46 63138-US-200110
5.3 Special Conditions
Radiation Fields Inside Vessels
You must measure the radiation fields inside a vessel when entering the vessel.
Use the following statements when defining those requirements:
• Equipment that is mounted on vessels or has accessible air gaps must
have written lockout procedures to ensure that access to the high levels
of the primary radiation beam is not possible.
• In North America, many of these types of installations are considered by
OSHA (Occupational Safety and Health Administration) as confined spaces
and the radiation is classified as "other known energy hazards". These
installations require lockout documentation consistent with OSHA rules.
At a minimum, follow the steps listed below, where applicable:
1. Verify, by signature, that the source holder is locked in the OFF (shutter
closed) position.
2. Ensure that one person, who controls individuals entering the air gap, holds
the key to the interlock system, if acquired.
3. Make certain the radiation field is very low by using the gauge electronics or
a survey meter.
4. Check that the gauge electronics shows a high reading or maximum
density, since no radiation is reaching the detector.
5. Make sure the survey meter allows for quantitative measurements. The fields
measured should match very closely to background readings.
6. Ensure that the vessel is vacant and the entrance door is locked, after the
work is completed.
7. Complete these steps before inserting the source holder and returning it to
the "ON" position.
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