University of Notre Dame
Department of Risk Management and
Safety
Machine Produced
Radiation Safety
Training
University of Notre Dame
Risk Management and Safety
Radiation Safety
• Overview
– Ionizing Radiation
• Sources
• Effects
• Dosage
– Risks of Exposure
– Minimizing Risk
– Safety in Radiation Producing Machine Use
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
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
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
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
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
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
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
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)
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/r2 decay from source
– Radiation is absorbed by
matter; air is matter
– Energy dependant
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
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
Exposure Prevention
• Distance Decay
I2 = I1 . (x1/x2)2
–
–
–
–
I2 = Dose at x2
I1 = Dose at x1
x1 = Distance 1
x2 = 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)
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
Pregnancy – A Right to Declare
• A pregnant co-worker has the right to declare
the pregnancy
• Declaration must be in writing, dated and signed
• If a pregnancy is declared, the dose limit to the
fetus is 500 mrem over the entire pregnancy
(<45 mrem/month)
• The declaration may be revoked
• If a pregnancy is not declared, no special safety
considerations are implemented
Safety Guidelines
• First and foremost: Safety is Common Sense
• All of the commentary leads to:
ALARA
As Low As Reasonably Achievable
Consider what you are doing
Consider what the risks are
Minimize those risks
Be Mindful
Pregnancy – A Right to Declare
• A pregnant co-worker has the right to declare
the pregnancy
• Declaration must be in writing, dated and signed
• If a pregnancy is declared, the dose limit to the
foetus is 500 mrem over the entire pregnancy
(<45 mrem/month)
• The declaration may be revoked
• If a pregnancy is not declared, no special safety
considerations are implemented
Safety Guidelines
• The campus Radiation Safety Manual is available in the
Laboratory
• At any time you may utilize the Geiger counter if you are
unsure about the radiation safety of an instrument
• If you have a concern you may: contact a supervisor, the
Radiation Safety Specialist (Notre Dame: Andy Welding,
RM&S, ext. 1-5037), the Nuclear Regulatory
Commission (NRC, 1-800-695-7403)(radioactive
materials), or the Indiana State Department of Health
(ISDH, 1-317233-7564)(machines.) Please contact a
supervisor first if possible.
• If there is an accident call 911 or 1-5555 from a campus
phone
General Laboratory Safety
• The X-ray Facility is considered a Laboratory
• Please exercise the same precautions you would in
any Laboratory:
–
–
–
–
–
Long pants/dress (below knee length)
Close-toed shoes
No Food in the Facility
No Drink in the Facility
Be mindful of your actions