Nuclear Science Me Nuclear Science Me rit Badge rit Badge Howard Matis - hsmatis@lb Howard Matis - hsmatis@lb l.gov l.gov 1 Nuclear Science Merit Badge Howard Matis Howard Matis Lawrence Berkeley National Laboratory Lawrence Berkeley National Laboratory
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Nuclear Science Merit Badge Howard Matis - [email protected] 1 Nuclear Science Merit Badge Howard Matis Lawrence Berkeley National Laboratory.
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The symbol is placed on a placard with the word CAUTION or DANGER or GRAVE DANGER centered about it. Under the symbol is the information addressing the types of hazards.Examples are:
Radiation Area High Radiation AreaAirborne Radioactivity Area
Alpha particle or helium nucleus Alpha particle or helium nucleus emittedemitted
Nucleus changes mass by four Nucleus changes mass by four units and charge by two unitsunits and charge by two units
Common for heavy elementsCommon for heavy elements Changes chemical propertiesChanges chemical properties Alpha particle easily stoppedAlpha particle easily stopped
4 x nucleon mass4 x nucleon mass +2 Charge +2 Charge BigBig
FissionFissionThe heavy parent nucleus The heavy parent nucleus fissions …fissions …
… … into two lighter (radioactive) fission fragment nuclei plus into two lighter (radioactive) fission fragment nuclei plus some left over neutronssome left over neutrons
Sometimes a very heavy Sometimes a very heavy nucleus will fall apart nucleus will fall apart before it can emit an before it can emit an alpha particle.alpha particle.
Fission can release an enormous amount of energy and is Fission can release an enormous amount of energy and is utilized in power plants and fission bombs (A-bomb).utilized in power plants and fission bombs (A-bomb).
How Unstable Is It?How Unstable Is It? The The “Half-life”“Half-life” describes how quickly Radioactive Material describes how quickly Radioactive Material
decays away with time.decays away with time.
It is the time required for It is the time required for halfhalf of the unstable atoms to decay. of the unstable atoms to decay.
Some Examples:Some Examples: Some natural isotopes (like uranium and thorium) have half-lives that Some natural isotopes (like uranium and thorium) have half-lives that
are billions of yearsare billions of years Since Earth is about 5 billion years old, short lived naturally produced Since Earth is about 5 billion years old, short lived naturally produced
isotopes goneisotopes gone Most medical isotopes (like Most medical isotopes (like 99m99mTcTc) last only a few days) last only a few days
Some Isotopes & Their Half LivesSome Isotopes & Their Half LivesISOTOPEISOTOPE HALF-HALF-
LIFELIFEAPPLICATIONSAPPLICATIONS
238238U – UraniumU – Uranium billions billions of yearsof years
Natural uranium is comprised of several different isotopes. Natural uranium is comprised of several different isotopes. When enriched in the isotope of When enriched in the isotope of 235235U, it’s used to power U, it’s used to power nuclear reactor or nuclear weapons. nuclear reactor or nuclear weapons.
1414C – CarbonC – Carbon 5730 y5730 y Found in nature from cosmic interactions, used to “carbon Found in nature from cosmic interactions, used to “carbon date” items and as radiolabel for detection of tumors.date” items and as radiolabel for detection of tumors.
137137Ce – CesiumCe – Cesium 30.2 y30.2 y Blood irradiators, tumor treatment through external Blood irradiators, tumor treatment through external exposure. Also used for industrial radiography.exposure. Also used for industrial radiography.
192192Ir – IridiumIr – Iridium 74 d74 d Implants or "seeds" for treatment of cancer. Also used for Implants or "seeds" for treatment of cancer. Also used for industrial radiography.industrial radiography.
9999Mo – Mo – MolybdenumMolybdenum
66 h66 h Parent for Parent for 99m99mTc generator.Tc generator.
