Reactor Facility Uses

Research reactors have broad range of uses. The International Agency for Atomic Energy has a somewhat techncial online guide to use of research reactors.  The following infomration identifies the basic principles underlying technciques that have been used at the K-State reactor, how the techniques are applied to real-wrold problems, typical examples, and how K-State has supported research, experimental and industrial efforts with the techniques.

Radiosotope Production

The fission process releases neutrons; a fraction of the neutrons end up being absorbed in fuel to cause more fissions, and the remaining neutrons are absorbed in other materials, including

Many materials become radioactive when they absorb neutrons.  The International Agency for Atomic Energy has a somewhat techncial online guide to production and use of radioisotopes.  Radioisotope radiation has properties that make it useful in research and industrial applications:

Typical uses for radioactive materials include (please note that this is not a complete list):

• Gauging generally commpares the amount of radiation that moves into a volume or surface to the radiation after it leaves. 

The incoming radiation compared to the exiting radiation is a direct measure of the amount and/or type of material. If material density is known, this comparison can measure thickness.  If the thickness or volume is known, this comparison can measure density (e.g., mass density or moisture content).  If the material is a mixture, this comparison can measure mixture homogeniety or the location of surfaces between the individual components.

Sometmies it is not possible to measure how much radiation is transmitted through a material; incoming radiation is compared to the radiation reflected. The information that can be obtianed is similar.

    Typical examples of gauging with radiation:

• Tracing measures radiation coming from radioactive materials. 

If the radioactive materials are moving, then flow can be measured.  If the radioactive materials are part of a process (mechanical or biological), the amount of material transferred in the process can be measured.

       Typical exampled of tracing with radiation inlcude:

1. Locating natural gas leaks
2. Locating obstructions in pipes
3. Measuring flows of liquids & gasses
4. Measuring processes in refnieries
5. Measuring chemical separations
6. Measuring uptakes of specific elements

• Portable radiography sources

Industrial radiography at remote locations can be performed using radioative materials such as ¹⁹²Iridium and ⁶⁰Cobalt generated at research reactors.

Radioistotope-Production Projects at K-State

Experiments were performed to evaluate how well a special material removes contamination from water.  The target contaminantion (that should be removed by the mateiral) was made with an element that was made radioactive.  The target contaminaiton was introduced into the cleanup apparatus.  Radiation readings at the inlet and outlet indicate how well the cleanup material performed.

A laboratory at another university developed a resin bed column instrumented with radiation detectors.  The instruments triangulate to determine the position of radioactive particles suspended in water flowing through the column.  The K-State reactor provided nearly microscopic particles.

A company is interested in reducing the hazard level in spent ligts.  The company worked with the K-State reactor to identify a process that "labeled" the hazardous component by making it radioactive.  The company is implementing instrumentation to allow precisely locating the material as it plates out during operation.  Different manufacturing processes can then be used to vary type of materials that contribute to plate-out and the concentration of the material.  The lights will be operated to cause plate-out of the radioactive materials; the instrumentation will be used to detemine the amoutn and distribution of material plated.

A student performed an experiment to evaluate water-uptake time constants for plants.  A component of soluble fertilizer was made radioactive.  Various types of plants were supplied wiht the fertilizer solution.  The leaves of the plant were periodically monitored to determine how quickly the material reached the plant leaves.

Neutron Activation Analysis

As noted above, neutron activation analysis (NAA) begins by making samples radioactive.  The energy of the radiation emitted from elements made radioative (or radioisotopes) provides a kind of fingerprint, allowing the radiosotope (consequently, the element that was made radioative) to be identified, with the amount of the radiation at that energy direclty related to the amount of the element in the sample.  Note that this analysis determines elements and (in absence of additional information) is not useful for molecules. The International Agency for Atomic Energy has a somewhat techncial online guide to the applications of neutron activation analysis. 

NAA Lab Facilities		NAA in Progress

The samples are typically a small fraction of a gram.  The material properties of the samples are not changed by the process, permitting multiple or alternate analysis applications.  NAA is generally very sensitive, detecting concentrations as low as fractions of parts per million.  The analysis is generally best for heavier elements like metals, and not useful for light elements such as hydrogen, carbon, and boron.  The process can be combined with chemistry to enhance sensitivity by removing elements if they have some kind of interference, but generally does not require any processing or treatment.  Since all of the elements in the sample are being exposed to radiation, the analysis can provide simoltaneous infomration about multiple elements.

The process is usually applied in trace element analysis generally to get information of provenance (origins), processes, contamination, and composition in the fields like:

Neutron Activation Analysis Projects Projects at K-State

This is not a comprehensive list, but somewhat illustrates the breadth of research that can be supported by neutron activation analysis.

• Trace elements introduced in processing aluminum-nitride (a candidate for semi-conductor materials)
• Drilling fluid uptake in a marine environment
•  Stream water, sediment, and plant life analysis of metals, and identification of the point of entry
•  Seashells used by American Indians in trade and commerce to determin trade routes
• Sulfur content in coal prior to use in a power plant
• Trace elements in rat diet based on elements identified in rat bones
• Carbohydrate content of grains (NAA only detects elements, this was an indirect measurement, using specific elements as indicators of carbohydrate content)
• Forensics analysis of sawed-off shotgun used in a murder, linked to metal filings in a suspect's home
• Identification of origin for a set of moths from capture traps; a set was grown in a hot-house on a diet rich in rare earth elements
• Poultry grown on a small farm was compared to poultry grown on a "factory farm"
• Characterization of Chert (geologic processes convert Chert to flint) at locations mined by native Americans
• Charge transport in DNA using ionic bromide as a primary indicator
• Detecting cancer in animals using serum copper levels as an indicator
• Detectnig cancer in humans using serum copper levels
• Tree nutrition and ferilizer studies
• Trace elements in food/turkey muscle
• Evaluation of lantanide and rare eath elements as markers for rate of passage of feedstuffs
• Toxicology studies
• Study of uranium and thorium in Morrocan ores
• Determination of heavy elements and pathfinder elements in soil
• Determination of trace elements in thermoluminescent dosimeter materials
• Analysis of surface resdidues on metal parts after metallurical treatment
• Affects of weathering on trace element composition for mineral samples
• Trace element characterization of volcanic rocks
• Provenance of California mountain range
• Enviromental conditions for geologic formations

