Contents
Restoring
Our Oil IndependenceCategories:
TIGHT OIL
Contents
Restoring
Our Oil Independence
Categories:
Recycling coal burning power plants
into thorium nuclear power plants
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(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.
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
1) Part 2 Directory:
Replacing coal-fired Loeffler boilers with molten salt boiler emulators.
7)
8)
The control system
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.
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. A
lready paid for - NO NEW COSTS FOR MOST OF THE EQUIPMENT2. Already wired to our cities - NO NEW TRANSMISSION LINE RIGHT-OF-WAYS NEEDED
3. A
lready have cooling water - NO NEW RIPARIAN OR PRIOR APPROPRIATION RIGHTS NEEDED4. A
lready have access roads - NO NEW ROAD RIGHT-OF-WAYS NEEDED5. A
lready have railroad tracks - NO NEW RAILROAD RIGHT-OF-WAYS NEEDED6. U
sually have ample land for several additional future units - NO NEW LAND NEEDED, COAL YARD LAND WILL BECOME LAWN SOON7. N
o construction delays - THEY ARE ALREADY RUNNING, CAN CONTINUE TO RUN DURING UPGRADE EQUIPMENT INSTALLATION8. A
lready have proven operators who know the equipment - FEWER OPERATORS LOOSE JOBS, EXISTING OPERATORS WOULD BE BETTER PAID9. C
leaner 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.
FUN COMMENT: (From another reader:)
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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.
(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: 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:
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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
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 ˝ 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 (third 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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Repowering an old coal burning power plant previously repowered with cleaner burning natural gas
Repowering an
old coal burning power plant previously repowered with cleaner burning natural
gas.
- Common these days.
(Below) Repowering a power plant and long steam pipe lines are commonplace. A few miles to the North of Big Bend, also on Tampa Bay, is Tampa Electric Company's (TECO) "Bayside" power plant. Bayside was originally a coal burner - you can see the old, original stacks for two large coal boilers, the boiler house, and turbine gallery on the left. Notice two of the old boilers attached to the right end of the turbine gallery are larger than the other four. To become both cleaner and more powerful, Bayside was converted from coal to combined cycle natural gas turbines (natural gas turbine - think of a 747 size jet engine driving an electric generator). In addition to making electricity, the hot exhaust blast of the jet engine is used to heat a heat recovery steam generator which, in turn, drives an old, existing steam turbine which also makes electricity.
It's not unusual for over a
billion dollars to be spent upgrading an old power plant to be cleaner and more
powerful. Worldwide, there are perhaps 15,000 power plants the size of
Bayside or larger.
Gas
turbines are much smaller in power than most large steam turbines so several
have to be hitched up like teams of horses to repower a large steam turbine. In
the case of Bayside, 3 gas turbines, in addition to making their electricity,
provide steam for one large, old, steam turbine with the other four gas turbines
heating small boilers (just above the turbine stacks) for a second, larger old
steam turbine.
Notice how long the steam lines are? - bottom of picture, many expansion "U" - from the gas turbines to the old coal steam turbine gallery. Steam pipe lines a half mile long or longer are common worldwide. So while they may look long in the marked up Big Bend photo above, in practice they would be considered of only medium length.
This also points out that converting power plants from one fuel to another has become commonplace.
(Left) Bayside natural gas turbine heat recovery
steam generator stack row. Natural gas makes 2/3 as much CO2
as coal. Bayside Power Plant Tour
.pdf
These steam plants are conventional sub-critical superheated steam technology. According to the IEA, supercritical status for hard coal plants is defined as achieving outlet steam temperatures of 540-566 °C (1,000-1,050 °F) and a pressure of 250 bar (3,600 psi). Ultra-supercritical units are defined as those with outlet steam temperatures above 590 °C (1,100°F) and pressures above 250 bar (3,600 psi). Supercritical and ultrasupercritical plants can achieve efficiencies of up to 45%; conventional sub-critical plants rarely achieve thermal efficiencies of 40%.
Repowering an old coal burning power plant previously repowered with cleaner burning natural gas.
Repowering an
old coal burning power plant previously repowered with cleaner burning natural
gas.
(It is unlikely the turbines would be as
powerful after being converted to Sterling turbines.)
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