Integral Fast Reactor

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The Integral Fast Reactor or Advanced Liquid-Metal Reactor is a design for a nuclear fast reactor with a specialized nuclear fuel cycle. A prototype of the reactor was built in the United States, but the project was cancelled by the U.S. government in 1994, three years before completion.

1 Overview
2 Safety
3 Efficiency and Fuel cycle
4 Key benefits
5 Key disadvantages
6 History
7 See also
8 References
9 External links

[edit] Overview

This reactor is cooled by liquid sodium and fueled by a metallic alloy of uranium and plutonium. The fuel is contained in steel cladding with liquid sodium filling in the space between the fuel and the cladding.

[edit] Safety

In traditional water cooled reactors the core must be maintained at a high pressure to keep the water liquid at high temperatures. In contrast, since the IFR used a liquid metal as a coolant, the core could operate at close to ambient pressure, dramatically reducing the danger of a loss of coolant accident. The entire reactor core, heat exchangers and primary cooling pumps were immersed in a pool of liquid sodium, making a loss of primary coolant extremely unlikely. The coolant loops were also designed to allow for cooling through natural convection, meaning that in the case of a power loss or unexpected reactor shutdown, the heat from the reactor core would be sufficient to keep the coolant circulating even if the primary cooling pumps were to fail.

The IFR also utilised a passively safe fuel configuration. The fuel and cladding was designed such that when they expanded due to increased temperatures, more neutrons would be able to escape the core thus reducing the rate of the fission chain reaction. At sufficiently high temperatures this effect would completely stop the reactor even without external action from operators or safety systems. This was demonstrated in a series of safety tests on the prototype.

A safety disadvantage of using liquid sodium as coolant arises due to sodium's chemical reactivity. Liquid sodium is extremely flammable and ignites spontaneously on contact with air or water. Thus leaking sodium pipes could give rise to sodium fires, or explosions if the leaked sodium comes into contact with water. To reduce the risk of explosions following a leak of water from the steam turbines the IFR had an extra intermediate coolant loop between the reactor and the turbines. The purpose of this loop was to ensure that any explosion following accidental mixing of sodium and turbine water would be limited to the secondary heat exchanger and not pose a risk to the reactor. The requirement of such an extra loop significantly added to the cost of the reactor.

[edit] Efficiency and Fuel cycle

The goals of the IFR project were to increase the efficiency of uranium usage by breeding plutonium and eliminating the need for transuranic isotopes ever to leave the site. The reactor was an unmoderated design running on fast neutrons, designed to allow any transuranic isotope to be consumed (and in some cases used as fuel).

Compared to current light-water reactors with a once-through fuel cycle that uses less than 1% of the energy in the uranium, the IFR has a very efficient (99.5% usage) fuel cycle. The basic scheme used electrolytic separation to remove transuranics and actinides from the wastes and concentrate them. These concentrated fuels were then reformed, on site, into new fuel elements.

The available fuel metals never separated the plutonium, and therefore there was no direct way to use the fuel metals in nuclear weapons. Also, plutonium never had to leave the site, and thus was far less open to unauthorized diversion.

Another important benefit of removing the long half-life transuranics from the waste cycle is that the remaining waste becomes a much shorter-term hazard. After the actinides and transuranics are removed from the spent fuel, the remaining waste elements have half lives of a few decades at most. The result is that within 300 years, such wastes are no more radioactive than the ores of natural radioactive elements.

[edit] Key benefits

Enhanced passive safety because of the high thermal conductivity of the fuel. Able to withstand both a loss of flow without SCRAM and loss of heat sink without SCRAM.[1][2]
Ease of fuel fabrication. Because the sodium fills the space between the fuel and cladding, the fuel need not be precisely fabricated. The fuel is simply cast. Because casting is simple, the fuel can be fabricated remotely, reducing the hazards of its radioactivity.
On-site reprocessing by pyroprocessing and electrorefining is simplified because there is no need to stringently reduce the radioactivity of the fuel. Actinides including transuranics can be incorporated into the fuel.
Proliferation hazards are reduced by the high radioactivity of the fuel. Because the fuel contains significant levels of transuranics with high spontaneous fission rates, it is not possible to produce nuclear weapons using IFR fuel without extremely difficult centrifugal separation. This is even more difficult than uranium enrichment due to the smaller atomic mass difference between Pu-239 and Pu-240 as compared to U-235 vs U-238, and is rendered even more difficult by the high levels of activity of the fuel.
The two forms of waste produced, a noble metal form and a ceramic form, contain no plutonium or other actinides. The radioactivity of the waste decays to levels similar to the original ore in about 300 years. Both forms are suitable for geological disposal.
The onsite reprocessing of fuel means that the quantity of nuclear waste leaving the plant is tiny relative to other nuclear facilities.^[1] This makes storage simpler and reduces the security risk associated with nuclear waste transportation.

