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THORIUM APPLICATIONS Contents Industrial Nuclear Reactors
Chapter 3, Page 6: Recycling Our Largest Coal Burning Power Plants Into Thorium Power Plants. < 5 Page 7 >
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Recycling Coal Burning Power Plants Into Thorium Power Plants

Why Recycle Existing Coal Burning Power Plants to Nuclear?

The proposed rule — years in the making and approved by the White House after months of review — will require any new power plant to emit no more than 1,000 pounds of carbon dioxide per megawatt of electricity produced. The average U.S. natural gas plant, which emits 800 to 850 pounds of CO₂ per megawatt, meets that standard; coal plants emit an average of 1,768 pounds of carbon dioxide per megawatt. - - Juliet Eilperin, Published: March 26

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Replacing very large coal burning power plant boilers with thorium reactor boilers
ADVANTAGES OVER BUILDING A NEW POWER PLANT ON A NEW SITE: COST, TIME, COAL HANDLING EQUIPMENT

(Below, click on image to enlarge.) The basic concept is simple: Install a small silo type thorium-fueled molten salt reactor and its steam generator building near the power plant's stack. Run steam and feedwater lines to the pulverizer area of the coal boiler, disconnect the turbine's steam lines from the boiler and reconnect them to the new steam generator.

(Below) With the boiler in the background.

The electricity generator's turbine (red) is disconnected from the coal burning boiler (center, faded), then reconnected to the nuclear boiler.
Man standing in various places with 10 foot surveyor's rod to show approximate size. Larger image.
Key novel features: Steam generators not integrated with reactor. No pressurized vessels - only the steam pipes are pressurized.
Molten Salt heat transfer makes driving multiple steam generator sets from a single reactor practical.

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Contents of Part 1 of this page
1) Part 2 Directory: Replacing coal-fired Loeffler boilers with molten salt boiler emulators.
2) Doing it: Replacing a coal burning boiler with a molten salt nuclear boiler
3) Thermodynamics:
4) Why conversion from coal to nuclear is a new idea
5) Converting a typical large coal burning power station
6) Powering two large steam turbines with one large nuclear boiler..
7) Repowering an old coal burning power plant with cleaner burning natural gas - common these days
8) The control system

Boiler Replacement Advantages

Boiler Swapping Offers Many Economic and Speed Advantages. A little boiler changing can go a long way. Consider France's experience with changing from coal to nuclear. Now using nuclear fuel to produce 78% of their electricity, France now makes 1/3 the CO2 the United States makes on a per person basis. France closed their last coal mine in April, 2004. Japan now makes over 50% of their electricity from nuclear fuels.

Swapping just the power plant's boiler preserves the power plant, its worker's jobs, its operating permits, the plant's access to cooling water, electrical grids and heavy transportation. What's not to like from a deal like this?

Boiler Swapping Examples: Several quick and simple examples of how both coal and natural gas boilers could be replaced by thorium boilers are offered: Taichung, perhaps the world's largest coal-burning power plant, and the U.S. Capitol Building Complex, which is heated and cooled by industrial-sized natural gas boilers.

The Advantages of Swapping Out Mega-Boilers: Supersized Power Plants are job one: 2% of the world's 60,000 fossil fuel power plants, 1,200 supersized power plants are making over 3/4 of coal's Global Warming. The world will never be willing or able to provide much money for Global Warming mitigation and we can make it go furthest if we mass-produce a low-cost thorium boiler to replace coal burning boilers. This will enable us to re-use everything else at the power plant - including an already experienced workforce - a strategy much wiser than building the equivalent amount of generating capacity in new windmills.

As of July, 2008, carbon uncertainties have driven new coal-burning power plant costs to $3.50 per watt to construct (Synapse Energy Economics, Inc.). Florida's new Crystal River nuclear plant has been stated (July, 2008) as $17 billion dollars for 3 gigaWatts, or $5.60 per watt. The author speculates it is unlikely that the construction cost for a new Hybrid thorium plant would exceed $3.00 per watt for the 10th Hybrid plant built. The 10th conversion of an existing coal-burning power plant to thorium barge should cost less than $1 per watt. Do the homework.

