【国外标准】 Standard Test Method for Measuring Reaction Rates and Fast-Neutron Fluences by Radioactivation of Sulfur-32

5.1 Refer to Guides E720 and E844 for the selection, irradiation, and quality control of neutron dosimeters. 5.2 Refer to Practice E261 for a general discussion of the determination of fast-neutron fluence and fluence rate with threshold detectors. 5.3 The activation reaction produces 32P, which decays by the emission of a single beta particle in 100 % of the decays, and which emits no gamma rays. The half life of 32P is 14.284 (36)3 days (1) 4 and the maximum beta energy is 1710.66 (21) keV (1). 5.4 Elemental sulfur is readily available in pure form and any trace contaminants present do not produce significant amounts of radioactivity. Natural sulfur, however, is composed of 32S (94.99 % (26)), 34S (4.25 % (24)) (2), and trace amounts of other sulfur isotopes. The presence of these other isotopes leads to several competing reactions that can interfere with the counting of the 1710-keV beta particle. This interference can usually be eliminated by the use of appropriate techniques, as discussed in Section 8. 1.1 This test method describes procedures for measuring reaction rates and fast-neutron fluences by the activation reaction 32S(n,p)32P. 1.2 This activation reaction is useful for measuring neutrons with energies above approximately 3 MeV. 1.3 With suitable techniques, fission-neutron fluences from about 5 × 108 to 1016 n/cm 2 can be measured. 1.4 Detailed procedures for other fast-neutron detectors are described in Practice E261. 1.5 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. 1.6 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.