ASTM-E526 2008(Redline)

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E526-08 Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Titanium (Redline)

Published By	Publication Date	Number of Pages
ASTM	2008	5

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Description

Significance and Use

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

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

Titanium has good physical strength, is easily fabricated, has excellent corrosion resistance, has a melting temperature of 1675 ° C, and can be obtained with satisfactory purity.

⁴⁶ Sc has a half-life of 83.79 days. The ⁴⁶ Sc decay emits a 0.8893 MeV gamma 99.984 % of the time and a second gamma with an energy of 1.1205 MeV 99.987 % of the time.

The isotopic content of natural titanium recommended for ⁴⁶ Ti is 8.25 %.

The radioactive products of the neutron reactions ⁴⁷ Ti(n,p) ⁴⁷ Sc ( τ _1/2 = 3.3492 d) and ⁴⁸ Ti(n,p) ⁴⁸ Sc ( τ _1/2 = 43.67 h), might interfere with the analysis of ⁴⁶ Sc.

Contaminant activities (for example, ⁶⁵ Zn and ¹⁸² Ta) might interfere with the analysis of ⁴⁶ Sc. See Sections 7.1.2 and 7.1.3 for more details on the ¹⁸² Ta and ⁶⁵ Zn interference.

⁴⁶ Ti and ⁴⁶ Sc have cross sections for thermal neutrons of 0.59 and 8 barns, respectively ; therefore, when an irradiation exceeds a thermal-neutron fluence greater than about 2 × 10 ²¹ cm ^{– 2} , provisions should be made to either use a thermal-neutron shield to prevent burn-up of ⁴⁶ Sc or measure the thermal-neutron fluence rate and calculate the burn-up.

Fig. 1 shows a plot of cross section versus neutron energy for the fast-neutron reactions of titanium which produce ⁴⁶ Sc [that is, ^Nat Ti(n,X) ⁴⁶ Sc]. Included in the plot is the ⁴⁶ Ti(n,p) reaction and the ⁴⁷ Ti(n,np) contribution to the ⁴⁶ Sc production, normalized (at 14.7 MeV) per ⁴⁶ Ti atom. This figure is for illustrative purposes only to indicate the range of response of the ⁴⁶ Ti(n,p) reaction. Refer to Guide E 1018 for descriptions of recommended tabulated dosimetry cross sections.

1. Scope

1.1 This test method covers procedures for measuring reaction rates by the activation reactions ⁴⁶ Ti(n,p) ⁴⁶ Sc + ⁴⁷ Ti(n, np) ⁴⁶ Sc.

Note 1—Since the cross section for the (n,np) reaction is relatively small for energies less than 12 MeV and is not easily distinguished from that of the (n,p) reaction, this test method will refer to the (n,p) reaction only.

1.2 The reaction is useful for measuring neutrons with energies above approximately 4.4 MeV and for irradiation times up to about 250 days (for longer irradiations, see Practice E 261).

1.3 With suitable techniques, fission-neutron fluence rates above 10 ⁹ cm ^{– 2} · s ^{– 1} can be determined. However, in the presence of a high thermal-neutron fluence rate, ⁴⁶ Sc depletion should be investigated.

1.4 Detailed procedures for other fast-neutron detectors are referenced in Practice E 261.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 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.

2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

ASTM Standards

E170 Terminology Relating to Radiation Measurements and Dosimetry E181 Test Methods for Detector Calibration and Analysis of Radionuclides E261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques E262 Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques E844 Guide for Sensor Set Design and Irradiation for Reactor Surveillance, E 706 (IIC) E944 Guide for Application of Neutron Spectrum Adjustment Methods in Reactor Surveillance, E 706 (IIA) E1005 Test Method for Application and Analysis of Radiometric Monitors for Reactor Vessel Surveillance, E 706 (IIIA) E1018 Guide for Application of ASTM Evaluated Cross Section Data File, Matrix E706 (IIB)

Keywords

activation reaction; cross section; dosimetry; nuclear metrology; pressure vessel surveillance; reaction rate; titanium; Activation reactions; Dosimetry; Fast neutron flux/fluence; Neutron activati

Additional information

Standard Title	E526-08 Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Titanium (Redline)
Published Code	ASTM
Publication Date	2008
Pages Count	5

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