BS 7516-1995 Nuclear instrumentation - Liquid-scintillation counting systems - Performance verification《核仪器 液态闪烁计数系统 性能鉴定》.pdf

1、BRITISH STANDARD BS 7516:1995 IEC 1304:1994 Nuclear instrumentation Liquid-scintillation counting systems Performance verificationBS7516:1995 This British Standard, having been prepared under the directionof the Engineering SectorBoard (E/-), was publishedunder the authority ofthe Standards Board an

2、d comesinto effect on 15February1995 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference NCE/8 Special announcement in BSINews December 1994 ISBN 0 580 23682 X Committees responsible for this British Standard The preparation of this British Standard was

3、entrusted by the Engineering Sector Board to Technical Committee NCE/8, upon which the following bodies were represented: AEA Technology British Nuclear Forum British Nuclear Fuels plc Electricity Association GAMBICA (BEAMA Ltd.) Health and Safety Executive Institution of Nuclear Engineers Ministry

4、of Defence Amendments issued since publication Amd. No. Date CommentsBS7516:1995 BSI 11-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope and object 1 2 Normative reference 1 3 Definitions and symbols 1 4 Sources and materials 3 5 Operations a

5、nd tests 4 6 Precautions 6 Annex A (informative) Statistical tests of reproducibility The # 2test and other criteria 9 Annex B (informative) Performance monitoring log for liquid-scintillation counter 11 Annex C (informative) Physical properties of liquid scintillators and requirements for toluene a

6、cceptance 12 Table A.1 Result of 10 determinations and deviations from the mean 10 Table A.2 # 2values 10 List of references Inside back coverBS7516:1995 ii BSI 11-1999 National foreword This British Standard has been prepared under the direction of the Engineering Sector Board and is the English la

7、nguage version of IEC 1304:1994 Nuclear instrumentation Liquid-scintillation counting systems Performance verification, published by the International Electrotechnical Commission (IEC). IEC 1304 was produced as a result of international discussions in which the United Kingdom took an active part. Th

8、e Technical Committee has reviewed the provisions of ISO 582:1977 to which normative reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of

9、British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-reference International Standard Corresponding British Standard IEC 1304 BS 5541:1978 Specification for dimensions of vials for liquid

10、scintillation counting (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 12, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated

11、in the amendment table on the inside front cover.BS7516:1995 BSI 11-1999 1 Introduction Liquid-scintillation counting systems are widely used for radionuclide assay in industrial applications, nuclear medicine and life-science research. A typical system is a combination of a sample-changing device w

12、ith a liquid-scintillation spectrometer such that a number of samples may be counted automatically. The liquid-scintillation spectrometer usually consists of a sample chamber, two horizontally opposed photomultiplier tubes viewing the sample chamber and the associated electronics to detect and recor

13、d the presence of radioactivity in the sample. The sample compartment may be either air-cooled or refrigerated (controlled temperature). The liquid-scintillation counter is so named because the usual radioactive sample assayed is either dissolved or dispersed in a solution containing one or more org

14、anic scintillators. This International Standard is particularly useful for tritium and carbon-14 counting but is applicable also for counting of other radionuclides. 1 Scope and object The purpose of this International Standard is to provide the user with a means of verifying the performance of typi

15、cal liquid-scintillation counting systems. Measures of performance considered in this standard are: counting system efficiency; reproducibility of sample and background count rates. This standard does not cover the calculation of sample activity for quenched samples. Accordingly, this standard does

16、not deal with sample preparation, efficiency correlation (quench correction) procedures, or the identification of unknown radionuclides. 2 Normative reference The following normative document contains provisions which, through reference in this text, constitute provisions of this International Stand

17、ard. At the time of publication, the edition indicated was valid. All normative documents are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated belo

18、w. Members of IEC and ISO maintain registers of currently valid International Standards. IEC 582:1977, Dimensions of vials for liquid scintillation counting. 3 Definitions and symbols 3.1 Definitions For the purpose of this International Standard, the following definitions apply. background check so

