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University of Notre Dame Department of Risk Management and Safety.

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Presentation on theme: "University of Notre Dame Department of Risk Management and Safety."— Presentation transcript:

1 University of Notre Dame Department of Risk Management and Safety

2 Machine Produced Radiation Safety Training University of Notre Dame Risk Management and Safety

3 Radiation Safety Overview –Ionizing Radiation Sources Effects Dosage –Risks of Exposure –Minimizing Risk –Safety in Radiation Producing Machine Use

4 Ionizing Radiation Radiation –Energy in the form of a Particle or Electromagnetic Wave –Emitted from atoms or via effects applied to charged particles Ionizing Radiation –Radiation with sufficient Energy to eject an electron from an atom

5 Ionizing Radiation - Sources Sources –Extraterrestrial Cosmic Radiation Solar Radiation –Terrestrial Atomic Decay Radiation Producing Machines Particle Accelerators Nuclear Reactors –Internal Atomic Decay Types of Ionizing Radiation – Alpha particles Radioactive decay He nucleus – Beta particles Radioactive decay / particle accelerators “free” electron – Neutrons Radioactive decay / nuclear reactors Particle – X-rays/Gamma Rays Radioactive decay Radiation Producing Machines Electromagnetic Wave

6 Ionizing Radiation - Effects X-ray Radiation –Primary radiation source for diffraction experiments –Penetrates matter –Dose depends on several factors “Hardness” of X-rays Exposure time Distance Effects of Ionizing Radiation – Energy from radiation can eject an electron Radical formation Radicals react strongly with other molecules – Scission of atomic bonds Fragmentation of molecules

7 Ionizing Radiation - Effects Effects: –Most of the damage is rapidly repaired –If repair is faulty, burns (erythema) and mutations can occur –Erythema most common side-effect –Mutations include: Alteration of local DNA Cancer –Cell Death Exposure – Units are measured in Röntgen (Roentgen) (R) – 1 Röntgen is 2.58 x 10 -4 Coulomb (C) of charge yielded by energy given to 1 kg of air. – Usually measured in milliRöntgen (mR) – Doses measured in mR/h

8 Ionizing Radiation - Dosage Radiation Absorbed Dose (RAD) –Quantifies amount of energy released to matter from any radiation source –1 RAD = 100 erg/g of matter –Measured in Gray (Gy) –1 Gy = 1 J/kg = 100 RAD Radiation Equivalent Man (REM) – Quantifies biological impact of a radiation dose – rem = RAD x weighting factor – Weighting factor accounts for radiation type X-rays = 1 Alpha particle = 20 – Measured in Sieverts (Sv) 100 mrem = 1 Sv

9 Ionizing Radiation - Dosage Radiation Limits –Set by the World Health Organization (WHO) via Nuclear Regulatory Committee (NRC) –500 mrem/yr - General Public –Exposure is chronic Sources Contributing to Count – Background ~300 mrem/yr Radon Ingested Food Terrestrial Cosmic Radiation – Indirect Medical X-rays ~50 mrem/yr – Direct Medical X-rays

10 Ionizing Radiation There is thought to be no lower limit to potential detrimental effects occurring from an exposure Small increase in birth defects and cancers due to acute exposure. Cancer risk increase is 0.04% per rem of exposure

11 Radiation Notices Radiation Producing Machines are required to display a notification when energized Clear notification of an open port/open shutter must be apparent (visual notification)

12 Exposure Prevention Length of time –“Fleeting” exposure? –Prolonged exposure? Long period of time allows more radiation to be absorbed, higher risk of deleterious effects Minimize amount of time near a potential radiation source Shielding – Appropriate for Radiation? – Appropriate for Instrument? Distance – Radiation “suffers” from a 1/r 2 decay from source – Radiation is absorbed by matter; air is matter – Energy dependant

13 Radiation Notices International Standards for Radiological Work Magenta-on-Yellow or Black-on-Yellow Trefoil Notices must be apparent and external to the work area

14 Exposure Risks Radiation Producing Machines (RPM) –RPM X-rays are “soft” Nearly all of energy is deposited in matter Primary Beam –Acute exposure –High dose (100’s – 1000’s of R/min) –Less likely due to beam-stop Secondary Scatter – Lower count rate (~0.2 mR/h) – More likely since is scattered radiation from sample – Extremity rather than whole body – Easily detected with a radiation counter

15 Exposure Prevention Distance Decay I 2 = I 1. (x 1 /x 2 ) 2 –I 2 = Dose at x 2 –I 1 = Dose at x 1 –x 1 = Distance 1 –x 2 = Distance 2 Sample is measured at 25 mR/h at 0.1 m from source, what is the dose at 0.3 m from the source 25 mR/h x (0.1/0.5) 2 25 mR/h x 0.04 = 1mR/h Nota Bene: On Radiation Producing Machines the counter should read no more than 0.2 mR/h at 5 cm from the sample (back scatter)

16 Exposure Prevention Shielding –Primary prevention/protection –Appropriate Shielding is required Radiation sources and appropriate shielding –Alpha particle: Paper –Beta particle: Plastic/thin metal – X-rays: metal sheeting/leaded glass – Gamma Rays: lead-lined metal sheeting – Neutrons: water, paraffin, plexiglass Do NOT remove radiation shielding – Contact a supervisor or Radiation Safety Officer if you need to do so Do NOT override safety interlocks