Applications of Nuclear Science I PAN 2015 Dr. Robert McTaggart
South Dakota State University July 29, 2015
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Outline Isotopes for Medicine Isotopes for Industry Gamma
Sterilization Food Irradiation Environmental Analyses Isotopes from
Fission NORMs Neutron Activation Analysis Medical Physics Radiation
Therapy Medical Imaging Health Physics
http://world-nuclear.org
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Isotopes for Medicine Radioisotopes can either be used for
localized radiation therapy, sterilization of equipment or fluids,
or as radiotracers that can be tracked by medical imaging Probably
the most ubiquitous of the medical isotopes is Technetium- 99m,
which is used in imaging the skeleton and the heart, but also in
many other studies They are typically produced by a nuclear
reactor, an accelerator, or a cyclotron.
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Isotopes of Interest Iodine-131 (8 days) Emits both gammas and
betas Primarily used in treating thyroid cancer since the thyroid
uptakes iodine. Also produced by fission Arthritis Erbium-169 (9.4
days) Dysprosium-165 (2 hours) Yttrium-90 (64 hours)
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Radiation Therapy Alpha Therapy Bismuth-213 (46 minutes), very
high gamma ray (8.4 MeV) Lead-212 (10.6 hours), melanoma, breast
cancer, ovarian cancer Brachytherapy Iodine-125 (60 days), prostate
and brain Palladium-103 (17 days), prostate Yttrium-90 (64 hours),
liver Copper-67 (2.6 days) Neutron Capture Therapy Boron-10
Gadolinium-157
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Medical studies Iron-59 (46 days), iron metabolism in the
spleen Sodium-24 (15 hours), electrolytes Technetium-99m (6 hours),
bone, heart, brain, lungs, etc. Xenon-133 (5 days), lung
ventilation Ytterbium-169 (32 days), cerebrospinal fluid
Chromium-51 (28 days), blood flow
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Gamma Sterilization Cobalt-60 (5.27 years) Higher energy gamma
rays (1.17, 1.33 MeV) Requires more shielding, but sterilizes the
entire volume in a shorter time Cesium-137 (30 years) Lower energy
gamma rays (0.662 MeV) Takes more time to deliver a dose Less
Shielding required Alternative: Electron Beam Irradiation Good for
irradiating surfaces only
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Medical Imaging Positron Emission Tomography Carbon-11,
Nitrogen-13, Oxygen-15, Fluorine-18 can be attached to sugars to
study brain behavior. Gallium-68 (68 minutes) A positron is
emitted, it annihilates with a nearby electron, and two gammas are
released back-to-back. Detectors based upon particle physics
register the gamma rays and determine where the gammas came
from.
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Carbon-14 and Hydrogen-3 Carbon-14 is a major research tool for
biology as a radiotracer. Carbon-14 dating is important for
archaeological studies. Tritium (Hydrogen-3) is used as a tracer in
drug development. Used copiously in Exit signs!
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By special request, Fe-55, 2.7 years Emits X-rays Used in space
missions for power-free source of X-rays to use in X-ray
Fluorescence for elemental composition. Analyzes electroplating
solutions, detects Sulphur content in the air. Also used in
metabolism research
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Neutron Activation Analysis Another method of isotopic analysis
that complements X-ray Fluorescence and Mass Spectrometry. Some
isotopes can absorb a neutron (i.e. it gets activated by becoming
radioactive) and emit a set of characteristic photons. The photons
are detected using a high purity germanium detector. Typically it
is the heavier metals that are useful in NAA.
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Elements accessible to neutron activation
http://serc.carleton.edu/research_education/geochemsheets/techniques/INAA.html
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Sample Preparation Irradiation Let short-lived isotopes decay
Counting of Nuclear Decays Data Analysis
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Counting Once the foil is removed, the isotope is no longer
produced and only undergoes decay. In general, there is an
irradiation time, a delay time between irradiation and counting,
and the actual counting time. The number of counted events is
related to the neutron flux. Irradiation Delay Counting Activity
Time
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Signal to noise Background events are produced by partially
captured gamma-rays from our source or from the environment. Some
of this cannot be helped, since the detector often contains only
part of the incoming radiations energy, not all of it. There is a
lower limit of detection based upon the count of a null sample and
the gaussian nature of the response from the detector.
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Neutron Activation Analysis examines many elements at once
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Sample NAA spectrum
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Examples of NAA Analysis of mercury, arsenic, or other metals
in hair or fingernails. Isotopic analyses for meteorites, volcanic
rocks, Native American pottery. Impurities in industrial and
agricultural products. Environmental analysis. Sulfur content in
coal prior to use in a power plant. Nutritional studies for plants,
animals, people. Forensics of metals in guns/bullets. Trace
elements in semi-conductors and photovoltaics. Assay of rare earth
metals in raw materials. Beneficial for areas that require
knowledge of composition and contamination.
http://reactor.engr.wisc.edu/naa/applic.htm
http://www.mne.ksu.edu/research/centers/reactor/uses
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Naturally Occurring Radioactive Materials (NORMs): No
activation necessary
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Medical Physics Radiation Therapy
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How do photon radiation beams interact with matter? Attenuation
of a photon beam by an absorbing material is caused by 5 major
processes in the energy ranges produced by medical linear
accelerators Coherent Scattering Photoelectric Effect* Compton
Effect* Pair Production* Photodisintegration
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Biological Basis of Radiation Therapy in a Nutshell Ionizing
radiation can induce detrimental biological effects in organs and
tissues by depositing energy that may damage DNA Rapidly
proliferating tissues are relatively radiosensitive
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Why use protons in therapy?
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Imaging with X-rays X-rays are scattered by elements with lots
of electrons. This produces a dark image for the negative. Bone
appears white because calcium has more electrons than tissue, which
is oxygen, hydrogen, and carbon.
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Imaging with neutrons (a reverse X-ray) Neutrons are absorbed
or scatter off of lighter Z materials, particular hydrogen. Carbon
and Boron also have high neutron cross sections. Metals have low
neutron cross sections, so one may use neutron radiography to image
organic material wrapped in metals. Metals prevent X-rays from
getting through, but not neutrons.
http://nucleus.iaea.org/RRDB/Content/Util
/NeutronRadioGraphy.aspx
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Health Physics The health physicist is dedicated to supporting
a safe working environment for radiation workers and the public.
Such efforts include Environmental Analyses of air/water/soil for
radionuclides Development of procedures for nuclear power
operations Construction of radiation shielding for medical physics
facilities Production and delivery of radioisotopes in nuclear
medicine Design and use of radiation detectors Emergency management
operations Studies of radiation biology Oversight of radiation
doses received by workers. Use of irradiation to sterilize medical
products
