Irradiation Facilities at the Advanced Test Reactor Page: 3 of 10
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bottom and is attached to its own individual pressurized water coolant system. The cooling system includes
pumps, valves, electrical heaters, heat exchangers, ion exchangers and a pressurizer to control the
experiment flow rate, temperature, chemistry and pressure. Loop tests can precisely represent conditions in
a commercial pressurized water power reactor, and can include transient testing using one of ATR's two
Powered Axial Locator Mechanisms (PALM). The PALM tests usually last from a few hours to a few days,
and are described in more detail later. Some other experiments may be removed from the reactor during a
PALM test due to the changing reactor conditions. Hence, this is perhaps the most costly type of test to
perform in the ATR. Each of these types of experiments is described in detail later.
Cranes and special handling tools are available to either remove or insert customer hardware into the
reactor. Underwater storage facilities and working trays (for experiment assembly/disassembly) are available
in the large ATR canal adjacent to the reactor vessel. Facilities and specialized counting equipment are
available at the Reactor Technology Complex to analyze flux wires from experiment irradiations and
calculate total neutron fluence or neutron spectra data. Based on the complexity of the experimental needs
of the customer, ATR operations can also provide real time monitoring and data collection equipment.
ATR Operations, Quality and Safety Requirements
Operation of the Advanced Test Reactor is based on a yearly schedule divided into multiple time intervals
called "cycles". The length of a reactor cycle (specified in days) and the reactor power (specified in
Megawatts) is variable, and dependent upon the customer's experimental requirements and the design basis
reactor safety documentation . In order to maintain reactor operational efficiency, equivalent reactor
availability, and meet the needs of the customers, the reactor schedule is prepared a year in advance.
Integrated into this schedule are planned reactor outages for routine reactor/plant maintenance and
removal/insertion of customer experiments.
All experiments to be irradiated in the ATR are controlled by an American Society of Mechanical Engineers
(ASME) NQA-1 quality assurance program with multiple reviews/approvals prior to acceptance of customer
hardware for irradiation. In addition, for every ATR cycle, complex multi-group neutron diffusion and transport
theory calculations are performed, reviewed, and approved for both fuel and experiments to verify the reactor
will operate within the required safety parameters to protect the public and environment. Experiment
operational parameters (flow, temperature, pressure, and heat generation) and experiment failure modes are
compared to the ATR design basis safety documentation to complete the necessary reviews to ensure safe
operation of the ATR and the experiment.
Static Capsule Experiments
Static capsules (commonly referred to as drop-in capsules) may include special passive instrumentation for
monitoring specific parameters (i.e. melt wires for temperature, flux wires for neutron fluence, etc.) during
irradiation (Fig. 1). The temperature of a static capsule may also be controlled, within limits, by incorporating
a small insulating gas jacket (filled with an inert gas) between the specimens and the outside capsule
pressure boundary. The width of the gas jacket, the type of gas, and the gamma and reaction heating
characteristics of the specimens and capsule materials are used to provide the irradiation temperature
desired by the experimenter. Static capsules may vary in length (from a few centimeters to 1.2 meters) and
diameter (from 1.2-cm to 12.7-cm), and are usually sealed in aluminum, zircaloy, or stainless steel tubing to
provide containment. Depending upon the contents and pressure of the capsule, a secondary containment
may be included to meet the ATR safety requirements. Static capsules, which are usually contained in a
basket, are uniquely designed for each customer's needs. This type of experimentation is usually less
expensive and requires less lead time to insert an experiment into the ATR than any of the other types of
experiments due to their simplicity. However, this type of experiment also has less flexibility and control of
operating parameters during the irradiation. In addition, the passive instrumentation (if included) can only be
removed during reactor outages and examined later to determine the conditions that occurred during the
experiment irradiation.2
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Grover, S. Blaine. Irradiation Facilities at the Advanced Test Reactor, article, December 1, 2005; [Idaho Falls, Idaho]. (https://digital.library.unt.edu/ark:/67531/metadc881166/m1/3/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.