ASTM E481-15
Standard Test Method for Measuring Neutron Fluence Rates by Radioactivation of Cobalt and Silver

Standard No.

ASTM E481-15

Release Date

2015

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM E481-16

Latest

ASTM E481-23

Scope

3.1 This test method uses one monitor (cobalt) with a nearly 1/v absorption cross-section curve and a second monitor (silver) with a large resonance peak so that its resonance integral is large compared to the thermal cross section. The pertinent data for these two reactions are given in Table 1. The equations are based on the Westcott formalism ((2, 3) and Practice E261) and determine a Westcott 2200 m/s neutron fluence rate nv₀ and the Westcott epithermal index parameter . References 4, 5, and 6 contain a general discussion of the two-reaction test method. In this test method, the absolute activities of both cobalt and silver monitors are determined. This differs from the test method in the references wherein only one absolute activity is determined.

(A) The numbers in parenthesis following given values are the uncertainty in the last digit(s) of the value; 0.729 (8) means 0.729 ± 0.008, 70.8(1) means 70.8 ± 0.1.

(B) A 2200 m/s cross section (E = 0.0253 eV, T = 20°C) was taken from the sources indicated in Ref (9).

(C) Cross section uncertainty data is taken from Ref (7) , the cross section comes from the other reference.

(D) Calculated using Eq 10.

(E) Cross section uncertainty comes from convariance data provided in the cross section source. The other reference indicates the source of the cross section.

(F) In Fig. 1, Θ = 4E_rkT/AΓ ² = 0.2 corresponds to the value for ¹⁰⁹Ag for T = 293 K, ∑_r = N₀σ_{r, max}. σ_{r, max}=29999 barn at 5.19 eV (