Types of Radiation Detection and Biological Effects HalfLife

Types of Radiation, Detection and Biological Effects

Half-Life Equation • As a class, come up with a working half-life equation. • Activity final = Activity initial (1/2) time passed/half-life

Presentation and Debate Teams • Tyler/Patrick – Con side in debate • Aaron/Jason – Pro side in debate • Danielle/Tim – Pro side in debate • Jessica/Josh – Con side in debate • Nick/Raquel – Con side in debate • Kristin/Cortney – Pro side in debate • Sean B. /Zack – Pro side in debate • Cameron/Sean P. – Con side in debate

Presentation and Debate Team Feedback Form • Pros/Cons Feedback Form • Presenting Team ______ Date ____ • Time __ Research __ Materials __ Pros/Cons __ • I really liked ____ about your presentation. – (One copy to the team and one to the instructor) • Debate Feedback Form • Debate Teams ______ Date ____ • Convincing _ Research _ Presenting _ Debate _ • I really liked ______ when you debated your point. • (One copy to the team and one to the instructor)

GLE • Review the different types of radiation • Describe penetrating abilities and detection of each • Define Roentgen, RAD, and REM. Objective • Student will characterize alpha, beta, positron, neutron, and gamma radiation in terms of composition and penetrating power. Students will use a Geigercounter to detect and measure background radiation. Student will describe three methods of detection and units of measure, especially units that relate to biological damage.

Radioactivity • In nuclear reactions, the nuclei of unstable isotopes, called radioisotopes, gain stability by undergoing changes accompanied by the emission of large amounts of energy. • The process by which materials give off such energy, in the form of waves (rays), is called radioactivity. • Waves and particles emitted are called radiation.

Different Types of Radiation • Beta – an electron ejected from or captured by the nucleus. • Positron – positively charged particle of same mass as an electron ejected from the nucleus • Neutron – particle given off during fission process • Alpha – Helium (He) nucleus with no electrons • Gamma – High energy wave (no mass/no charge).

Ionizing Radiation • Ionizing radiation is radiation with enough energy to knock electrons off some atoms of the bombarded substance to produce ions. • One such device, a Geiger-counter, uses a gas-filled metal tube to detect radiation. – Geiger-counters are used primarily to detect beta/positron and gamma radiation.

– – Ionizing Radiation Ionizing radiation penetrates a thin window at end of detector Gas becomes ionized, free electrons are produced Each time this occurs, current flows Current flows drive a counter or cause and audible “click”

Neutron Detectors • The fast neutrons from fission are slowed down (thermalized) by the material that surrounds the detector. • The thermal neutrons then interact with a material in the detector tube that has a high cross section for absorption. • After the neutron is captured, free electrons are given off • The gas becomes a conductor and causes current flow through the detector • The current drives a counter or causes an audible “click”.

Alpha Radiation • A scintillation counter uses a specially coated phosphor surface to detect radiation • Ionizing radiation striking the phosphor surface causes flashes of light • The number of flashes are detected electronically, converted into electronic pulses, then measured and recorded. Similar to what takes place inside some television tubes that are coated with phosphor on the inside.

Film Badges and Dosimeters • Film badges consist of several layers of photographic film which darken when exposed to radiation – Workers wear the badges the entire time at work, the badges are “developed” at regular intervals to monitor the worker’s exposure to ionizing radiation • Dosimeters are hand held devices that are designed for short duration use only. They consist of a filament that has been charged and is calibrated such that at full charge the dosimeter indicates zero exposure. As the worker is exposed to ionizing radiation the charge in the dosimeter is reduced and the filament moves across a scale indicating how much ionizing radiation has been received by the worker.

Let’s Go Outside • Use the Geiger-counter inside and outside • Put a table on a piece of paper to record number of clicks per minute and max meter reading Clicks per Minute Inside Outside Max Meter Reading

Geiger - Counters • Was there any difference between inside and outside – Why might there be more ionizing radiation outside? • The unit of measure on the Geiger-counter measures ionizing radiation in m. REM/hr – REM is an acronym for Roentgen Equivalent Man • Terms for measuring radiation dose rate are RAD, Roentgen, and REM

Roentgen, RAD, and REM • Roentgen – Measure of the strength of the radiation field with regard to the ionization of the molecules in a mass of air. – Best suited for the ability to directly measure on a meter. • RAD (Radiation Absorbed Dose) – Amount of energy that ionizing radiation imparts to a given mass of matter (not air) – It is not specific for living tissue alone, but for a given mass of any matter – SI Unit – Gray, where 1 Gray = 100 RADs • REM (Roentgen Equivalent in Man) – Takes into consideration interaction with living tissue and the fact that some types of radiation cause more damage to living tissue than others – SI Unit - Sievert

REM Dose Comparisons • • • • Common Radiation Exposures vs. Exposures in Radiation Events Common medical and natural background sources of radiation Approximate dose in rem Chest x-ray up to 0. 03 Average annual dose from cosmic radiation to people living in Rocky Mountain States 0. 06 - 0. 08 Average annual dose from cosmic radiation to flight crew members 0. 16 Average annual dose from exposure to natural sources of ionizing radiation to the US population (e. g. , radon, cosmic rays) 0. 2 - 0. 3 CAT scan (whole body) 1 Recommended annual occupational exposure limit, excluding personal medical exposures and exposures from natural sources up to 5 rem per year Adverse health effects from higher dose exposures, including those possibly found after radiation events Approximate dose in rem No symptoms 15 No symptoms of illness; minor and temporary drop in counts of white blood cells and platelets 50 Possible Acute Radiation Syndrome; 10% of exposed individuals may have nausea/vomiting within 48 hours and a mild drop in blood counts 100 50% of exposed individuals will die within 30 days in the absence of appropriate medical care (LD 50/30) 300 - 400

Homework • WORK ON YOUR PRESENTATIONS/DEBATES • Page 844, # 2 and Page 861, # 19.