This page is a cache of the
IFR page at UC
Berkeley which became unavailable on July 31, 2008 for reasons unknown.
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.