1.1 本规程涵盖了光束纯度指示器（BPI）的材料和制造，该指示器可用于确定直接热中子射线照相检查产生的射线照相图像的相对质量。 1.2 单位- 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 BPI旨在产生有关中子束和图像系统参数的定量信息，这些参数有助于胶片曝光，从而影响整体图像质量。为了正确测量中子束成分引起的薄膜曝光，必须根据本规程制造BPI。 5.2 在制造与试验方法一起使用的所有光束纯度指示器时，应遵循本规程 E545 确定直接热中子照相中的图像质量。

1.1 This practice covers the material and fabrication of a Beam Purity Indicator (BPI), which can be used to determine the relative quality of radiographic images produced by direct, thermal neutron radiographic examination. 1.2 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 The BPI is designed to yield quantitative information concerning neutron beam and image system parameters that contribute to film exposure and, thereby, affect overall image quality. For proper measurements of film exposure due to the neutron beam constituents, the BPI must be fabricated in accordance with this practice. 5.2 This practice shall be followed for the fabrication of all Beam Purity Indicators to be used with Test Method E545 to determine image quality in direct thermal neutron radiography.