Introduction: If push comes to shove
Fermi I - A Molten Sodium Cooled Fast Breeder Reactor
A
Good Introduction To Molten Salt Reactors From Wikipedia
Part One:
TRISO molten salt cooled very high temperature reactor
Part Two:
Liquid Fluoride Thorium Reactor - the LFTR (The author is still
trying to sort this one out.)
Part Three:
Part Four:
IFR - The Integral Fast Reactor. A molten metal reactor.
Liquid Reactors, Introduction:
If push comes to shove
Global Warming is a real emergency. A
conversion demonstration facility project might emerge far sooner rather than
expected. What I, as an application engineer, must do: Go with
what I find in the catalogs. The other
sufficiently hot reactor types shown on other pages - TRISO
Pebble Beds, TRISO
Prisms, and TRIGA-like
Liquid metal and salt cooled reactors, on paper, appear to have both the temperature and sufficient BTU output to be considered as possible candidates for Nuclear Repowering and Hybrid Nuke applications but have never been used in any commercial application in the United States. As an application engineer, I can't specify anything for immediate use that isn't in a vendor's catalog. In some ways, these reactors look like the most promising of the bunch, and at 800°C, 1,500°F, are plenty hot enough to produce the supercritical water needed to drive a 1,000°F superheated steam generator. The jury's is still out on these reactors and I personally hope very much they get a "Two Thumbs Up" when the jury returns.
Why use high temperature - instead of conventional - nuclear reactors to replace coal?
A 550°F conventional nuclear reactor can't power a 1,000°F coal plant . . . It simply isn't hot enough. Coal can produce heat over 2,000°F. Coal power plants use 1,000°F steam for high efficiency. Conventional nuclear reactors cannot produce steam hotter than 550°F, so conventional nuclear reactors cannot be used to produce coal's 1,000°F steam. High-temperature reactors will work just fine.
Why stay with steam?
Water is a wonderful way to turn heat energy into mechanical energy
because when you turn water into steam it changes state, expanding its volume
1,600 times. If the steam is not allowed to expand freely in volume, its
pressure will go up drastically. That's where all that piston-pushing
power in a steam locomotive comes from. If the steam is turned back into
water by cooling it changes state again, this time contracting in volume 1,600 times, creating a powerful vacuum.
Both the Nuclear Repowering and the Hybrid Nuke are "State of the Market", not "State of the Art", applications where economics plays the pivotal role.
Why use a liquid coolant in a reactor?
A cubic foot of water will carry about 3,000 times as much heat as a cubic foot of air. Gas cooled reactors are odd man out in the reactor world.
This brings us to what the
author thinks is the world's best hope:
The Russian Rosatom BN-800
The Russian Rosatom BN-600 reactor, now succeeded by the BN-800, currently scheduled to come on line in 2012. The original reactor, the BN-350 went into service in 1973. Its successor, the BN-600, has been in service since 1980, and its successor, the BN-800, is both more refined - its 3 secondary cooling loops are now steam, not the fire-prone sodium outside the primary reactor vessel of the BN-600 - and slightly more powerful. Having 3 independent heat exchangers, it could drive both a 550 mWe and a 250 mWe turbine generator simultaneously.
Rosatom literature indicates there is now a BN-1200 (downsized from earlier 1800 design, based upon BN-600 experience) in the works scheduled to come on line in 2020. There are no coal-burning power plants large enough to need a BN-1200 but that is an attractive size for many of the world's larger cities. Six of them could power the entire New York City complex.
Note: The drawing above shows 2,000 psi, 940°F steam going into a single stage condensing turbine. Have the Russians actually achieved this? In the west, that much steam pressure would call for a three stage turbine - see drawing below.
Here we see the safety differences between large, low power reactors like the pebble bed and small, extremely powerful reactors like the BN series. A pebble bed can only be about 1/5 as powerful as a BN-800 and only BN-800s can power a plant as large as Taichung.
A pebble bed has 1/30th the energy density of a conventional water-cooled reactor. A pebble bed is walk away safe in any condition, cannot melt down, operators cannot be ignorant enough or careless enough to cause damage. This is the German THTR-300 thorium pebble bed reactor that Greenpeace killed. The author cannot imagine a greater, more ill-starred, disservice to Mankind.
