Useful applications of radioactivity and nuclear energy Power for good... and evil

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

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

Nuclear power prevalent in Europe

Nuclear power: environmental friend The greatest environmental threat is perceived to be global warming – the build-up of greenhouse gases from fossil fuels The greatest environmental threat is perceived to be global warming – the build-up of greenhouse gases from fossil fuels Nuclear power offers a greenhouse-free alternative Nuclear power offers a greenhouse-free alternative

Nuclear dangers: live or Memorex? A nuclear plant can NEVER result in a nuclear explosion A nuclear plant can NEVER result in a nuclear explosion But accidents have occurred: But accidents have occurred: Chernobyl Chernobyl Three Mile Island Three Mile Island Varying views on Chernobyl Varying views on Chernobyl Anti-nuke 500,000 deaths Anti-nuke 500,000 deaths Actual scenario 4,000 deaths Actual scenario 4,000 deaths Chernobyl compares favourably with coalmines Chernobyl compares favourably with coalmines Mount St Helens eruption leaked radiation thousands of times greater than Three Mile Island Mount St Helens eruption leaked radiation thousands of times greater than Three Mile Island

Useful radioisotopes and half-lives Selection of nuclide will depend on Selection of nuclide will depend on Chemical considerations – use of iodine in thyroid for example Chemical considerations – use of iodine in thyroid for example Half-life: Half-life: Short for medical applications – 123 I Short for medical applications – 123 I Long for dating applications - 14 C Long for dating applications - 14 C

Radioisotopes have wide range of uses H-3 Triggering nuclear weapons, luminous paints and gauges, biochemical tracer H-3 Triggering nuclear weapons, luminous paints and gauges, biochemical tracer I-131 Thyroid treatment and medical imaging I-131 Thyroid treatment and medical imaging Co-60 Food irradiation, industrial applications, radiotherapy Co-60 Food irradiation, industrial applications, radiotherapy Sr-90 Tracer in medical and agricultural studies Sr-90 Tracer in medical and agricultural studies U-235/238 Nuclear power generation, depleted U used in weapons and shielding U-235/238 Nuclear power generation, depleted U used in weapons and shielding Am-241 Thickness and distance gauges, smoke detectors (low energy gamma – safe for domestic use) Am-241 Thickness and distance gauges, smoke detectors (low energy gamma – safe for domestic use)

Biological Effects of Radiation Penetrating power of radiation is function of mass:  -rays >  -particles >>  -particles. Penetrating power of radiation is function of mass:  -rays >  -particles >>  -particles. Ionizing radiation removes electron from water to form H 2 O + ions in tissue. Ionizing radiation removes electron from water to form H 2 O + ions in tissue. H 2 O + ions react with H 2 O molecule to produce H 3 O + and a highly reactive OH radical. H 2 O + ions react with H 2 O molecule to produce H 3 O + and a highly reactive OH radical. Free radicals generally undergo chain reactions, producing many radicals in biomolecules. Free radicals generally undergo chain reactions, producing many radicals in biomolecules.

Measuring the damage

Biological Effects of Radiation Not all forms of radiation have the same efficiency for biological damage. Not all forms of radiation have the same efficiency for biological damage. To correct, the radiation dose is multiplied by the relative biological effectiveness (RBE), which gives the roentgen equivalent for man (rem). To correct, the radiation dose is multiplied by the relative biological effectiveness (RBE), which gives the roentgen equivalent for man (rem). RBE is about 1 for  - and  - and 10 for  radiation. RBE is about 1 for  - and  - and 10 for  radiation. SI unit for effective dosage is the Sievert (1 Sv = RBE x 1 Gy = 100 rem). SI unit for effective dosage is the Sievert (1 Sv = RBE x 1 Gy = 100 rem).

Biological Effects of Radiation

Somatic and Genetic damage Somatic damage. High-energy radiation causes extensive damage to important structural and functional molecules Somatic damage. High-energy radiation causes extensive damage to important structural and functional molecules Sickness and/or death generally result Sickness and/or death generally result Genetic damage. Lower levels of exposure cause more subtle changes to the DNA Genetic damage. Lower levels of exposure cause more subtle changes to the DNA Physical defects appear in offspring Physical defects appear in offspring

Biological Effects of Radiation

So what is my exposure? Worksheet for calculating annual exposure Worksheet for calculating annual exposure Is nuclear power so dangerous? Is nuclear power so dangerous? Under normal working conditions, exposure to radiation from a power station is negligible Under normal working conditions, exposure to radiation from a power station is negligible Concerns center on disasters and waste disposal Concerns center on disasters and waste disposal What is worse, long-term discharge of greenhouse gases and acid rain on a global scale or more localized sites of radioactive waste storage? What is worse, long-term discharge of greenhouse gases and acid rain on a global scale or more localized sites of radioactive waste storage? Calculate Your Radiation Dose

The Dating Game Carbon-14 is produced in the upper atmosphere by the bombardment of nitrogen atoms with neutrons: Radioactive 14 CO 2 is produced, which mixes with ordinary 12 CO 2 and is taken up by plants during photosynthesis.

Carbon Dating During an organism’s life, 14 CO 2 and 12 CO 2 are in a dynamic equilibrium at a ratio of 1 part in When an organism dies, the 14 C/ 12 C ratio decreases as 14 C undergoes  decay to 14 N. Measuring the 14 C/ 12 C 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 14 C is 5730 years.

The age of the earth U-238 decays eventually to Pb-206 U-238 decays eventually to Pb-206 Since half-life of U-238 is much longer (4.5 billion years) than the intermediates, Pb-206 appears almost instantly after its decay Since half-life of U-238 is much longer (4.5 billion years) than the intermediates, Pb-206 appears almost instantly after its decay If the mineral was once pure U-238, after some billions of years it becomes a mixture of U and Pb only If the mineral was once pure U-238, after some billions of years it becomes a mixture of U and Pb only Measuring the ratio of Pb:U gives us the age of the rock Measuring the ratio of Pb:U gives us the age of the rock 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 billion years old it would not work 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 billion years old it would not work