Integral Fast Reactor: Gen IV reactor ready for prime time???
- From: nada <dwaltersMIA@xxxxxxxxx>
- Date: Wed, 20 Aug 2008 19:32:06 -0700 (PDT)
[I do not yet support this concept for a fast breeder reactor
primarily because it's based on the use of sodium. I remain to be
convinced this is the best way to go--David Walters]
From:http://www.nuc.berkeley.edu/designs/ifr/anlw.html
An Introduction to Argonne National Laboratory's INTEGRAL FAST REACTOR
(IFR) PROGRAM
The Integral Fast Reactor (IFR) program was the nation's premier
research and development effort focused on the basic design concepts
and testing the next generation nuclear power plant. The IFR
development work provides solutions in the areas of concern for
today's nuclear plants. These solutions are integrated into a single,
coherent nuclear plant concept. The work at Argonne included real-
world testing, not just computer simulation, so that the results are
not open to question. This was being done to allow larger, commercial
plants to be built with confidence. The IFR work included research and
development in plant safety, waste, transportation, economics,
prevention of the diversion of nuclear materials, and includes a plant
for which the fuel is so plentiful that fuel costs cannot reasonably
outrun inflation.
These important areas of focus are all included in the IFR, hence the
name "Integral". The objective for this work was to determine the best
approach for the design of the next generation nuclear plant -- to
build on the excellent record of today's nuclear plant, but to
simplify, integrate, and take maximum advantage of natural phenomenon
for protection and operation. A system has been worked out in which a
new fuel type has allowed major advances in improving safety,
economics, and minimizing the need for waste storage. It is now clear
that the IFR effort would have resulted in a "new and improved"
nuclear plant -- one that can serve as the electric power source of
choice for an energy hungry, but environmentally aware and concerned
world. The following describes important features of the IFR and some
of the facilities at Argonne West that were devoted to the development
of the IFR concept. The IFR work required the analytical and design
capabilities of numerous people at the main headquarters of Argonne,
near Chicago, and the developmental, operational, and Testing
Capabilities at Argonne - West in Idaho.
Safety
The IFR gains safety advantages through a combination of metal fuel
(an alloy of uranium, plutonium, and zirconium), and sodium cooling.
By providing a fuel which readily conducts heat from the fuel to the
coolant, and which operates at relatively low temperatures, the IFR
takes maximum advantage of expansion of the coolant, fuel, and
structure during off-normal events which increase temperatures. The
expansion of the fuel and structure in an off-normal situation causes
the system to shut down even without human operator intervention. In
April of 1986, two special tests were performed on the Experimental
Breeder Reactor II (EBR-II), in which the main primary cooling pumps
were shut off with the reactor at full power (62.5 Megawatts, thermal)
- By not allowing the normal shutdown systems to interfere, the
reactor power dropped to near zero within about 300 seconds. No damage
to the fuel or the reactor resulted. This test demonstrated that even
with a loss of all electrical power and the capability to shut down
the reactor using the normal systems, the reactor will simply shut
down without danger or damage. The same day, this demonstration was
followed by another important test. With the reactor again at full
power, flow in the secondary cooling system was stopped. This test
caused the temperature to increase, since there was nowhere for the
reactor heat to go. As the primary (reactor) cooling system became
hotter, the fuel, sodium coolant, and structure expanded, and the
reactor shut down. This test showed that an IFR type reactor will shut
down using inherent features such as thermal expansion, even if the
ability to remove heat from the primary cooling system is lost. Events
such as the loss of water to the steam system would cause a condition
such as the test demonstrated. Another major feature of the IFR
concept is that the reactor uses a coolant, sodium, which does not
boil during normal operation nor even in overpower transients such as
described above. This means that the coolant is not under significant
pressure. When coolant is not under pressure, the reactor can be
placed in a "pool" of coolant, contained in a double tank, so that
there is no real possibility for a loss of coolant. Even if the normal
pumps are lost, some coolant flow through the reactor occurs due to
natural convection. The features described above allow for greater
simplification of a nuclear plant, resulting in cost savings, greater
ease in operation, and a safety system that relies on natural
phenomenon that cannot be defeated by human error.
Waste
Discussions on waste, nearly unlimited fuel supply, transportation,
and a nearly diversion-proof fuel all hinge on the fuel type and the
fuel reprocessing scheme. To describe the waste advantages, fuel
reprocessing will first be described. Reprocessing of fuel is a key
requirement of the IFR. However, IFR reprocessing is very different
from processes which have been proposed or which are in use in other
countries. Basically, reprocessing IFR fuel consists of two simple
steps: 1. fission fragments are removed from the fuel, and 2. unused
fuel is recovered, along with the transuranic elements (sometimes
called actinides). Normally, the transuranic elements would go to the
waste stream with the fission products, but in the IFR, they are kept
with the fuel and sent back to the reactor to also serve as fuel. In
the above description, note that the waste stream consists of only the
fission products. The result is that instead of a waste that remains
radioactive for many thousands of years, as would be the case if the
transuranic elements were present, the radioactivity in the waste will
decay to a value less than that of the original uranium ore in about
200 years. An additional advantage to the waste side of the IFR
operation is that the IFR plant produces less low-level waste than
today's nuclear plants. The sodium coolant used in the IFR does not
corrode the piping or structure, and, as a result, there are no
radioactive corrosion products to remove from the primary system and
send to a low-level radioactive waste repository. The fission product
waste from an IFR type plant will amount to about 1700 pounds of waste
per year for a plant of about 1000 megawatts electric output. This is
in contrast to the waste from an equivalent coal plant of about
1,275,000 tons per year. These figures are for a plant that operates
about 70 percent of the year.
