An Introduction to Argonne National
Laboratory's INTEGRAL FAST REACTOR
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.
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.
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.
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.
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.
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.
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.