Useful applications of Useful applications of radioactivity and nuclear radioactivity and nuclear

energyenergy

Power for good... and Power for good... and evilevil

Power generationPower generation

Heat energy from the nuclear fission is used to Heat energy from the nuclear fission is used to create steam that generates electricity by create steam that generates electricity by turning a turbineturning a turbine

Dimming of the dayDimming of the day

Nuclear power offered the promise of plentiful Nuclear power offered the promise of plentiful cheap power. It has failed to deliver.cheap power. It has failed to deliver. Public hostility and fearPublic hostility and fear Periodic accidents and disastersPeriodic accidents and disasters Availability of nuclear fuelAvailability of nuclear fuel Problems of disposalProblems of disposal Costs of power productionCosts of power production

Nuclear power prevalent in EuropeNuclear power prevalent in Europe

Nuclear power: environmental Nuclear power: environmental friendfriend

The greatest environmental threat is perceived The greatest environmental threat is perceived to be global warming – the build-up of to be global warming – the build-up of greenhouse gases from fossil fuelsgreenhouse gases from fossil fuels

Nuclear power offers a greenhouse-free Nuclear power offers a greenhouse-free alternativealternative

Nuclear dangers: live or Memorex?Nuclear dangers: live or Memorex?

A nuclear plant can NEVER result in a nuclear A nuclear plant can NEVER result in a nuclear explosionexplosion

But accidents have occurred:But accidents have occurred: ChernobylChernobyl Three Mile IslandThree Mile Island

Varying views on ChernobylVarying views on Chernobyl Anti-nuke 500,000 deathsAnti-nuke 500,000 deaths Actual scenario 4,000 deathsActual scenario 4,000 deaths Chernobyl compares favourably with coalminesChernobyl compares favourably with coalmines

Mount St Helens eruption leaked radiation thousands Mount St Helens eruption leaked radiation thousands of times greater than Three Mile Islandof times greater than Three Mile Island

Useful radioisotopes and half-livesUseful radioisotopes and half-lives

Selection of nuclide will depend on Selection of nuclide will depend on Chemical considerations – use of iodine in thyroid Chemical considerations – use of iodine in thyroid

for examplefor example Half-life: Half-life:

Short for medical applications – Short for medical applications – 123123II Long for dating applications - Long for dating applications - 1414CC

Radioisotopes have wide range of usesRadioisotopes have wide range of uses

H-3 Triggering nuclear weapons, luminous paints and H-3 Triggering nuclear weapons, luminous paints and gauges, biochemical tracergauges, biochemical tracer

I-131 Thyroid treatment and medical imagingI-131 Thyroid treatment and medical imaging Co-60Co-60 Food irradiation, industrial applications, Food irradiation, industrial applications,

radiotherapyradiotherapy Sr-90 Tracer in medical and agricultural studiesSr-90 Tracer in medical and agricultural studies U-235/238 Nuclear power generation, depleted U U-235/238 Nuclear power generation, depleted U

used in weapons and shieldingused in weapons and shielding Am-241 Thickness and distance gauges, smoke Am-241 Thickness and distance gauges, smoke

detectors (low energy gamma – safe for domestic use)detectors (low energy gamma – safe for domestic use)

Biological Effects of RadiationBiological Effects of Radiation

Penetrating Penetrating powerpower of radiation is function of mass: of radiation is function of mass: -rays-rays > > -particles-particles >> >> -particles-particles..

Ionizing radiationIonizing radiation removes electron from water to form H removes electron from water to form H22OO+ +

ions in tissue. ions in tissue.

HH22OO++ ions react with H ions react with H22O molecule to produce HO molecule to produce H33OO+ + and a and a

highly reactive •OH radical.highly reactive •OH radical.

Free radicals generally undergo chain reactions, producing Free radicals generally undergo chain reactions, producing many radicals in biomolecules.many radicals in biomolecules.

Measuring the damageMeasuring the damage

Biological Effects of RadiationBiological Effects of Radiation

Not all forms of radiation have the same efficiency Not all forms of radiation have the same efficiency for biological damage.for biological damage.

To correct, the To correct, the radiation doseradiation dose is is multipliedmultiplied by the by the relative biological effectiveness (RBE)relative biological effectiveness (RBE), which gives , which gives the the roentgen equivalent for man (rem)roentgen equivalent for man (rem). .

RBE is about 1 for RBE is about 1 for - and - and - and 10 for - and 10 for radiation. radiation. SI unit for effective dosage is the SI unit for effective dosage is the Sievert Sievert

(1 Sv = RBE x 1 Gy = 100 rem).(1 Sv = RBE x 1 Gy = 100 rem).

Biological Effects of RadiationBiological Effects of Radiation

Somatic and Genetic damageSomatic and Genetic damage

Somatic damage. High-energy radiation Somatic damage. High-energy radiation causes extensive damage to important causes extensive damage to important structural and functional moleculesstructural and functional molecules Sickness and/or death generally resultSickness and/or death generally result

Genetic damage. Lower levels of exposure Genetic damage. Lower levels of exposure cause more subtle changes to the DNAcause more subtle changes to the DNA Physical defects appear in offspringPhysical defects appear in offspring

Biological Effects of RadiationBiological Effects of Radiation

So what is my exposure?So what is my exposure?

Worksheet for calculating annual exposureWorksheet for calculating annual exposure

Is nuclear power so dangerous?Is nuclear power so dangerous? Under normal working conditions, exposure to Under normal working conditions, exposure to

radiation from a power station is negligibleradiation from a power station is negligible Concerns center on disasters and waste disposalConcerns center on disasters and waste disposal What is worse, long-term discharge of greenhouse What is worse, long-term discharge of greenhouse

gases and acid rain on a global scale or more gases and acid rain on a global scale or more localized sites of radioactive waste storage?localized sites of radioactive waste storage?

Calculate Your Radiation Dose

The Dating GameThe Dating Game

Carbon-14 is produced in the upper atmosphere by the

bombardment of nitrogen atoms with neutrons:

Radioactive 14CO2 is produced, which mixes with

ordinary 12CO2 and is taken up by plants during

photosynthesis.

147

N + 10

n 146

C + 11

H

Carbon DatingCarbon Dating

• During an organism’s life, 14CO2 and 12CO2 are in a dynamic equilibrium at a ratio of 1 part in 1012.

• When an organism dies, the 14C/12C ratio decreases as 14C undergoes decay to 14N.

• Measuring the 14C/12C ratio determines the age of the sample with a high degree of certainty.

• Ages of 1000–20,000 years are commonly determined. The half-life for 14C is 5730 years.

The age of the earthThe age of the earth U-238 decays eventually to Pb-206U-238 decays eventually to Pb-206 Since half-life of U-238 is much longer (4.5 billion Since half-life of U-238 is much longer (4.5 billion

years) than the intermediates, Pb-206 appears almost years) than the intermediates, Pb-206 appears almost instantly after its decayinstantly after its decay

If the mineral was once pure U-238, after some If the mineral was once pure U-238, after some billions of years it becomes a mixture of U and Pb billions of years it becomes a mixture of U and Pb onlyonly

Measuring the ratio of Pb:U gives us the age of the Measuring the ratio of Pb:U gives us the age of the rockrock

Note that the U-238 half-life is of the order of the age Note that the U-238 half-life is of the order of the age of the earth. If the earth was 6,000 years old or 50 of the earth. If the earth was 6,000 years old or 50 billion years old it would not workbillion years old it would not work