- Experimental Breeder Reactor II
:"There is also a separate, closed, unrelated facility called
Experimental Breeder Reactor I".Experimental Breeder Reactor-II (EBR-II) is a reactor at the Materials and Fuels Complex of the Idaho National Laboratory, formerly the Argonne West complex of Argonne National Laboratoryin Idaho.
It is a
sodiumcooled reactor with a thermal power rating of 62.5 megawatts (MW), an intermediate closed loop of secondary sodium, and a steamplant that produces 19 MW of electrical power through a conventional turbinegenerator. The original emphasis in the design and operation of EBR-II was to demonstrate a complete breeder-reactor power plant with on-site reprocessing of metallic fuel. The demonstration was successfully carried out from 1964to 1969. The emphasis was then shifted to testing fuels and materials for future, larger, liquid metal reactors in the radiationenvironment of the EBR-II reactor core. It operated as the Integral Fast Reactorprototype. Costing more than $32 million, it achieved first criticality in 1965and ran for 30 years. It was designed to produce about 62.5 megawatts of heat and 20 megawatts of electricity, which was achieved in September 1969 and continued for most of its lifetime.
The fuel consists of
uraniumrods 5 millimeters in diameter and 13 inches ( 33 cm ) long . Enriched to 67% uranium-235when fresh, the concentration dropped to approximately 65% upon removal. The rods also contained 10% zirconium. Each fuel element is placed inside a thin-walled stainless steeltube along with a small amount of sodiummetal. The tube is welded shut at the top to form a unit 29 inches (73 cm) long. The purpose of the sodium is to function as a heat-transfer agent. As more and more of the uranium undergoes fission, it develops fissures and the sodium enters the voids. It extracts an important fission product, caesium-137, and hence becomes intensely radioactive. The void above the uranium collects fission gases, mainly krypton-85. Clusters of the pins inside hexagonal stainless steel jackets 92 inches ( 234 cm ) long are assembled honeycomb-like; each unit has about 10 pounds (4.5 kg ) of uranium. All together, the core contains about 680 pounds (308 kg ) of uranium fuel, and this part is called the driver.
The EBR-II core can accommodate as many as 65 experimental sub-assemblies for irradiation and operational reliability tests, fuelled with a variety of metallic and ceramic fuels - the
oxides, carbides, or nitrides of uranium and plutonium, and metallic fuel alloys such as uranium-plutonium-zirconium fuel for the IFR. Other sub-assembly positions may contain structural-material experiments.
Integral Fast Reactor(IFR) design 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 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.
EBR-II is now defueled. The EBR-II shutdown activity also includes the treatment of its discharged spent fuel using an electrometallurgical fuel treatment process in the Fuel Conditioning Facility located next to the EBR-II
The clean-up process for EBR-II includes the removal and processing of the sodium coolant, cleaning of the EBR-II sodium systems, removal and passivating of other chemical hazards and placing the deactivated components and structure in a safe condition.
Integral Fast Reactor
* [http://web.archive.org/web/20051029040849/http://www.anlw.anl.gov/anlw_history/reactors/ebr_ii.html EBR-II] at Argonne National Laboratory (archived copy at the
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