2,500 megaWatt (thermal) 1,000 megaWatt (electrical) reactor that was detail designed by EBASCO for ORNL but never built.  There are smaller 1,000°F reactors such as the 25 megaWatt (electrical) Gen4 energy's reactor, (A well-respected Russian submarine "fast" reactor currently in advanced development for civilian applications in the US.) that will do a better job of replacing fossil fuels for the world's several million general industrial and boilers and furnaces.  Once 25 megaWatt (e) reactors actually appear in the energy marketplace, smaller, perhaps as small as 5 megaWatt (thermal), reactors are sure to follow.  World wide, there are perhaps 500 million fossil fuel boilers and furnaces in this industrial, commercial, and institutional power range.

How a Thorium-Fueled Molten Salt nuclear reactor works.

The schematic diagram at right depicts how a single fluid molten salt reactor works.

Yellow depicts salt heated so hot it is a fluid like water.  Darker yellow indicates salt with nuclear fuel dissolved in it.  It is called "Fuel Salt."  Lighter yellow indicates non-radioactive "Clear Salt."  The arrows indicate the direction of salt flow.

Molten salt has several advantages over water in nuclear reactor technology.  It is immune to radioactivity, so, unlike water, does not pick up any radioactivity when in contact with radioactive equipment.  This means salt can safely carry heat out of a radioactive area to a "safe for humans" area.  Unlike water, the heated salt does not boil, so no explosive steam pressure is made.  Salt carries heat almost as well as water.  More about this salt.

Notice there are no radioactive fuel rods and only a few control rods. 

The radioactive fuel salt passes through tubes drilled in the black block of graphite located in the reactor tank.  Being near the graphite causes the salt's radioactive fuel to fission, fission releases heat and makes the fuel salt hotter.  The now-heated fuel salt circulates to the primary heat exchanger where its heat is transferred to the clear coolant salt, which, in turn, carries the heat to the secondary heat exchanger where the heat is transferred to water to make steam to power an electricity generator.

Something radioactive needs to be used to start the reactor.  Uranium, concentrated to 18% U-235, was commonly used.  Once up and running, non-radioactive thorium can be added to the fuel salt stream to replace the used-up uranium.  Thorium, circulating through the radioactivity in the reactor tank, will turn into radioactive uranium-233 after 27 days and take over for the starter uranium.  From this point on, only thorium needs to be added to the fuel salt for about 30 years of continuous full-power running before the salt becomes saturated and needs cleaning.  At saturation, full power will have dropped 20%.

The graphite in the reactor tank will be degraded by the 30 years of radioactivity it has undergone and will need replacing.  Pencil "lead" is actually graphite, a form of coal, so graphite supply will never be a problem.

The thermal expansion and contraction of salt determines to some extent the concentration of radioactive fuel materials in the reactor's black graphite core and thus tends to keep the fuel salt's temperature within a smaller range.  Not unlike the cruise control on your car as you drive over hills.

For most of the reactor's power range, this natural action is like a thermostat keeping it to its preset temperature.  The control rods enable operational temperature set-point changes between maximum power and idle.  Recall this reactor was originally intended to be the power source for an airplane, which gives you some idea of operational "throttle" response.  People who have test run this type of reactor describe it as sluggish at low power settings but very stable (1.4 meg pdf).

Due to the reactor's docile nature, operators were deemed to be unnecessary.

     (What a wonderful thing for power plant operators to contemplate. - JH)

At the bottom of the reactor tank is a "Freeze Plug."  It is simply a place in the pipe that is kept cool by a fan so that the salt at that point in the pipe forms a solid plug.  The heat of the reactor is always trying to melt the freeze plug, the fan is always preventing melting.  If the reactor gets too hot for any reason, the heat overpowers the fan and the freeze plug melts.  Once this happens, the fuel salt drains by gravity into the Emergency Drain Tanks.  Once this happens, away from the black graphite, the fuel salt stops fissioning and begins to cool and eventually go solid.  If a loss of electricity occurs, the fan stops and, again, the freeze plug melts.

The Emergency Drain Tanks have heaters and small pumps to re-melt the salt and refill the reactor to restart it.  Drain tanks with heaters and pumps are also needed for the secondary clear salt.  Otherwise, when reactor is shut down, the salt will turn solid in the heat exchangers, pumps, and pipes.  Freezing salt, unlike freezing water, contracts when it freezes, so no damage should result.

