RADIATION SAFETY
Definitions

Roentgen
–

RAD
–

2.58 x104 coulombs/kg air
Radiation Absorbed Dose- Density
dependant (to convert roentgens to rads
you must include a density factor)
REM
–
Roentgen Equivalent Man
REM


RAD * Q factor = REM
GRAY * Q factor = Sievert
Definitions


Gray = 100 RAD
Sievert = 100 REM
Definitions

Curie = 3.7 * 1010 dps
–

cps vs dps
Becquerel = 1 dps
Definitions

Linear Energy Transfer (LET)
–

Energy given up per unit distance
traveled
Specific Ionization (SI)
–
–
Ion pairs formed per distance traveled
Note a high LET or SI gives greater
radiotoxicity
LET or SI
+
+
+
_
_
+
+
_
_
_
+
_
Definitions

Background Radiation
–

Erythema Dose
–

1-2 msieverts/year
1 gray to the skin
LD50
–
5 gray whole body exposure
Definitions

ALARA
As Low As Is Reasonably Achievable
– Because we don’t
know
–
ALARA Continued

While the regulatory limit is 50
msievert per year (about 12.5
msievert/quarter) At BYU I will
investigate any quarterly dose above
100 mrem (1 msievert)
Definitions

Gamma ray
–
–
–
Origin Nucleus
Low mass, charge
Low LET
Definitions


X-ray just like gamma but origin is an
electron
Beta Particles
–
–

Mass and charge = electron
high LET
KERMA = kenitic energy released per
unit mass
Definitions



Electron capture
Beta Decay
Alpha Decay
Definitions



Total Effective Dose Equivalent
Cumulative Committed Effective Dose
Equivalent
Deep Dose Equivalent
Biological Effects


Acute
Chronic
Biological Effects



Direct chemical damage due to
ionization of important biological
molecules
Most damage is done by radical
formation – the most common is the
hydroxyl radical
H2O + radiation > H+ + OH (unpaired
electron)
Biological Effects

Acute
Biological Effects




Erythema (skin gets red) 1 gray
Bone Marrow and white blood cells
destroyed (about 5 gray or 500 RAD)
this is the LD50. Ionizing radiation is a
“metabolic poison” it preferentially
damages rapidly metabolizing cells.
Gi tract -10 to 20 gray whole body
(death certain)
CNS is destroyed at 50 gray and above
Biological Effects

Chronic
Biological Effects



Cancer
Mutations
Teratogens
Biological Effects

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
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DNA Damage
RNA Damage
Enzyme Damage
NOTE: Damage to DNA is amplified
through transcription and replication
excess cancers (lifetime)
Dose Response
20
15
10
Series1
5
0
0
0.5
1
Exposure (sieverts)
1.5
Biological Effects

Linear No Threshold Theory states that if
the dose is doubled the risk of toxic effects
(due to ionizing radiation) is doubled
– Not definitively demonstrated at low doses
– Not applicable to acute dose, applicable to
stochastic or random events like cancer
– Always RBE (rem or sievert)
Biological Effects



Internal vs External Hazard (epithelial
barrier)
Some nuclides can only hurt you if
they get inside you. Examples low
energy beta emitters such as 35S, 3H,
14C and alpha emitters
Radiotoxicity
–
LET, Target Organ, Effective Half Life
Interactions (Photons)




Compton scattering
Photoelectric effect
Pair Production
Half Value Layer
Interactions (Beta
Particles)



Bremsstraahlung
Ionization
Range
Interactions (Beta
Particles)

Bremsstraahlung (x-rays)
–
–
Increased by high atomic number
materials
Increased by high energy electrons
Nuclide Characteristics
Tritium 3H
 Very Low energy –Beta emitter
 Cannot be detected with Geiger
Counter
 LSC and Gas proportional counters
 12 year half-life
 6 keV

Nuclide Characteristics
35S and 14C
 Low Energy Beta
 10 percent 2pi efficiency
 87 day half-life
 50 keV, range in air 22 cm

Nuclide Characteristics
32P
 High energy – bremsstraahlung
 GM detector gives high efficiency
 14.29 days half life
 700 keV energy, range in air 6 meters
 LET is inversely proportional to energy

Nuclide Characteristics
•
•
•
•
•
125I
Gamma emitter low energy (electron
capture)
Target organ – thyroid
60 day half-life
Solid scintillation is best detection
method
Nuclide Characteristics
33P Low energy beta emitter 27 day
half life
 14C low energy beta emitter 5000
year half life

Waste Disposal



Decay
Sewer
Ship
Chemicals
Management 2-6156 (characterization)

Waste Disposal

Decay
–
–
Half life less than 90 days
Remove all labels
Waste Disposal

Sewer
–
–
–
–
–
100 microcuries
100 microcuries
100 microcuries
100 microcuries
No Iodine
of
of
of
of
tritium
35S
14 C
32P
Waste Disposal



Remove all labels
List Nuclide
Note quantity
Waste Disposal



Liquids must be in Plastic leak proof
containers
Solids should be in a closed plastic bag
List laboratory
Waste Disposal



Never mix hazardous chemical wastes
with radioactive wastes without RSO
Approval
Never mix short half life nuclides with
long half life nuclides without RSO
approval
Get approval from the RSO before
using radioactive isotopes in animals
Dosimetry


TLD badges for
external hazard
materials
Significant
Quantities
–
–
Over 2 millicuries in
one package
Over 3 millicuries in
one month
Dosimetry

Thermoluminescent Dosimetry
– Heat



Wear the badge on or near your lapel
Wear ring badge with TLD crystal to
the inside (exposed) portion of your
hand
Wear fetal badge near stomach
Iodinations




E 238 BNSN
Perform thyroid assay before,
following and 24 hrs later
Use RSO’s survey meter
Keep results in your book and send
them to the RSO
Bioassay


If you handle 5 mCi or more you will
do bioassays
Bioassays required for all iodinations
– Solid Scintillator
– Urine (early morning – 1 ml count one
minute)
Leak Check


All new material should be leak
checked prior to use
Call the RSO if a leak is detected
Protection


Time, Distance, Shielding and Quantity
Use Personal Protective Equipment
–
Gloves, goggles, lab coat
Eating and Drinking

Never eat, drink or apply makeup in a
laboratory authorized for use of
radioactive isotopes
Regulations



R313-15 and R313-18, 10 CFR 20,
License
Allowable Exposure 5 Rem/Year
Pregnancy
500 mrem/pregnancy
Regulations
The University has an obligation to the
pregnant woman and her unborne
baby. But this obligation begins with a
formal (written) declaration of the
pregnancy.
Regulations

Security
–
–
Locked Up –double locks
Under personal supervision of an
authorized individual
Regulations

Required Notice
– DRC04 must be posted
– Dosimetry Report annually.
Instrumentation



Ionization Chamber
Gas proportional counter
Geiger Mueller counter
Laboratory Surveys



Survey your laboratory each day that
isotopes are in use
Log the survey values
Identify the survey meter and person
Instrumentation
+ _
+
_
_
+
Gas Filled
Chamber
Electronics
Instrumentation

Solid Scintillator
– Most sensitive for photons (required if
you use 125I)

Liquid Scintillation
– 4 π geometry
– Tritium detection
Instrumentation

Efficiency
–
–
–
Geometry - surface area of a sphere =4π
r2
Coincidence
Window
Instrumentation

Calibration must be completed at least
annually.
– Photon detectors must be sent out
– Beta survey instruments may be
calibrated by Risk Management
Laboratory Surveys



Check hands, telephone, bench, floor
in front of bench, soles of shoes,
computer keyboard, centrifuges, door
handle
Survey at the end of each day that rad
material is used.
Be prepared to calculate surface
contamination
Laboratory Surveys

Documentation
– Date
– Instrument SN
– Battery check
– Check Source count
– ID of person completing the survey
– Survey result
– Anything above background is positive
Laboratory Surveys

Important variables
– Nuclide energy
– Distance from the surface
– Speed of detector movement
– Audible is more sensitive than instrument
reading
Documentation



Receipt logs
Disposal logs
Survey logs
Documentation

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Certification
User Authorization
Facility Authorization
Training list
Emergencies


Call 2-2222 if no risk of life or health
Call 911 if risk of life or health
Emergency Procedures



Get Help - Emergencies call 911 on a
campus phone
If help is needed immediately call 22222
Radiation Safety Officer 2-4468
Emergency Procedures


First priority Human life and safety
Second priority limit the spread
(consistent with first priority)
– Clean the spill up
– Block off the area
– Survey for contamination on yourself and
the ‘clean areas around you’ pay
particular attention to your shoes.