1、Designation: E2059 06 (Reapproved 2010)E2059 15Standard Practice forApplication and Analysis of Nuclear Research Emulsions forFast Neutron Dosimetry1This standard is issued under the fixed designation E2059; the number immediately following the designation indicates the year oforiginal adoption or,
2、in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 Nuclear Research Emulsions (NRE) have a long and illustrious history of applicati
3、ons in the physical sciences, earthsciences and biological sciences (1,2)2. In the physical sciences, NRE experiments have led to many fundamental discoveries insuch diverse disciplines as nuclear physics, cosmic ray physics and high energy physics. In the applied physical sciences, NREhave been use
4、d in neutron physics experiments in both fission and fusion reactor environments (3-6). Numerous NRE neutronexperiments can be found in other applied disciplines, such as nuclear engineering, environmental monitoring and health physics.Given the breadth of NRE applications, there exist many textbook
5、s and handbooks that provide considerable detail on thetechniques used in the NRE method. As a consequence, this practice will be restricted to the application of the NRE method forneutron measurements in reactor physics and nuclear engineering with particular emphasis on neutron dosimetry in benchm
6、arkfields (see Matrix E706).1.2 NRE are passive detectors and provide time integrated reaction rates.As a consequence, NRE provide fluence measurementswithout the need for time-dependent corrections, such as arise with radiometric (RM) dosimeters (see Test Method E1005). NREprovide permanent records
7、, so that optical microscopy observations can be carried out anytime any time after exposure. Ifnecessary, NRE measurements can be repeated at any time to examine questionable data or to obtain refined results.1.3 Since NRE measurements are conducted with optical microscopes, high spatial resolution
8、 is afforded for fine structureexperiments. The attribute of high spatial resolution can also be used to determine information on the angular anisotropy of thein-situ neutron field (4,5,7). It is not possible for active detectors to provide such data because of in-situ perturbations andfinite-size e
9、ffects (see Section 11).1.4 The existence of hydrogen as a major constituent of NRE affords neutron detection through neutron scattering on hydrogen,that is, the well known (n,p) reaction. NRE measurements in low power reactor environments have been predominantly based onthis (n,p) reaction. NRE hav
10、e also been used to measure the 6Li (n,t) 4He and the 10B (n,) 7Li reactions by including 6Li and 10Bin glass specks near the mid-plane of the NRE (8,9). Use of these two reactions does not provide the general advantages of the(n,p) reaction for neutron dosimetry in low power reactor environments (s
11、ee Section 4). As a consequence, this standard will berestricted to the use of the (n,p) reaction for neutron dosimetry in low power reactor environments.1.5 LimitationsThe NRE method possesses three major limitations for applicability in low power reactor environments.1.5.1 Gamma-Ray SensitivityGam
12、ma-rays create a significant limitation for NRE measurements. Above a gamma-rayexposure of approximately 3R, 0.025 Gy, NRE can become fogged by gamma-ray induced electron events. At this level ofgamma-ray exposure, neutron induced proton-recoil tracks can no longer be accurately measured. As a conse
13、quence, NREexperiments are limited to low power environments such as found in critical assemblies and benchmark fields. Moreover,applications are only possible in environments where the buildup of radioactivity, for example, fission products, is limited.1.5.2 Low Energy LimitIn the measurement of tr
14、ack length for proton recoil events, track length decreases as proton-recoilenergy decreases. Proton-recoil track length below approximately 33m in NRE can not be adequately measured with opticalmicroscopy techniques.As proton-recoil track length decreases below approximately 3, 3 m, it becomes very
15、 difficult to measuretrack length accurately. This 3 3 m track length limit corresponds to a low energy limit of applicability in the range ofapproximately 0.3 to 0.4 MeV for neutron induced proton-recoil measurements in NRE.1.5.3 High-Energy LimitsAs a consequence of finite-size limitations, fast-n
16、eutron spectrometry measurements are limited to15 MeV. The limit for in-situ spectrometry in reactor environments is 8MeV.1 This practice is under the jurisdiction of ASTM Committee E10 on Nuclear Technology and Applications, and is the direct responsibility of Subcommittee E10.05 onNuclear Radiatio
17、n Metrology.Current edition approved Oct. 1, 2010Oct. 1, 2015. Published November 2010. Originally approved in 2000. Last previous edition approved in 20062010 asE2059 - 06.E2059 - 06(2010). DOI: 10.1520/E2059-10.10.1520/E2059-15.2 The boldface numbers in parentheses refer to the list of references
18、at the end of the text.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that
19、users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States11.5.4 Track Density Limit
