Experiment Facilities

Hydraulic Tube Facility

The High Flux Isotope Reactor (HFIR) hydraulic tube facility consists of the necessary piping, valving, and instrumentation to move aluminum capsules containing materials to be irradiated into and from the flux trap and the capsule loading station during reactor operation. The capsule loading station is located in one of the storage pools adjacent to the pool containing the reactor vessel. The pressure drops that exist in the primary coolant system are used as the driving forces for moving the capsules through the system. A full facility load consists of nine vertically stacked capsules centered about the core's horizontal midplane. Figure 7 is a sketch of a typical capsule.

Normally, the heat flux from neutron and gamma heating at the surface of the capsule is limited to 74,000 Btu/h-ft² (2.3 x 105 W/m²). Further, the neutron poison content of the facility load is limited such that the reactor is not tripped by a significant reactivity change upon removal of the samples.

Target Positions

Thirty-one target positions are provided in the flux trap (see Figure 8). These positions are usually occupied by target rods used for the production of transuranic elements; however, experiments can, in principle, be irradiated in any of these positions. Figure 9 shows a typical transuranium production rod. Irradiation experiments designed to this configuration are cooled by primary system water at a velocity of about 42 ft/s (12.80 m/s) under normal full-flow conditions. A typical target position experiment is illustrated in Figure 10. In experiments of this type the volume normally occupied by the major coolant flow path in a standard transuranium rod is occupied by part of the experiment itself. Experiments designed to this configuration must be such that they can be adequately cooled by the coolant velocity available outside the target-rod shrouds, which is approximately 3 ft/s (0.91 m/s). Excessive neutron poison loads in experiments in target positions are discouraged because of their adverse effects on both transuranic production rates and fuel cycle length. Such experiments require careful coordination with and accommodation to the requirements of the transuranium production program. Two positions are now available for instrumented target experiments: positions E3 and E6 (see Figure 8).

Peripheral Target Positions

Six peripheral target positions (PTPs) are provided for experiments located at the outer radial edge of the flux trap (see Figure 8). Fast-neutron fluxes in these positions are the highest accessible in the reactor, although a steep radial gradient in the thermal-neutron flux exists at this location (see Figure 6).

Figure 11 shows a typical PTP experiment. At normal full system flow, a pressure drop of 36 psi (2.48 x 105 Pa) is available to provide coolant for the experiment. A typical experiment contains a neutron poison load equivalent to that associated with 200 g of aluminum and 35 g of stainless steel distributed uniformly over a 20-in. (50.8-cm) length. PTP experiments containing neutron poison loads significantly in excess of that described are discouraged because of their adverse effects on transuranium production rates, fuel cycle length, and fuel element power distribution.

All PTP experiments are noninstrumented because no provision is made in the design for accommodating access tubes or instrument leads for these positions.

Experiment Facilities in the Beryllium Reflector

Large Removable Beryllium Facilities

The number of large removable beryllium (RB) facilities was recently increased from four to eight. These are designated as RB-1A and -1B, RB-3A and -3B, RB-5A and -5B, and RB-7A and -7B. In generic terms, these are referred to as the RB* positions. They are located in the removable beryllium near the control region.

The vertical centerline of these facilities is located 10.75 in. (27.31 cm) from the vertical centerline of the reactor. These facilities are lined with a permanent aluminum liner having an inside diameter of 1.811 in. (4.6 cm). Either instrumented or noninstrumented experiments can be irradiated in these facilities. Instrument leads and access tubes are accommodated through penetrations in the upper shroud flange and through special penetrations in the pressure vessel upper cover. These positions can accommodate spectral-tailored (i.e., shielded) experiments, making them well suited for fusion materials irradiation. When not in use, these facilities contain beryllium or aluminum plugs.

To date, these particular facilities have been used primarily for two types of irradiations: (1) High Temperature Gas-Cooled Reactor (HTGR) fuel irradiations and (2) production of radioisotopes.

Figure 12 illustrates schematically the routing of instrument leads, access tubes, and gas lines associated with typical experiments in the RB* positions. Figure 13 shows the loaded "quad holder," which has been used for the production of radioisotopes. Experiments in these facilities are carefully reviewed with respect to their neutron poison content, which is limited because of its effect on fuel element power distribution and fuel cycle length.