19、urce sealed vial of liquid-scintillation solution containing no added radioactive material background count rate (in radioactivity counters) count rate recorded by the instrument when measuring a background check source check source radioactive source, not necessarily calibrated, that is used to con

20、firm the continuing satisfactory operation of an instrument counting channel region of the pulse-height spectrum that is defined by upper and lower boundaries set by discriminators counting efficiency ratio of the count rate, R, to the disintegration rate, A, usually expressed as a percentage: E = (

21、R/A) 100 counting region identifies the first and last memory location of a contiguous series to be summed in a multichannel analyserBS7516:1995 2 BSI 11-1999 gain, photomultiplier tube ratio of the signal output current to the photoelectric signal current from the photocathode liquid-scintillation

22、solution solution consisting of a solvent (or mixture of solvents) and one or more scintillator solutes organic-scintillator solute material organic compound that can absorb radiant energy and immediately (typically within 10 9s) re-emit this energy as photons in the ultra-violet range pulse height

23、analyser circuit that produces an output signal if it receives an input pulse whose amplitude falls between preset upper and lower values pulse height analyser, multichannel circuit that accepts all input pulses and assigns each pulse to a memory location corresponding to its amplitude quenched samp

24、le counting sample (material of interest plus liquid-scintillation solution) that contains chemical impurities that reduce the photon output resolving time minimum time that shall exist between successive events if they are to be counted as separate events unquenched sample counting sample (material

25、 of interest plus liquid-scintillation solution) that contains a minimum of quenching admixtures (coloured species and chemical impurities) that would reduce the light output to the photomultiplier tubes vial glass or plastic sample container which meets the dimensional specifications of IEC 582 3.2

26、 Symbols A = activity of the radionuclide contained in the check source. In this standard, activity is expressed in disintegrations per unit time. (The recommended unit for activity is the becquerel, where1Bq=1 transition per second.) B = background count rate, counts per unit time E = counting syst

27、em efficiency: E = (R/A) 100 i = any individual measurement in a series of measurements; used as subscript notation, for example, n i n = number of measurements in a series N = total number of counts accumulated in an individual measurement R = net count rate in an individual measurement, counts per

28、 unit time t = counting time t c = elapsed counting time for a short-lived radionuclide, expressed in the same units of time as the half-life 2 = radioactivity decay constant s = computed standard deviation of a measured distribution = an estimate of B B = true standard deviation for the measured di

29、stribution = average of n measurements of N as defined by equation (1) # 2 = statistical quantity used to compare the observed variance of a distribution with a hypothetical variance; # 2= s 2 /B 2 X 2 = computed value of # 2for a real distribution; see 5.2.2.4.2, equation (4) B NBS7516:1995 BSI 11-

30、1999 3 4 Sources and materials 4.1 Radioactivity standard material A material having a known specific activity of a specified radionuclide. Such material shall be either of the following when such standards are available: a) a radioactivity standard reference material that has been certified by a la

31、boratory recognized as a countrys National Standardizing Laboratory for radioactivity measurements; b) a radioactivity standard material that has been obtained from a supplier that participates in measurement assurance activities with the National Standardizing Laboratory. In such measurement assura

32、nce activities, the suppliers calibration value should agree with the National Standardizing Laboratorys value within the overall uncertainty stated by the supplier in its certification of the same batch of sources or in its certification of similar sources. 4.2 Check sources Four types of check sou

33、rces which are of the vial type may be used: A) flame-sealed glass (activity known); B) flame-sealed glass (activity unknown); C) screw-capped glass or plastic (activity known); D) screw-capped glass or plastic (activity unknown). Check sources of type A) can be used for all measurements described i

34、n this standard. Such sources are available from instrument manufacturers and suppliers of radiochemicals. They are often designated as unquenched standards. The use of types B, to D) is limited to specific tests. Type B) can be used wherever relative data are sufficient and no computation of the di

35、sintegration rate is required. Types C) and D) shall be used only for short-term performance tests. The scintillation characteristics of a source in screw-capped vials can change rapidly for several reasons, one of which is the evaporation of volatile components. When polyethylene vials are used, th

