Reed Reactor Experimenter Information

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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 are looking for a trace element and want to ignore the presence of organic materials in a sample.
  • You need radioactive material
  • You need to use radiation.

The reactor is available for Reed Student use regardless of your major or type of thesis, and is free of charge.

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Overview

If you plan to use the reactor for your thesis, it is ideal to start preparing the experiment during the first semester of your thesis. Once your samples are prepared, it may take some time before you can analyze your samples depending on the method, size, and elements in your experiment.

There are several methods by which we can analyze samples. The method used depends on what you are looking for and the size of the samples that you are analyzing. If you are performing any form of trace element analysis, neutron activation analysis will be used. If you are specifically looking for boron, carbon, cadmium, or lithium, prompt gamma neutron activation analysis will be used. If you want to study the biological effects of radiation on something, the gamma irradiation racks will be used.

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

If you want to set up an experiment, contact the director of the reactor, at reactor@reed.edu or in Chem 102.

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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 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.

There are two usual methods by which we activate samples. One method is for samples that either activate very quickly or have short half-lives. To do this, we rapidly insert and remove the sample from the core via air pressure in the pneumatic transfer system, which is fondly known as the rabbit. Samples are run quickly and counted quickly when using the rabbit, 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 75-100 samples), please be sure to let us know about your experiment at least a month before any deadlines involving the results of that experiment.

The other method is for samples that must be irradiated for longer periods of time and have longer half-lives. This method also will let unwanted nuclides with short half-lives decay away before analysis is performed. To do this, we insert a number of samples into the rotary specimen rack, known also as the lazy susan. Up to eighty samples may be irradiated at one time with the lazy susan, and the samples may be irradiated for very long periods of time if necessary. Samples irradiated in the lazy susan will generally be counted for longer than those irradiated with the rabbit, so it may be some time before all of your data is available.

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.

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Prompt Gamma Neutron Activation Analysis

Prompt gamma neutron activation analysis (PGNAA) can determine the presence of an element by measuring the gamma ray emitted when a nucleus captures a neutron. The gamma ray is emitted immediately upon absorption of the neutron; thus, prompt gamma. Whatever happens in the nucleus after the neutron is absorbed is irrelevant, so this method is ideal for isotopes with extremely short half-lives, elements that do not emit gamma rays when they decay, or elements that produce only stable isotopes. PGNAA is less sensitive than NAA. As we must measure these gammas at the moment of neutron capture, we cannot use our standard NAA experimental facilities. Instead, we bring a beam of neutrons up to the sample through our central thimble and place the detector above the pool.  The neutron flux inside the central thimble is 1x106 n-cm2/s, which is one millionth of the flux inside the reactor. The PGNAA detector also reads the high background gamma dose from the reactor, which further decreases the sensitivity.

Thus far, we have detected cadmium with PGNAA, but have not yet used it to detect boron, lithium, or carbon, which are the elements for which this method is designed.

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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 several ways in which we can perform gamma irradiation. We can use our gamma irradiation racks, which will put samples next to a gamma source. The source used to provide these gammas is usually Ir-192, which produces gammas with a half-life of 73 days. The source is activated in the reactor, but the samples themselves are irradiated outside of the reactor. Dose rates up to 15 rad per hour can be arranged.

The samples may also be put into the lazy susan, set near to the core, or placed into the central thimble while the reactor is shut down so that the sample is irradiated by gammas alone. The method used will depend on the size of the sample and the radiation dose needed.

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From Experiment Request to Results: Sample Preparation, Scheduling, and You.

The first thing that you will need to do is to contact the director and request an experiment. You will be provided with an experiment request form. Once this has been started, you can begin preparing your samples.

If you plan to use the rabbit or lazy susan for NAA, you will prepare your samples for irradiation by putting small amounts of material into clean sample vials. If you plan to use the gamma irradiation racks of PGNAA, the sample preparation will vary depending on what you are analyzing. 

If you will be doing NAA, please be sure to allow a lot of time to prepare your samples and for us to run them. We want you to have a lot of time to analyze your samples, but irradiating and counting your samples could take several days, or possibly weeks, depending on the content and amount of your samples.

Allow about five to ten minutes for each sample that you must prepare. Cleaning the sample vials and preparing your workspace may take up to one hour on top of that. Times when you can prepare samples may be limited, so please contact us to make an appointment.

The sample vials for the lazy susan and for rabbits are 2/5 dram in volume, and should only be filled half-full at the most. If you need to irradiate something larger for NAA, let us know and we’ll do our best to accommodate that.

Once your samples have been prepared, we will schedule a time for your samples to be irradiated. This may not be right away, but hopefully will be shortly after your samples are finished.

If you used NAA or PGNAA, 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.

Once 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.