A pressure drop of 10 psi (6.89 x 104 Pa) at normal full system flow is available in these facilities to provide primary system coolant flow to cool experiments.

Small Removable Beryllium Facilities

Four small RB facilities (designated RB-2, RB-4, RB-6, and RB-8) are located in the removable beryllium near the control region (see Fig. 5). The vertical centerline of these facilities is located 10.37 in. (26.35 cm) from the vertical centerline of the reactor. These unlined facilities have an inside diameter of 0.5 in. (1.27 cm). When not in use, these facilities contain beryllium plugs. These facilities have been used primarily for the production of radioisotopes. (Figure 14 shows a typical irradiation capsule for one of these facilities.) The neutron poison content limit and the available pressure drop given in the preceding section apply as well to experiments in the small RB facilities.

Control-Rod Access Plug Facilities

The semipermanent beryllium contains four control-rod access plugs (see Figure 5), the removal of which provides access to the coupling between the safety rods and their associated drive mechanisms. Each standard control-rod access plug contains two 0.5-in. (1.27-cm)-I.D. unlined irradiation facilities, making a total of eight in the reactor (designated CR-1 through CR-8). Normally, these facilities accommodate standard target rods of the type and configuration usually irradiated in the small removable beryllium facilities, although, in principle, experiments having other configurations can be accommodated. The vertical centerlines of all control-rod access plug facilities are located 12.68 in. (32.2 cm) from the vertical centerline of the reactor. Only noninstrumented experiments can be irradiated in these facilities because no provision is made for accommodating instrument leads and/or access tubes. When not in use, these facilities contain beryllium plugs.

A pressure drop of 10 psi (6.89 x 104 Pa) at full system flow is available to provide primary system coolant flow for cooling experiments.

Small Vertical Experiment Facilities

The permanent reflector is penetrated by 16 vertical holes, referred to as the small vertical experiment facilities (VXFs), which extend completely through the beryllium. Each of these facilities has a permanent aluminum liner having an inside diameter of 1.584 in. (4.02 cm). The facilities are located concentric with the core on two circles of radii 15.43 in. (39.2 cm) and 17.36 in. (44.1 cm), respectively (see Figure 5). Those located on the inner circle (11 in all) are referred to as the inner small VXFs. Those located on the outer circle (five in all) are referred to as the outer small VXFs. VXF-7 contains one of the pneumatic irradiation facilities and is unavailable for other use. Normally, noninstrumented experiments are irradiated in these facilities.

A pressure drop of approximately 100 psi (6.89 x 105 Pa) at full system flow is available to provide primary system coolant flow for cooling experiments. When not in use, these facilities may contain beryllium or aluminum plugs or an orifice and no plug.

Large neutron poison loads in these facilities are of no particular concern with respect to fuel element power distribution perturbations or effects on fuel cycle length because of their distance from the core.

Large Vertical Experiment Facilities

The permanent reflector is penetrated by six vertical holes referred to as the large vertical experiment facilities (see Figure 5). These facilities are similar in all respects (as to characteristics and capabilities) to the small vertical experiment facilities described in the preceding section except for location and size (and, of course, available neutron fluxes). The aluminum liners in the large VXFs have an inside diameter of 2.834 in. (7.20 cm), and the facilities are located concentric with the core on a circle of radius 18.23 in. (46.3 cm). When not in use, these facilities contain beryllium or aluminum plugs.

Neutron Activation Analysis (NAA) Laboratory and Pneumatic Tube Facilities

Two pneumatic tube facilities, designated PT-1 and PT-2, are available in the HFIR. These facilities, operated by the Analytical Chemistry Division, consist of flight tubes, air supply and exhaust lines, loading stations at which sample containers (rabbits) are introduced into the flight tubes, and irradiation stations to which the rabbits move to be irradiated (see Figure 15). The inner diameter of the flight tubes is 0.62 in. (15.88 mm), and the outer diameter of the rabbit is 0.56 in. (14.48 mm). Both flight tubes accept the same rabbits, which have an internal volume of about 1 cm³. Both systems operate with air entering both ends of the flight tube. Capsules are inserted into the reactor and returned to shielded loading stations in the laboratory. The capsules stop on air columns, which permits them to be made of graphite as well as plastic. Graphite capsules can be irradiated for many hours, thus making NAA extremely sensitive for many elements. The capsules can be stopped at decay stations in the pool if they are temporarily too radioactive to return to the laboratory. The facilities are used to measure the trace element content in a variety of materials by neutron activation analysis. About 65 of the chemical elements can be measured in the range of 10-6 to 10-15 g. The induced radioactivity of the samples is measured with high-resolution germanium detectors interfaced to a personal computer-based analyzer.