Radiation Quantities and UnitsRadiation Quantities and Units
RadioactivityRadioactivityQty: ActivityQty: ActivityUnit: Curie (Bequerel)Unit: Curie (Bequerel) 1 Ci = 1000 mCi1 Ci = 1000 mCi 1 Bq = 1 disintegration/sec1 Bq = 1 disintegration/sec 1 Ci = 3.7 1 Ci = 3.7 10 101010 Bq Bq
Radiation RiskRadiation RiskQty: Dose EquivalentQty: Dose EquivalentUnit: rem (Sievert)Unit: rem (Sievert) 1 rem = 1000 mrem1 rem = 1000 mrem 1 Sv=100 rem1 Sv=100 rem
Radiation Absorbed DoseRadiation Absorbed DoseQty: DoseQty: DoseUnit: rad (Gray)Unit: rad (Gray) 1 rad = 1000 mrad1 rad = 1000 mrad 1 rad = 100 erg/gram1 rad = 100 erg/gram 1 Gy =100 rad1 Gy =100 rad
Convert from Curies to RadConvert from Curies to Rad
Curie is the number of decays/sCurie is the number of decays/s 1 Curie = 3.7 1 Curie = 3.7 10 101010 decays/s (exactly) decays/s (exactly)
Rad is the absorbed dose or physical doseRad is the absorbed dose or physical dose Amount of energy deposited in unit massAmount of energy deposited in unit mass
human tissue or other mediahuman tissue or other media 1 Rad = 100 erg/g1 Rad = 100 erg/g
Often use grayOften use gray 1 J/kg1 J/kg 1 gray = 100 rad1 gray = 100 rad
Ionizing Radiation can Damage DNAIonizing Radiation can Damage DNAIonizing radiation has Ionizing radiation has the ability to ionizethe ability to ionize** atoms and molecules, atoms and molecules, possibly altering possibly altering structure and function.structure and function.
* ionize = produce* ionize = produce positive and negative positive and negative electrical chargeelectrical charge
Types of Exposure & Health EffectsTypes of Exposure & Health Effects
Acute Dose - DeterministicAcute Dose - Deterministic Large radiation dose in a short period of timeLarge radiation dose in a short period of time Large doses may result in observable health effectsLarge doses may result in observable health effects
Early: Nausea & vomitingEarly: Nausea & vomiting Hair loss, fatigue, & medical complicationsHair loss, fatigue, & medical complications Burns and wounds heal slowlyBurns and wounds heal slowly
Examples: medical exposures andExamples: medical exposures andaccidental exposure to sealed sourcesaccidental exposure to sealed sources
Chronic Dose - StochasticChronic Dose - Stochastic Radiation dose received over a long period of time Radiation dose received over a long period of time Body more easily repairs damage from chronic doses Body more easily repairs damage from chronic doses Does not usually result in observable effectsDoes not usually result in observable effects Examples: Background Radiation andExamples: Background Radiation and
At HIGH Doses, We KNOW Radiation At HIGH Doses, We KNOW Radiation Causes HarmCauses Harm
High Dose effects seen inHigh Dose effects seen in Radium dial paintersRadium dial painters Early radiologistsEarly radiologists Atomic bomb survivorsAtomic bomb survivors Populations near ChernobylPopulations near Chernobyl Medical treatmentsMedical treatments Criticality AccidentsCriticality Accidents
CancerCancer Leukemia (A-bomb data)Leukemia (A-bomb data) Thyroid (Chernobyl data)Thyroid (Chernobyl data) Bone and other solid cancers (A-bomb data)Bone and other solid cancers (A-bomb data)
1 in 1 million chance of 1 in 1 million chance of fatalityfatality 40 tablespoon peanut butter (aflotoxin)40 tablespoon peanut butter (aflotoxin) 2 days in New York City (air quality)2 days in New York City (air quality) 3 mrem radiation (cancer)3 mrem radiation (cancer) 1 mile on motorcycle (collision)1 mile on motorcycle (collision) 300 miles in car (collision)300 miles in car (collision) 10 charbroiled steaks10 charbroiled steaks Smoking 1 cigaretteSmoking 1 cigarette