2. Radiation

3. What makes something radioactive? The nucleus of an atom contains protons and neutrons The nucleus of an atom contains protons and neutrons They are packed together with a lot of repulsive charge They are packed together with a lot of repulsive charge –Opposites attract, same charges repel If atom has too few neutrons, positron emission occurs If atom has too few neutrons, positron emission occurs If atom has too many neutrons, beta emission occurs If atom has too many neutrons, beta emission occurs Another type of radioactive decay is loss of an  particle Another type of radioactive decay is loss of an  particle

4. Examples of Radioactive decay

5. Band of Stability Notice most elements are stable & elements possess a driving force to try to become stable Notice most elements are stable & elements possess a driving force to try to become stable

6. Radioactivity There are 114 or so elements & 340 isotopes of all the elements, only about 70 are radioactive There are 114 or so elements & 340 isotopes of all the elements, only about 70 are radioactive All isotopes with atomic numbers greater than 83 are radioactive All isotopes with atomic numbers greater than 83 are radioactive Most are not significant contributors to our overall radiation dose because of their low abundance Most are not significant contributors to our overall radiation dose because of their low abundance

7. Naturally occurring radiation Travel from Los Angeles to Paris on a conventional flight will result in additional 10 millirems of radiation Travel from Los Angeles to Paris on a conventional flight will result in additional 10 millirems of radiation 1. Cosmic radiation: At sea level average annual dose is 26 millirem a year 1. Cosmic radiation: At sea level average annual dose is 26 millirem a year

8. Naturally occurring radiation 2. Cosmogenic radiation: Most common is 14 C Contributes 1 millirem per year 2. Cosmogenic radiation: Most common is 14 C Contributes 1 millirem per year Nuclear reaction: Nuclear reaction: Carbon 14 has a half life of 5730 years & decays by beta emission

9. Half life What is a half life? What is a half life? –The amount of time for half of the remaining material to decay.

10. Half lives illustrated After 5730 years (1 half life) there is half a pie left After 5730 years (1 half life) there is half a pie left Imagine the pie is some radioactive carbon 14, originally there is one pie worth of carbon 14 Imagine the pie is some radioactive carbon 14, originally there is one pie worth of carbon 14

11. Half lives illustrated After 11,460 years (2 half lives) there is ¼ of a pie left After 11,460 years (2 half lives) there is ¼ of a pie left After 17,190 years, 1/8 of the pie is left After 17,190 years, 1/8 of the pie is left Notice the absolute amount of material that is lost gets smaller and smaller the greater # of half lives Notice the absolute amount of material that is lost gets smaller and smaller the greater # of half lives

12. Half lives If the pie illustrated here was all 14 C and it originally weighed 750 g, how many grams would be remaining after 22,920 years? If the pie illustrated here was all 14 C and it originally weighed 750 g, how many grams would be remaining after 22,920 years?

13. Naturally occurring radiation 3. Terrestrial radiation: Arises from radioisotopes whose half lives are comparable to the age of the earth, most comes from uranium series Annual dose 28 mrem externally & 240 mrem internally 3. Terrestrial radiation: Arises from radioisotopes whose half lives are comparable to the age of the earth, most comes from uranium series Annual dose 28 mrem externally & 240 mrem internally Radon gas is another important source here Radon gas is another important source here

14. Radon Enters buildings through dirt floors, cracks, floor drains, and from building materials like gypsum and stone fireplaces Enters buildings through dirt floors, cracks, floor drains, and from building materials like gypsum and stone fireplaces Small amounts are dissolved in groundwater and in natural gas supplies Small amounts are dissolved in groundwater and in natural gas supplies

15. Radon continued Radon isotopes have a fairly short half life but they decay to insoluble solids that can get deposited in lungs Radon isotopes have a fairly short half life but they decay to insoluble solids that can get deposited in lungs Radon is most problematic in tight, well sealed basements in the winter, little air flow Radon is most problematic in tight, well sealed basements in the winter, little air flow EPA estimates radon contributes 14,000 deaths per year from lung cancer EPA estimates radon contributes 14,000 deaths per year from lung cancer

16. Radon half-life problem 222 Rn has a half life of 3.8 days. If there is 40.0 grams of 222 Rn and it is allowed to decay 11.4 days, how much will remain? 222 Rn has a half life of 3.8 days. If there is 40.0 grams of 222 Rn and it is allowed to decay 11.4 days, how much will remain?

17. Radiation from consumer products Radioluminescent paint Radioluminescent paint Radioluminescent signs Radioluminescent signs Camping lantern mantles Camping lantern mantles Smoke detectors Smoke detectors Ceramics and glassware Ceramics and glassware Salt substitute Salt substitute Tobacco products Tobacco products

18. Distribution of Sources of Radiation Exposure SourceNatural SourcesExposure (%) Radon55 Cosmic radiation8 Terrestrial radiation8 Internal radiation11

19. Distribution of Sources of Radiation Exposure SourceMan-made sources Exposure (%) Medical x-rays11 Nuclear medicine4 Consumer products 3 Occupational exposure, nuclear fallout, nuclear fuel cycle, other sources <1

20. Typical dose 360 mrem per year is average dose each person can expect, 82% is natural, 18% is man-made 360 mrem per year is average dose each person can expect, 82% is natural, 18% is man-made

21. Radiation & Safety Continued Type of radiation also important Type of radiation also important  particles can be stopped by skin  particles can be stopped by skin  particles can be stopped by Al foil  particles can be stopped by Al foil  rays are ultimately most dangerous, dominant problem in nuclear waste storage  rays are ultimately most dangerous, dominant problem in nuclear waste storage Half life  Shorter half life will emit more of its radiation over a given period of time Half life  Shorter half life will emit more of its radiation over a given period of time 131 I half life of 8 days 131 I half life of 8 days 238 U half life of 4.5 billion years 238 U half life of 4.5 billion years

22. Radiation

23. Nuclear Applications Far more lives have been saved from nuclear chemistry than have been lost, even including Nagasaki and Hiroshima Far more lives have been saved from nuclear chemistry than have been lost, even including Nagasaki and Hiroshima Nuclear Medicine is used in diagnosis of cancers and other diseases also used in treatment of diseases Nuclear Medicine is used in diagnosis of cancers and other diseases also used in treatment of diseases

24. Food irradiation E. coli bacteria has killed numerous people and sickened thousands of times more E. coli bacteria has killed numerous people and sickened thousands of times more Food spoilage can sometimes account for 50% food loss Food spoilage can sometimes account for 50% food loss Food irradiation can prevent or lessen both things Food irradiation can prevent or lessen both things

25. What is food irradiation? Uses gamma rays from 60 Co or 137 Cs Uses gamma rays from 60 Co or 137 Cs Irradiates the food, effectively killing bacteria such as Trichinella and Salmonella Irradiates the food, effectively killing bacteria such as Trichinella and Salmonella Does not cause the food to become radioactive! Does not cause the food to become radioactive!