1、 l Designation:D 2459-72(Reapproved 1981)AMERICAN SOCIETY FOR TESTING AND MATERIALS 1916 Race St.,Philadelphia,Pa.19103 Reprited rom the Annual Book of ASTM Standards,Copyright ASTM If not listed m the current combined index,will appear in the next edition.Standard Test Method for GAMMA SPECTROMETRY
2、 OF WATER1 This stana.rd is issue unde:the fixed desigtion D 2459;the number immediately following the designation indicates the year of ongmal adopt1n or,1 the ce o reviSion,te Y.ear oflast rvision.A number in parentheses indicates the year oflast reapproval.A superscnpt eps1lon(e)md1cates an edlto
3、nal change smce the last revision or reapproval.NoTE-Section 2 was added editorially and subsequent sections renumbered in December 1981.1.Scope 1.1 This method covers the measurement by means of gamma spectrometry of gamma ra dioactivity of water.It is applicable to nuclides emitting gamma rays wit
4、h energies greater than 0.1 MeV.The count rate of the sample to be counted should be in the range from 105 counts per minute to twice the background count rate.1.2 The method can be used for either ab-solute or relative determinations.In tracer work,the results may be expressed by compar-ison with a
5、n initial concentration of a given nuclide which is taken as 100%.For radioassay the results may be expressed in terms of known nuclidic standards if the radionuclides are known.In addition to the quantitative mea-surement of gamma radioactivity,gamma spec-trometry can be used for the identification
6、 of specific gamma emitters in a mixture of radio-nuclides.General information on radioactivity and measurement of radiation has been pub-lished(1).2 Information on specific application of gamma spectrometry is also available in the literature(2).2.Applicable Document 2.1 A STM Standard:D 1129 Defmi
7、tions of Terms Relating to Water3 3.Summary of Method 3.1 Gamma spectra are measured with a gamma-ray spectrometer.The spectrometer as-sembly is used to analyze the gamma spectra of radionuclides in a manner similar in general to the analysis of emission spectra of elements with the emission spectro
8、graph.The sensing unit required for the detection of the emitted 1 gamma radiation is a thallium-activated so-dium iodide crystal or a lithium-drifted ger-manium semiconductor.Interaction of a gamma photon with the atoms in a sodium iodide crystal results in a transfer of some or all of the energy o
9、f the photon to one or more electrons in the crystal.The energetic electrons collide with bound electrons,and the bound electrons are removed from the ground state orbits of the atoms.As the ground state orbits are subsequently filled,energy is released in the form of photons in the visible region w
10、hich can be detected by a multiplier phototube.In a semiconductor detector,gamma photons pro-duce electron-hole pairs,which are collected by an applied electric field.Such a device is often called a solid state ionization chamber.A very stable,low noise preamplifier is needed,which utilizes field ef
11、fect transistors;it ampli-fies the pulses of electric charge resulting from the gamma photon interaction.3.1.1 The output from the multiplier photo-tube anode or the preamplifier is directly pro-portional to the energy lost by the incident gamma photon.These current pulses are fed into an amplifier
12、of sufficient gain to produce voltage output pulses in the amplitude range typically from 0 to 10 or 0 to 100 V.3.2 The method of analysis of the pulse spec-tra is by use of a pulse-height analyzer,either 1 This method is under the jurisdiction of ASTM Com-mittee D-.19 on Water and is the direct res
13、ponsibility of Subcomffilttee Dl9-04 on Methods of Radiochemical Anal-ysis.Current edition approved July 28,1972.Published Sep-tember 1972_ Originally published as D 2459-72.Last pre-vious edition D 2459-69.2 The boldface numbers in parentheses refer to the list of references appended to this method
14、.3 Annual Book of ASTM Standards,Part 31.NOTICE:This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International(www.astm.org)for the latest informationmultiple or single channel.The multiple-chan-nel(or multi-channel)analyzeretermines the amplitude of e
15、ach pulse produced in the mul-tiplier phototube and accumulates in a memory the number of pulses in each amplitude band(or channel)in a given counting time.The single-channel analyzer similarly classifies pulses according to amplitude but passes on to a scaler or ratemeter only those pulses falling
16、within a single preset amplitude range,the rest being discarded.Some single-channel analyzers are equipped with a motor-driven potentiome-ter and can scan the complete pulse distribution and register the counting rate on a strip chart recorder.In general,single-channel analyzers are not recommended for semi-conductor de-tectors.3.3 The frequency distribution of the ampli-tudes(pulse heights)of the pulses can be sep-arated into two principal components.One of these components has a Gaussian distr