A power plant is a legal entity with both obligations and rights

If you own a coal burning power plant here is the biggest reason why you would want to convert to thorium:

Permits. Permits. PERMITS. PERMITS. PERMITS!

Would you rather have an existing site that is already permitted or do you want a new site so badly you are willing to fight in court forever against anti-nuclear environmentalists in the pay of your competition?

An existing old coal burning power plant has enormous local support for the idea that adding a small modular nuke electricity generation unit is far better than shutting the plant down.

Always get the identities and photographs of protesters and make sure everyone at every discussion meeting knows where THEY live. Always photograph any protest demonstrations with a wide-angle lens - leaving plenty of space on either side - so everyone can see how few protesters there really are.

1. Already paid for - NO NEW COSTS FOR MOST OF THE EQUIPMENT

2. Already wired to our cities - NO NEW TRANSMISSION LINE RIGHT-OF-WAYS NEEDED

3. Already have cooling water - NO NEW RIPARIAN OR PRIOR APPROPRIATION RIGHTS NEEDED

4. Already have access roads - NO NEW ROAD RIGHT-OF-WAYS NEEDED

5. Already have railroad tracks - NO NEW RAILROAD RIGHT-OF-WAYS NEEDED

6. Usually have ample land for several additional future units - NO NEW LAND NEEDED, COAL YARD LAND WILL BECOME LAWN SOON

7. No construction delays - THEY ARE ALREADY RUNNING, CAN CONTINUE TO RUN DURING UPGRADE EQUIPMENT INSTALLATION

8. Already have proven operators who know the equipment - FEWER OPERATORS LOOSE JOBS, EXISTING OPERATORS WOULD BE BETTER PAID

9. Cleaner working environment - THORIUM PLANTS ARE CLEAN

[A helpful power plant operator reader suggested I add the following. (Thank you)]

A few advantages you may want to list in terms of BOP. Feel free to use them or not...

1. Construction is made *cheaper* because all necessary roads, water transport and rail lines are already in place. A huge savings relative to a green field plant and even a currently operating nuclear plant.

2. Licensing:
a. Water usage for everything from cooling to potable water. In place.
b. Sewage and waste water discharge. In place.
c. Air pollution (not that it's needed) in place, frees up carbon licenses if this occurs.
d. Hazardous waste storage/processing (all industrial facilities have to pay for this, regardless). In place.
e. Lube oil and chemical usage/storage licenses. In place.

3. Control Room(s). Only a retrofit of the existing coal plant (to bring it up to N-stamp standards) controls have to occur.

4. Grid access. The grid and switchyard is *in place* and ready to swap over. If MW out put is close to the same, it's even possible the same main bank transmission can be used, a huge savings, along with, BTW, all the associated remote monitoring (relays for undervoltage, overvoltage, shorts, grounds, etc etc), already in place. No major transmission upgrades needed if MWs are to stay the same and even then, only minor ones at worse.

5. Human Resources. The coal plant will have trained operators and maintenance personnel many/some/a lot of whom will be able to migrate over (literally by walking) to the new plant after NRC qualifications.

6. Overall reduced footprint. Wildlife (my personal favorite) sanctuaries can be built as security belts around the formally soot-laden, coal spewed, plant site. Allows room for expansion for subsequent PBMR/LFTR use (desalination, chemical/hot process steam usage, etc etc).

If we built nothing but new nuclear, what would we do with all the existing fossil-fuel burning power plants we now have? This is a major economic and grid logistics question no one is asking. Many have 40 or more years of productive and profitable life remaining. This is the most important consideration when second and third world countries think about ending their Global Warming CO2.