36、e solvents and solutes can diffuse into the walls, causing swelling of the vial as well as changes in the scintillation properties of the wall. A given set of check sources (for example, tritium, carbon-14, background) should be made from the same solvent and organic-scintillator solutes in the same

37、 concentration. 4.2.1 Tritium check source The tritium check source shall contain 15 ml 0,2 ml of toluene with a concentration of 5 g 1 g 2,5-diphenyloxazole (PPO) per litre of toluene at 20 C. If a secondary organic scintillator is included, it shall be at a concentration of 0,01 g/l 0,5 g/l. The c

38、heck-source vial should be purged with inert gas before sealing. Tritiated toluene with an activity of 2 kBq to 5 kBq (2 000 to 5 000 disintegrations per second) shall be contained in a type II glass vial (see 3.1: vial). 4.2.2 Carbon-14 check source The carbon-14 check source shall contain 15 ml 0,

39、2 ml of toluene with a concentration of 5 g 1 g PPO per litre of toluene at 20 C. If a secondary scintillator is included, it shall be at a concentration of 0,01 g/l 0,5 g/l. The check-source vial should be purged with inert gas before sealing. Carbon-14 toluene with an activity of 0,5 kBq 3 kBq (50

40、0 to 3 000 disintegrations per second) shall be contained in a type II glass vial (see 3.1: vial). 4.2.3 Background check source The background check source shall contain 15 ml 0,2 ml of toluene with a concentration of 5 g 1 g PPO per litre of toluene at 20 C. If a secondary scintillator is included

41、, it shall be at a concentration of 0,01 g/l to 0,5 g/l. The background check source vial should be purged with inert gas before sealing. 4.2.4 Background sources (unquenched blank) Flame-sealed background sources are equivalent to type A) check sources with no added activity, and are used to monito

42、r the reproducibility of the counter background. Such sources are sold as unquenched background sources by commercial suppliers. The glass vials and the dimensions shall conform to IEC 582.BS7516:1995 4 BSI 11-1999 4.3 Expiration date of check sources All flame-sealed check sources shall be dated wh

43、en made and should be used no longer than five years after sealing. (Check sources shall not be stored in direct sunlight or under fluorescent lights.) 4.4 Materials 4.4.1 Organic-scintillator solutes A primary scintillator, 2,5-diphenyloxazole (PPO), shall be used in preparing check sources. The ph

44、ysical properties of this compound are listed in Annex C. Some of the following secondary scintillators may be included in preparing check sources: a) 1,4-bis-2-(5-phenyloxazolyl)-benzene; b) 1,4-bis-2-(4-methyl-5-phenyloxazolyl)-benzene; c) p-bis-(O-methylstyryl)-benzene. Their physical properties

45、are listed in Annex C. 4.4.2 Radioactive material Tritium-labelled and carbon-14-labelled toluene shall be used as radioactivity standard material. 4.4.3 Sample container The sample container shall conform to IEC 582 for type II glass vials, except for the overall height, which shall not exceed the

46、specified maximum. For small-vial counting systems, see 6.4.3. The glass shall be low-potassium, borosilicate glass. The sample shall be contained within the cylindrical portion of the vial. 4.4.4 Purging gas The purging gas shall be any inert gas such as argon or nitrogen of at least 99,995 % purit

47、y, containing no more than 2 ppm oxygen and no more than 1 ppm water. 5 Operations and tests 5.1 General All instruments shall be operated in conformance with the manufacturers recommendations. 5.2 Test procedures 5.2.1 Frequency of testing Instrument performance shall be monitored by the user follo

48、wing installation, service, replacement of sealed check sources, or any other circumstance that may affect the accuracy of the data obtained using the counter. Details of these performance tests are given in 5.2.2. In addition, a quality-control programme shall be established to monitor the day-to-d

49、ay performance of the instrument. These routine performance tests are given in 5.2.3. 5.2.2 Initial performance tests The following tests shall be performed by the user upon installation of the counting system and following any of the events set forth above. a) Determination of the counting system efficiency E of the type A) check source. b) Determination of the counting rate of a background check source B in each counting channel/region that is used under normal conditions. c) Estimation of dispersion in the counting data by: