The Advanced Test Reactor (ATR) is the third generation and largest test reactor built in the Reactor Technology Complex (RTC - formerly known as the Test Reactor Area), located at the Idaho NationalLaboratory (INL), to study the effects of intense neutron and gamma radiation on reactor materials and fuels. The RTC was established in the early 1950s with the development of the Materials Testing Reactor (MTR), which operated until 1970. The second major reactor was the Engineering Test Reactor (ETR), whichoperated from 1957 to 1981, and finally the ATR, which began operation in 1967 and will continue operation well into the future. These reactors have produced a significant portion of the world's data on materials response to reactor environments. The wide range of experiment facilities in the ATR and the unique ability to vary the neutron flux in different areas of the core allow numerous experiment conditions to co-exist during the same reactor operating cycle. Simple experiments may involve a non-instrumented capsule containingtest specimens with no real-time monitoring or control capabilities1. More sophisticated testing facilities include inert gas temperature control systems and pressurized water loops that have continuous chemistry, pressure, temperature, and flow control as well as numerous test specimen monitoring capabilities. There are also apparatus that allow for the simulation of reactor transients on test specimens.

"The Advanced test Reactor (ATR) is the third generation of test reactors built at the Test Reactor Area (TRA), located in the Idaho National Engineering and Environmental Laboratory (INEEL), to study the effects of intense neutron and gamma radiation on reactor materials and fuels. ART has a maximum power of 250MW and can provide maximum thermal neutron fluxes of 1E15 neutrons per square centimeter per second. this allows considerable acceleration of accumulated neutron fluence to materials and fuels over what would be seen in a typical power reactor. Since power operation of the ATR began in 1969, numerous testing methods have been developed to take advantage of the capabilities of the ATR. The wide range of experimental facilities in the ATR and the unique ability to vary the neutron flux in different areas of the core allow numerous experiment conditions to co-exist during the same reactor operating cycle. Simple experiments may involve a non-instrumented sealed capsule containing test specimens with no real-time monitoring and control capabilities. More sophisticated testing facilities include inert gas temperature control systems and pressurized water loops that have continuous chemistry, pressure, temperature, and flow control as well as numerous test specimen monitoring capabilities. There are also apparatus that allow for the simulation of reactor transients on test specimens. The Irradiation Test Vehicle, installed in 1999, is the newest testing apparatus in the ATR that accommodates up to fifteen separate tests, each with its own temperature control and monitoring capabilities as well as neutron spectral tailoring capability. The U.S. Department of Energy intends to maintain and expand the capabilities of the ATR to ensure it remains a viable facility for the Department's materials and fuels testing programs for the foreseeable future." -- Page[1].

"This handbook explains the design and operation of the ATR [advanced test reactor], the types of irradiation experiments and tests it can perform, its irradiation facilities and hardware (including the ATR Critical facility), and how potential customers can plan for and schedule ATR irradiation positions and experimental test services" -- Page 1.

The Advanced Test Reactor (ATR), at the Idaho National Laboratory (INL), is a large test reactor for providing the capability for studying the effects of intense neutron and gamma radiation on reactor materials and fuels. The ATR is a pressurized, light-water, high flux test reactor with a maximum operating power of 250 MWth. The INL also has several hot cells and other laboratories in which irradiated material can be examined to study material irradiation effects. In 2007 the US Department of Energy (DOE) designated the ATR as a National Scientific User Facility (NSUF) to facilitate greater access to the ATR and the associated INL laboratories for material testing research by a broader user community. This paper highlights the ATR NSUF research program and the associated educational initiatives.

The ATR is one of the world's premiere test reactors for performing long term, high flux, and/or large volume irradiation test programs. It is a very versatile facility with a wide variety of experimental test capabilities for providing the environment needed in an irradiation experiment. These different capabilities include passive sealed capsule experiments, instrumented and/or temperature-controlled experiments, and pressurized water loop experiment facilities. The Irradiation Test Vehicle (ITV) installed in 1999 enhanced these capabilities by providing a built in experiment monitoring and control system for instrumented and/or temperature controlled experiments. This built in control system significantly reduces the cost for an actively monitored/temperature controlled experiments by providing the thermocouple connections, temperature control system, and temperature control gas supply and exhaust systems already in place at the irradiation position. Although the ITV in-core hardware was removed from the ATR during the last core replacement completed in early 2005, it (or a similar facility) could be re-installed for an irradiation program when the need arises. The proposed Gas Test Loop currently being designed for installation in the ATR will provide additional capability for testing of not only gas reactor materials and fuels but will also include enhanced fast flux rates for testing of materials and fuels for other next generation reactors including preliminary testing for fast reactor fuels and materials. This paper discusses the different irradiation capabilities available and the cost benefit issues related to each capability.

Current research and development programs being conducted in the United States for advanced fuels and materials to support the Advanced Fuel Cycle Initiative (AFCI), Generation-IV reactors (GEN-IV), and space nuclear programs require an irradiation testing facility capable of simulating anticipated operating environments. The lack of domestic irradiation facilities to meet these programmatic goals has led to a proposed Gas Test Loop (GTL) for fuel and material irradiation to be installed in the Advanced Test Reactor (ATR) located at the Idaho National Laboratory (INL). The GTL will utilize highly enriched U2́3Si2́2 fuel plates to increase the fast neutron flux density to simulate actual fast reactor conditions. The INL has chosen the computer code PLATE 2.0 (Plate Lifetime Accurate Thermal Evaluation, version 2.0) to model the steady-state thermal properties of the fuel plates. The INL requires all new computer software used in modeling applications to undergo qualification before it can be used for safety analysis. The qualification plan specified by the INL requires a user's manual be developed for PLATE 2.0 along with verification and validation (V & V) of the output results against benchmark data. This thesis presents a study of foreign and domestic fast neutron irradiation facilities, a description of PLATE 2.0 and its user's manual, and the results from the V & V of PLATE 2.0 for U2́3Si2́2 fuel plates.