FUN COMMENT: (From another reader:)

Jim: Stumbled on your web site and want to congratulate you on your mission. I have been working on a similar unsolicited proposal to convert one of our largest coal plants in [deleted] to nuclear. The interest in the large plants is that one saves the incredible investment in siting, cooling towers, electric generators, some of the lower pressure stages of the turbines( as you are aware the nuclear plants have lower steam pressures and temperatures but multistage turbines can be converted to salvage some of their cost), the condensing equipment, the switching yard, and most importantly the transmission lines and towers. A very rough estimate is that half the cost of a new nuclear plant of the same size could be salvaged. The federal government could loan the money and the utility smart enough to make this change could return the loan in carbon credits. Large nuclear plants are very labor intensive and we obviously need the jobs. Keep pounding your drum. Solar and wind won’t hack it. [deleted] (This author regards this approach viable.)

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Doing It

Replacing a coal burning boiler with a molten salt nuclear boiler

(Below) For repowering an existing coal burning power plant the reactor and first heat exchanger arrangement (right) would be the same but a different multiple second heat exchanger arrangement (shown below) to replace a conventional coal burning power plant's steam evaporator, superheater, reheater, and economizer would be needed. The MSR's 1,300°F outlet temperature is hot enough to replace any coal boiler ever made and also to make good any losses from long steam pipes coming from a new reactor located in an existing coal burning power plant's old coal yard.

Molten Salt Reactor

(Above) A 500 mWe conventional superheated steam coal burning power plant unit repowered with a air-cooled,
1,000 mWe Thorium-Fueled Molten Salt Reactor
Nuclear boiler on the left, steam generators middle, old coal fired steam plant on the right, energy flowing from left to right.

Notice? There's no heat being lost up the stack. Who says steam is inefficient? It's the coal boiler that makes coal burners inefficient!
(Roughly, 30% of the energy goes out the wires, 20% out the stack, 50% out the heat sink - cooling tower or pond.)
Over 50% of the world's largest coal burning power plants are on water. Barge mounted reactors can be towed away for refueling, repair, or disposal, leaving no residual radioactivity at the user's site.
(As far as the author knows, this is the only drawing in the world that shows how to drive a standard superheated steam coal burning power plant with a nuclear reactor of any type, much less a molten salt reactor. To see it, the author had to sketch it himself. Notice how stone-simple the MSR is?)
(Order of magnitude scale: The man on barge is holding a 10 foot long surveyor's rod.)

Unpressurized shell-type molten salt-to-water shell and tube heat exchangers provide pre-heated water, water evaporation (saturated steam), superheated steam, and reheated steam. Tall evaporation-superheat unit is from an 880 mWe Russian Rosatom BN-800 sodium cooled fast-neutron reactor. (Unneeded coal boiler and stack shown faded in background.) Larger, sharper View. To power two superheated steam turbines from the same large reactor, simply add a second pair of steam generator heat salt lines coming off the second salt-to-salt heat exchanger (see diagram below).

To give the reader some sense of the temperatures and pressures involved, I will quote a few specifications from the booklet "Fabrication of the heat exchanger tube bundle for the Molten-Salt Reactor Experiment" by R. G. Donnelly and G. M. Slaughter, Dec. 9, 1963, for the design of the fuel (or primary) salt-to-clear (or secondary) salt heat exchanger.

"Design temperature: 1,300°F; Design Pressures (psig): Shell, 75; Tube 125; Terminal Temperatures (°F): Fuel Salt, Inlet 1,225; Outlet 1,175; Coolant Salt, Inlet 1,025; Outlet 1,100; Effective log mean temperature difference (°F): 133."

With pressures and temperatures like these, any country that can build an ocean-going fishing boat can build this reactor and its steam generator. ORNL brazed the heat exchanger.

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Thermodynamics

Thermodynamics: Extremely low-cost Molten Salt reactor heat can compete very well indeed with coal, natural gas, and oil fires.

Here's what a typical supersized steam turbine needs and what a conventional solid-fuel PWR reactor can deliver:

                                           Taichung's 550 MWe GE Turbine                 30-Year Molten Salt reactor           Conventional Westinghouse PWR reactor
                                                                                                                                                                          (Turbine Steam Loop)
Steam Type                                    Superheated                         Superheated, Supercritical, Ultrasupercritical                   Subcooled
Pressure (psia)                                     2,524                                                     up to 4,000                                              900
Temperature (°F)                                   1,000  (331°F superheat)                              1,100                                                     530
Sat. Temperature (°F)                             669                                                             706                                                    532
Reheat Temperature (°F)                        1,000  (from 550)                                         1,100                                                   None
Enthalpy (Btu/lbm)                                 1,461                                                 Depends upon turbine                                     524
Internal Energy (Btu/lbm)                        1,318                                                                                                                   520
Entropy (Btu/lbm-F)                                      1.53                                                                                                                      0.725
Specific Volume (ft3/lbm)                              0.321                                                                                                                     0.021
Density (lbm/ft3)                                           3.111                                                                                                               47.231     (Water = 62.4)
Cp (Btu/lbm-F)                                              0.665                                                                                                                1.249

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Why conversion from coal to nuclear is a new idea

Why no one has been thinking about repowering coal power plants with solid-fuel conventional nuclear reactors.

The reactor on a barge is a radical innovation that is easily overlooked. It is as if the fire was in one building and the boiler's kettle in another, connected by two low pressure pipes. Such a configuration confers new advantages and flexibilities. The blue walls and floor are insertable slab lapped 3-foot-thick, 2-ton-per-cubic-yard steel rod reinforced concrete containment walls. Supplementary shielding is possible by mounding earth around the barge. Fuel salt is drained from reactor and above-deck containment slabs are removed before re-floating. Example barge: http://www.mcdonoughmarine.com/ocean_marmac400.htm

Russian Nuclear Barge

Important Point. Most of these supersized coal burning power plants went on-line 20 to 30 years ago and are 1/3 to 1/2 worn out so a 30-year disposable nuclear boiler which is saving the owners perhaps as much as 100 million dollars in coal each year should hit the financial "sweet spot" regardless of how the environmental winds blow.

Big Bend is on Tampa Bay, a location subject to hurricane storm surges that could go as high as 20 feet. The air-tight reactor silo protrudes 40 feet above sea level to prevent being inundated. The 5 foot thick reactor confinement cell walls plus 3 foot thick concrete barge walls make a total of 8 feet of concrete radiation shielding. Three feet of concrete is sufficient to stop all nuclear radiation. (Concrete is cheap, we make roads out of it.) Natural convection air cooling for the reactor and confinement cell comes from the dual passive 2 foot thick heat exchanger downcomers and risers. This particular type of molten salt reactor runs for 30 years between refuelings.

Only the molten fuel salt is radioactive. If any leaks, it is kept within the blue containment cell. In the unlikely event molten fuel salt escapes the confinement cell, the barge will act as a catch basin. If the molten fuel salt escapes both the confinement cell and the barge due to a bombing attack, the radioactive fuel salt will turn solid when it cools below about 680°F, forming easy to find lumps (it's radioactive) that can be recovered. Compare this level of safety with today's pressurized water reactors that don't need bombing attacks to explode. When their radioactive water gets out, it sinks into the ground, spreading radioactivity far and wide via underground aquifers.

Shipyards, now equipped with computer controlled cutting and precision welding machines, are well-suited for mass-producing large objects made out of heavy metal such as the MSR T-FRR reactor and its heat exchangers shown above. Mass production always drives costs down and quality up.

MSRs have the “high ground.” Never underestimate the power of price. Repowering a coal burning power plant generating unit is estimated to salvage half the value of the equipment impacted – perhaps as much as ½ billion dollars. MSR technology is, by its very nature, frugal, safe, inexpensive, and durable. MSR’s unpressurized “Shell and Tube” components are extremely simple and safe compared to their conventional reactor counterparts. This translates into a highly profitable mass-market product.

