1.1 This guide addresses methods used to prepare for and to perform, using gamma-ray measurements, the nondestructive assay (NDA) of radioisotopes, for example, ²³⁵U, or ²³⁹Pu, remaining as holdup in nuclear facilities. Holdup occurs in facilities where nuclear material is processed. This guide includes the measurement of holdup of Special Nuclear Material (SNM) in places where holdup may occur, such as in process equipment, and in exhaust ventilation systems. This guide includes information useful for management planning, selection of equipment, consideration of interferences, measurement program definition, and the utilization of resources.

1.2 The measurement of nuclear material help up in process equipment is both an art and a science. It is subject to the constraints of politics, economics plus health and safety requirements, as well as to the laws of physics. The measurement process often is long and tedious and is performed under difficult circumstances of location and environment. The work combines the features of a detective investigation and a treasure hunt. Nuclear material held up in pipes, ductwork, gloveboxes, heavy equipment, and so forth, usually is distributed in a diffuse and irregular manner. It is difficult to define the measurement geometry, identify the form of the material, and measure it without interference from adjacent sources of radiation. A scientific knowledge of radiation sources and detectors, calibration procedures, geometry and error analysis also is needed ().

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.