Class Notes (839,315)
Canada (511,260)
Biology (2,271)
BIOL 354 (37)
Lecture 5

Lecture 5 Summary.docx

3 Pages
169 Views

Department
Biology
Course Code
BIOL 354
Professor
Bruce Greenberg

This preview shows page 1. Sign up to view the full 3 pages of the document.
Description
BIOL354 – Environmental Toxicology I Spring 2012 Lecture 5: Radioactivity - Review: PAHs can be anthropogenic or can be naturally emitted through volcanic activity & forest fires. - Radioactive Elements & Isotopes: o Naturally occurring radioisotopes @ low level o Anthropogenic Sources: (CONCERN)  Mining of the reactor fuel - Uranium  Normal operational release of nuclear plants  Accidental releases from nuclear reactors & power plants  Medical or industrial effluents containing radioactive isotopes  Reprocessing of DU for Uranium weapons  Storage of DU @ nuclear cores o Uranium (6 isotopes, all radioactive/unstable)  Naturally occurring Uranium consists of U-238 (99.2%) & U-235 (0.72%).  U-235 can undergo spontaneous fission; the predominant U-238 is not fissile.  Neutron of 1 U-235 strikes the nucleus of the 2 U-235, 2 nucleus splits into fission fragments + 2 more neutrons + photons (energy) -> cycle.  U-235 Self-Sustaining Nuclear Fission Chain Reaction -> highly exothermic.  Uranium Enrichment: Removal of some U-238 [U-235 + U-238 = 100%]  Critical Mass: smallest amount of fissile material (U-235) needed to sustain NCR.  Slow & Long-lasting NCR (Nuclear Reactor Grade): Low enriched U-235 (3-4%)  Rapid & Short-duration NCR (Nuclear Weapon Grade): High enriched U-235 (90%)  Depleted Uranium (DU): U-238, by-products of Uranium Enrichment  Extremely dense, less radioactive than natural Uranium (removal of U-235).  Radiation Shield (Medical Clinic) & Armor Piercing Projectile (War).  DU has no biological role = Toxic Metal o Adversely effects major organs & continual exposure -> birth defects. o Radioactive t½ = 4.468 bil years, biological t½ = 15 days. o Powder produced during impact/combustion of DU munitions (Uranium Bullets) can spread & contaminate areas around.  Iraq: 2000 tonnes DU munitions -> inhalation -> elevated number of cancers & birth defect s. - Radioisotopes: Unstable isotopes undergoing spontaneous “decay” to lose excessive neutrons. o Isotopes: Same proton # but different neutron # (Check atomic mass #)  Different proton # = Different element; Different neutron # = Stable or Unstable element. o Ionizing Radiation: Sub-Atomic Particles (α & β) & Electro-Magnetic Radiation (γ-rays & X-rays)  Exponential Decay, rate is the isotopes’ half-life (t½ <<1s to > 1000yrs).  Rapid decline @ beginning & later slows down (Never 0 regardless of the # of t½s). - The Electromagnetic Spectrum o Non-ionizing Radiation (Grey area): Lower energy photons.  Longer wavelength = Lower frequency = Lower energy = Less dangerous  Radio waves & light (infrared, visible & aV )  Radiation generated by Human > Radiation generated y Microwave o Ionizing Radiation: Enough energy per photon to ionize atoms or molecules (Higher energy photons)  Shorter wavelength = Higher frequency = Higher energy = Dangerous  Tissue penetration & DNA bond breakage (UV ,bX-ray, γ-rays)  The e & p leads to ROS (free radical) generation in biological systems. BIOL354 – Environmental Toxicology I Spring 2012 - Ionizing Radiation: First releases α or β particles & then γ-rays or x-rays o After fission (release of Alpha or Beta particles)  UNSTABLE, EXCITED daughter nucleus - γ-rays = Lower energy Ground State o Alpha (α) Particles = He (Ejected chunk of nucleus with a+charge) +  Large subatomic particle (2x protons & 2x neutrons)  New Atomic Mass # (Proton + Neutron) = Original – 4, new element.  New Atomic # (Proton) = Original -2 o Parent Uranium-235 – Helium Nucleus (α) = Daughter Thorium-231  Highly ionizing, minimal penetrating depth due to its huge size  Protection: Stopped by few cm of air, skin, sheet of paper, etc.  Ingestion: Extremely dangerous o Beta (β) Particles (2 types depending on whether electrons or positrons are generated) -  Electron (β decay) (99.9%) Excess neutrons, 1 neutron converted to 1 proton & 1 electron  Positron (β decay) (0.1%) Excess protons, 1 proton converted to 1 positron  Positron (anti-electrons): + charged electron  High speed, very small, travels further  Less ionizing, can penetrate peripheral tissue & damage external organs due to small size.  Protection: Stopped by a layer
More Less
Unlock Document

Only page 1 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit