High Flux Isotope Reactor
The thermal and cold neutrons produced by HFIR are used to study physics, chemistry, materials science, engineering, and biology.
In November 2007 ORNL officials announced that time-of-flight tests on a newly installed cold source (which uses liquid helium and hydrogen to slow the movement of neutrons) showed better performance than design predictions, equaling or surpassing the previous world record set by the research reactor at the Institut Laue–Langevin in Grenoble, France.
[1] In January 1958, the U.S. Atomic Energy Commission (AEC) reviewed the status of transuranium isotope production in the United States.
After thorough reevaluation last over two years, modifications to extend the life of the plant while protecting the integrity of the pressure vessel, and upgrades to management practices, the reactor was restarted at 85 MW.
Technical specifications were amended and reformatted to keep abreast of the design changes as they were accepted by the U.S. Department of Energy (DOE), formerly the AEC.
The primary coolant pressure and core power were reduced to preserve vessel integrity while maintaining thermal margins, and long-term commitments were made for technological and procedural upgrades.
HFIR is the western world's sole supplier of californium-252, an isotope with uses such as cancer therapy and detection of pollutants in the environment and explosives in luggage.
The fuel (93% 235U enriched U3O8-Al cermet[4]) is non-uniformly distributed along the arc of the involute to minimize the radial peak-to-average power density ratio.
The control plates, in the form of two thin, nuclear poison-bearing concentric cylinders, are in an annular region between the outer fuel element and the beryllium reflector.
The outer control cylinder consists of four separate quadrant plates, each having an independent drive and safety release mechanism.
A fuel cycle for HFIR normally consists of full-power operation at 85 MW for 21-23 days (depending on experiment and radioisotope load in the reactor), then an end-of-cycle outage for refueling.
The HB-2 thermal neutron beam tube is situated radially relative to the reactor core, pointed directly at the fuel.
The shutter has provisions for routing the cryogenic hydrogen transfer line, gaseous helium, and vacuum piping needed to support the cold source.
The hydraulic tube facility provides the ability to irradiate materials for durations less than the standard ~23 day HFIR fuel cycle, which is ideal for the production of short half-life medical isotopes that require retrieval on demand.
Also, the neutron poison content of the facility load is limited such that the reactor cannot be tripped by a significant reactivity change upon insertion and removal of the samples.
The use of this type of irradiation capsule simplifies fabrication, shipping, and post-irradiation processing which translates to a cost savings for the experimenter.
Excessive neutron poison loads in experiments in target positions are discouraged because of their adverse effects on both transplutonic isotope production rates and fuel cycle length.
Use of this type of irradiation capsule simplifies fabrication, shipping, and post-irradiation processing which translates to a cost savings for the experimenter.
The uninstrumented configuration has a top plug which is used for installation of the samples and to support the inert gas lines and maintain a leak-tight environment while underwater.
Neutron activation analysis (NAA) is a powerful analytical technique used to probe the elemental makeup of a wide variety of materials.
NAA is free of classical "matrix" effects and is capable of very precise measurements with detection limits commonly in fractions of PPM.
PT-1 has the highest thermal neutron flux in the western world and offers many advantages in sensitivity for ultra-trace level determinations and for limited isotope production.
The PT-2 facility offers a highly thermalized flux coupled with delayed neutron counting, giving the ability to measure very low quantities of fissile materials in minutes.
Samples of smears, vegetation, soil, rock, plastics, wood, metal, and sand are equally amenable to delayed neutron analysis.
This tool facilitates International Atomic Energy Agency (IAEA) efforts to establish wide area monitoring and enables individual inspectors to get large numbers of samples in the hopes of finding required evidence.
A recent application involves irradiation of programmable memory devices that have been coated with a small amount of a fissile isotope.
The fate of the dinosaurs was investigated by analyzing iridium in fossilized bone dated near in time to known major meteorite impacts.
Recently, bioremediation strategies have been examined and rates of absorption of heavy elements have been determined in indigenous plants and animals.
A recent example is the dose response investigation of dichroic mirror ceramic materials for the fusion energy research program.
The PT-1 and PT-2 facilities are well suited to fill the niche between the very high fluxes in the HFIR target region and the much lower ones in the beam tubes.
