Significance and Use SNM monitors are an effective and unobtrusive means to search for concealed SNM, and facility security plans use them to prevent SNM theft or unauthorized removal from SNM access areas. Functional testing of monitors on a daily basis with radioactive sources can assure that they are in good working order. The significant use of a less frequent, in-plant evaluation of an SNM monitor is to verify that the monitor achieves an expected probability of detection for an SNM or alternative test source. Note 1—An SNM test source used for in-plant evaluation is normally shielded only by protective encapsulation and the parts of a vehicle that may lie between the source and the monitor’detectors. However, the evaluation procedure could just as well be used to verify an expected level of detection for SNM inside of containers or shields.Scope1.1 This guide is one of a series on special nuclear material (SNM) monitors and their performance evaluation. Others in the series provide information on SNM monitoring, monitor calibration, and methods of evaluation (see ), but Guide C 993, in particular, provides much of the basis for this guide. The purpose for a guide to in-plant performance evaluation is to provide a comparatively rapid way to verify whether SNM monitors perform as expected for detecting SNM or an alternative test source.1.2 Guide C 993 points out that in-plant evaluation is one part of a program to keep SNM monitors in proper operating condition and that in-plant evaluation can be used as a routine operational evaluation or can be used to verify performance after a monitor is calibrated. 1.3 This guide is based on ASTM standards that describe applying and evaluating SNM monitors.
