Module 11: Radioecology in the North

• The three types of radiation• Identify radiation as a normal part of the

environment• Define the concept of half-life and nuclear

fission• Man-made radionuclides and their effects

on the environment

Overview• Awesome energies are locked in the nuclei of

atoms (e.g. explosion of first atomic bomb in 1945)

• All humankind shares the benefits and danger of atomic energy (a dilemma in itself)

• Chernobyl and Amchitka events have left a legacy that the circumpolar North has to deal with

• Nuclear energy represents both opportunities (e.g. economic benefit of uranium mining) and challenges (e.g. high radio-activity)

ConceptsChemical Energy• Energy produced (exothermic) or absorbed

(endothermic) in the process of a chemical reaction. In such a reaction, energy losses or gains usually involve only the outermost electrons of the atoms (or ions) of the system undergoing change.

• Note: A chemical bond is established or broken without disrupting the original atomic or ionic identities of the constituents.

Concepts

Nuclear energy• Energy stored in the bonds of the sub-

atomic particles in the nuclei of atoms. Such energy can be released through nuclear reaction such as (1) emission of radioactivity, (2) nuclear fission, and (3) nuclear fusion.

Nuclear Fission

Concepts

Radioactivity• The phenomenon of an unstable nucleus

breaking down and giving off energy-loaded radiation (electromagnetic radiation and sub-atomic particles)

• Note: X-rays is a form of radioactivity used in medical imaging (invented by Marie Curie)

Nuclear Chemistry and Radioactivity

• Basic building block of matter is the atom• The atom is composed of three basic particles: a

proton with a positive charge, an electron with a negative charge, and a neutron with no charge

• The protons and neutrons in an atom are located in a very small volume called the nucleus

• Each atomic element is characterized by the number of its electrons, its protons, and its neutrons

• Many atoms bonded together is called a molecule

• Each element has an atomic number equal to its number of protons– Hydrogen, H: has atomic number 1 (1 proton in the

nucleus)– Radon, Rn: has atomic number 86 (86 protons in the

nucleus)• Atoms of a given element contain the same number of

protons, but may contain different numbers of neutrons in the nucleus (i.e. isotopes)

protium (0 neutron)H deuterium (1 neutron)

tritium (2 neutrons)

Nuclear Chemistry and Radioactivity (cont’d)

Nuclear Chemistry and Radioactivity (cont’d)

• Protons and neutrons are held together by forces that are very strong

• There are limits to the stability of nuclear forces• Changes of the nucleus from a less stable to a

more stable condition always release radioactive emission

• Energies of nuclear reactions are 100,000 times as much as those associated with molecular re-arrangements

Radioactivity• Spontaneous disintegration of certain unstable

nuclei• Many of these unstable nuclei occur naturally

(e.g. each of you is emitting radioactivity right now, due to K isotopes in your body!)

• Living organisms receive a “normal” dose of radioactivity from cosmic and terrestrial sources

• Primary terrestrial sources include carbon-14, strontium-90, and cesium-37 from uranium and thorium ores

Alpha Decay Reaction

(Uranium) (Thorium) (Helium)

Radioactivity (cont’d)

• There are 3 types of transformation by which a naturally occurring radioactive nuclei can decay:

1. Alpha particle (He nuclei)2. Beta particle (electrons)3. Gamma rays (photons)

Radioactivity (cont’d)

• Different nuclei disintegrate, or decay, at different rates

• The rate of decay is reflected by the half life of the nuclei (13Cs = 30 years half life, 14C is 5770 years)

Half life

2 x Half life4 x Half life

Sources of RadioactivityChernobyl (nuclear accident)

Chernobyl: Global Radiation Patterns

Chernobyl: Radiation Fallout

Released one hundred times more radiation than the atom

bombs dropped over Hiroshima and Nagasaki

Chernobyl: Radiation Fallout

Sources of Radioactivity: Nuclear TestingAmchitka

Amchitka

Physics of Radioactivity

• Radioactivity emits energy-loaded particles (He nuclei, protons, electrons, neutrons, and photons)

• Damages to living tissues relate to how the energy of particles are dissipated

• Water, when irradiated, contains H+ and OH- (free radical) ions that are very reactive

Radioactivity: Damages to Tissues

• Radiation creates “ions” in our cells and these ions disrupt cell processes

• Radiation may alter bio-molecules like DNA (most important), proteins, and lipid cell membranes

• Radiation, through DNA dysfunctions, may result in cells becoming tumors

Radioactivity: Biological Effects

Dose (rem)

Effects

<50 Inconsistent effects

50-250 Fatigue, nausea, decreased production of white cells and platelets in blood

250-500 Vomiting, diarrhea, damage to intestinal lining; very susceptible to infections because of low white cell count; hemorrhaging because of impaired clotting mechanism

500-1,000

Damage to cardiovascular system, intestinal tract, and brain; death within weeks

1,000-10,000

Coma, Death within hours at 10,000 rem

100,000 Immediate Death

Radioactivity: the Good Parts

• The body has the ability to repair radiation damage

• Protection against source-radiation can be achieved through the use of barriers (lead, concrete)

• Natural sources of radiation are about 300 mrem/year, mostly from radon-222 (a by-product of uranium-238 decay)

Radioactive Contamination(due to man-made radionuclides)

(Finland)

Radioactive Contamination

Radioactive Contamination

Iodine-129 (a new issue)

Radionuclide Behaviour in Marine Systems

• Transport pathways:– Water movements– Precipitation– Sediments from rivers

• Marine ecosystems are less vulnerable to atmospheric radiocesium than freshwater and terrestrial systems

Radionuclides in Rivers

Radionuclides in Rivers