Nuclear Science Merit Badge: http://fresnobeehive.com/news/Nuclear%20plant.JPG Radiation Health & Safety

Radiation http://www.med.yale.edu/library/exhibits/curie/hand.html http://livefromcern.web.cern.ch/livefromcern/antimatter/history/historypictures/e+e-event.jpg

Learning Objectives Types of Radiation Consequences of exposure to radiation Uses in the medical field Radiation containment

What is Radiation? Radiation is the process in which energetic particles or waves travel through a medium or space. Generally refers to electromagnetic (EM) radiation (charged particles) Examples: Sunlight, Microwaves, Sound waves (non-EM)

Types of EM Radiation Non-Ionizing Ionizing Radio waves Visible light Microwaves Ionizing X-rays Gamma rays http://www.stevesportfolio.co.uk/work/easy_gcse/img/diagrams/Electromagnetic-Spectrum.png

Ionizing Radiation Ionization is caused when an electron is added to or removed from an atom. Ionizing radiation is radiation that has sufficient energy to strip electrons from atoms, thus making them ions. The remaining positively charged atom and the free electron are called “ion pairs.”

Ionizing Radiation An X-ray is a type of ionizing radiation that has a wavelength in the range of 0.01 to 10 nanometers. A Gamma ray is a type of ionizing radiation that has higher energy than X-rays and has a wavelength less than .01 nanometers. Concrete or lead are needed to shield against these radiations

Electroscope http://www.mikeconrady.com/Documents/electroscope1.bmp http://www.mikeconrady.com/Documents/electroscope1a.bmp

History Behind Radiation X-rays were first discovered by Wilhelm Roentgen in 1895. He noticed how the rays could pass through some materials and not others. The rays could be detected using a photographic plate

History Behind Radiation Henri Becquerel discovered that uranium caused a photographic plate to be fogged, just like X-rays. In 1898, Marie Curie gave this property the name radioactivity. Radioactivity is the tendency of an element to give off charged particles or rays (i.e., to emit energy).

Charged Particles Two charged particles that are emitted by a radioactive element are Alpha (α) particles Beta (β) particles http://en.wikipedia.org/wiki/File:Alphadecay.jpg 11

Charged Particles An alpha particle has two protons and two neutrons Same as He2+ Mass: 4 AMU No electrons! http://en.wikipedia.org/wiki/File:Alphadecay.jpg 12

Charged Particles A beta particle is an electron or a positron. Electron charge: -1 e Positron charge: +1 e http://en.wikipedia.org/wiki/File:Alphadecay.jpg

Cloud Chamber A cloud chamber can be used to track the path of electrically charged particles. When a magnetic field is applied it is able to identify the charge and velocity of the particle. Cloud Chamber Video

Radioisotopes Isotopes of an atom that are radioactive are called radioisotopes. These atoms are radioactive because they have too much energy to be stable; they will release energy until they become stable. This is called radioactive decay. The modern words are “spontaneous nuclear transformation.”

Radioactive Decay In the process of radioactive decay, an atom actually changes from one element to another by changing its number of protons. The half-life of a radioactive substance is the amount of time required for it to lose one half of its radioactivity and transform into another element.

Activity Time!! Let’s demonstrate half-life using a piece of paper!

Radioactive Decay Radioactivity (or “activity”) is measured in units of: “curie” Ci Defined as 3.7 x 1010 decays per second The traditional unit “becquerel”. Bq Defined as 1 decay per second The SI unit

Types of Radioactive Decay Alpha decay Nucleus emits an α particle Loses 2 protons, 2 neutrons Beta decay Nucleus emits a β particle Converts a neutron into a proton and an electron (i.e., the beta particle)

Examples Half life = 5.2 years Half life = 4,468,000,000 years colbolt-60 that is used in cancer therapy, decays to nickel-60 with loss of a β particle. Half life = 4,468,000,000 years radioactive decay of Uranium-238 by alpha emission.

Radiation Hazards and Safeguards http://www.sas.org/E-Bulletin/2003-05-23/features/art/classroomGeiger.jpg http://www.uchsc.edu/safety/Images/RadiationSymbol.gif http://www.nrc.gov/images/reading-rm/basic-ref/glossary/cosmic-radiation.gif

The International Radiation Symbol The international radiation symbol (also known as trefoil) first appeared in 1946, at the University of California, Berkeley Radiation Laboratory. At the time, it was rendered as magenta with a blue background. The modern version is black against a yellow background

Why should ionizing radiation be controlled? Ionizing radiation can damage living tissue in the human body. It can create reactive molecules that are poisons in the body.

Acute (Deterministic) Radiation Effects Acute radiation symptoms are caused by high levels of radiation usually over a short period of time They cannot be predicted with certainty. Examples: erythema (redness of the skin) and epilation (hair loss)

Chronic (Stochastic) Radiation Effects Chronic radiation symptoms are caused by low-level radiation over a long period of time. Effects are based on probabilities. Exposure to low levels of radiation increase a person’s chances to get cancer.

Radiation Exposure Levels & Effects 0.62 rem/y – average annual radiation exposure in the U.S. 2 rem/y – international radiation exposure limit 5 rem/y – current US NRC radiation exposure limit 25 rem – measureable blood changes 100 rem – onset of radiation sickness

Radiation Exposure Levels & Effects 200 rem – radiation sickness with worse symptoms in less time 400 rem – approximately the lethal dose for 50% of the population in 30 days 1,000 rem – death probable within about 2 weeks, effects on the gastrointestinal tract 5,000 rem – death probable within 1-2 days, effects on the central nervous system

Nuclear Technologies http://blogs.phillyburbs.com/news/intelligencer/wp-content/blogs.dir/4/files/2009/March/Saturday/smokeDetector.jpg\ http://en.wikipedia.org/wiki/File:Flughafenkontrolle.jpg http://en.wikipedia.org/wiki/File:PET-image.jpg

Radiation in Medicine Radiology: X-ray imaging. Nuclear Medicine: Following radioactive tracers in the body. Radiation Therapy: for the treatment of cancer http://www.missouristate.edu/assets/HPER/rib_x-ray.jpg

Radiation Therapy External beam treatments Radionuclide (brachytherapy)

Radiation in Agriculture Radiation used to kill pests, preserve harvested crops. Helps detect level of pollution and fertilizer in crops. Delay sprouting and spoilage

Radiation in Industry Process control using radiation gauges Check for leaks in underground pipes. Control thickness of manufactured materials Americium 241-alpha emmiter http://www.gcsescience.com/Thickness-Control-Radioactivity.gif

Radiation in Security X-ray checks of baggage Whole-body scanners of passengers Smoke detectors in homes and offices

Radiation in Space Mars rovers Satellites International Space Station Deep-space Probes Radioisotope Thermoelectric Generators (RTG)

Radiation in Science Radiocarbon Dating – Carbon-14 Neutron activation - “Finding a needle in a haystack” Engine testing

Differences in dose types

Thought experiment Alpha particles do MUCH more biological damage with a given amount of dosage than gamma rays. Why?

Answer Gamma rays penetrate straight through virtually any material, including tissue, while alpha particles are easily stopped by thin barriers, including human skin. Alpha particles will thus deposit their energy into a human much more readily than gamma rays, resulting in more tissue damage.

Typical Radiation Detectors Film packet Thermoluminescent Dosimeter (TLD) Ionization chamber Geiger-Müller (GM) Detector Scintillation Detector

Radiation Kit

Thought experiment 2 How does distance effect the measurement of radiation? How does shielding effect the measurement of radiation? How does time effect the measurement of radiation?

Answer With increasing distance the radiation dose rate drops since the concentration of particles decreases

Answer #2 Shielding reduces the amount of radiation that reaches you, reducing the dose rate

Answer #3 A shorter time period doesn’t reduce the dose rate, however since you’re exposed to the source for less time you receive less dose.

Background Radiation Rocks and soil Cosmic radiation Solar radiation Background Radiation is radiation that is a natural part of our environment. Rocks and soil Cosmic radiation Solar radiation Radon gas Food and water From human made sources X-ray machines Other medical uses Tritium dial wristwatches Gas lantern mantles Smoke detectors

Radiation Regulations ALARA- As Low As Reasonably Achievable Time, Distance, and Shielding National and International limit – 5 rem/y (5000 mrem/y) Public limit – 100 mrem/y Radiation Hazard symbol Displayed at places where radioactive materials are used and stored. http://www.uchsc.edu/safety/Images/RadiationSymbol.gif

ALARA SCENARIOS

What we learned Types and effects of Radiation Uses of radiation Consequences of exposure Containment techniques