Reed Research Reactor

Reed Reactor Experimenter Information

[ Overview | Student Research | NAA | Experimental Facilities | Gamma IR | Scheduling | Material Limits | Request an Experiment ] 

Overview

The reactor specifically aims at providing students with unique educational and research experience, and may not be appropriate for industry use. You may want to use the reactor if:

• You are looking for the presence of an element in a sample.
• You are performing a trace element analysis on a sample.
• You want to study the biological effects of radiation without making the sample itself radioactive.
• You need to use radioactive materials or radiation.

Some materials may require special approval before they are irradiated. Please discuss the exact contents and materials that you plan to use with us well before any experiment is due to begin. We will provide you with the necessary tools, workspace, and step-by-step instructions for preparing your samples for irradiation.

[ Overview | Student Research | NAA | Experimental Facilities | Gamma IR | Scheduling | Material Limits | Request an Experiment ] 

Student Research

The Reed Research Reactor has supported many student-run experiments, including senior theses, independent projects for biology, chemistry, and physics courses. We have also supported student projects from other educational institutions, including local colleges and high schools. 

Students have studied the effect of radiation on developing organisms, radioresistant bacteria, neutron flux calculations, and more! As part of the operator and senior operator training programs, staff are expected to conduct their own independent research projects.

The reactor is available for Reed Student use regardless of your major or type of thesis, and is free of charge. The reactor is available to students at other educational institutions pending a formal proposal. Use of the reactor for students at other educational institutions is often free or low-cost.

[ Overview | Student Research | NAA | Experimental Facilities | Gamma IR | Scheduling | Material Limits | Request an Experiment ] 

Neutron Activation Analysis

Neutron activation analysis (NAA) is a method of analysis that detects one or more nuclides in a sample. NAA can also determine the amount of the nuclide present, even in very small quantities. The sample in question may be solid, liquid, or gaseous. NAA is the experiment type most often performed at the reactor.

Samples are activated in the reactor by neutron absorption. When a nucleus absorbs a neutron, a particle and a gamma ray are generally produced. Each nuclide produces a characteristic gamma ray, so analysis of the energy and frequency of these gamma rays will indicate the presence and amount of a nuclide in a sample.

Not all elements can be activated by neutron absorption, and we can only analyze gamma-emitting nuclides. While this means that not all elements can be found with NAA, it also means that organic materials will be ignored completely in the analysis. However, this does mean that the nuclides that can be found are somewhat limited. Appended is a list of the nuclides that we can find and their detection limits.

NAA has been used at the Reed Reactor Facility in the fields of geology (rock sample analysis), anthropology (tracing trade routes by elemental fingerprinting of sources), medicine (detection of selenium concentrations in the internal organs of rats), archeology (age dating), chemistry (identification of contaminants), biology (trace element analysis), forensics (matching powder to guns), computers (silicon wafer analysis), and environmental science (testing for elements in factory air filters).

If you are planning to look for an element in quantities on the order of micrograms to nanograms, you should talk with us about the minimum detectable quantity of that element in our reactor. If we do not have a suitable known minimum detectable quantity for an appropriate interval of kilowatt-hours on record, we can help you set up an experiment to find the minimum detectable quantity yourself.

[ Overview | Student Research | NAA | Experimental Facilities | Gamma IR | Scheduling | Material Limits | Request an Experiment ] 

Experimental Facilities

The reactor has three in-core experimental facilities (below), plus a Cs-137 source. Two plastic vials are usually used to irradiate each sample in these facilities, an inner vial and an outer vial. The inner vial has an inner diameter of about 10 mm and a height of about 23 mm. The outer vial has an inner diameter of about 15 mm and a height of about 55 mm. If a sample cannot fit in an inner vial but can fit in an outer vial, it may be placed in a small plastic bag in the outer vial. 

Rotary Specimen Rack (Lazy Susan)

The Rotary Specimen Rack is a watertight assembly located in a well on top of the graphite reflector which surrounds the core. The rack consists of a circular array of 40 tubular receptacles which can be continuously rotated about 1.2 rpm to ensure each sample receives the same neutron flux. 

Containers called TRIGA tubes are used to irradiate samples in the Lazy Susan. The TRIGA tubes have an inner diameter of about 25 mm, and a height of about 100 mm. One TRIGA tube can hold one outer vial, and two TRIGA tubes can be screwed together to hold two outer vials. Each position in the Lazy Susan can accommodate two TRIGA tubes, such that up to 80 separate samples may be irradiated at any one time.

The average thermal neutron flux in the rotating rack position is approximately 2 × 10¹² n/cm²s at full power. The specimen rack can also be used for gamma irradiations when the reactor is shutdown. The shutdown gamma flux in the specimen rack is approximately 8 Rad per minute.

Generally the Lazy Susan is used to activate samples with long half-lives for a longer period of time (hours to days). This will allow unwanted nuclides with short half-lives to decay away before the samples are analyzed. Lazy Susan samples may take longer to analyze due to a larger number of samples and the higher dose rates. 

Pneumatic Transfer System (Rabbit)

The Pneumatic Transfer System is a series of pipes and a blower motor with an irradiation chamber located in the outer ring of the core. It uses air pressure to quickly move samples into or out of the core while the reactor is operating. Since it moves samples so quickly it is called the Rabbit. 

