Overview

The Advanced Test Reactor User Facility - Unparalleled Capabilities

The Advanced Test Reactor (ATR), owned by the U.S. Department of Energy and operated at Idaho National Laboratory, is one of the world's most versatile and best-designed test reactors. The ATR is located at the Reactor Technology Complex on the INL desert Site, about 50 miles west of Idaho Falls.

The ATR has been operating continuously since 1967. Because its internal components are periodically changed out and new components installed, it remains a valuable research and test machine capable of decades more service. These change-outs occur every seven to 10 years, which means researchers have a new reactor to work with.

The reactor is designed to study the effects of intense radiation on reactor materials and fuels. Irradiation test services are performed for government agencies, private companies, other nation's nuclear agencies and universities. In addition, ATR irradiates targets to produce valuable isotopes for medical, industrial and research applications.

INL is the DOE's national nuclear energy technology research and demonstration laboratory. It is INL's vision to be the national preeminent nuclear energy laboratory, and the ATR will play a major role as it provides the capability to test fuels and materials for the next generation of nuclear plants for this country.

A 'time machine'

The ATR has been compared to a time machine because the intense concentration of neutrons and gamma rays it is able to produce can duplicate years of irradiation of materials in a matter of days, weeks or months. Test results can show how the materials will react to high radiation levels. For instance: plastics can disintegrate, metals can become brittle, electrical conductivity and corrosion resistance can be affected, and burn up of fuel produces fission products that eventually may swell, distort or rupture the fuel.

Tests are run on cycles of about six to eight weeks. Then the reactor is shut down, the fuel replaced, experiments removed, new experiments inserted, and the ATR is brought back to operating power for another test cycle.

Besides its high intensity of irradiation, termed "high flux" (the number of neutrons per centimeter squared that bombard a test specimen each second), the design of the core and the ability to run multiple tests simultaneously and under different conditions in some test positions makes the ATR a unique research reactor.

The ATR has a serpentine fuel arrangement. This design provides nine high-intensity, neutron flux traps where irradiation levels, temperatures and pressures for the experiments can be individually regulated. There are 68 additional irradiation positions inside the reactor core and reflector regions, and 34 additional low-flux or low intensity irradiation positions outside the reactor core.

Advanced Test Reactor Critical (ATRC) Facility

The effect of an experiment on core reactivity must be known with good accuracy and precision before it can be placed in the ATR core. Sometimes it is necessary to determine this experimentally in the ATR Critical (ATRC) facility, which is designed to evaluate prototypical experiments before the actual experiments are irradiated in the ATR. When ATRC testing is necessary, experimenters are required to furnish prototypes of capsule experiments. It is not unusual to test these designs in the ATRC prior to each ATR cycle to ensure the reactivity effects are known.

The ATRC is a full-size, low-power, pool-type nuclear replica of the ATR, and is located in an extension of the ATR canal. Its normal operating power level is about 100 W with a maximum power rating of 5 kW.

The ATRC provides valuable reactor physics data that contribute to evaluating (a) the worth and calibration of control elements, (b) excess reactivities and charge lifetimes, (c) thermal and fast neutron distributions, (d) gamma heat generation rates, (e) fuel loading requirements, (f) effects of inserting and removing experiments and experiment void reactivities, and (g) temperature and void reactivity coefficients.

Canal Operations

Experiments that are completed (and used fuel that is to be removed from the ATR) are moved from the reactor and lowered through a discharge chute into the ATR canal, located in an adjacent room. Once there, the experiments are moved to an appropriate location for temporary storage. There are facilities in the canal where underwater operations with long-handled tools can be conducted. Such operations may include rearranging capsules in a basket, experiment examination, or removal of the experiments.

Gamma Facility

In addition to the neutron irradiation facilities inside the ATR, the ATR Gamma Facility (located in the ATR Canal) accommodates gamma irradiation experiments. The Gamma Facility is essentially a 12.7-cm (5-inch) tube projecting from the spent fuel rack to the top of the ATR canal. A shielding plug on the top of the tube blocks sky-shine of the gamma radiation passing up the tube. The intensity of the gamma irradiation that can be achieved in the gamma facility will depend on the freshness of the fuel and its proximity to the gamma tube. A typical value for fuel freshly removed from the reactor place adjacent to the tube is 5 x 106 R/hr. That intensity will fall off at the rate of about 5 percent per day as the fission products in the fuel elements decay away.

Hot Fuel Examination Facility (HFEF)

The Hot Fuel Examination Facility (HFEF), located at the Materials and Fuels Complex, is a large, heavily shielded hot cell facility designed to remotely characterize highly irradiated fuel and structural materials. Capabilities include nondestructive examination, such as dimensional measurements, and neutron radiography, and destructive examination, such as mechanical testing or metallographic/ceramographic characterization. HFEF can accept full-size Light Water Reactor (LWR) assemblies and examine full-size LWR fuel elements.

The HFEF consists primarily of two adjacent large, highly-shielded hot cells in a three-story building. The main cell (argon atmosphere) has 15 workstations, each with a viewing window and a pair of remote manipulators. A decontamination cell (air atmosphere) has six similarly equipped workstations. The cells are equipped with overhead cranes and overhead electromechanical manipulators. Cell exhaust passes through two stages of HEPA filtration. The facility is linked to analytical laboratories and other facilities by pneumatic sample transfer lines.

HFEF also has a Neutron Radiography Reactor (NRAD) for neutron radiography irradiation of small test components. The NRAD is a 250 kW Training Research Isotope General Atomics (TRIGA) reactor. It is equipped with two beam tubes and two separate radiography stations that make it one of the finest facilities in the world for neutron radiography irradiation of small components, a process not possible using conventional x-ray methods.