ASTM E1297 - 08(2013)

    Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Niobium

    Active Standard ASTM E1297 | Developed by Subcommittee: E10.05

    Book of Standards Volume: 12.02

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    Significance and Use

    5.1 Refer to Practice E261 for a general discussion of the determination of decay rates, reaction rates, and neutron fluence rates with threshold detectors (1-29).3 Refer to Practice E1006, Practice E185 and Guide E1018 for the use and application of results obtained by this test method.(34-36)

    5.2 The half-life of 93mNb is 5730 ± 220 days (30) and has a K X-ray emission probability of 0.1099 ± 0.0025 per decay (30). The Kα and Kβ X-rays of niobium are at 16.5213–16.152 and 18.618–18.953 keV, respectively. The recommended 93Nb (n,n)93mNb cross section comes from the IRDF-90 cross section compendium (31), was drawn from the RRDF-98 cross section evaluations (37) and is shown in Fig. 1.

     IRDF-90 Cross Section Versus Energy for the Nb(n,n′)Nb Reaction
    FIG. 1 IRDF-90 Cross Section Versus Energy for the 93Nb(n,n) 93mNb Reaction

    5.3 Chemical dissolution of the irradiated niobium to produce very low mass-per-unit area sources is an effective way to obtain consistent results. The direct counting of foils or wires can produce satisfactory results provided appropriate methods and interpretations are employed. It is possible to use liquid scintillation methods to measure the niobium activity provided the radioactive material can be kept uniformly in solution and appropriate corrections can be made for interfering activities.

    5.4 The measured reaction rates can be used to correlate neutron exposures, provide comparison with calculated reaction rates, and determine neutron fluences. Reaction rates can be determined with greater accuracy than fluence rates because of the current uncertainty in the cross section versus energy shape.

    5.5 The 93Nb(n,n)93mNb reaction has the desirable properties of monitoring neutron exposures related to neutron damage of nuclear facility structural components. It has an energy response range corresponding to the damage function of steel and has a half-life sufficiently long to allow its use in very long exposures (up to about 40 years). Monitoring long exposures is useful in determining the long-term integrity of nuclear facility components.

    1. Scope

    1.1 This test method describes procedures for measuring reaction rates by the activation reaction 93Nb(n,n) 93mNb.

    1.2 This activation reaction is useful for monitoring neutrons with energies above approximately 0.5 MeV and for irradiation times up to about 30 years.

    1.3 With suitable techniques, fast-neutron reaction rates for neutrons with energy distribution similar to fission neutrons can be determined in fast-neutron fluences above about 1016 cm−2. In the presence of high thermal-neutron fluence rates (>1012cm−2·s−1), the transmutation of 93mNb due to neutron capture should be investigated. In the presence of high-energy neutron spectra such as are associated with fusion and spallation sources, the transmutation of 93mNb by reactions such as (n,2n) may occur and should be investigated.

    1.4 Procedures for other fast-neutron monitors are referenced in Practice E261.

    1.5 Fast-neutron fluence rates can be determined from the reaction rates provided that the appropriate cross section information is available to meet the accuracy requirements.

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

    1.7 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

    D1193 Specification for Reagent Water

    E170 Terminology Relating to Radiation Measurements and Dosimetry

    E181 Test Methods for Detector Calibration and Analysis of Radionuclides

    E185 Practice for Design of Surveillance Programs for Light-Water Moderated Nuclear Power Reactor Vessels

    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)

    E1006 Practice for Analysis and Interpretation of Physics Dosimetry Results for Test Reactors, E 706(II)

    E1018 Guide for Application of ASTM Evaluated Cross Section Data File, Matrix E706 (IIB)

    ICS Code

    ICS Number Code 27.120.01 (Nuclear energy in general)

    UNSPSC Code

    UNSPSC Code 26140000(Atomic and nuclear energy machinery and equipment)

    Referencing This Standard
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    DOI: 10.1520/E1297-08R13

    Citation Format

    ASTM E1297-08(2013), Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Niobium, ASTM International, West Conshohocken, PA, 2013,

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