Transportation
Today, there is concern about the safety of shipping radioactive
substances over the nation's highways. Whether the concern is
warranted, based on comparisons to other hazardous materials that are
shipped in huge quantities, will not be discussed here. It appears
that the public perception is that radioactive shipments should be
minimized. The IFR reactor is a breeder reactor, that is, during
operation, it can convert materials (such as uranium 238) which cannot
be used in today's reactors for fuel, to a very good fuel, plutonium
239. The conversion takes place in the reactor. In the fuel recycle
process, plutonium is separated from the fission products and returned
to the reactor (along with other transuranic elements) where it is
fissioned to produce power. (NOTE: all reactors create some plutonium,
today's reactors receive about 30% of their power from plutonium
created and then fissioned within the reactor) The breeding process
reduces the requirement for fissile materials being transported to the
plant. Only the original fuel loading must be shipped in, and a
quantity of uranium 238 -- which is not a fissile material. These
shipments are made at the beginning life of the IFR plant, and no
further fuel shipments into the plant need be made for the entire
plant lifetime, approximately 60 years. The uranium 238 necessary to
fuel the plant for its lifetime would make a cube of less than 6 feet
per side. Shipment of waste is also reduced. The volume is such that
the radioactive waste can be stored at the plant site for the entire
life of the plant, and then shipped at one time to a waste repository.
Economics
For a new power source to be viable, the cost of power must be
competitive with today's power systems. The proof of costs in any
project only comes when full- sized systems are built and operated.
Although no full-sized IFR plant has been built, several facts suggest
that the IFR will be very economic. Costs of today's nuclear plants
are just slightly above that of coal as a national average. Several
nuclear plants have operated with costs significantly below that of
coal however. A new IFR should cost less than either a new nuclear
(typical of today's technology) or coal plant based on the following.
The IFR does not require some of the complex systems that today's
reactors require. Examples include the low level radwaste cleanup
station, the emergency core cooling system, and fewer control rod
drives and control rods for comparable power. Because of the low
pressure in the sodium systems, less steel is required for the plant
piping and reactor vessel. There are studies that suggest that the
reactor containment will be less massive. Other cost savings will be
made because the IFR does not require the services of the Isotopic
Separation Plants for fuel enrichment. Additional costs to the IFR
include the integral fuel reprocessing capability, and a secondary
sodium system (but the IFR fuel process costs are somewhat offset by
the extremely low cost for raw fuel and the improved waste product).
Some studies have been done which indicate that an IFR would be very
economical and competitive to build, own, and operate, but the final
proof of economics can only come in the construction and operation of
a commercial sized plant.
Diversion
The diversion of nuclear fuel for the purpose of making bombs has been
a concern, although presently the handling and destruction of nuclear
weapons material is the primary issue. In the IFR, the nature of the
fuel reprocessing is such that the fuel remains highly radioactive at
all times. Fuel can only be handled in shielded cells or transported
in casks weighing many tons. In addition, because the fuel recycle
facility is located on-site, there is no transportation of nuclear
which could create an opportunity for diversion. In any event, IFR
fuel is not suitable for weapons without extensive processing in very
expensive facilities. The potential also exists for the IFR to use
weapons material for fuel, thus eliminating it, while producing
electricity.
"Limitless" Fuel Supply
There is sufficient fuel to power IFR type facilities for well over
100 thousand years. This results because the IFR is a breeder reactor
which can utilize uranium 238. Today's reactors only use uranium 235
which is less than 1% of the uranium found in nature. The IFR, with
its fuel reprocessing capability, can use all the uranium. There is
enough uranium that has been mined and placed in barrels (uranium 238)
for IFR-type plants to provide all the electricity for the United
States for over 500 years -- without mining. Also, the IFR can likely
reprocess the spent fuel from today's reactors, and use the recovered
materials for fuel. Uranium is as abundant in the earth as many of the
commonly used materials such as bismuth, cadmium, mercury, silver,
etc. In fact the uranium in a typical 1 ton block of granite
(concentration of about 5 ppm) is the energy equivalent (if used in
the IFR) of 10 tons of coal! The abundance of uranium suggests that
its price will likely not increase as a fuel material for the
foreseeable future.
CONCLUSION
The IFR story is important to the world because the very foundation of
an industrial society depends on inexpensive and abundant energy. The
IFR can provide the base energy supplies needed, and with very little
impact on the environment. Mining of fuel for the IFR is not needed
for several hundred years. The IFR does not produce gases or other
effluents that would harm the biosphere. The long-term waste problem,
of concern today, no longer is a problem with the IFR. In addition,
the IFR should be economic and a safe, easy to operate plant. These
features make the IFR the candidate for the next generation nuclear
power plant. -- standard disclaimers apply --
.
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