Now for the Feature Presentation…

321NuclearNuclear

R D TIONR D TION

Since Antoine Henri Becquerel’s accidental “stumble” onto the phosphorescent ability of uranium and Marie and Pierre Curie’s discovery and coining of the term “radio-active,” nuclear radiation has traveled a long way in its history of construction and destruction. It played an important role in World War II and the Cold War. Now, nuclear radiation pervades modern society, making its appearance in medicine, in nuclear electric plants, and in never-ending research. This is a journey to uncover its fundamental mechanics…

A. H. Becquerel 1896

•Natural radioactivity was first observed in 1896 by A. H. Becquerel, who discovered that when salts of uranium are in an unexposed photographic plate carefully protected from light, the plate becomes exposed.

• the salts exhibit phosphorescence and are able to produce fluorescence. Since these effects are produced both by salts and by pure uranium, radioactivity must be a property

The Discovery

of Radioactivity

Marie and Pierre Curie 1898

THE CURIES

•Won the Nobel Prize in 1903 for their research on the

phenomena Marie named radioactivity.

•Marie and Pierre Curie extended the work on radioactivity, demonstrating the radioactive properties of thorium.

•Their work also led to the discovery of two new

elements--polonium and radium in 1898.

Others who Others who contributed...contributed...

Frédéric and Irène Joliot-

Curie

Harriet Brooks

E. Rutherford

In 1899 E. Rutherford discovered and named alpha and beta radiation, and in 1900 P. Villard identified gamma radiation.

Harriet Brooks' first real discovery came from working with radium, After studying and observing the emanation from radium, Brooks decided that it had

to be a gas.

Frédéric and Irène Joliot-Curie discovered the first example of artificial radioactivity in 1934 by bombarding nonradioactive elements with alpha particles.

RadioactivityRadioactivityRadioactivity refers to the phenomenon in which particles are emitted from the nucleus of an atom due to nuclear instability

The products of radioactivity—alpha, beta, and gamma—were distinguished when scientists found that they could be separated by either a magnetic or electric field

Radioactive ElementsRadioactive Elements

Not all nuclei are stable; however, they will decay into a more stable atom. This radioactive decay is completely spontaneous.

•an alpha particle (symbol )

There are three ways that a nucleus can decay. It may give out :

•a beta particle (symbol )

•a gamma ray (symbol )

Radioactive Decay EquationsRadioactive Decay Equations

EAtomic Number

Mass Number

Element Symbol

Half-LifeHalf-LifeThe one way to apply half-life is the explain the process of radioactive decay and its relationship to the concept of half-life. The primary intent is to demonstrate how the half-life of a radionuclide can be used in practical ways to "fingerprint" radioactive materials, to "date" organic materials, to estimate the age of the earth, and to optimize the medical benefits of radionuclide usage.

Half-Life CalculationsDefinition: The length of time for half of a given number of atoms of a radioactive nuclide to decay

Equations: n = Number of half life cycles = Time passed

Half life of isotope

Original amount(g) x 0.5n = Final remaining amount(g)

Final amount (g) x 2n = Original amount (g)

Radiation UnitsRadiation UnitsGray (Gy): Gray (Gy): One joule of energy per kilogram of tissue; absorbed doseOne joule of energy per kilogram of tissue; absorbed doseRad:Rad: Absorbed dose Absorbed doseBecquerel (Bq): Becquerel (Bq): Measure of actual radioactivity in material; S.I. unit Measure of actual radioactivity in material; S.I. unit Curie (Ci): Curie (Ci): Activity of radioactive source Activity of radioactive source Sievert (Sv):Sievert (Sv): Takes into account biological effects of different types of radiation Takes into account biological effects of different types of radiation REM: REM: Converted dose-equivalent from rads or grays; biologically effective doseConverted dose-equivalent from rads or grays; biologically effective doseRoentgens: Roentgens: Intensity of radiation sourceIntensity of radiation sourceDose Equivalent (DE):Dose Equivalent (DE): may be regarded as an expression of dose in terms of may be regarded as an expression of dose in terms of

its biological effect.its biological effect.

ConversionsConversions::1 Bq = 1 disintegration per second (dps)1 Bq = 1 disintegration per second (dps)1 Ci = 3.7 x 101 Ci = 3.7 x 101010 dps dps1 Ci = 3.7 x 101 Ci = 3.7 x 101010 Bq Bq 1 gray = 100 rads1 gray = 100 rads1 sievert = 100 rem1 sievert = 100 rem1 becquerel = 27 picocuries or 2.7 x 101 becquerel = 27 picocuries or 2.7 x 10-11-11 curies curies

Sources of RadiationSources of Radiation

Two types of radiation: nonionizing and ionizingTwo types of radiation: nonionizing and ionizing GraysGrays (Gy) measure the energy of radiation (Gy) measure the energy of radiation

absorbed by the target in joules per kilogram. absorbed by the target in joules per kilogram. Rems (Sv) measure dose quantity in joules per Rems (Sv) measure dose quantity in joules per

kilogram. kilogram. The Rems and Grays both measure the effect of The Rems and Grays both measure the effect of

radiation on the target, but the rem takes into account radiation on the target, but the rem takes into account the effects of different types of radiation on human the effects of different types of radiation on human tissue. tissue.