The tragedy of Global
Warming is that we do not have to make CO2 to make electricity.
Not making electricity from nuclear in the 1970s is what brought us Global
Warming in the 1990s.
Fermi 1 - A Solid Metal Fuel Rod, Molten Sodium Cooled, Fast Breeder Reactor
As an electrical engineering
student, the author worked as a designer in 1959 on the molten
sodium Fermi I reactor being built at Monroe, Michigan, drawing
wiring diagrams for instrumentation systems such multi-point
http://en.wikipedia.org/wiki/Enrico_Fermi_Nuclear_Generating_Station About Fermi 1
http://en.wikipedia.org/wiki/Sodium-cooled_fast_reactor Son of Fermi 1?
http://en.wikipedia.org/wiki/Integral_Fast_Reactor GE-Hitachi ARC - Advanced Reactor Designs.pdf GE-Hitachi Advanced Recycling Center.pdf
A Good Introduction To Molten Salt Reactors From Wikipedia:
http://en.wikipedia.org/wiki/Molten_salt_reactor Wikipedia's page on Molten Salt Reactors
"Research is currently picking up again for reactors that utilize molten salts for coolant. Both the traditional molten salt reactor and the Very High Temperature Reactor (VHTR) have been picked as potential designs to be studied under the Generation Four Initiative (GEN-IV).
A version of the VHTR currently being studied is the Liquid Salt Very High Temperature Reactor (LS-VHTR). It is essentially a standard VHTR design that uses liquid salt as a coolant in the primary loop, rather than a single helium loop. It relies on "TRISO" fuel dispersed in graphite. The fuel graphite would be in the form of graphite rods that would be inserted in hexagonal moderating graphite blocks. The molten salt would pass through holes drilled in the graphite blocks.
The LS-VHTR has many
attractive features, including: the ability to work at very high
temperatures (the boiling point of most molten salts being
considered are >1400 °C, 2,600
LFTR: Liquid Fluoride-Thorium Reactor, A Molten Salt Reactor
![[thm.jpg]](http://1.bp.blogspot.com/_-1USRv70-rY/SClzQvabLMI/AAAAAAAAAAM/mkD0coPMD-o/S220/thm.jpg)
In many designs the nuclear fuel
is dissolved in the molten fluoride salt coolant as uranium tetrafluoride (UF4).
The fluid becomes critical in a graphite core which serves as the moderator. --
Wikipedia
(Right)
MSR Liquid Reactors Molten-Salt-Reactor Technology Gaps .pdf by Charles W. Forsberg, ORNL, (2006), is a good introductory paper addressing modern thinking about LFTR/MSRs.
MSR = Molten Salt Reactors . . . LFR = Liquid Fluoride Reactors . . . LFTR = Liquid Fluoride - Thorium Reactor
In Nuclear Repowering service, the secondary (or possibly tertiary) cooling loop could be a gas such as helium or nitrogen and would drive a liquid-lead pressure isolating dual-tube calandria supercritical water heater in much the same manner as the 1,700°F pebble bed reactor. Perhaps multiple heaters in the spirit of THTR-300 or IRIS for increased reliability. Pressures would probably be similar and efficiency would nothing to brag about. But, as with the pebble bed, emissions, not efficiency, would be the name of the game here and no one doubts the ability of a LFTR to make the supercritically hot water needed to simultaneously drive a variety of old superheated and non-superheated steam turbines.
If
the reactor could be located close enough to, and dedicated to, a single
turbine, a Hybrid nuclear reactor, coal turbine, power plant using a
A good place to go to find a lot of papers on the LFTR: http://www.energyfromthorium.com/pdf/
A thorium energy metal company:
http://thoriumenergy.com/
Websnags:
"The molten salt reactor is a
nice design. As I understand it; one of the major drawbacks is that the
reactor operator [ the electric utility company that would employ such a reactor
] would have to operate the molten salt reactor's chemical processing facility.
That is; a facility to continually reprocess the reactor's molten fuel is an
integral part of the operation of such a reactor.
