Radioactivity

January 2015

Recall Isotope Notation• Why are some isotopes radioactive?• How do you find the number of neutrons?• What is alpha, beta, gamma decay?

Nuclear Reactions- Fission and Fusion

• Why are some nuclei unstable?• In the nucleus, P+ and Nْ are held together by the strong

nuclear force (SNF)• Protons having the same electrical charge “repel” each

other.• SNF must overcome this repulsion for the nucleus to hold

together• (Small nucleus: SNF > repulsion …= stable• Large nucleus: SNF and repulsive force are similar

strength… =unstable)• All nuclei with 83↑ protons are radioactive.

Fission (Division)

• Fission (division): a large nucleus is broken into smaller nuclei. Or a more massive nucleus forming 2 less massive nucli

• The nucleus is bombarded by a particle… (nْ)• When the nucleus splits, it releases nْ and Energy• Can lead to a chain reaction.• Uncontrolled = bomb

• https://www.youtube.com/watch?v=qT4mSoZsbzM

Fission (Division)• Controlled = nuclear power plant

• https://www.youtube.com/watch?v=MGj_aJz7cTs• https://www.youtube.com/watch?v=_AdA5d_8Hm0

• Nuclear power plants use fission of Uranium atoms to generate electricity.• Pros- use small mass to generate a lot of energy• Cons

• While it does not produce a lot of waste it produces other pollution such as radioactive material and using lakes and rivers to cool reactors leading to thermal pollution

• the half life of Uranium is…

Thermal Pollution

https://www.youtube.com/watch?v=dLjow_jZjLA (power plants

http://www.google.com/imgres?q=fission&hl=en&safe=active&sa=X&biw=904&bih=610&tbm=isch&prmd=imvns&tbnid=aUBuW-9VcN6ZkM:&imgrefurl=http://www.arpansa.gov.au/radiationprotection/basics/other.cfm&docid=2CFFp0CR0Z0NiM&imgurl=http://www.arpansa.gov.au/images/basics/fission.jpg&w=580&h=304&ei=2uNQT72KGcXEtgfSidmpDQ&zoom=1

• Critical mass: smallest possible mass that can sustain a nuclear reaction

Fusion• Fusion: Small nuclei combine to form a larger nucleus.• Releases lots of E• Occurs at very high temperatures…10,000,000 ْC, this

is why it is not yet suitable for energy production• Our sun and most stars are fusion reactors

• http://www.youtube.com/watch?v=fSr3V498A3I&feature=related (animation)

• http://www.youtube.com/watch?v=sSi-zSeS0_YRates(Torus Facility)

Benefits of Radioactivity

• Nuclear power generates electricity

• Radioactive tracers used to follow chemicals through living organisms and the environment (groundwater)

Benefits of Radioactivity

• Medical imaging: PET scans, autoradiography, etc...

Benefits of Radioactivity• Cancer treatment• Detection …smoke detectors, explosives in luggage,

leaks in pipes, location of underground conduit, moisture content of soil, etc…

• Foods are preserved by radiation…spices and dried fruits/vegetables are irradiated to destroy pathogens. Potatoes and onions are irradiated to retard their sprouting. Fruits and vegetables are irradiated to slow down the ripening process.

• Used to control the thicknesses of paper, plastics, metal foil

• Radiometric dating of ancient objects

Radiation Dangers

• Damages/destroys cells….Red blood cells lose ability to carry oxygen, burns the skin, causes cataracts, destroys bone marrow cells, genetic mutations (damages DNA) which can lead to birth defects, etc…

• High doses/prolonged exposure = radiation sickness = hair loss, sterility, bone deterioration, cancer, death, etc…

Nuclear Power Plants: Pros and Cons

• No pollutants released during the electricity production(compared to coal or natural gas power)

• No dams on rivers interrupting natural aquatic ecosystems (compared to hydroelectric power)

• Risk of a melt down causing radioactive matter to be released into the environment

• Problems storing the nuclear waste (Radioactive Daughter Isotopes)

• https://www.youtube.com/watch?v=mFeboB2u3QI -Darlington Pros/Cons• https://www.youtube.com/watch?v=vnjzVNG18jo- Chernobyl • https://www.youtube.com/watch?v=kBmc8SQMBj8- Fukishima