1、Designation: E1893 15Standard Guide forSelection and Use of Portable Radiological SurveyInstruments for Performing In Situ RadiologicalAssessments to Support Unrestricted Release from FurtherRegulatory Controls1This standard is issued under the fixed designation E1893; the number immediately followi
2、ng the designation indicates the year oforiginal adoption or, 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 This standard provi
3、des recommendations on the selec-tion and use of portable instrumentation that is responsive tolevels of radiation that are close to natural background. Theseinstruments are employed to detect the presence of residualradioactivity that is at, or below, the criteria for release fromfurther regulatory
4、 control of a component to be salvaged orreused, or a surface remaining at the conclusion of decontami-nation and/or decommissioning.1.2 The choice of these instruments, their operating charac-teristics and the protocols by which they are calibrated andused will provide adequate assurance that the m
5、easurements ofthe residual radioactivity meet the requirements established forrelease from further regulatory control.1.3 This standard is applicable to the in situ measurement ofradioactive emissions that include:1.3.1 alpha1.3.2 beta (electrons)1.3.3 gamma1.3.4 characteristic x-rays1.3.5 The measu
6、rement of neutron emissions is not includedas part of this standard.1.4 This standard dose not address instrumentation used toassess residual radioactivity levels contained in air samples,surface contamination smears, bulk material removals, orhalf/whole body personnel monitors.1.5 This standard doe
7、s not address records retention require-ments for calibration, maintenance, etc. as these topics areconsidered in several of the referenced documents.1.6 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.2. Referenced Documents2.1
8、 ASTM Standards:2C998 Practice for Sampling Surface Soil for RadionuclidesC999 Practice for Soil Sample Preparation for the Determi-nation of RadionuclidesC1000 Test Method for Radiochemical Determination ofUranium Isotopes in Soil by Alpha SpectrometryC1133 Test Method for Nondestructive Assay of S
9、pecialNuclear Material in Low-Density Scrap and Waste bySegmented Passive Gamma-Ray ScanningE170 Terminology Relating to Radiation Measurements andDosimetryE181 Test Methods for Detector Calibration and Analysis ofRadionuclidesC1215 Guide for Preparing and Interpreting Precision andBias Statements i
10、n Test Method Standards Used in theNuclear Industry2.2 ANSI Standards:ANSI N323AB American National Standard for RadiationProtection Instrumentation Test and Calibration, PortableSurvey Instrumentation3ANSI N42.17A American National Standard for Perfor-mance Specifications for Health Physics Instrum
11、entation-Portable Instrumentation for Use in Normal Environmen-tal Conditions3ANSI N42.17C American National Standard for Perfor-mance Specifications for Health Physics Instrumentation-Portable Instrumentation for Use in Extreme Environmen-tal Conditions31This guide is under the jurisdiction of ASTM
12、 Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.03 on Radiological Protection for Decontamination and Decommissioning ofNuclear Facilities and Components.Current edition approved Feb. 1, 2015. Published April 2009. Originallyapproved in 1997.
