Radiation Basics. Dr. Finis H. Southworth

Transcription

1 Radiation Basics Dr. Finis H. Southworth

2 8 November 1895 A Brief History Dr. Wilhelm Roentgen discovers phenomenon Passing cathode rays through tubes, and noticed tubes fluoresced Theorized and proved existence of X-rays Two weeks later 1896 Took image of wife s hand An x-ray department established at the Glasgow Royal Infirmary the first x-ray of a kidney stone; an x-ray showing a penny in the throat of a child an image of a frog's legs in motion use an x-ray to make a diagnosis - he discovered a needle embedded in a woman's hand x-rays were used to treat soldiers fighting in the Boar war and in WWI, finding bone fractures and imbedded bullets. Excitement surrounded the new technology, and x-ray machines started to appear as a wondrous curiosity in theatrical shows. 2 MAR Review 16 May 2011

3 History 1905-Eistein s Theory of Relativity The Radium Girls Using radioactive element to paint glow-in-the-dark clock and watch dials Told paint was harmless Licked paintbrushes to sharpen them Painted their nails and even their teeth Ingested massive quantities Many became ill, some died from the poisoning 1926 Muller Demonstrated mutations in fruit flies with x-rays Gofman-Linear, No Threshold model Initially rejected, then largely adopted Assumes some statistical risk associated with any exposure

4 Hormesis Theory History It has been impossible to prove a linear relationship between dose and biological effects, particularly when evaluating chronic exposure Some studies have led to theory that chronic exposure may stimulate the immune system and drive better health

5 Definitions Matter is defined as the substance of which a physical object is composed, or a material substance that occupies space, and has mass. All matter such as trees, rocks, air, and water is composed of tiny particles called atoms. Atoms with too much energy in their nuclei are said to be radioactive. They get rid of their excess energy by emitting radiation.

6 Definitions Ionizing Radiation Emission of subatomic particles or energy in the form or rays or waves, which have adequate energy to create ions (charged particles). Radioactive Anything which emits radiation Contamination Radioactive material anywhere it is not desired. It may be loose or physically entrained in a substance. Irradiation Irradiation is the process by which an object is exposed to radiation. The exposure can originate from various sources, including natural sources. Most frequently the term refers to ionizing radiation, and to a level of radiation that will serve a specific purpose, rather than radiation exposure to normal levels of background radiation. The term irradiation usually excludes the exposure to non-ionizing radiation, such as microwaves from cellular phones or electromagnetic waves emitted by radio and TV receivers and power supplies. Something that has been irradiated is not necessarily contaminated.

7 The Energy Spectrum

8 Types of Ionizing Radiation Alpha (α) - 4 AMUs in size,2 protons, 2 neutrons, +2 charge Gives up energy quickly Travels a few centimeters in air Won t penetrate dead skin cells; no external hazard Greatest internal hazard Beta (β) - an electron, 1/1836 th of an AMU in size, -1 charge Travels a few feet in air Stopped by thin layers of plastic, water or hydrogenous material Hazard to skin and lens of eye Gamma (γ) Pure energy (photons like x-rays); No mass; No charge Virtually infinite path May deposit energy at any depth of body Shielded by high density materials like lead Neutron ( 0 n 1 )- 1 AMU in size; No charge; Essentially a proton and electron A product of the fission process Shielded by boron, cadmium A whole body exposure hazard

9 Penetrating Ability of Radiation Types

10 Sources of Radiation In Day to Day Living Average Annual Millirem Dose Dental x-rays Rocks and soil 28 Medical x-rays 39 Salt substitute 44 Radon 200 Coleman lantern mantle 400 Cigarette (1/2 pack/day) 8,000 Porcelain in false teeth 60,000

11 Sources of Radiation

12 The Earth and Radiation

13 Natural Radiation

14 Biological Hazards Chronic exposure Low doses over a long period of time Includes exposure from nature and occupational exposure Difficult to demonstrate biological effects Delayed effects Cancer Tumors Cataracts Acute exposure High doses in a short period time Radiation Sickness syndrome (Prompt Effects) Can predict biological symptoms for given exposure ranges

15 Acute Radiation Syndrome

16 Statistical Risks Estimated loss of Life Expectancy From Health Risks It is useful to compare the estimated average number of days of life lost from occupational exposure to radiation with the number of days lost to other events. Health Risk Smoking 20 cigarettes a day Overweight (by 15 %) Alcohol Consumption (U.S. Average) All accidents combined Motor vehicle accidents Home accidents Drowning All natural hazards (earth quakes, lightning, flood, etc.) Medical Radiation Occupational Exposure to Radiation Estimated Loss of Life Expectancy 207 days 74 days 24 days 6 years 2 years 1 year 1 year 7 days 6 days 0.3 rem/y from age 18 to days 1 rem/y from age 18 to days Cohen, B.L. and L.S. Lee; A Catalogue of Risks Extended and Updated, Health Physics, Vol 61, September 1991 (In: Regulatory Guide 8.29 Risks Associated with Occupational Exposure to Radiation).

17 Loss of Life Expectancy from Industrial Accidents Estimated Loss of Life Expectancy From Industrial Accidents Industry Type Estimated Days of Life Expectancy Lost All industries 60 Agriculture 320 Construction 227 Mining and Quarrying 167 Transportation and Public Utilities 160 Government 60 Manufacturing 40 Trade 27 Services 27 Inserted For Comparison Occupational Exposure to Radiation 0.3 rem/y from age 18 to rem/y from age 18 to Cohen, B.L. and L.S. Lee; A Catalogue of Risks Extended and Updated, Health Physics, Vol 61, September 1991 (In: Regulatory Guide 8.29 Risks Associated with Occupational Exposure to Radiation).

18 ALARA & Regulations As Low As Reasonably Achievable Regulations regarding occupational exposure to ionizing radiation are built upon the premise that exposure should be maintained as low as reasonably achievable given all factors. 3 Means of Exposure Reduction Time-Minimize time in area of source Distance-Maximize distance from source. Point source strength decreases with the square of the distance. Shielding 10 CFR 19 `Federal Regulation-This regulation requires that personnel engaged in the conduct of licensed radiological activities receive specific training to ensure their safety and recognition of the facts regarding the work. 10 CFR 20 Federal Regulation-This regulation governs the reporting and control of occupational exposure of personnel to ionizing radiation. 10 CFR 49 Federal Regulation-This regulation governs the transportation of radioactive material within the U.S.

19 Summary»As with many things, radiation in excess can be harmful.»the proper use and handling of radioactive materials can provide socio-economic benefits and improved health care.