Containers called Rabbit tubes are used to irradiate samples in the Rabbit. The Rabbit tubes have an inner diameter of about 17 mm, and a height of about 112 mm. One Rabbit tube can hold one outer vial. The Rabbit facility can only irradiate one Rabbit tube at a time. 

The transfer time from the core to the terminal is less than seven seconds, making this method of irradiating samples particularly useful for experiments involving radioisotopes with short half-lives. The flux in the core terminal is approximately 5 × 10¹² n/cm²s when the reactor is at full power.

Generally the Rabbit is used to activate samples with short half-lives. Samples are run quickly and counted quickly but they must be run individually. If you will need to analyze a large number of samples with short half-lives (e.g. upwards of 25 samples), please be sure to let us know about your experiment at least a month before any implementation.

Central Thimble

[ Overview | Student Research | NAA | Experimental Facilities | Gamma IR | Scheduling | Material Limits | Request an Experiment ] 

Gamma Irradiation

When something is irradiated with gamma rays instead of neutrons, the sample will not become radioactive itself. This way, the biological effects of radiation can be observed without the hassle of analyzing a radioactive sample. When irradiating a sample with gammas, there will be no spectra produced. You will instead receive your irradiated sample for your own analysis once we are satisfied that it is neither radioactive nor contaminated.

There are two main ways in which we can perform gamma irradiation. We can use our 0.6 Ci Cs-137 source or place the samples in the reactor while it is shutdown. 

The Cs-137 source, known as the Shepherd Source, produces 661.7 keV gammas and betas with average energies of 174 and 416 keV. The Shepherd Source can produce up to 5 R/hr of gamma dose. 

Samples placed in the core will receive between 1 x 10⁴ and 1 x 10⁵ R/hr of gamma dose, although the exact amount is not quantifiable. Samples will also receive a very small neutron dose, but not enough to activate the sample. 

The method used will depend on the size of the sample and the radiation dose needed.

[ Overview | Student Research | NAA | Experimental Facilities | Gamma IR | Scheduling | Material Limits | Request an Experiment ] 

Scheduling

The first thing that you will need to do is to contact us and request an experiment. We will discuss sample material and size, neutron flux or dose requirements, and sample return or disposal before we can approve your experiment. 

If you plan to use an in-core facility for NAA, we will prepare your samples for irradiation by putting small amounts of material into clean sample vials. Once they are irradiated, your samples will produce characteristic gamma rays when removed from the core, and these gammas will be interpreted by a high purity germanium (HPGe) detector and displayed on a spectrum using the GammaVision program. After your samples have been counted, you will be able to analyze the spectra produced. We will show you how to interpret the raw data so that you can perform your own analyses. Depending on how you structured your experiment, you will be able to determine what elements are present in your samples and, if desired, the amount of the detected elements. If you would like your sample(s) back, we will only be able to return them to you once they're no longer radioactive, unless you make special arrangements to ship them as radiactive material. If you don't want your samples back we will dispose of them. Here is a standard schedule for NAA irradiations:

• Sample preparation: This could take 1-8 hours.
• Sample irradiation: You are not required to attend, but are welcome. Depending on the experiment this could take anywhere from a couple of minute to 8 or more hours.
• Decay time: Samples may need to decay before counting, anywhere from 2 minutes to several days or weeks.
• Counting time: Samples are counted for as few as 5 minutes or as long as 8 hours.
• Analysis time: Depending on the experiment this can take up to an hour per sample.
• Return or disposal: Depending on the half-life, samples may be ready to be returned immediately after analysis, or it may take a few weeks or even months for them to decay enough to be returned.

If you plan to perform a gamma irradition, the sample preparation will vary depending on what you are analyzing. Because they will not be radioactive, your samples may be returned immediately.  Here is a standard schedule for gamma irradiations:

• Sample preparation: Generally very little sample preparation is needed, probably around a few minutes. 
• Sample irradiation: You are not required to attend, but are welcome. Depending on the experiment this could take anywhere from a couple of minute to 8 or more hours.
• Decay time: not applicable. 
• Analysis time: Generally we will not analyze your samples.
• Return or disposal: Immediately after the gamma irradiation

Detectable Elements and Detection Limits

The following materials need special approval before irradiation, and may not be approved at all:

• Samples containing elemental mercury, or substances where mercury is a major component.
• Samples containing more the 1 mg of uranium or thorium per sample container.
• Samples containing materials which are classified as flammable, water reactive, or corrosive. If approved, such experiments must at minimum be doubly encapsulated.
• Organic solvents and other potentially unstable chemicals (even if not flammable). Evaluation of the potential to off-gas, sublime, volatilize or produce aerosols may be required. If approved, such experiments must at minimum be doubly encapsulated.
• Samples containing, or irradiated in association with, more than trace amounts of elements with large neutron-absorption cross sections, including cadmium, indium, and boron. An assessment of the reactivity effect, or the reactivity effect of previously run similar samples, may be required.
• Materials which, for any reason, cannot be encapsulated.
• Explosive materials may not be irradiated under any circumstances.
• No experiment shall be performed which may lead to the failure of a fuel element.

Request an Experiment

If you are interested in performing an experiment with us, please fill out the following (https://forms.gle/ZoT8G1AJTeeopKHMA if it won't load in-page). We will try to respond to your request within 3-5 business days.  

[ Overview | Student Research | NAA | Experimental Facilities | Gamma IR | Scheduling | Material Limits | Request an Experiment ]