13、Last previous edition approved in 2008 as E1893-08a. DOI:10.1520/E1893-15.2For referenced 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
14、ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.3 National Council on Radiation Protection a
15、nd Measure-ments:NCRPReport No. 57 Instrumentation and Monitoring Meth-ods for Radiation Protection, National Council on Radia-tion Protection and Measurements, May 19784NCRP Report No. 58 A Handbook of Radioactivity Mea-surement Procedures, National Council on Radiation Pro-tection and Measurements
16、, 2nd Ed. February 19854NCRP Report No. 112 Calibration of Survey InstrumentsUsed in Radiation Protection for the Assessment ofIonizing Radiation Fields and Radioactive SurfaceContamination, National Council on Radiation Protectionand Measurements, December 199142.4 International Organization for St
17、andardization (ISO):ISO-4037-4 : 2004 X and Gamma Reference Radiations forCalibrating Dosimeters and Dose-rate Meters and forDetermining their Response as a Function of PhotonEnergy, International Organization for Standardization,19795ISO-6980-2 : 2005 Nuclear energy Reference beta particleradiation
18、 - Part 2: Calibration fundamentals related tobasic quantities characterizing the radiation field5ISO-8769 Reference Sources for the Calibration of SurfaceContamination Monitors Beta Emitters (Maximum BetaEnergy Greater than 0.15 MeV) and Alpha Emitters,International Organization for Standardization
19、, 19885ISO 8769-2 : 1996 Reference sources for the calibration ofsurface contamination monitors-Part 2: Electrons of en-ergy less than 0.15 MeV and photons of energy less than1.5 MeVISO-7503-1 Evaluation of Surface Contamination - Part 1:Beta Emitters (Maximum Beta Energy Greater than 0.15MeV) and A
20、lpha Emitters, International Organization forStandardization, 19885ISO-7503-2 Evaluation of Surface Contamination - Part 2:Tritium Surface Contamination, International Organiza-tion for Standardization, 19885ISO-7503-3 : 2003 Evaluation of Surface Contamination -Part 3: Isomeric Transition and Elect
21、ron Capture Emitters,Low Energy Beta Emitters (Emax0.15 MeV) emitters - ISO7503-15.5.2.3 tritium - ISO 7503-25.5.2.4 beta (E 4s.NOTE 4Experiments using hidden sources (Co-57) with signal-to-background ratios from 0.6-6 resulted in approximately 75 % beinglocated based on ratemeter observation alone,
22、 compared to approximately90 % for audio response (6).6.4.5 Direct (fixed) Measurements. The estimate of the levelof residual radioactivity is based on a measurement with thesource-detector geometry fixed (stationary). When makingthese fixed measurements, the following requirements, as aminimum, sho
23、uld be complied with:6.4.5.1 The detector should be coupled to a scaler for thismeasurement.6.4.5.2 If a ratemeter is used with this measurement, a longresponse time should be used ( 20 s). The detector shall bekept in position for at least three times the time constant of theratemeter.6.4.5.3 The e
24、ffects of the concavity of the surfaces beingmeasured on instrument efficiency shall be evaluated when thesurface is not flat (examples are given inAppendix X5 for betaemissions).E1893 1556.4.5.4 For conditions where a visible layer of dirt,oxidation, or other coating cannot be removed, the effect o
25、nsource-detector response shall be included for alpha and betameasurements (examples are given in Appendix X5 for betaemissions).6.5 Data Interpretation:6.5.1 Alpha and Beta Emissions:6.5.2 The evaluation of surface activity for alpha or betaemissions (in dpm/100 cm2) is given by the expression(ISO-
26、7503-1)As5n 2 nB!i3s3W100where:n = total count rate in cpmnB= background count rate in cpmi= instrument efficiency for alpha or beta radiation in cpmper dpmW = total physical window area of the detector in cm2s= source correction factor to account for differencesbetween the calibration source and th
27、e residual activity,such as backscatter, self absorption, source protectivecoatings and/or surface coatings, geometry, etc.(unitless)NOTE 5The factor imay be defined for either a point source or asurface source. The point source efficiency should be used to quantify hotspots. The surface source effi
28、ciency should be used to evaluate surfaceswithout hot spots.NOTE 6Further explanation of the factor iand its relative magnitudeare given in Appendix X5.6.5.3 Gamma Emissions:6.5.3.1 Gamma detection and subsequent interpretation isnormally employed to evaluate the levels of residual activitythat are
29、distributed within a source matrix expressed aspCi/gm, Bq/kg, etc. For a uniformly distributed source, thevolumetric source term is provided by the expressionSv5n 2 nBwhere:Sv= volumetric source term in pCi/gmn = total count rate in cpmnB= background count rate in cpm= instrument efficiency for an u