PT-1 was installed in the HFIR in 1970. This pneumatic tube is placed in one of the previously mentioned small vertical experiment facilities (in VXF-7) . This is a vertical irradiation hole in the permanent beryllium reflector about 7 in. (180 mm) from the edge of the fuel element. The thermal flux in PT-1 is about 2.8 x 1014 neutrons/(cm²·s). The thermal/epithermal flux ratio is approximately 40.

PT-2 was installed in the HFIR in 1986 and was constructed primarily to replace an existing pneumatic tube that had been in operation at another research reactor. This pneumatic tube has a special delayed neutron counter (DNC) for fissile nuclide analysis that will replace the DNC in the lost Oak Ridge Research Reactor system. The DNC can be operated in a manual or automatic mode.

This pneumatic tube is located in a slant engineering facility that intersects the outer edge of the permanent beryllium reflector. This places the irradiation station approximately 12.5 in. (320 mm) from the fuel element. The thermal flux for the facility is about 5.9 x 1013 neutrons/(cm²·s). The thermal/epithermal ratio is approximately 200. PT-2 is expected to permit thermal-neutron NAA that is unusually free of interferences caused by fast neutrons.

The NAA systems support ORNL (DOE) programs, are used in work-for-others projects, and are available for use by students and faculty of universities through Oak Ridge Associated Universities and other programs. Several students and faculty members have previously used the system.

From 1975 to 1985, approximately 100,000 samples were analyzed for uranium by the DNC in the ORR system. Most of those samples were generated by the National Uranium Resources Evaluation and the remaining ones from the Formerly Utilized Sites Remedial Action Program.

NAA at ORNL was also used to analyze evidence related to the 1961-62 French-connection heroin case and the 1963 assassination of President Kennedy. More recently, it has been used in environmental analysis and in determining levels of uranium in materials used in the semiconductor industry.

Slant Engineering Facilities

Provision has been made for installation of up to four engineering facilities to provide additional neutron beams for experiments. These facilities consist of 4-in. (10.16-cm)-O.D. tubes that are inclined upward 49° from horizontal. The inner ends of the tubes terminate at the outer periphery of the beryllium and have lower flux than the main beam tubes. The upper ends of the tubes terminate at the outer face of the pool wall in an experiment room one floor above the main beam room.

One of the engineering facilities houses the newest pneumatic tube, which was installed in the HFIR in 1986.

Gamma Irradiation Facility

Since 1968, a large variety of materials have been irradiated in the HFIR pool with the gamma flux generated from the decay of fission products in the spent HFIR fuel assemblies. In 1972, two 3-in. (7.6-cm)-diam stainless steel tubes were fabricated to provide a conduit through which specimens and any associated equipment could be inserted and withdrawn from the gamma fields. Air supply lines are available to provide a purge gas for temperature control within the tubes. The fuel assemblies used for these measurements range in decay time (time since the reactor was shut down) from 30 to 48 hours initially to 6 or 7 months, depending on the experiment. Facilities are also available wherein the flux trap sections of depleted fuel elements can be used to irradiate experiments requiring a high gamma flux. To date, such experiments have included studies of the effects of gamma radiation on salt, insulating materials, paint samples, and a variety of other materials.

The facility provides for a nominal 3-in. opening for irradiation of samples. The initial (maximum) dose rate in the facility is approximately 1 x 108 R/h.

Contacts

For information on the experiment review and approval process, contact the Research Reactors Division Experimenter Interface or the Experiment Coordinator:
Experimenter Interface
Steve Burnette 		Experiment Coordinator
Randy Hobbs
Oak Ridge National Laboratory
P.O. Box 2008
Oak Ridge, TN 37831-6398 		Oak Ridge National Laboratory
P.O. Box 2008
Oak Ridge, TN 37831-6387
Phone: (865) 576-0214 (865) 574-8789

Please send comments or inquiries to Cindy Brackett.
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