20、The ability to measure proton recoil track length with optical microscopy techniques depends ontrack density.Above a certain track density, a maze or labyrinth of overlapping tracks is created, which precludes the use of opticalmicroscopy techniques. For manual scanning, this limitation arises above
21、 approximately 104 tracks/cm2, whereas interactivecomputer based scanning systems can extend this limit up to approximately 105 tracks/cm2. These limits correspond to neutronfluences of 106 107 cm2, respectively.1.6 Neutron Spectrometry (Differential Measurements)For differential neutron spectrometr
22、y measurements in low powerreactor environments, NRE experiments can be conducted in two different modes. In the more general mode, NRE are irradiatedin-situ in the low power reactor environment. This mode of NRE experiments is called the 4pi mode, since the in-situ irradiationcreates tracks in all
23、directions (see 3.1.1). In special circumstances, where the direction of the neutron flux is known, NRE areoriented parallel to the direction of the neutron flux. In this orientation, one edge of the NRE faces the incident neutron flux, sothat this measurement mode is called the end-on mode. Scannin
24、g of proton-recoil tracks is different for these two different modes.Subsequent data analysis is also different for these two modes (see 3.1.1 and 3.1.2).1.7 Neutron Dosimetry (Integral Measurements)NRE also afford integral neutron dosimetry through use of the (n,p) reactionin low power reactor envi
25、ronments. Two different types of (n,p) integral mode dosimetry reactions are possible, namely theI-integral (see 3.2.1) and the J-integral (see 3.2.2) (10,11). Proton-recoil track scanning for these integral reactions is conductedin a different mode than scanning for differential neutron spectrometr
26、y (see 3.2). Integral mode data analysis is also different thanthe analysis required for differential neutron spectrometry (see 3.2). This practice will emphasize NRE (n,p) integral neutrondosimetry, because of the utility and advantages of integral mode measurements in low power benchmark fields.2.
27、 Referenced Documents2.1 ASTM Standards:3E706 Master Matrix for Light-Water Reactor Pressure Vessel Surveillance Standards, E 706(0) (Withdrawn 2011)4E854 Test Method for Application and Analysis of Solid State Track Recorder (SSTR) Monitors for Reactor Surveillance,E706(IIIB)E910 Test Method for Ap
28、plication and Analysis of Helium Accumulation Fluence Monitors for Reactor Vessel Surveillance,E706 (IIIC)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 Su
29、rveillance3. Alternate Modes of NRE Neutron Measurements3.1 Neutron Spectrum MeasurementsThe neutron energy range of interest in reactors environments covers approximately nineorders of magnitude, extending from thermal energies up to approximately 20 MeV. No single high-resolution method of neutron
30、spectrometry exists that can completely cover this energy range of interest (12). Work with proton-recoil proportional counters hasnot been extended beyond a few MeV, due to the escape of more energetic protons from the finite sensitive volume of the counter.In fact, correction of in-situ proportion
31、al counters for such finite-size effects can be non-negligible above 0.5 MeV (13). Finite-sizeeffects are much more manageable in NRE because of the reduced range of recoil protons. As a consequence, NRE fast neutronspectrometry has been applied at energies up to 15 MeV (3). For in-situ spectrometry
32、 in reactor environments, NRE measurementsup to 8.0 MeV are possible with very small finite-size corrections (14-16).3.1.1 4pi ModeIt has been shown (3-6) that a neutron fluence-spectrum can be deduced from the integral relationshipME! 5np V *E npE! E!E dE (1)where:(E) = neutron fluence in n/(cm2MeV
33、),np(E) = neutron-proton scattering cross section (cm2) at neutron energy, E,E = neutron or proton energy (MeV),np = atomic hydrogen density in the NRE (atoms/cm3),V = volume of NRE scanned (cm3), andM (E) = proton spectrum (protons/MeV) observed in the NRE volume V at energy E.The neutron fluence c
34、an be derived from Eq 1 and takes the form:E! 5 2EnpE!npVdMdE (2)Eq 2 reveals that the neutron fluence spectrum at energy E depends upon the slope of the proton spectrum at energy E. As aconsequence, approximately 104 tracks must be measured to give statistical accuracies of the order of 10 % in the
35、 neutron fluence3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4 The last approved version of this historica
36、l standard is referenced on www.astm.org.E2059 152spectrum (with a corresponding energy resolution of the order of 10 %). It must be emphasized that spectral measurementsdetermined with NRE in the 4pi mode are absolute.3.1.2 End-On ModeDifferential neutron spectrometry with NRE is considerably simpl
37、ified when the direction of neutronincidence is known, such as for irradiations in collimated or unidirectional neutron beams. In such exposures, the kinematics of(n,p) scattering can be used to determine neutron energy. Observation of proton-recoil direction and proton-recoil track lengthprovide th
38、e angle of proton scattering relative to the incident neutron direction, , and the proton energy, Ep, respectively. In termsof these observations, the neutron energy, En, is simply:En 5 Epcos2 (3)In collimated or unidirectional neutron irradiations, the emulsion is exposed end-on as depicted in Fig.