In Conclusion

If you think that the reactor might be a good resource for your thesis, discuss this with your advisor to figure out the best method for you, and talk to us to see how we can best help you. If you have any questions, email reactor@reed.edu or stop by Chem 102.

Good luck!

The Reed Research Reactor is staffed by 33 Reedies in addition to the Director, Stephen Frantz, and the Associate Director, Robin Bjorkquist (’09). We perform experiments, run educational labs, and give tours. Every year, several Reedies undergo a year-long training course and take an exam administered by the NRC to become licensed operators. 

The pretty blue glow is due to Čerenkov radiation, which occurs when an electron moves faster than light in some polar medium – in this case, water. It is often called the electromagnetic equivalent of a sonic boom. The glow is only visible when the reactor is operating. 

The reactor was established in 1968, and is a TRIGA Mark I water-cooled reactor. We are currently licensed to operate at powers up to 250 kW.

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Detectable Elements and Detection Limits

 

 
Element
Detection Limit (µg)
Isotope
Halflife
 <
Aluminum
0.05
Al-28
2.25
m
Antimony
0.045
Sb-124
60.2
d
Arsenic
0.01
As-76
26.3
h
Barium
0.25
Ba-131
11.53
d
Bromine
0.005
Br-82
1.471
d
Cadmium
0.45
Cd-115
2.228
d
Calcium
200
Ca-49
8.42
m
Cerium
1
Ce-141
32.38
d
Cesium
0.02
Cs-134
754.24
d
Chlorine
0.1
Cl-38
37.3
m
Chromium
10
Cr-51
27.7
d
Cobalt
0.045
Co-60
1925.23
d
Copper
0.01
Cu-66
5.1
m
Dysprosium
0.000002
Dy-165
2.33
h
Erbium
0.02
Er-171
7.52
h
Europium
0.000045
Eu-152
4923.57
d
Gadolinium
0.1
Gd-153
241.6
d
Gallium
0.02
Ga-72
14.1
h
Germanium
0.0025
Ge-75
1.38
h
Gold
0.01
Au-198
2.7
d
Hafnium
0.35
Hf-181
42.5
d
Indium
0.00025
In-114m
49.5
d
Iodine
0.05
I-128
24.99
m
Iridium
0.001
Ir-192
74.02
d
Iron
500
Fe-59
45.1
d
Lanthanum
0.02
La-140
1.68
d
Lutetium
0.00045
Lu-177
6.71
d
Magnesium
2.5
Mg-27
9.46
m
Manganese
0.00025
Mn-56
2.58
h
Mercury
0.1
Hg-203
46.59
d
Molybdenum
0.5
Tc-99m
2.76
d
Neodymium
1
Nd-147
11.06
d
Nickel
0.2
Ni-65
2.52
h
Niobium
5
Nb-94m
6.29
m
Osmium
0.2
Ir-191m
15.4
d
Palladium
0.01
Pd-109m
4.69
m
Platinum
0.2
Pt-191
2.96
d
Potassium
0.1
K-42
12.36
h
Praseodymium
0.005
Pr-142
19.13
h
Rhenium
0.002
Re-186
3.78
d
Rubidium
2
Rb-86
18.6
d
Ruthenium
0.1
Ru-103
39.35
d
Samarium
0.0045
Sm-153
1.95
d
Scandium
0.1
Sc-46
83.85
d
Selenium
1
Se-75
120.4
d
Silver
0.005
Ag-110m
249.9
d
Sodium
0.02
Na-24
15.03
h
Strontium
0.045
Sr-85
64.73
d
Tantalum
0.45
Ta-182
115
d
Tellurium
0.5
I-131
8.04
d
Terbium
0.25
Tb-160
72.1
d
Thorium
0.35
Pa-233
27.4
d
Thulium
0.1
Tm-170
128.6
d
Tin
1
Sn-113
115.1
d
Titanium
0.05
Ti-51
5.79
m
Tungsten
0.01
W-187
23.9
h
Uranium
0.02
Np-239
2.36
d
Vanadium
0.005
V-52
3.75
m
Ytterbium
0.02
Yb-175
4.19
d
Zinc
1
Zn-65
243.8
d
Zirconium
10
Zr-95
64.6
d

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Sample Preparation Instructions

This provides guidelines for preparing samples for routine irradiation at the Reed Reactor Facility. To request and schedule NAA for these samples, please fill out and submit this form.

Equipment which may be needed

  • 5/8 dram polyethylene vials (called small inner vials in this procedure)
  • 2 dram polyethylene vials (called large outer vials in this procedure)
  • ethanol, methanol, or other cleaning agent approved by the director
  • disposable gloves
  • plastic tweezers to hold the vials
  • a diamond scribe
  • a permanent ink marker
  • soldering gun (which has never been used on metal) to heat seal polyethylene vials
  • micro-pipette and appropriate sized tips (for liquid samples)
  • large Kim-Wipes or equivalent
  • High precision balance
  • Western Family brand sandwich bags
  • other containers approved by the director

The following materials need special approval before irradiation

  • samples containing elemental mercury, or substances where mercury is a major component
  • material 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 Cd, In, and B. 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.

