Hologic DISCOVERY A, Technical Manual

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Discovery QDR Series Technical Manual
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3.5.5.1 Principles
Radiation leakage from the HVPS/S results from a defect in the lead liner of the tank or its
cover. If there is a hole in the lead liner, the resulting leakage will produce a pencil beam
of X-rays. If there is a crack in the lead liner, the resulting leakage will produce a fan
beam. In either case, the initial survey must be taken close to and almost touching the tank
with the survey meter probe. If a leak is found, the meter indicates a spike in the reading.
If this occurs, you must then move the probe one-meter (approx. 40”) along the beam from
that spot to determine if the leakage is within acceptable levels.
The Victoreen 450P has a response time of:
3.5.5.2 Performing the Leakage Test Procedure
1. Remove the tank cover and set the X-ray leakage test shield (099-0566) over the
aperture slot.
Figure 3-29. Leakage Test Shield (099-0566)
2. Start the Utility by selecting Utilities|Service Utilities|X-Ray Survey (see “X-
Ray Survey” on page 9-1 for information on the utility).
3. Change X-Ray Mode to 3 and Aperture to 7 to lock in the changes.
Range Time
0-4mR/h 3.3 seconds
0-40mR/h 4.5 seconds