Thus the operation of a molten salt reactor is more complex than even operating
a commercial light water reactor. This was more complexity than most electric
utility companies at the time wanted to undertake - they were in the business of
generating power, not operating a chemical processing plant.
The IFR concept also includes an on-site reprocessing facility - but a facility
based on electrorefining would be simpler to operate than a chemical processing
plant.
For both concepts; it is a matter of how much complexity the reactor owner wants
to manage."
Dr. Gregory Greenman
Physicist
[Note: The circulating core material that is being processed is both very thermally hot and also very radioactive. On the plus side, the liquid does not need to be pressurized. -- JH]
Δ
"Here at Ohio State University, my
class in nuclear design (a team based approach) investigated the LFR. It is a
research based class, and each year, the class builds upon the previous year's
work. It was started (I believe) here at OSU in 2004 or 2005).
The reactor does indeed use a FLiBe salt using thorium, with a blanket
surrounding it as a breeder material. There were some promising results, but
yes, the online processing turned out to be one of the major challenges, as well
as initial startup. It required a substantial amount of U-233 to start, but
eventually enough U-233 was bred so that it could supply startup uranium for
additional reactors. I went through the class Fall 2007, so I don't know what
advances (if any) were made this past quarter."
The author thinks that, for Global Warming mitigation retrofit service, LFTRs are best suited to power the world's 5,000 biggest CO2 offenders. One to six pairs of 1 GWt each would drive a pair of supercritical water trunk lines to as many as 10 steam generators, replacing 10 coal burning boilers. The size of the system would help justify the additional burden of their radioactive core/coolant cleaning facilities.
Cleaning up the world's 5,000 biggest coal burning power plants would push the tipping point back several decades.
Bob Hargraves' "Aim High" LFTR presentation.
You need to watch the entire "Video" (slide + audio)
presentation at:
he also suggests:
Also, a really good 1 hour video on liquid reactors:
(Images below are a few screenshots from from Bob Hargraves' "Aim High" presentation.)
The Integral Fast Reactor
TOSHIBA 4S Reactor
4S
(Toshiba)
Synonyms: Super Safe, Small, and Simple
Approximate Capacity (electric): 10 MWe, larger possible
Reactor Type: Sodium-cooled
NRC Design Certification Status: Manufacturer and sponsor are developing a
pre-application approach.
Supporting Generating Companies (potential site): Town of Galena, Alaska
The 4S is a very small molten sodium-cooled reactor designed by Toshiba. The
reactor presently being considered is 10 MWe though larger and smaller versions
exist. The 4S is intended for use in remote locations and to operate without
refueling during its 30-year life. The 4S has been compared with a nuclear
“battery” because it does not require refueling. The lack of refueling would
mean that the reactor’s fuel supply would be a capital cost rather than an
operating cost. It has been suggested that the fuel might be relatively low
cost, reprocessed spent fuels originating from more conventional power reactors.
Other potential fuels are uranium or uranium-plutonium alloys. If uranium is
the fuel in the United States, plans call for 19.9 percent fuel enrichment, just
below the 20 percent definition of highly enriched uranium. The use of
molten-sodium as a coolant is not new, having been used in many fast breeder
reactors. Toward the end of 2004 the town of Galena, Alaska granted initial
approval for Toshiba to investigate building a 4S reactor in that remote
location. The design is also under consideration for other locations in
Alaska. Most recent discussions target completion around 2013, though the
schedule is not firm. Galena and Toshiba officials discussed their plans with
the NRC in early February 2005 and plan additional filings over the coming
years. The NRC indicated that it was not familiar with the 4S design and that
design certification (at vendor expense) might be costly and prolonged. Design
certification can be incorporated in the COL process thus it is unclear if a
separate design certification will be pursued, if the project continues.
Further Information:
http://en.wikipedia.org/wiki/Toshiba_4S
http://www.atomicinsights.com/AI_03-20-05print.html
http://www.iser.uaa.alaska.edu/Publications/Galena_power_draftfinal_15Dec2004.pdf#search='Toshiba
4S'
Contact:
