RadiationRadiation

What makes What makes something something radioactive?radioactive? The nucleus of an The nucleus of an

atom contains atom contains protons and neutronsprotons and neutrons

They are packed They are packed together with a lot of together with a lot of repulsive chargerepulsive charge– Opposites attract, Opposites attract,

same charges repelsame charges repel If atom has too few If atom has too few

neutrons, positron neutrons, positron emission occursemission occurs

If atom has too If atom has too many neutrons, many neutrons, beta emission beta emission occurs occurs

Another type of Another type of radioactive decay radioactive decay is loss of an is loss of an particleparticle

Examples of Examples of Radioactive decayRadioactive decay

Band of StabilityBand of Stability

Notice most Notice most elements are elements are stable & stable & elements possess elements possess a driving force to a driving force to try to become try to become stablestable

RadioactivityRadioactivity

There are 114 or so elements & 340 There are 114 or so elements & 340 isotopes of all the elements, only isotopes of all the elements, only about 70 are radioactiveabout 70 are radioactive

All isotopes with atomic numbers All isotopes with atomic numbers greater than 83 are radioactivegreater than 83 are radioactive

Most are not significant contributors Most are not significant contributors to our overall radiation dose to our overall radiation dose because of their low abundancebecause of their low abundance

Naturally occurring Naturally occurring radiationradiation

Travel from Los Travel from Los Angeles to Paris on a Angeles to Paris on a conventional flight will conventional flight will result in additional 10 result in additional 10 millirems of radiationmillirems of radiation

1. Cosmic 1. Cosmic radiation: At sea radiation: At sea level average level average annual dose is 26 annual dose is 26 millirem a yearmillirem a year

Naturally occurring Naturally occurring radiationradiation 2. Cosmogenic radiation: Most 2. Cosmogenic radiation: Most

common is common is 1414C Contributes 1 C Contributes 1 millirem per yearmillirem per year

Nuclear reaction:Nuclear reaction:

Carbon 14 has a half life of 5730 Carbon 14 has a half life of 5730 years & decays by beta emissionyears & decays by beta emission

Half lifeHalf life

What is a half life?What is a half life?– The amount of time for half of the The amount of time for half of the

remaining material to decay.remaining material to decay.

Half lives illustratedHalf lives illustrated

After 5730 years (1 After 5730 years (1 half life) there is half half life) there is half a pie lefta pie left

Imagine the pie is Imagine the pie is some radioactive some radioactive carbon 14, originally carbon 14, originally there is one pie there is one pie worth of carbon 14worth of carbon 14

Half lives illustratedHalf lives illustrated

After 11,460 years After 11,460 years (2 half lives) there is (2 half lives) there is ¼ of a pie left¼ of a pie left

After 17,190 years, 1/8 After 17,190 years, 1/8 of the pie is leftof the pie is left

Notice the absolute Notice the absolute amount of material that amount of material that is lost gets smaller and is lost gets smaller and smaller the greater # of smaller the greater # of half liveshalf lives

Half livesHalf lives

If the pie illustrated here was all If the pie illustrated here was all 1414C and it originally weighed 750 C and it originally weighed 750 g, how many grams would be g, how many grams would be remaining after 22,920 years?remaining after 22,920 years?

Naturally occurring Naturally occurring radiationradiation 3. Terrestrial radiation: Arises 3. Terrestrial radiation: Arises

from radioisotopes whose half lives from radioisotopes whose half lives are comparable to the age of the are comparable to the age of the earth, most comes from uranium earth, most comes from uranium series Annual dose 28 mrem series Annual dose 28 mrem externally & 240 mrem internallyexternally & 240 mrem internally

Radon gas is another important Radon gas is another important source heresource here

RadonRadon

Enters buildings through dirt Enters buildings through dirt floors, cracks, floor drains, and floors, cracks, floor drains, and from building materials like from building materials like gypsum and stone fireplacesgypsum and stone fireplaces

Small amounts are dissolved in Small amounts are dissolved in groundwater and in natural gas suppliesgroundwater and in natural gas supplies

Radon continuedRadon continued

Radon isotopes have a fairly short half Radon isotopes have a fairly short half life but they decay to insoluble solids life but they decay to insoluble solids that can get deposited in lungsthat can get deposited in lungs

Radon is most problematic in tight, Radon is most problematic in tight, well sealed basements in the winter, well sealed basements in the winter, little air flowlittle air flow

EPA estimates radon contributes EPA estimates radon contributes 14,000 deaths per year from lung 14,000 deaths per year from lung cancercancer

Radon half-life Radon half-life problemproblem 222222Rn has a half life of 3.8 days. If Rn has a half life of 3.8 days. If

there is 40.0 grams of there is 40.0 grams of 222222Rn and it Rn and it is allowed to decay 11.4 days, is allowed to decay 11.4 days, how much will remain? how much will remain?

Radiation from Radiation from consumer productsconsumer products

Radioluminescent paintRadioluminescent paint Radioluminescent signsRadioluminescent signs Camping lantern mantlesCamping lantern mantles Smoke detectorsSmoke detectors Ceramics and glasswareCeramics and glassware Salt substituteSalt substitute Tobacco productsTobacco products

Distribution of Sources Distribution of Sources of Radiation Exposureof Radiation ExposureSource Natural Sources Exposure (%)

Radon 55

Cosmic radiation 8

Terrestrial radiation 8

Internal radiation 11

Distribution of Sources Distribution of Sources of Radiation Exposureof Radiation Exposure

Source Man-made sources

Exposure (%)

Medical x-rays 11

Nuclear medicine 4

Consumer products

3

Occupational exposure, nuclear fallout, nuclear fuel cycle, other sources

<1

Typical doseTypical dose

360 mrem per year is average 360 mrem per year is average dose each person can expect, dose each person can expect, 82% is natural, 18% is man-made82% is natural, 18% is man-made

Radiation & Safety Radiation & Safety ContinuedContinued

Type of radiation also Type of radiation also importantimportant

particles can be particles can be stopped by skinstopped by skin

particles can be particles can be stopped by Al foilstopped by Al foil

rays are ultimately rays are ultimately most dangerous, most dangerous, dominant problem in dominant problem in nuclear waste nuclear waste storagestorage

Half life Half life Shorter Shorter half life will emit half life will emit more of its radiation more of its radiation over a given period over a given period of timeof time

131131I half life of 8 daysI half life of 8 days 238238U half life of 4.5 U half life of 4.5

billion years billion years

RadiationRadiation

Nuclear ApplicationsNuclear Applications

Far more lives Far more lives have been saved have been saved from nuclear from nuclear chemistry than chemistry than have been lost, have been lost, even including even including Nagasaki and Nagasaki and HiroshimaHiroshima

Nuclear Medicine is Nuclear Medicine is used in diagnosis of used in diagnosis of cancers and other cancers and other diseases also used in diseases also used in treatment of diseasestreatment of diseases

Food irradiationFood irradiation

E. coli bacteria has killed E. coli bacteria has killed numerous people and sickened numerous people and sickened thousands of times morethousands of times more

Food spoilage can sometimes Food spoilage can sometimes account for 50% food lossaccount for 50% food loss

Food irradiation can prevent or Food irradiation can prevent or lessen both thingslessen both things

What is food What is food irradiation?irradiation?

Uses gamma rays Uses gamma rays from from 6060Co or Co or 137137CsCs

Irradiates the food, Irradiates the food, effectively killing effectively killing bacteria such as bacteria such as Trichinella and Trichinella and SalmonellaSalmonella

Does not cause the Does not cause the food to become food to become radioactive!radioactive!