Over half of the 1,200 supersized power plants are on navigable water, making shipyard mass produced concrete “Reactor Barges” a cost-attractive approach. They would be parked in filled-in slips cut next to a power plant’s turbine gallery. If desired, a great deal of physical security can be economically added. Such “Reactor Barges” would act as catch basins in the event of an accidental spill, “float” on the ground during an earthquake, be “high and dry” in the more likely event of a storm surge, be easily returned to a factory for its 30-year refurbishing-refueling, and be easily removed forever when no longer needed, leaving no residual radiation or nuclear power site decommissioning costs.

REACTOR: Since the reactor is UNPRESSURIZED, the reactor vessel can be made from relatively inexpensive 1/2 inch thick welded nuclear-rated Hastelloy-N instead of the massive 10 inch thick steel forgings needed for conventional nuclear reactors. Also, since the reactor is filled with nothing but blocks of graphite with tubes drilled through them, (that is why the reactor cut-away is shown as black in the sketches) we have a relatively easy to construct system. The shape of the reactor reflects the Gen-IV sketch rather than the less readily understandable 1,000 mWe EBASCO design. ORNL's 1,000 mWe reactor vessel design called for: 20'-2" dia., 1.7" thick INOR-8, max temperature 1,400°F, weight including internals 125 tons, radiation heating in support plates 2 watts/cm³ , radiation heating in vessel wall 0.6 watts/cm³ , maximum temperature rise in wall 40°F.

HEAT EXCHANGERS: ALL the salt heat exchangers are UNPRESSURIZED shell and tube types so they are also very cheap to build. In essence, they are unpressurized shells with steam pipes running through them. The only pressurized containers or vessels in the entire system are the steam pipes.

CONTAINMENT VESSEL: Since there is nothing nuclear that can explode, there is ZERO need for a containment vessel, just a conventional "NRC Nuclear Hot Room" but building it as a containment silo for added safety will add only about 10% to the construction costs.

GOING SOLID: The salt will go solid when cold, so all vessels, pipes, and pumps that carry molten salt will have to be traced with Nichrome wires to re-melt the salt. Also the dump tanks for the fuel salt loop, clean salt loop, and HITEC water heat exchanger loops should be equipped with a package gas fired boiler to reheat their dump tanks for "dark" start up in case the grid is down.

I've shown one of those Russian BN-800 superheated steam generators located at the reactor - making the right steam for the high pressure stage, plus just a heat exchanger to do the reheat for the intermediate turbine stage. Hitec salt, a commercial heat salt, which has a relatively low melting temperature and good nucleonics seems to be the salt of choice for the third - water contact - salt loop.

Following from: ESTIMATED COST OF ADDING A THIRD SALT-CIRCULATING SYSTEM FOR CONTROLLING TRITIUM MIGRATION IN THE lOOO - MW(e) MSBR

ABSTRACT (From ORNL-TM-3428)

"Controlling tritium migration to the steam system of the 1000-MW(e) reference design MSBR power station by interposing a KN03-NaNOa-NaN03 salt-circulating system to chemically trap the tritium would add about $13 million to the total of $206 million now estimated as the cost of the reference plant if Hastelloy N is used to contain the LiF-BFa salt employed to transport heat from the fuel salt to the nitrate-nitrite salt, and about $10 million if Incoloy could be used.

The major expenses associated with the modification are the costs of the additional heat exchangers ($9 million), the additional pumps ($5 million), and the 7LiF-BeFa inventory ($4.8 million).

Some of the expense is offset by elimination of some equipment from the feedwater system ($2 million), through use of less expensive materials in the steam generators and reheaters (about $2 million), and through an improved thermal efficiency of the plant (worth about $1 million).

In addition to acting as an effective tritium trap, the third circulating system would make accidental mixing of the fuel and secondary salts of less consequence and would simplify startup and operation of the MSBR. A simplified flowsheet for the modified plant, a cell layout showing location of the new equipment, physical properties of the fluids, design data and cost estimates for the new and modified equipment are presented." - - (From ORNL-TM-3428)

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Repowering a typical coal burning power station with nuclear barges.

Here's how two 1,000 mWe Molten Salt Reactors could be used to repower 4-unit "Big Bend" at Apollo Beach, Tampa Florida.

