Health, Safety and Environment

Radiation Basics 101 Atomic Structure

Nuclear Formula A29-38 X Sulphur Z 16 A = Mass Number (P+N) Z = Atomic Number (P)

Hydrogen - + Deuterium - + Tritium - + X A Z H 1 1 H 1 2 H 1 3 _

Nuclear Stability Stability related to the ratio of protons to neutrons: Name:Protons / NeutronsStability Hydrogen1/0 Deuterium1/1 Tritium1/2 Carbon-126/6 Carbon-136/7 Caron-146/8

Radioactivity Spontaneous nuclear transformations that result in the formation of atoms of a different element. During the decay process energy and/or particles are emitted that are capable of ionizing matter

Radioactive Decay Unstable isotopes undergo a spontaneous decay of the nucleus which improves proton to neutron ratio = more stable Particle decay: Alpha (α ++ ) Beta (β - ) Positron (β + ) Electron Capture

Alpha Decay Nuclear Fragment ~ Helium nucleus 2 Protons and 2 Neutrons A A-4 X  Y +  ++ Z Z-2

Alpha Decay External Exposure: Not significant hazard Internal Exposure: Very hazardous- highly ionizing e.g. Polonium 210

Alexander Litvinenko Polonium 210 poisoning Ingested 2GBq (50 mCi ~10ug) ~200x med. lethal dose (Click on photo for story) (November 2006)

238 Pu Uranium U +  Alpha Decay Plutonium e.g. Plutonium 238

Click on photo for a video on alpha decay

Beta Decay Negative Electron Very Small Mass A A X  Y + ß - Z Z+1

32 P  S C  N MeV MeV Max. Energy eg. Cl-36 Beta Decay

A.K.A:

Click on photo for a video on beta decay

Beta Decay Internal Exposure: Can result in high internal exposure depending on isotope and activity External Exposure: Can give high dose to skin : erythema Can damage eyes Secondary radiations can be penetrating Bremsstrahlung

Bremsstrahlung Produces X-rays

Dental X-ray Unit

Inside a Dental X-Ray Tube

Positron Decay Positive Electron Same mass as negative electron Annihilation radiation 511 keV

Positron Decay A X  Y + ß + Z Z-1 22 Na ß Ne 10 ß-ß-ß-ß- 511 keV *

Positron Decay Positrons are not hazardous –Immediately disappear upon emission. The secondary x-ray ‘annihilation radiations’ are hazardous. Internal Exposure: –Can result in high internal dose. External Exposure: –Can give equally high dose to skin and deep body core.

PET Scan

Electron Capture Electron falls into nucleus + proton=Neutron Releases daughter related gamma radiation

Photons – Ionizing Radiation No Mass No Charge Gamma- originate from within nucleus X-ray- originate from outside nucleus (Bremsstrahlung)

Photons Internal and External Exposure:Internal and External Exposure: Can give equally high dose to skin and deep body core.Can give equally high dose to skin and deep body core. Highly Penetrating Highly Penetrating function of photon energy function of photon energy Shielding efficacy is mass dependent Shielding efficacy is mass dependent eg. Cs-137

Temperature drop 60 o C - 37 o C 280 joules absorbed energy X-rays LD/50/60 – 280 joules absorbed energy COFFEE

Click on photo for a video on gamma rays

Linear Energy Transfer AirTissue β   * * * * * * * * * * * * * * * * ******** * * * * * *

Ionizing Radiation: Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions. Examples include alpha particles, beta particles, gamma rays or x rays, and cosmic rays. The minimum energy of ionizing radiation is a few electron volts (eV).

Energy (eV)Frequency (Hz)Wavelength (m) 12.4 eV IR UV VIS

Penetration

-Radioisotope produced by absorption of a neutron -The resulting radioisotope is unstable and may emit a proton, alpha particle, beta particle, gamma ray or a combination Mo-99* Tc-99m* T 1/2 = 66h T 1/2 = 6h MDS-Nordion Neutron Activation

1 n 0 + U-235 U-236* fission heat Fission fragments neutrons Radiopharmaceuticals

Questions? An unstable isotope has a shortage of neutrons (too many protons), what type of particles might be emitted? –Alpha, positron For the same isotope, what kind of shielding would be most useful? –Alpha – anything thin –Positron – lead due to production of gamma radiation

Questions? An unstable isotope has a shortage of protons (too many neutrons), what type of particles might be emitted? –Beta particle For the same isotope, what kind of shielding would be most useful? –Beta particle = plexiglass

So…Something to think about… Current debates: –Use of UV light to sterilize water? –Use of ionizing radiation to kill pathogens on food? What do you think?