QSA Global, Inc.
40 North Avenue Burlington, MA 01803
888.272.2242
781.272.2000
qsa-global.com
Operations Manual
MAN-038 March 2019
Page 23 of 100
STEP 4 Continued
Projecting Continued
During retraction of the source assembly from the exposure head to the gamma-ray source projector,
the sequence will reverse. The survey meter should indicate a continually increasing radiation level
as the source assembly is retracted, then drop to background when the source assembly is stored in
the gamma-ray source projector.
During the radiographic exposure, use the survey meter to check the boundary dose rate, but spend
as little time as possible in and near the restricted area to minimize personal exposure.
Retracting
At the end of the required exposure time, set the brake to the OFF position and rapidly turn
the crank handle in the RETRACT (clockwise) direction until it no longer moves. You may
hear the lock slide ‘click’ back into its original position depending on the ambient noise level
at the job site. From the control crank you may be able to observe the
GREEN MARKING
on
the slide bar. The source assembly is secured in the fully shielded position by the automatic
securing mechanism.
Apply a slight amount of forward pressure on the crank handle as if to expose the source to
ensure that the positive locking mechanism has actuated.
Allow the crank handle to return to a neutral position, thereby relieving any tension (force) on the
control cable that would cause source movement when unlocking the projector. At this point the
source cannot be moved out of the stored position.
In the unlikely event the lock slide moves toward the lock position before the source is fully stored in
the gamma-ray source projector, turn the crank handle in the
RETRACT
(clockwise) direction until it
stops turning. (The lock slide is designed to lock on the stop ball, not the control cable). Do not use
excessive force. The source assembly will be in the gamma-ray source projector but not in the fully
shielded position. Approach the gamma-ray source projector, from the rear, with a survey meter. The
survey meter will measure approximately 400 µSv/hr (40 mR/hr) at the rear plate of the SENTINEL
SENTRY 330 gamma-ray source projector when a 12 TBq (330 Ci) Co-60 source is in use. The
survey meter will measure approximately 700 µSv/hr (70 mR/hr) at the rear plate of the SENTINEL
SENTRY 110 gamma-ray source projector when a 4 TBq (110 Ci) Co-60 source is in use
CAUTION
Remain clear of the front of the gamma-ray source projector (outlet port side) to minimize personal
exposure. Reset the lock slide to the open position. Return to the control crank and turn the crank
handle in the
RETRACT
(clockwise) direction and store the source assembly in the normal manner.
The odometer (if supplied) should read approximately zero when the source assembly has returned
to the projector.
Confirmatory Survey
Approach the gamma-ray source projector while observing the survey meter – observe the
GREEN
MARKING
on the lock slide and survey the gamma-ray source projector. The survey meter should
indicate the same radiation level as observed before the exposure. Note particularly the outlet port
reading.
Survey the entire length of source guide tube with the survey meter. If the meter shows a sharp
increase, the source is exposed or incompletely shielded.
If the source is still exposed, attempt to store it properly by cranking the source a short distance
towards the exposure head and retracting it, repeating if necessary.
