Advanced Test Reactor

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ATR building grounds in Idaho
ATR building grounds in Idaho

The Advanced Test Reactor (ATR) is a research reactor at the Idaho National Laboratory. This reactor is primarily designed and used to test materials to be used in other, larger-scale and prototype reactors. It can operate at a maximum power of 250MW and has a "Four Leaf Clover" design that allows a myriad of testing locations. The unique design allows for different flux in various locations and specialized systems also allow for certain experiments to be run at their own temperature and pressure.

The ATR is light water moderated and cooled, with a beryllium neutron reflector. It is pressurized and housed in a stainless steel tank.

Workers replacing a fuel plate in the ATR core.
Workers replacing a fuel plate in the ATR core.

As well as its role in materials irradiation work, ATR is the USA's only source of Cobalt-60 for medical applications and of Plutonium-238 for radioisotope thermoelectric generators used in space probes.

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[edit] History

ATR core, powered up. The serpentine arrangement of fuel plates can be seen glowing bright blue (Cherenkov radiation).
ATR core, powered up. The serpentine arrangement of fuel plates can be seen glowing bright blue (Cherenkov radiation).

Since 1951, fifty-two reactors have existed on the grounds of the Idaho National Laboratory's National Reactor Testing Station. Constructed in 1967, the ATR is the second-oldest of three reactors still in operation at the site.[1] Its primary function is to intensely bombard samples of materials and fuels with neutrons to simulate long-term exposure to high levels of radiation, as would be present in a commercial nuclear reactor. The ATR is one of only four test reactors in the world with this capability.[2] The reactor also produces rare isotopes for use in medicine and industry.[3]

In April of 2007, the ATR was designated a "National Scientific User Facility" to encourage use of the reactor by universities, laboratories, and industry.[4] This status is intended to stimulate experiments to extend the life of existing commercial reactors and encourage nuclear power development. These experiments will test "materials, nuclear fuel, and instruments that operate in the reactors."[2] Under this program, experimenters will not have to pay to perform experiments at the reactor, but are required to publish their findings.

[edit] ATR compared with commercial reactors

Test reactors are very different in appearance and design from commercial, nuclear power reactors. Commercial reactors are large, operate at high temperature and pressure, and require a large amount of nuclear fuel. A typical commercial reactor has a volume of 48 cubic meters with 5400kg of Uranium at 550°F and 177 atm.[3] Because of their large size and stored energy, commercial reactors require a robust "containment structure" to prevent the release of radioactive material in the unlikely event of an emergency situation.

By contrast, the ATR does not require a large containment structure--it has a volume of 1.4 cubic meters, contains 43kg of Uranium, and operates at 140°F and 26.5 atm (conditions similar to a hot water heater).[3] The reactor vessel itself, which is made of stainless steel surrounded by concrete that extends more than 20 feet underground, is hardened against accidental or intentional damage. The entire reactor area is also surrounded by a confinement structure (as opposed to a "containment structure") designed to further protect the surrounding environment from any potential release of radioactivity.

[edit] Reactor design and experimental capabilities

Cross section of the core, showing each test location.
Cross section of the core, showing each test location.

The ATR core is designed to be as flexible as possible for research needs. It can be brought online and powered down safely as often as necessary to change experiments or perform maintenance. The reactor is also powered down automatically in the event of abnormal experimental conditions or power failure.

Components of the reactor core are replaced as necessary every 7-10 years to prevent fatigue due to exposure to radiation and to ensure experimenters always have a new reactor to work with. The neutron flux provided by the reactor can be either constant or variable, and each lobe of the four-leaf-clover design can be controlled independently to produce up to 1015 thermal neutrons per second per square centimeter or 5*1014 fast neutrons s-1 cm-2. [5] There are 77 different testing locations inside the reflector and another 34 low-intensity locations outside the core (see figure at right), allowing many experiments to run simultaneously in different test environments.[6] Test volumes up to 5.0 inches in diameter and 4 feet long can be accommodated. Experiments are changed on average every seven weeks, and the reactor is in nominal operation (110MW) 75% of the year.[7]

Three types of experiments can be performed in the reactor:[7]

  • Static Capsule Experiment: The material to be tested is placed in a sealed tube made of aluminum, stainless steel, or zircaloy, which is then inserted in the desired reactor location. If the tube is less than the full 48" reactor height, several capsules may be stacked. In some cases, it is desirable to test materials (such as fuel elements) in direct contact with the reactor coolant, in which case, the test capsule is not sealed. Very limited monitoring and temperature control are available for the static capsule configuration, and any instances would have to be built into the capsule experiment (such as temperature melt wires or an insulating air gap).
  • Instrumented lead experimental configuration.
    Instrumented lead experimental configuration.
  • Instrumented Lead Experiment: Similar to the Static Capsule configuration, this type of experiment allows for real-time monitoring of temperature and gas conditions inside the capsule. An umbilical connects the test capsule to a control station to report test conditions. The control station automatically regulates the temperature inside the test capsule as desired by pumping a combination of helium (conducting) and neon or argon (nonconducting) gases through the capsule. The circulated gas can be examined though gas-liquid chromatography to test for failure or oxidation of the material being tested.
  • Pressurized Water Loop Experiment: More complex than the Instrumented Lead configuration, this type of experiment is available in only five of the flux tubes. Test material is isolated from the primary ATR coolant by a secondary coolant system, allowing for precise conditions of a commercial reactor to be simulated. Extensive instrumentation and control systems in this type of experiment generate a large amount of data, which is available to the experimenter in real-time so that changes can be made to the experiment as required.

Research experiments at the reactor include:

  • Advanced Graphite Capsule: This experiment will test the effects of radiation on several types of graphite under consideration for the Next Generation Nuclear Plant program that currently have no high-flux temperature data available.[8]
  • Advanced Fuel Cycle Initiative / Light Water Reactor: The goal of the AFCI is to transmute longer-life fuels into shorter-life ones which would be able to be used in commercial light water reactors, to reduce the amount of waste that must be stored while increasing the fuel available for commercial reactors.[8]
  • Cobalt-60 Production: The least complex of current uses of the Advanced Test Reactor is the production of the Co-60 isotope for medical uses. Disks of Cobalt-59 1mm-diameter by 1-mm thick are inserted into the reactor (Static Capsule Experiment), which bombards the sample with neutrons, producing Cobalt-60. Approximately 200kCi are produced per year, entirely for medical uses.[8]

[edit] References

  1. ^ INL's 52 Reactors. Idaho National Laboratory. Retrieved on 2008-02-28.
  2. ^ a b "Idaho test reactor opens to universities". USA Today. Retrieved on 2008-02-29.
  3. ^ a b c ATR Factsheet. Idaho National Laboratory. Retrieved on 2008-02-28.
  4. ^ ATR Home Page. Idaho National Laboratory. Retrieved on 2008-02-29.
  5. ^ "Advanced Test Reactor Testing Experience: Past, Present and Future". Idaho National Laboratory. Retrieved on 2008-03-28.
  6. ^ "ATR National Science User Facility". Idaho National Laboratory. Retrieved on 2008-02-29.
  7. ^ a b Frances Marshall. ATR Irradiation Facilities and Capabilities. Idaho National Laboratory. Retrieved on 2008-02-29.
  8. ^ a b c Robert C. Howard. "Reactor Utilization for the Advanced Test Reactor". Idaho National Laboratory. Retrieved on 2008-04-03.

[edit] External links

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