ASTM E385-2011 8745 Standard Test Method for Oxygen Content Using a 14-MeV Neutron Activation and Direct-Counting Technique《使用14 MeV中子活化法和直接计算技术测定含氧量的标准试验方法》.pdf
《ASTM E385-2011 8745 Standard Test Method for Oxygen Content Using a 14-MeV Neutron Activation and Direct-Counting Technique《使用14 MeV中子活化法和直接计算技术测定含氧量的标准试验方法》.pdf》由会员分享,可在线阅读,更多相关《ASTM E385-2011 8745 Standard Test Method for Oxygen Content Using a 14-MeV Neutron Activation and Direct-Counting Technique《使用14 MeV中子活化法和直接计算技术测定含氧量的标准试验方法》.pdf(8页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: E385 11Standard Test Method forOxygen Content Using a 14-MeV Neutron Activation andDirect-Counting Technique1This standard is issued under the fixed designation E385; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、 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 This test method covers the measurement of oxygenconcentration in almost any matrix by using a 14-MeV neutron
3、activation and direct-counting technique. Essentially, the samesystem may be used to determine oxygen concentrationsranging from under 10 g/g to over 500 mg/g, depending onthe sample size and available 14-MeV neutron fluence rates.NOTE 1The range of analysis may be extended by using higherneutron fl
4、uence rates, larger samples, and higher counting efficiencydetectors.1.2 This test method may be used on either solid or liquidsamples, provided that they can be made to conform in size,shape, and macroscopic density during irradiation and countingto a standard sample of known oxygen content. Severa
5、lvariants of this method have been described in the technicalliterature. A monograph is available which provides a compre-hensive description of the principles of activation analysisusing a neutron generator (1).21.3 The values stated in SI units are to be regarded asstandard. No other units of meas
6、urement are included in thisstandard.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory lim
7、itations prior to use. Specific precau-tions are given in Section 8.2. Referenced Documents2.1 ASTM Standards:3E170 Terminology Relating to Radiation Measurements andDosimetryE181 Test Methods for Detector Calibration andAnalysis ofRadionuclidesE496 Test Method for Measuring Neutron Fluence andAvera
8、ge Energy from3H(d,n)4He Neutron Generators byRadioactivation Techniques2.2 U.S. Government Document:Code of Federal Regulations, Title 10, Part 2043. Terminology3.1 Definitions (see also Terminology E170):3.1.1 acceleratora machine that ionizes a gas and electri-cally accelerates the ions onto a ta
9、rget. The accelerator may bebased on the Cockroft-Walton, Van de Graaff, or other designtypes (1). Compact sealed-tube, mixed deuterium and tritiumgas, Cockcroft-Walton neutron generators are most commonlyused for 14-MeV neutron activation analysis. However,“pumped” drift-tube accelerators that use
10、replaceable tritium-containing targets are also still in use. Reviews of operationalcharacteristics, descriptions of accessory instrumentation, andapplications of accelerators used as fast neutron generators foractivation analysis are available (2,3).3.1.2 comparator standarda reference standard of
11、knownoxygen content whose specific counting rate (counts min1mgof oxygen1) may be used to quantify the oxygen content of asample irradiated and counted under the same conditions.Often, a comparator standard is selected to have a matrixcomposition, physical size, density and shape very similar tothe
12、corresponding parameters of the sample to be analyzed.3.1.3 14-MeV neutron fluence ratethe areal density ofneutrons passing through a sample, measured in terms ofneutrons cm2s1, that is produced by the fusion reaction ofdeuterium and tritium ions accelerated to energies of typically150 to 200 keV in
13、 a small accelerator. Fluence rate has beencommonly referred to as “flux density.” The total neutronfluence is the fluence rate integrated over time.1This test method is under the jurisdiction ofASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of Subcommittee
14、E10.05 on Nuclear Radiation Metrology.Current edition approved Nov. 1, 2011. Published November 2011. Originallyapproved in 1969. Last previous edition approved in 2007 as E385 07. DOI:10.1520/E0385-11.2The boldface numbers in parentheses refer to a list of references at the end ofthe text.3For refe
15、renced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from the Superintendent of Documents, U.S. Government Print
16、ingOffice, Washington, DC 20402.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.3.1 DiscussionThe3H(d,n)4He reaction is used to pro-duce approximately 14.7-MeV neutrons. This reaction has aQ-value of + 17.586 MeV.3.1.4 monitorany
17、 type of detector or comparison refer-ence material that can be used to produce a response propor-tional to the 14-MeV neutron fluence rate in the irradiationposition, or to the radionuclide decay events recorded by thesample detector. A plastic pellet with a relatively high oxygencontent is often u
18、sed as a monitor reference in dual sampletransfer systems. It is never removed from the system regard-less of the characteristics of the sample to be analyzed. It isimportant to distinguish that the monitor, whether an indepen-dent detector or an activated reference material, is not astandard used t
19、o scale the oxygen content of the samples to bemeasured, but rather is used to normalize the analysis systemamong successive analytial passes within the procedure.3.1.5 multichannel pulse-height analyzeran instrumentthat receives, counts, separates, and stores, as a function oftheir energy, pulses f
20、rom a scintillation or semi-conductorgamma-ray detector and amplifier. In the 14-MeV instrumentalneutron activation analysis (INAA) determination of oxygen,the multichannel analyzer may also be used to receive andrecord both the BF3neutron detector monitor counts and thesample gamma-ray detector cou
21、nts as a function of steppedtime increments (4-6). In the latter case, operation of theanalyzer in the multichannel scaler (MCS) mode, an electronicgating circuit is used to select only gamma rays within theenergy range of interest.3.1.6 transfer systema system, normally pneumatic, usedto transport
22、the sample from an injection port (sometimesconnected to an automatic sample changer) to the irradiationstation, and then to the counting station where the activity ofthe sample is measured. The system may include componentsto ensure uniform positioning of the sample at the irradiationand counting s
23、tations.4. Summary of Test Method4.1 The weighed sample to be analyzed is placed in acontainer for automatic transfer from a sample-loading port tothe 14-MeV neutron irradiation position of a particle accelera-tor. After irradiation for a pre-selected time, the sample isautomatically returned to the
24、 counting area. A gamma-raydetector measures the high-energy gamma radiation from theradioactive decay of the16N produced by the (n,p) nuclearreaction on16O. The number of counts in a pre-selectedcounting interval is recorded by a gated scaler, or by amultichannel analyzer operating in either the pu
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