ASTM E910 - 07(2013)

    Standard Test Method for Application and Analysis of Helium Accumulation Fluence Monitors for Reactor Vessel Surveillance, E706 (IIIC)

    Active Standard ASTM E910 | Developed by Subcommittee: E10.05

    Book of Standards Volume: 12.02


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    ASTM E910

    Significance and Use

    5.1 The HAFM test method is one of several available passive neutron dosimetry techniques (see, for example, Methods E854 and E1005). This test method can be used in combination with other dosimetry methods, or, if sufficient data are available from different HAFM sensor materials, as an alternative dosimetry test method. The HAFM method yields a direct measurement of total helium production in an irradiated sample. Absolute neutron fluence can then be inferred from this, assuming the appropriate spectrum integrated total helium production cross section. Alternatively, a calibration of the composite neutron detection efficiency for the HAFM method may be obtained by exposure in a benchmark neutron field where the fluence and spectrum averaged cross section are both known (see Matrix E706 IIE).

    5.2 HAFMs have the advantage of producing an end product, helium, which is stable, making the HAFM method very attractive for both short-term and long-term fluence measurements without requiring time-dependent corrections for decay. HAFMs are therefore ideal passive, time-integrating fluence monitors. Additionally, the burnout of the daughter product, helium, is negligible.

    5.2.1 Many of the HAFM materials can be irradiated in the form of unencapsulated wire segments (see 1.1.2). These segments can easily be fabricated by cutting from a standard inventoried material lot. The advantage is that encapsulation, with its associated costs, is not necessary. In several cases, unencapsulated wires such as Fe, Ni, Al/Co, and Cu, which are already included in the standard radiometric (RM) dosimetry sets (Table 1) can be used for both radiometric and helium accumulation dosimetry. After radiometric counting, the samples are later vaporized for helium measurement.

    TABLE 1 Neutron Characteristics of Candidate HAFM Materials for Reactor Vessel Surveillance

    HAFM Sensor Material

    Principal Helium Producing Reaction

    Thermal Neutron Cross Section, (b)

    Fission Neutron Spectrum

    Cross Section, (mb)A

    90 % Response
    Range, (MeV)A

      Li

    6Li(n,α)T

    942

      457

    0.167–5.66

      Be

    9Be(n,α)6He ;ra 6Li

    ...

      284

    2.5–7.3

      B

    10B(n,α)7Li

    3838

      494

    0.066–5.25

      N

    14N(n,α)11B

    ...

      86.2

    1.7–5.7

      F

    19F(n,α)16N

    ...

      27.6

    3.7–9.7

      AlB

    27Al(n,α)24Na

    ...

      0.903

    6.47–11.9

      S

    32S(n,α)29Si

    ...

      ...

    ...

      Cl

    35Cl(n,α)32P

    ...

      13 (Cl)

    2.6–8.3

      TiB

    47Ti(n,α)44Ca

    ...

      0.634 (Ti)

    6.5–12.8

      FeB

    56Fe(n,α)53Cr

    ...

      0.395 (Fe)

    5.2–11.9

      NiB

    58Ni(n,α)55Fe

    ...

      5.58 (Ni)

    3.9–10.1

      CuB

    63Cu(n,α)60Co

    ...

      0.330

    4.74–11.1

    Equation E0910-07R13_1

    Helium Production Largely
    from 56Fe and 58Ni

     

     

     

     

    A Evaluated 235U fission neutron spectrum averaged helium production cross section and energy range in which 90 % of the reactions occur. All values are obtained from ENDF/B-V Gas Production Dosimetry File data. Bracketed terms indicate cross section is for naturally occurring element.
    B Often included in dosimetry sets as a radiometric monitor, either as a pure element foil or wire or, in the case of aluminum, as an allaying material for other elements.

