Answer to Question #326 Submitted to "Ask the Experts"

Q

What is the recommended frequency for source response checks for fixed contamination monitors? I am trying to locate ANSI (or similiar) documents regarding frequency of source response checks for fixed contamination montors (i.e. portal monitors or personnel contamination monitors). We currently source check the monitors daily and are investigating the possibility of reducing the frequency to allow the monitors to be used seven days a week with only a source response check available Monday through Friday.

A

There are presently no ANSI standards that provide guidance or requirements for source response checks of fixed contamination monitors. ANSI N323A provides guidance for source response checks for portable instruments. Three related ANSI standards are being written: ANSI N323B, C, and D. One of the standards (ANSI N323D) will address fixed instrumentation and should include guidance on source response check frequency. However, at this time the draft standard is in its infancy, so it's not possible to anticipate what the standard will state. If you are in the Department of Energy (DOE) world, there is additional guidance in the DOE Radiological Control Standard. Item 553.4 states that ". . . area radiation monitors should be tested at least quarterly to verify audible alarm system operability and audibility under ambient working conditions and operability of visual alarms when so equipped." The standard includes guidance for continuous air monitors as well in article 555.8. This article states, "The proper operation of continuous air monitoring equipment should be verified daily by performing an operational check. Operational checks should include positive air flow indication, non-zero response to background activity, and internal check sources or 60 Hz electronic checks when available. Real-time air monitoring equipment operation should be verified weekly by checking for instrument response with a check source or with ambient levels of radon and thoron daughters." The standard, however, contains no guidance specific to personnel contamination monitors. The practice at Battelle (Pacific Northwest National Laboratory) is to perform weekly source checks on installed contamination monitors. The basis for the weekly checks is ANSI N323-1978 which states, in its scope, that the general guidance may be applicable to installed instruments. In this case, we applied the guidance to perform the source check but reduced the frequency to weekly because the instruments are installed so are not subjected to damage during handling/transport. There may be additional guidance in the Nuclear Regulatory Commission regulations, but I am not familiar with them.



Michelle Johnson, CHP

Pacific Northwest National Laboratory