Some forms of ExposureSome forms of Exposure Amount of exposure differs. Amount of exposure differs.

Sun’s ultraviolet raysSun’s ultraviolet rays

WaterWater

AtmosphereAtmosphere

Electromagnetic fieldsElectromagnetic fields

Nuclear bombs and reactorsNuclear bombs and reactors

OccupationOccupation

Nonionizing RadiationNonionizing Radiation The kind we are exposed to day-to-day (i.e. low-The kind we are exposed to day-to-day (i.e. low-

frequency electromagnetic fields)frequency electromagnetic fields) Generally harmlessGenerally harmless Electric appliances, power lines, radio/TV broadcasting, Electric appliances, power lines, radio/TV broadcasting,

thunderstorms, radar, telecommunicates, light, etc.thunderstorms, radar, telecommunicates, light, etc. Can pass through human bodies without apparent Can pass through human bodies without apparent

effectseffects Microwaves: high intensities can cause heating of Microwaves: high intensities can cause heating of tissue tissue

and burn injuries to skinand burn injuries to skin Ultraviolet: cause skin cancerUltraviolet: cause skin cancer Cell phones: expose sensitive parts of the human body to Cell phones: expose sensitive parts of the human body to

radiation; try not to use oftenradiation; try not to use often

Ionizing RadiationIonizing Radiation The more dangerous typeThe more dangerous type Where radioactive particles remove the valenceWhere radioactive particles remove the valence

electrons of the elements in living materials and electrons of the elements in living materials and changes the chemical reactivity of the affected atoms.changes the chemical reactivity of the affected atoms.

Damages biological molecules (proteins/nucleic acids) Damages biological molecules (proteins/nucleic acids) and ruptures cell membranes.and ruptures cell membranes.

Biological EffectsBiological EffectsDosage (Gy) Damage

>100 Central nervous system; loss of coordination and death within 1-2 days

9-100 Gastrointestinal tract; nausea, vomiting, and diarrhea. Dehydration results in death in several weeks

3-9 (Therapy) Bone marrow damage, loss of appetite and hair, hemorrhaging, inflammation, and secondary infections

<3 Non lethal, but can cause loss of appetite and hair, hemorrhaging and diarrhea.

**Average exposure for a U.S. resident is around 0.36 Rem per year

2 mSv/yearTypical background radiation experienced by everyone (av 1.5 mSv in Australia, 3 mSv in North America).

1.5 to 2.0 mSv/year Average dose to Australian uranium miners, above background and medical.

2.4 mSv/year Average dose to US nuclear industry employees.

up to 5 mSv/year Typical incremental dose for aircrew in middle latitudes.

9 mSv/year Exposure by airline crew flying the New York - Tokyo polar route.

10 mSv/year Maximum actual dose to Australian uranium miners.

20 mSv/year Current limit (averaged) for nuclear industry employees and uranium miners.

50 mSv/yearFormer routine limit for nuclear industry employees. It is also the dose rate which arises from natural background levels in several places in Iran, India and Europe.

100 mSv/yearLowest level at which any increase in cancer is clearly evident. Above this, the probability of cancer occurrence (rather than the severity) increases with dose.

350 mSv/lifetime Criterion for relocating people after Chernobyl accident.

1000 mSv/cumulativeWould probably cause a fatal cancer many years later in 5 of every 100 persons exposed to it (ie. if the normal incidence of fatal cancer were 25%, this dose would increase it to 30%).

1000 mSv/single doseCauses (temporary) radiation sickness such as nausea and decreased white blood cell count, but not death. Above this, severity of illness increases with dose.

5000 mSv/single doseWould kill about half those receiving it within a month. (The 28 people who died within four months of the Chernobyl disaster appear to have received more than 5000 mSv in a few days, while those who sufered acute radiation sickness averaged doses of 3400 mSv.)

10,000 mSv/single dose Fatal within a few weeks.

Invented from a German Physicist Hans Invented from a German Physicist Hans Geiger. Geiger.

Works by measuring the amount of Works by measuring the amount of ionization produced.ionization produced.

Radiation particles enter the tube and turn Radiation particles enter the tube and turn into ions.into ions.

Ions are electrically charged. Ions are electrically charged.

The Geiger Counter Are: The Geiger Counter Are: 1)1) Nuclear ChemistNuclear Chemist2)2) nuclear power plantsnuclear power plants3)3) TeachersTeachers4)4) emergency servicesemergency services5)5) HAZMATHAZMAT6)6) Homeland security Homeland security 7)7) EMT’sEMT’s

8)8) Golf ball companies.Golf ball companies.

The detector uses americium- 241. The detector uses americium- 241. It sends out a beam of neutrons in a straight line It sends out a beam of neutrons in a straight line When smoke enter the detector the smoke When smoke enter the detector the smoke

breaks the line, and that’s when it rings. breaks the line, and that’s when it rings.

Conclusion…The present advancement in the understanding of

nuclear radiation has been brought about by numerous people through years of research and experimentation. Its complexity is shown in the many units involved. This exploration has guided you through the fundamentals of nuclear radiation. It is now your turn to dive deeper into the areas specific to your interests. Perhaps one day your name will be written in the book of radioactive history…

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