ASTM E1496-05

Many requirements exist for accurate dimensional information in industrial quality control. Frequently, this information cannot be measured directly, may be very uncertain, or is expensive to obtain. If a radiograph of the object in question displays a sufficient film density variation near the edge of interest, however, dimensional radiography methods may be applied. This test method provides a technique for extracting quantitative dimensional information from the neutron radiograph of an object. Guide E 94 and Practices E 748 are helpful for understanding the principles involved in obtaining a high-quality neutron radiograph.

Dimensional radiography appears to be particularly relevant in determination of the following: (1) diameters of spent radioactive fuel, (2) gap sizes in contact-circuit mechanisms of shielded components, and (3) prescribed spacings between distinct materials.

While this test method addresses dimensional measurements using neutron radiography, the methods and techniques of dimensional radiography are also equally applicable to various types of radiography, such as x-ray, γ-ray, and neutron.

A fundamental assumption of this test method is that the user will have access to a system that permits the attainment of data describing the density response of the radiograph. Although a system may include any digitization equipment capable of providing the spatial resolutions recommended in 6.1.1, a typical system will include a high-resolution traveling-stage microdensitometer and a neutron radiograph of the object.

An object with accurately known dimensions must be available to calibrate the equipment used to measure the radiographic response, that is, the traveling-stage microdensitometer (or other digitization system capable of spatial resolution comparable to that of the detector).

1.1 This test method provides a technique for extracting quantitative dimensional information on an object from its neutron radiograph. The technique is based on the identification of changes in film density caused by material changes where a corresponding discontinuity in film density exists. This test method is designed to be used with neutron radiographs made with a well-collimated beam. The film densities in the vicinity of the edge must be in the linear portion of the density versus exposure curve. The accuracy of this test method may be affected adversely in installations with high-angular-divergence neutron beams or with large object-to-film distances.

1.2 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.