39、 1. The end-on mode canbe used to advantage in media where neutron scattering is negligible for two types of benchmark field experiments, namely:3.1.2.1 Benchmark field validation of the NRE method or characterization of point neutron sources, for example, the standard252Cf neutron field at the Nati
40、onal Institute of Standards and Technology (NIST) (17).3.1.2.2 Measurement of leakage neutron spectra at sufficiently large distances from the neutron source, for example, neutronspectrum measurements at the Little Boy Replica (LBR) benchmark field (18).3.2 Integral ModeIt is possible to use emulsio
41、n data to obtain both differential and integral spectral information. Emulsionwork is customarily carried out in the differential mode (3-6). In contrast, NRE work in the integral mode is a more recent conceptand, therefore, a fuller explanation of this approach is included below. In this integral m
42、ode, NRE provide absolute integral reactionrates, which can be used in spectral adjustment codes. Before these recent efforts, such codes have not utilized integral reactionrates based on NRE. The significance of NRE integral reaction rates stems from the underlying response, which is based on theel
43、astic scattering cross section of hydrogen. This np (E) cross section is universally accepted as a standard cross section and isknown to an accuracy of approximately 1 %.3.2.1 The I Integral RelationThe first integral relationship follows directly from Eq 1. The integral in Eq 1 can be defined as:IE
44、T! 5*ET E!E E! dE (4)Here I(ET) possesses units of proton-recoil tracks/MeV per hydrogen atom. Clearly I(ET) is a function of the lower proton energycut-off used for analyzing the emulsion data. Using Eq 4 in Eq 1, one finds the integral relation:IET! 5MET!npV(5)I(ET) is evaluated by using a least s
45、quares fit of the scanning data in the neighborhood of E = ET. Alternatively, since:MET! 5MRT! dRE!dE (6)where: R(E) is the proton-recoil range at energy E in the NRE and dR/dE is known from the proton range-energy relation forthe NRE. One need only determine M(R) in the neighborhood of R = RR = RT.
46、 Here M(R) is the number of proton-recoilFIG. 1 Geometrical Configuration for End-On Irradiation of NREE2059 153tracks/microntracks/m observed in the NRE. Consequently, scanning efforts can be concentrated in the neighborhood of R = RTin order to determine I(ET). In this manner, the accuracy attaine
47、d in I(ET) is comparable to the accuracy of the differentialdetermination of (E), as based on Eq 2, but with a significantly reduced scanning effort.3.2.2 The J Integral RelationThe second integral relation can be obtained by integration of the observed proton spectrumM(ET). From Eq 1:*Emin MET!dET
48、5npV *Emin dET *ET E!E E!dE (7)where: Emin is the lower proton energy cut-off used in analyzing the NRE data. Introducing into Eq 7 the definitions:Emin!5*Emin MET!dET (8)and:JEmin!5*Emin dET *ET E!E E! (9)has:JEmin!5Emin!npV(10)Hence, the second integral relation, namely Eq 10, can be expressed in
49、a form analogous to the first integral relation, namelyEq 5. Here (Emin) is the integral number of proton-recoil tracks per hydrogen atom observed above an energy Emin in the NRE.Consequently the integral J(Emin) possesses units of proton-recoil tracks per hydrogen atom. The integral J(Emin) can be reducedto the form:JEmin!5*Emin S12EminE DE!E!dE (11)In addition by using Eq 6, the observable (Emin) can be expressed in the form:Emin!5*Rmin MR!dR (12)Hence, to determine the second integral relat
