RADIATION UNITS OF MEASUREMENT
CEMP TRAINING SESSION 15-17 JULY 2013
RADIATION UNITS
OF MEASUREMENT
Instructor: Gary M. Sandquist, PhD, CHP
2013 Training Session
Slide 1
Activity Units
Disintegrations Per Unit Time
■  Traditional
(US) unit is Curie
-  1 Ci = 3.7 x 1010 dps (dis/sec)
-  1 Ci = 2.22 x 1012 dpm (dis/min)
-  1 Ci = 1 x 1012 pCi
-  1 Ci = 37 GBq ( G= 109 )
-  International unit is Becquerel
-  1 Bq = 1 dps = 2.70 x 10-11 Ci
-  1 GBq = 0.0270 Ci
Slide 2
Occupational Dose Equivalent
Limits
■ 
■ 
■ 
Slide 3
General Public
100 mrem/yr
Any Occupational Worker
(unmonitored)
100 mrem/yr
Radiation Worker (monitored)
5,000 mrem/yr = 5 rem/yr
DOE & USNRC
Occupational Dose Limits
Slide 4
Whole Body
5
rem per yr
Lens of Eyes
15
rem per yr
Extremities
50
rem per yr
Skin
50
rem per yr
Organ or Tissue
50
rem per yr
Unborn Child
0.5
rem pregnancy
US Background
0.62 rem per yr
~ 2 mrem per day
Emergency Dose Limits
■  Protecting
■ 
property if 5 rem not practical
10 rem
■  Lifesaving
or protection of small population
if dose limit not practical:
■ 
25 rem
■  Lifesaving
or protection of large population
(volunteer basis for person aware of risk)
■ 
Slide 5
> 25 rem
Absorbed Dose
Slide 6
■ 
Energy deposited by any form of ionizing
radiation in a unit mass of material
■ 
Roentgen Absorbed Dose (rad)
■ 
Gray (Gy)
■ 
1 Gy = 100 rad
US Radiation Symbol - Radioactivity
Slide 7
IAEA Radiation Symbol - Radioactivity
Slide 8
Slide 9
TABLE Radiation limits various
standards
Slide 10
Personal Dosimeter Alarming
Gamma Dose & Dose Rate
100 nSv/hr-10 Sv/hr
Ludlam Model 25 Series small-sized personal
dosimeter automatically alarms if dose rate or
accumulated dose (0-19.9Sv) setpoint exceeded
Audible signal & bright, blinking red light.
Displays time remaining before dose limit
exceeded at current dose rate
Worn on belt, lanyard, or armband
With R or Sv units and USA certification
Model Display Range Intrinsic Safety Part
Typical Ranges
0.01 mR/hr - 1,000 R/hr
100 nSv/hr - 10 Sv/hr
Slide 11
Gamma Field Measurements
(0-50 µSv/hr or 0-5000 µR/hr)
Ludlam Model 19 gamma µR meter
Internal 2.5cm-Dx2.5cm (1x1 in) NaI
Range of 0-50 µSv/hr (0-5000 µR/hr)
Aluminum cast instrument housing
with separate battery compartment
Front panel controls include
- rotary switch for 5-decade range
- instrument shut-off,
- audio on/off switch
- fast/slow response switch
- push buttons activates meter lamp
- count reset
- highvoltage display
- battery test
Alarm light on front panel with audio
signal
Slide 12
Alpha/Beta Contamination
Surveying
Model 2360 survey meter & Model
43-93, 100 cm2 alpha/beta detector
Measure alpha and beta as separate
counts and data log results
2360 meter analog/digital unit with
ratemeter, scaler, data logging
Detector ZnS(Ag) - 0.254 mm (0.01 in)
thick plastic scintillator
Background typically < 3 cpm alpha
< 300 cpm beta
Efficiencies (4π)
20% - 239Pu
15% - 99Tc
20% - 90Sr/Y
Slide 13
Alpha Sample Counter
Model 2000 Scaler Counter with
Model 43-10 Detector Alpha
counting system
Scaler reading on digital, 6-digit LED readout
Count 0.1 - 999 mins (or secs)
RS-232 port connects to PC for recording,
control or printer
Model 43-10 sample head holds 5.1 cm (2 in)
diameter samples
ZnS(Ag) detector background < 3 cpm
4π efficiency 37% for Pu-239
Slide 14
Alpha/Beta/Gamma Measurement
(0-500 kcpm) Model 3 analog ratemeter
with Model 44-9 GM pancake detector
Front panel controls has rotary switch
- four-decade range
- instrument shut-off
- battery test
- audio on/off switch
- fast/slow response switch
- count reset button
GM pancake halogen quenched with
5 sqcm window & protective screen
Typical efficiencies
5% - 14C (beta)
22% - 90Sr/90Y (beta – gamma)
19% - 99Tc (beta – gamma)
< 1% - 99mTc (beta – gamma)
32% - 32P (beta)
15% - 239Pu (alpha)
Slide 15
Hand & Feet Contamination
Monitoring
Model 4906AB industrial duty alpha/
beta monitoring system
for hands & feet
Color, touch-screen LCD system
Displays status & points of
potential contamination.
6 gas-flow proportional detectors
activated by optical switches
Alarms annunciate locally
Built-in ethernet interface
to connect to network
Slide 16
Neutron Measurements
(0-100 mSv/hr)
Model 12- 4 Neutron Dose Rate
Instrument
Range 0-100 mSv/hr (0-10 rem/hr)
for neutrons - thermal to 12 MeV
Detector 22.9 cm (9.0 in) 3He tube
gamma background reject
<10 cpm to 100 mSv/hr (10 R/hr)
Four-decade analog meter with
separate battery compartment
Front panel controls
- four decade range
- instrument shut-off and battery test
- audio on/off switch fast/slow count
- switch count reset
- high-voltage test push-button
Slide 17
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