(Right) A sketch of the MSR facility.  A simple industrial facility rather than an elaborate pressurized water reactor.  Since an MSR is unpressurized and cannot explode, it needs only to have its radioactive components confined, rather than to have a large explosion containment building. 

Red indicates radioactive fuel salt piping, yellow, non-radioactive clear salt piping.

The red zig-zag device is a night time photograph of ORNL's "Molten Salt Reactor Experiment" reactor's air cooled radiator.  The reactor and its pipes really will run red hot.  This means the reactor has to have both its radioactivity and its heat confined.  A several foot thick ceramic composite wall was part of EBASCO's design for their power plant reactor.  Since the salt is far from its boiling point, it makes no vapor pressure so the explosion risk of a water-cooled conventional reactor does not exist and a large explosion containment building is unnecessary. 

A practical fuel for early molten salt reactors has been described by Dr. David LeBlanc in this paper:
Denatured Molten Salt Reactors (DMSR):  An Idea Whose Time Has Finally Come?  (260k pdf)

Where other nuclear reactors cannot go.

The yellow circle in the diagram at right shows where the "Single-Fluid Converter" thorium-fueled molten salt reactor fits into the various families of nuclear reactors.

Reactors this hot can do far more than merely boil water to make electricity.

That is why this web site book was written.

The various applications sketches presented in this web site are intended to provide inspiration and guidance to design engineers and technology users, they are not final designs by professional engineers.

I think the diagram was drawn by Dr. Forsberg (above) of Oak Ridge National Laboratories and MIT.

Your author took the liberty of adding the black "coal boilers" block, typical pressures, and the Fahrenheit temperatures.

About the reactor families in the diagram:

The thorium-fueled molten salt reactor opens a new era in mankind's use of energy.  Molten salt reactors are the only source of nuclear heat that can, in theory, exceed both the temperature and the volume of heat energy produced by any of the other reactors and also most fossil fuels most of the time.   

At right is a diagram of the heats and pressures produced by the four most common families of nuclear reactors.  The author has drawn in the steam temperature and power range (black square) of most of the world's over 100,000 power plant boilers.  They are installed in the world's 30,000 coal power plants. 

There are another 400,000 smaller, lower pressure fossil fuel boilers in industrial and commercial use around the world.  Combined, they produce about 50% of all Global Warming.  Different sized thorium-fueled molten salt reactors can replace most of them.

As you can see, the red-colored molten salt reactor family is both hotter and more powerful than the black coal boiler family.  Not being under any pressure, they need only to be in a "Confinement Cell" to prevent the radiation and the radioactive fuel in the reactor from escaping.  Molten salt material that does leak turns into a solid lump as it cools rather than sinking into the ground and dispersing into the environment as radioactive water does.

The blue-colored reactor family at the bottom are the Light Water High Pressure reactors.  They produce the lowest temperature heat and need the highest operating pressures.  This makes them explosion-prone which is why they need to be inside containment buildings.  Being relatively low temperature water-boilers, they are not really very good at making an efficient steam for electricity generation.  That is why coal (and more recently, natural gas) remain the energy of choice for making electricity.

Colored yellow are the Liquid Metal Fast Reactors.  Hotter than the Light Water Reactors, they do not operate under any pressure and so, like molten salt reactors, are incapable of steam explosions.  Unfortunately, they fall just short of the temperature necessary to replace the steam produced by a standard Loeffler coal burning power plant boiler - 1,000°F - when you take into account the temperature losses of the steam generators.  Running power plant turbines on steam cooler than design causes the steam to turn into fog in the turbine.  Fog water droplets pelt the blades and buckets in the turbine and the resulting erosion quickly destroys a turbine that would last more than 20 years with properly hot steam.

The small brown-colored TRISO fueled Very High Temperature Reactors are cooled by a gas - typically helium or carbon dioxide - rather than a liquid.  Since liquids can carry perhaps 3,000 times as much heat in the same volume, gas cooled reactors have a size problem when a lot of power is needed.  Think about the 230 foot high coal boilers at power plants (air is also a gas).  Gas cooled reactors are under relatively high pressure so they also need to be operated in containment buildings.  The dynamite-like explosive power of water's steam phase change is not present, so a failure should resemble a punctured tire.

About the applications cited in the diagram:

Electricity generation and hydrogen generation temperatures and required energy amounts are indicated by the green bars.