Applications of Nuclear Science I PAN 2015 Dr. Robert McTaggart South Dakota State University July 29, 2015

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

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.

Isotopes of Interest Iodine-131 (8 days) Arthritis 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)

Radiation Therapy Alpha Therapy Brachytherapy Neutron Capture 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

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

Gamma Sterilization Cobalt-60 (5.27 years) Cesium-137 (30 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

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.

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!

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

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.

Elements accessible to neutron activation http://serc.carleton.edu/research_education/geochemsheets/techniques/INAA.html

Let short-lived isotopes decay Sample Preparation Irradiation Let short-lived isotopes decay Counting of Nuclear Decays Data Analysis

Counting Irradiation Delay Counting Activity Time 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.

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 radiation’s 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.

Neutron Activation Analysis examines many elements at once

Sample NAA spectrum

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

Naturally Occurring Radioactive Materials (NORMs): No activation necessary

Medical Physics Radiation Therapy

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

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

Why use protons in therapy?

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.

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

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