Radiation Safety and You

Brian Kessler

Zettl Group Safety Talk

September 7, 2006

Types of Radiation

• Ionizing Radiation– Ionization potentials of the elements range

from 3.89 eV (Cs) to 24.6 eV (He)• Alpha Rays – He4 nucleas• Beta Rays – electrons/positrons• X-rays and Gamma Rays - photons with λ<50 nm

• Non-Ionizing Radiation• Radio waves, Micro waves, visible light• Neutrons – interact with nuclei

http://ehswprod.lbl.gov/EHSTraining/GERT/html/02whatis.html

Radiation Producing Machines in the Lab

• Transmission Electron Microscope– Electrons, Secondary

X-Rays

• Scanning Electron Microscope– Electrons, Secondary

X-Rays

• Electron Beam Evaporator

Dosage and How to Measure It

• Units:– Gray (Gy) = J/kg, physical amount of energy

absorbed– Sievert (Sv) = Q*N*Gy, biological effect of

energy absorbed (1 Sv = 100 rem)• Quality Factor (Q) depends on the type of radiation

– photons, electrons Q=1, Protons Q=5, Alpha particles Q=20

• N Factor (Q) depends on the exposed area– Gonads, N=0.20, Colon, Lung, Stomach N=0.12,

Bladder, Brain, Uterus, N = 0.05, Skin N=0.01

http://www.npl.co.uk/ionrad/quantities.html

Typical Exposure

• Significant Background Sources of Radiation– Cosmic Rays, Radon

Gas, Naturally Occuring Isotopes, Medical Diagnostics

• Annual Dose: 2 mSv• Fly LA-NY: 0.025 mSv• GI X-Ray Series : 2.2 mSv

http://ehswprod.lbl.gov/EHSTraining/GERT/html/02whatis.html

Radiation Danger

• Primary Risk - Cancer– Risk to General Population:

20%– Risk to individual with 100

mSv excess exposure: 20.4%

• Secondary Risk – Genetic Effects– Increased Risk of Mental

Retardation in Exposed Fetuses: 0.8%

http://ehswprod.lbl.gov/EHSTraining/GERT/html/04risks.html

How to Protect Yourself

• ALARA – A Low As Reasonably Achievable– Minimize Time– Maximize Distance– Use Appropriate

Shielding• Alpha Particles – a sheet

of paper

• Beta Particles – a sheet of metal

• Gamma Rays – thick lead or concrete

http://www.ehs.berkeley.edu/radsafety/rpmtraininghandout.pdf

What You Should Do Now

• Review and Complete Your General Employee Radiation Training through LBL:– http://ehswprod.lbl.gov/EHSTraining/GERT/default.htm

• Review Berkeley EHS Radiation Safety Website:– http://www.ehs.berkeley.edu/radsafety.html

Stay Safe!