Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 3
WORKPLACE MONITORING
BACKGROUND
One requirement in a radiation protection programme is to perform a regular workplace monitoring. This should be sufficient to enable:
 evaluation of the radiological conditions in all workplaces;
 exposure assessment in controlled and supervised areas; and
 review of the classification of controlled and supervised areas
The primary objective of monitoring is to reduce or prevent exposure of staff
and the public to radioactive material. The secondary objectives are to detect any
loss of control resulting from failures of containment or departures from good operating practice, and to assist in preventing the spread of contamination from a controlled
area. Frequently such contamination spread must be restricted for reasons other
than control of exposures, e.g. to avoid contamination of low-level counting equipment in analytical or research laboratories.
In most countries the Regulatory Authority will specify the required frequency
of documented workplace monitoring.
AIM
The aim of this practical session is to learn how to set up a programme for workplace
monitoring and how to make the measurements using the correct instrument.
MATERIAL
A plan of the facilities should be available.
Instrumentation
 Dose rate monitor
 Contamination monitor
 Activity meter or gamma counter
Other equipment
 Protective clothing (laboratory coat or plastic apron, gloves and overshoes)
 Swabs, moistened with alcohol
 Tubes for samples
 Forceps
PROCEDURE
Use the plan to identify the points where the measurements should be performed.
Contamination monitoring should be done in areas where there is an increased risk
of contamination such as the work benches and equipment in the preparation area,
patient bed where injections are made, patient toilet etc. Dose rate monitoring should
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Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 3
be made in rooms where radionuclides are stored and in rooms permanently occupied by workers.
Wipe an area of a workbench, typical 10x10 cm 2 using a moistened
swab. Wipe from the periphery and inwards. Put the swab in a tube and measure the
activity in a calibrated gamma counter or an activity meter. Calculate the contamination according to:
contamination (Bq/cm2) =(cps-BG)/(Ec*Ew*A) (gamma counter)
contamination (Bq/cm2)= Am/( Ew*A)
(activity meter)
cps:
BG:
Ec:
Ew:
A:
Am:
counts per second for sample
instrument background
counter efficiency (cps/Bq)
wipe efficiency (assumed to be 0.1)
wiped area (cm2)
measured activity (Bq)
CONCLUSIONS
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Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 3
Workplace monitoring
Dose rate monitor:
Background:
Contamination monitor:
Background:
Wipe measurement devce:
Place of
measurement
Dose rate
(μSv/h)
Contamination
(cps)
Wipe test
(Bq/cm2)
Comment
3