Neutron Radiography

The nucleus of an atom is about 1/1000^th of the volume occupied by the atom, with most of the volume defined by the electron cloud.  Electrons are charged, and their movement generates a substantial electric field; electromagnetic radiation (gamma rays, x-rays) interacts with that field.  X-ray images show light spots where the electron (and therefore atom) density is high; atom density increases with atomic number.  Therefore, image contrast strictly shows variations in mass density.

Brass, Steel & Cadmium Strip		Neutron Radiograph Image (1/2 inch diameter view)

 Neutrons interact mainly with the nucleus of the atom.  An interaction between nucleus and neutron does not depend much on electric fields, but mostly involve momentum and energy exchanges that depend on the energy structure of the nucleus.  The nuclear energy structure is very complex, and the interaction probabilities can vary orders of magnitude between sequential atomic numbers.  Neutron based images therefore depend not only on nuclei density, but also the type of nuclei.  Image contrast shows a combination of nuclear density and the distribution of different types of elements.  Contrast of structures can be improved by loading elements with large interaction probabilities in the structure.

The K-State reactor has capabilities for neutron radiography using film, with a 13X17 in² film cassette and a 5X7 in² film cassette, as well as a neutron camera with a high-resolution (50 µm), small field of view (1/2 inch diameter) mode and a conventional resolution (0.1 mm) mode.

Neutron Radiography Projects at K-State

Current K-State efforts are based on

• Defining system capabilities,
• Developing a set of sample images showing the kinds of information available from the system,
• Developing the use of contrast agents in detecting material flaws
  
  

Radiation Detector Testing & Calibration

 In general, radiation detectors work when radiation increases the energy of electrons enough to free them from atoms in a gas or loosely bound states in a crystal.  An electrical signal is generated by electron movement towards the positive voltage (applied across the detector).  The signal can vary based on the age or condition of the detector and electronics, and the applied voltage. 

 National standards require periodic calibration checks for radiation detectors used to check doses for radiation workers.  Calibration involves exposing the detector to a known radiation field and comparing the reading to the known condition (count rate or dose rate).

 The K-State reactor facilities include radiation sources “traceable” to the national bureau of standards.  The sources include a

• TECH STANDARD source with a set of shields that provide a wide range of dose rates.
• Panoramic irradiator for calibrating personal monitoring devices
• Californium 252 “D20 Calibrator” for calibrating neutron dose rate meters

In addition, extracted neutron beams are used to test response of detectors that are being developed in conjunction with research projects

• Thermal and/or fast neutron beams to test and calibrate neutron detectors
• Iron filter for delivering 24 keV neutrons to test and calibrate low energy neutrino detectors
• Fast neutron beam to test and calibrate high energy neutrino detectors

Radiation Detector Calibration at K-State

• The radiation detectors used at the K-State reactor are calibrated as required by the Reactor Radiation Protection Program
• The reactor calibration facilities support detector calibraition required by the Kansas State Unviersity radiation protection program for laboratories and research centers at K-State
• Neutron detector calibration is perofromed for other research reactors

Radiation Detector Testing at K-State

• The University of Chicago (Enrico Fermi Institute) is developing new conceptes in neutrino detection
• The K-State SMART labs performs testing of a wide variety of new types of neutron detectors at the reactor facilities
• The K-State Radiation Measurement Application Laboratory uses the facility in testing and calibration of concepts to use radiation detectors to detect car-bombs
  
  

Gamma Irradiation

 Materials, electronic components, and biological specimen are exposed to gamma radiation fields for various purposes.  K-State has a small number of radioactive sources that can be used for some exposures, sample size, sampled configuration, and maximum total dose is limited.  

 An alterative exposure facility is under construction.  The reactor is operated to build in radioactive fission products, then the reactor is shutdown.  A short period of time after shutdown, the neutron flux is essentially background.  Samples occupying a volume up to 5 gallons are placed next to reflector; the sample is moved up and down while rotating to ensure a uniform dose across the volume for the time required to accumulate the desired total dose.

Gamma Irradiation Projects at K-State

• Spleen samples used in biological research, exposed to limit the growth of bacterial contamination
• Failure analysis of power plant sensors and transmitters
  
  

Fast Neutron Irradiation

 Cosmic radiation causes a small terrestrial neutron background.  Neutron exposure to materials and instruments in nuclear power plants can be extreme.  Changes in material properties occur with neutron exposure, and the changes can be beneficial or detrimental.  A basic understanding of the changes enables the benefits to be used or compensation for the detrimental effects (either in engineering resistant materials or in sensitive applications).  Material and solid state samples are subjected to known doses of fast neutrons to correlate doses to property changes, damage, and defects.

 One of the beam ports penetrates the reflector, providing access to high concentrations of high energy neutrons.  The thermal neutron component is minimized by a cadmium liner surrounding the irradiation volume.

Fast Neutron Irradiation Projects at K-State

• Characterization of fast neutron spectrum
• GaAs treatment