ASTM E265-07e1

Refer to Guides E 720 and E 844 for the selection, irradiation, and quality control of neutron dosimeters.

Refer to Practice E 261 for a general discussion of the determination of fast-neutron fluence and fluence rate with threshold detectors.

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 14.262 (14)³ days (1)⁴ and the maximum beta energy is 1710 keV(2).

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 (95.02 % (9)), ³⁴S (4.21 % (8)) (1), 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 E 261.

This standard does not purport to address all of the safety problems, 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.