    5.3 The HAFM method is complementary to RM and solid state track recorder (SSTR) foils, and has been used as an integral part of the multiple foil method. The HAFM method follows essentially the same principle as the RM foil technique, which has been used successfully for accurate neutron dosimetry for the past 20 to 25 years. Various HAFM sensor materials exist which have significantly different neutron energy sensitivities from each other. HAFMs containing 10B and 6Li have been used routinely in LMFBR applications in conjunction with RM foils. The resulting data are entirely compatible with existing adjustment methods for radiometric foil neutron dosimetry (refer to Method E944).

    5.4 An application for the HAFM method lies in the direct analysis of pressure vessel wall scrapings or Charpy block surveillance samples. Measurements of the helium production in these materials can provide in situ integral information on the neutron fluence spectrum. This application can provide dosimetry information at critical positions where conventional dosimeter placement is difficult if not impossible. Analyses must first be conducted to determine the boron, lithium, and other component concentrations, and their homogeneities, so that their possible contributions to the total helium production can be determined. Boron (and lithium) can be determined by converting a fraction of the boron to helium with a known thermal neutron exposure. Measurements of the helium in the material before and after the exposure will enable a determination of the boron content (7). Boron level down to less than 1 wt. ppm can be obtained in this manner.

    5.5 By careful selection of the appropriate HAFM sensor material and its mass, helium concentrations ranging from 10−14 to 10−1 atom fraction can be generated and measured. In terms of fluence, this represents a range of roughly 1012 to 1027 n/cm2. Fluence (>1 MeV) values that may be encountered during routine surveillance testing are expected to range from 3 × 1014 to 2 × 10 20 n/cm2, which is well within the range of the HAFM technique.

    5.6 The analysis of HAFMs requires an absolute determination of the helium content. The analysis system specified in this test method incorporates a specialized mass spectrometer in conjunction with an accurately calibrated helium spiking system. Helium determination is by isotope dilution with subsequent isotope ratio measurement. The fact that the helium is stable makes the monitors permanent with the helium analysis able to be conducted at a later time, often without the inconvenience in handling caused by induced radioactivity. Such systems for analysis exist, and additional analysis facilities could be reproduced, should that be required. In this respect, therefore, the analytical requirements are similar to other ASTM test methods (compare with Test Method E244).

    1. Scope

    1.1 This test method describes the concept and use of helium accumulation for neutron fluence dosimetry for reactor vessel surveillance. Although this test method is directed toward applications in vessel surveillance, the concepts and techniques are equally applicable to the general field of neutron dosimetry. The various applications of this test method for reactor vessel surveillance are as follows:

    1.1.1 Helium accumulation fluence monitor (HAFM) capsules,

    1.1.2 Unencapsulated, or cadmium or gadolinium covered, radiometric monitors (RM) and HAFM wires for helium analysis,

    1.1.3 Charpy test block samples for helium accumulation, and

    1.1.4 Reactor vessel (RV) wall samples for helium accumulation.

    1.2 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

    C859 Terminology Relating to Nuclear Materials

    E170 Terminology Relating to Radiation Measurements and Dosimetry

    E244 Test Method for Atom Percent Fission in Uranium and Plutonium Fuel (Mass Spectrometric Method)

    E261 Practice for Determining Neutron Fluence, Fluence Rate, and Spectra by Radioactivation Techniques

    E482 Guide for Application of Neutron Transport Methods for Reactor Vessel Surveillance, E706 (IID)

    E706 Master Matrix for Light-Water Reactor Pressure Vessel Surveillance Standards, E 706(0)

    E844 Guide for Sensor Set Design and Irradiation for Reactor Surveillance, E 706 (IIC)

    E853 Practice for Analysis and Interpretation of Light-Water Reactor Surveillance Results, E706(IA)

    E854 Test Method for Application and Analysis of Solid State Track Recorder (SSTR) Monitors for Reactor Surveillance, E706(IIIB)

    E900 Guide for Predicting Radiation-Induced Transition Temperature Shift in Reactor Vessel Materials, E706 (IIF)

    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)


    ICS Code

    ICS Number Code 17.240 (Radiation measurements)

    UNSPSC Code

    UNSPSC Code 26142100(Nuclear reactor equipment)


    DOI: 10.1520/E0910-07R13

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