Cleaning Sample Vials

Note: If measurement of the mass is necessary for your experiment, clean the vials at least one hour before preparing your samples. The samples and inner polyvials should be handled with clean plastic tweezers, gloves, and other similar clean surfaces to ensure that samples are not contaminated by material on hands, metal tweezers, or other elements from the environment.

For trace analysis all work should be performed in a laminar flow hood if it is available. Turn on the hood about 20 minutes before starting work. Clean a beaker of at least 400 mL capacity. Rinse the beaker at least twice with the purest water available and with pure ethanol, then fill it about half full with pure ethanol. Methanol and acetone are both acceptable substitutes for ethanol. Place a Kim-Wipe down on your work surface; be careful not to touch the side that is face up. Clean all of your plastic vials and pipette tips by immersing them in batches into the ethanol in the beaker. Also clean the gripping end of a pair of plastic tongs. Using the clean plastic tongs, agitate the vials. They should soak for a minimum of thirty seconds. Do not leave the vials immersed for long periods of time since they will discolor.

Remove the vials and pipette tips one at a time with the tongs. Allow the excess ethanol to drip back into the beaker. Place the vials and pipette tips on the clean Kim-Wipe. Wash your other tools at this time. If at any time the ethanol becomes visibly dirty dispose of it and use fresh ethanol. Allow the vials to air dry for at least an hour before weighing. Pipette tips may take longer.

Notes about sample containers
Only materials which have been tested in the reactor can be used to hold your samples. Usually you will be provided with high purity polyethylene vials. Do not use polyvinyl chloride (PVC) vials; chlorine activates very well and so vials made of PVC become highly radioactive. If you wish to use any other material (including plastic bags) you may arrange to have it tested first. At the time of this writing only Western Family brand sandwich bags are tested as safe for use in the reactor. Many plastics are made by metal catalysis and some have enough metal in them to become quite radioactive.

Preparing Your Work Area

It is very important to avoid contamination of samples and standards with anything that you don't want to measure. Dirt, dust, and fingerprints all will contaminate a sample. A clean work area helps prevent contamination. It should be cleaned at the time you use it. Do not assume that anything is clean. Clean all non paper surfaces and tools with alcohol (ethanol or methanol). Wear disposable gloves while cleaning to avoid spreading salt from your fingerprints around your work space and onto your tools. Avoid working on metal surfaces or surfaces painted with paints that are dissolved by alcohol or water. Clean absorbent paper, clean plastic, clean Formica or resin top tables are the best work surfaces. Absorbent paper can be changed quickly if you spill something. Change your gloves frequently. If you rub your nose or scratch your head it's time to change your gloves.

Weighing And Sealing the Sample

Weighing is not required if the irradiation is designed only to determine content, not concentration. Do not use the balance unless you have been shown how previously. Wear gloves while you handle the vials; do not use metal tools unless they are coated with plastic. Weigh the cleaned empty small inner vial and record its weight. Fill the small vial about 3/4 full with sample material and close it. Do not spill sample on the outside of the vial. If you spill any, wash the outside of the vial with alcohol and let it dry before proceeding. Do not clip the tabs yet! Now weigh the vial with the sample in it; record that weight. Clip the tabs from the vial. If you have a diamond scribe, etch a sample number on the vial. Do not use ink! If the sample is liquid, seal the small vial with a clean soldering iron. A clean soldering iron is one which has not been used on anything other than plastic vials. Soldering should occur under a functioning hood, since inhaling burning plastic is both unpleasant and unhealthy.

After sealing, rinse the outside of the small inner vial with ethanol and allow it to air dry. Rinse the large outer polyvial with ethanol and allow it to dry. Place the inner vial inside the outer vial, close the lid, and label the outer vial with a permanent marker. Labels should include the experimenter's initials and institution. For example, sample #1 from John Peter Doe at Portland State University should be labeled PSUJPD1. Set it aside in a clean place. The outer vial need not be washed on the outside if the sample will be transferred after irradiation, and may likewise be handled with bare hands. Nevertheless, keeping the outer vial clean is desirable in minimizing contamination after irradiation. If double encapsulation is necessary, heat seal the outer vial. When in doubt, seal the outer vial, but unless sealing is required by procedure, it unnecessarily forces the person transferring the samples to handle them for a longer period of time.

If the sample will not fit in the small inner vial, seal it in the outer vial, following the weighing procedure described above. The outer vial should be sealed. If desired, Western Family brand sandwhich bags may be sealed around the outer vial to prevent leaking. Samples which will not fit into an large vial shall be discussed with the director before irradiation.

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