SIGMA projetor - Manual (Page 36)

MAINTENANCE INSTRUCTIONS
4.5
Leak Testing
Leak Test of the Radioactive Sealed Source
Periodic leak tests of the radioactive sealed source are required by most national and international
regulations. The leak test provides a confirmation of the integrity of the hermetically welded sealed
source by determining the amount of removable contamination. In most regulatory jurisdictions, a leak
test of a sealed source must be performed every 6 months or prior to its first use after removal from
storage. Acceptable results of a radio-assay must indicate removable contamination is less than <185 Bq
(0.005 µCi). To perform a wipe of the radioactive sealed source, perform the following steps:
1
Survey the entire exterior surface of the exposure device to ensure the dose/rates are less than 2
mSv/hr (200 mR/hr).
2
Prepare a Model 518 wipe test swab according to the instruction sheet. Fill in all required information
for the source on the leak test form. Omission of the isotope, source model and serial number, etc.
will delay processing of the wipe test.
3
Install service bayonet fitting (part no. 88049) into the outlet port and rotate the cover to allow the
wipe test want to enter the ‘S’ tube.
4
Fully insert the wipe test swab into the ‘S’ tube and move back and forth to obtain the sample.
5
Carefully withdraw the wipe test swab from the outlet port while observing the survey instrument.
Withdraw the plastic bag over the wipe test wand without touching. Always assume the sample is
contaminated.
6
Remove the service bayonet fitting from the outlet port and rotate the outlet port cover into the closed
position.
7
In a low background (no radiation) area, switch the survey meter to the lowest scale and obtain a
background measurement. Leaving the survey meter stationary, move the plastic wrapped swab
towards the survey meter's detector to determine if a gross quantity of contamination is on the wipe
test. If the survey meter measures greater than 1 µSv/hr (0.1 mR/hr), contact QSA Global, Inc. for
instructions. If there is no measurable increase above background, the sample may be sent to the
SENTINEL™ laboratory for radio-assay. The SENTINEL™ laboratory will send a leak test certificate
after performing the radio-assay. Retain this certificate in your records.
In the event you are informed by the radio-assay laboratory that your leak test results indicate
greater than >185 Bq (0.005 µCi), you must immediately remove from service the radioactive sealed
source, the exposure device and all remote controls, source guide tubes, collimators, lab stands, etc.
that were used in conjunction with that sealed source. You must cause the equipment to be repaired
or decontaminated and notify the regulatory agency (USA) within 5 days (check local regulations for
reporting requirements). Contact the sealed source manufacturer for assistance.
Leak Test for Depleted Uranium (DU)
Some regulatory jurisdictions require periodic leak tests every twelve months of all projection-type
exposure devices that utilize DU for shielding. The purpose of the leak test is to detect the long-term wear
through of the device's source tube that may consequently expose the DU shielding. A wipe-test wand
that is both flexible and long enough to reach a bend radius or a wear point is required to perform a leak
test. The wand enables direct contact with the DU where the device’s source tube has worn through. A
direct wipe of the DU is required due to the low specific activity of depleted uranium. The wipe test for DU
is obtained in the same fashion as a leak test of a sealed source utilizing the same radiation safety
procedures.