[edit] Key disadvantages

Because the current cost of reactor-grade enriched uranium is relatively low compared to the expected cost of large-scale pyroprocessing and electrorefining equipment and the cost of building a secondary coolant loop, the higher fuel costs of a thermal reactor over the expected operating lifetime of the plant are offset by the increased capital cost of an IFR. (Currently, companies building nuclear reactors do not bear the costs associated with long-term storage of transuranic waste. If these costs were passed on to the industry, IFR would become more financially competitive.)
Reprocessing nuclear fuel using pyroprocessing and electrorefining has not yet been demonstrated on a commercial scale. As such, investing in a large IFR plant is considered a higher financial risk vis-a-vis a conventional light water reactor.
The flammability of sodium. Sodium burns easily in air, and will ignite spontaneously on contact with water. The use of an intermediate coolant loop between the reactor and the turbines minimizes the risk of a sodium fire in the reactor core.
Under neutron bombardment, sodium-24 is produced. This is highly radioactive, emitting an energetic gamma ray of 2.7 MeV followed by a beta decay to form magnesium-24. Half life is only 15 hours, so this isotope is not a long term hazard - indeed it has medical applications. Nevertheless, the presence of sodium-24 further necessitates the use of the intermediate coolant loop between the reactor and the turbines.

[edit] History

Research on the reactor began in 1984 at Argonne National Laboratory in Argonne, Illinois. Argonne is a part of the U.S. Department of Energy, and is co-run by the DOE and the University of Chicago.

Argonne also has a branch campus nicknamed "Argonne West" in Idaho Falls, Idaho. At the branch campus, physicists from Argonne had built what was known as the Experimental Breeder Reactor II (EBR II). In the mean time, physicists at Argonne had designed the IFR concept, and it was decided that the EBR II would be converted to an IFR. Charles Till, a Canadian physicist from Argonne, was the head of the IFR project, and Yoon Chang, was the deputy head. Till was positioned in Idaho, while Chang was in Illinois.

With the election of President Bill Clinton in 1992, and the appointment of Hazel O'Leary as the Secretary of Energy, there was pressure from the top to cancel the IFR. Sen. John Kerry (D, MA) and O'Leary led the opposition to the reactor, arguing that it would be a threat to non-proliferation efforts, and that it was a continuation of the Clinch River Breeder Reactor Project that had been cancelled by Congress. Despite support for the reactor by then-Rep. Richard Durbin (D, IL) and U.S. Senators Carol Mosley Braun (D, IL) and Paul Simon (D, IL), funding for the reactor was slashed, and it was ultimately cancelled in 1994.

[edit] See also

v • d • e Nuclear technology
Nuclear engineering	Nuclear physics • Nuclear fission • Nuclear fusion • Radiation • Ionizing radiation • Atomic nucleus • Nuclear reactor • Nuclear safety • Nuclear chemistry
Nuclear material	Nuclear fuel • Fertile material • Thorium • Uranium • Enriched uranium • Depleted uranium • Plutonium
Nuclear power	Nuclear power plant • Radioactive waste • Fusion power • Future energy development • Inertial fusion power plant • Pressurized water reactor • Boiling water reactor • Generation IV reactor • Fast breeder reactor • Fast neutron reactor • Magnox reactor • Advanced gas-cooled reactor • Gas-cooled fast reactor • Molten salt reactor • Liquid-metal-cooled reactor • Lead-cooled fast reactor • Sodium-cooled fast reactor • Supercritical water reactor • Very high temperature reactor • Pebble bed reactor • Integral Fast Reactor • Nuclear propulsion • Nuclear thermal rocket • Radioisotope thermoelectric generator
Nuclear medicine	PET • Radiation therapy • Tomotherapy • Proton therapy • Brachytherapy
Nuclear weapons	History of nuclear weapons • Nuclear warfare • Nuclear arms race • Nuclear weapon design • Effects of nuclear explosions • Nuclear testing • Nuclear delivery • Nuclear proliferation • List of states with nuclear weapons • List of nuclear tests