Sometimes a single reactor can carry more than just one original turbine. The steam generator salt loop (the third salt loop) can be divided up like a common hot water boiler heating several zones.

To explain a bit:

This is how a couple of Molten Salt Reactor (MSR) barge-boilers next to Big Bend's turbine gallery (white and tan roof) would look.

(Big Bend, Tampa Electric Company, (TECO) quad 445 mWe unit coal burning power plant, located at Apollo Beach, Florida.)

Since the Molten Salt nuclear boilers are 1,000 mWe each, each MSR can drive two of Big Bend's 445 mWe units. The "U" in the lines is for pipe expansion.

Powering two steam turbines with one large nuclear boiler.

(Big Bend uses water from Tampa Bay for cooling instead of cooling towers. The Manatees have learned the discharge water is warmer than bay water in the winter and, over time, some have made it their winter home. The power plant's discharge canal is now a wildlife sanctuary and a visitor's viewing center has been constructed there. The author has visited it several times and found the canal to be full of all kinds of large and small fish.) http://www.tampaelectric.com/manatee/

Powering two large steam turbines with one large nuclear boiler. (Larger image: click on image, then click again.)

(Above) With proper isolation valves on the tertiary salt loop, dual 445 megaWatt (e) pair of turbogenerators such as found at TECO's Big Bend plant can be driven by a single 1,000 megaWatt electrical (or 2,500 megaWatt thermal) MSR reactor.

In a like manner, all 5 of Muskegon, Michigan's, B C Cobb plant's small steam turbogenerators (which happen to add up to exactly 500 mWe) PLUS an additional new low-cost generic Korean, Chinese, or Indian 500 mWe turbogenerator could be driven by a single 1,000 mWe MSR reactor barge (BC Cobb is also on navigable water, in this case, Lake Michigan). A great way for the United States to salvage the great power plant value and the skilled trade jobs that remain in its hundreds of B C Cobb-size power plants.

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Cost Outlook For OxyFuel, Post Combustion, and Reference Hardcoal - Not Gas.

This chart appeared in the 2012 April-May issue of the "Carbon Capture Journal."

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OxyFuel Carbon Capture for a Coal-Burning Electricity Generation Steam Turbine

Above shows how natural gas can be burned without releasing its carbon dioxide to the atmosphere. The flue gas is almost pure carbon dioxide (CO2). This CO2 is first cooled, then compressed to about 1,000 pound per square inch to liquefy it. Then it is injected into an underground disposal strata where it is hoped it will remain and not leak into the atmosphere through cracks in the earth. A 10% concentration of CO2 in the air is lethal to humans and a Bhopal-like industrial disaster is a concern.

If you have a generating unit below about 200 megaWatts (electrical), converting to natural gas combined cycle carbon capture is worth investigating.

While gas is more expensive than coal, you don't have all the muss, fuss, and expense of keeping all the nasty chemicals in coal out of the air. In the above plan, the electricity generation capacity of the plant is increased by the installation of a new gas turbine generator. To enable Carbon Capture, a small air separation plant is also added to provide the oxygen needed to keep the jet turbine running. The jet turbine's exhaust (flue gas, in power plant terms), which can easily be as hot as 1,000°F, is first routed through a heat recovery boiler which provides steam to the power plant's original steam turbine. Then 80% of the flue gas is blended with the pure oxygen to provide a mixture identical to air's natural 20% oxygen + 80% nitrogen ratio. This mixture then has natural gas added and is combusted in the turbine.

The other 20% of the flue gas is drawn off, cooled, compressed to about 1,000 psi to turn the gas into liquid carbon dioxide, and sent off to a disposal well.

Voilà! absolutely no Global Warming carbon dioxide gets into the atmosphere.

The new exhaust heat recovery boiler gives the old electricity turbine-generator an almost free ride. Combined cycle is about as efficient as you can get.

OxyFuel Carbon Capture for a Natural Gas Burning Electricity Generation Steam Turbine is much easier, but less efficient.

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