Answer to Question #306 Submitted to "Ask the Experts"

Q

When source-checking portable survey instruments prior to use, is it acceptable to perform a source check at the end of shift if the instruments will not be used until the start of the next shift and that shift starts within 24 hours of the source check? If that second shift is such that continuous instrument use extends past 24 hours from the source check, is it unnecessary to perform an additional check?

A

It sounds like you are looking for an interpretation of ANSI N323-1978, which states, "A performance check shall be made prior to each use, during intermittent use conditions, and several times a day during continuous use." The good news is that the above standard has been replaced by ANSI-N323A-1997, "Radiation Protection Instrumentation Test and Calibration," which is less rigorous in the area of concern. The new standard labels the old performance test as a source response check and states, ". . . each instrument . . . shall be checked with a source during operation at least daily, or prior to each intermittent use, whichever is less frequent." For auditors, the main issue will likely be whether the radiation protection group of interest meets its own procedure requirements, rather than the exact definition of a day or shift. The reader should also be aware that calibration quality standards are higher in the new ANSI standard. Many labs do not come close to meeting the standard. The definition of a proper calibration will likely keep auditors busy for the next few years. For more information on ANSI Standards go to the American Nuclear Standards website.

Roger Schanzenbach, CHP
San Onofre Nuclear Station