30、niformly distributedgamma source in cpm per pCi/gm.NOTE 7The gamma efficiency will normally be composed of twofactors; a dose conversion in units of cpm/(mR/hr) measured with a knowncalibration source, and a source conversion factor in units of (mR/hr)/(pCi/gm) based on shielding theory. In general,
31、 the dose conversion factorfor a particular detector is provided for a single photon energy, whereas,the source conversion factor includes scattered photons (buildup) whichleads to an estimate of the gamma source strength that is conservative.Theresponse of various NaI detector geometries as a funct
32、ion of photonenergy is shown in Appendix X9.APPENDIXES(Nonmandatory Information)X1. MINIMUM DETECTABLE ACTIVITY (MDA)X1.1 When measuring residual radioactivity that must bewithin limits or guidelines that are very near to the levels thatare present from natural background, the minimum amount ofradio
33、activity that may be detected by a particular measurementsystem must be determined. With radiation measurement, thephysical amount of the residual radiation source (pCi, dpm, Bq,etc.) is not directly measurable, but is observed as a measure-ment instrument response (digital counts, voltmeter deflect
34、ion,etc.). Because radioactive decay follows statisticalrelationships, the statistics of detection and determinationapply directly to the observed (or observable) signal (meterreading) and its associated random fluctuations. When measur-ing for the presence of low residual activity, one mustdistingu
35、ish between two fundamental aspects of the detectionproblem (6).X1.2 Given a net signal that is greater in value than a similarsignal that has been established as defining background, has a“real” activity above background been detected? (The “falsepositive” or Type I error)X1.3 Given a completely sp
36、ecified measurement process,what is the minimum “real” activity that will produce anobserved signal that will be detected? (The “false negative” orType II error)X1.4 The first aspect relates to making an a posterior (afterthe fact) decision based upon the net signal(s) and a definedcriterion for det
37、ection. This leads to the establishment of a“critical level” (Lc) for which a signal exceeding this level willbe interpreted as a residual activity with a probability , whenin fact it is only background, (error of the first kind).Conversely, the second aspect relates to making an a priori(before the
38、 fact) estimate of the detection capabilities of themeasurement process that yields a signal exceeding the criticallevel that is in fact from a “real” residual source of activity.This“ detection limit” (LD) is the smallest value such that realresidual radioactive material greater than LDwill be inte
39、rpretederroneously as background with a probability less than .Mathematically these concepts are given as (7):E1893 156Lc5 K01B0(X1.1)LD5 Lc1K0(X1.2)where: = standard deviationK = statistical constant based error probability for normallydistributed eventsThe relationships between Lcand LDare shown o
40、n Fig.X1.1.X1.5 The quantity Lcis used to test an experimental result,whereas LDrefers to the capability of the measurement processitself (6). The concept of “detection limit” (LD) has also beenidentified as “limit of detection” (8) and “minimum detectableactivity” (MDA) (4). The term minimum detect
41、able activity ismost commonly encountered in radiation measurement reports,and will be utilized here. The basic relationship for estimatingthe MDA at the 95% confidence level is (9):MDA 5 Co3.014.65 o! (X1.3)where:Co= proportionally constant relating the detector responseto an activity0= standard de
42、viation of the backgroundFor purposes of this discussion, MDA will be defined inunits of activity expressed as dpm or pCi. This mathematicalrelationship for MDA will be applied to point source or “hotspot” residual. The concept of detection limit for distributedactivity will be expressed using the “
43、minimum surface sensi-tivity” (MSS) of the detector, which will incorporate thedetector area as a function that will allow values of minimumsurface sensitivity to be compared directly to surface activityregulatory guidelines.X1.6 For time integrated measurements using a scalerreadout:MSS 53.014.65 =
44、Bo*tt0Ad/100!(X1.4)For measurements involving a ratemeter signal, the relation-ship is:MSS 54.65 =Bo/20Ad/100!(X1.5)where:Bo= background count rate (cpm)Ad= window area of detector probe (cm2)0= detector efficiency in counts/disintegration (includes allsource surface and self attenuation effects - s
45、ee Appen-dix X5)t = scaler count time (min) = ratemeter time constant (min) = 0.438 = time for meter to reach 90 % of steady state (X3.5)X1.7 Typical minimum sensitivities for scalers and rateme-ters using common detector types are shown in Table X1.1.FIG. X1.1 Hypothesis TestingErrors of the First
46、and Second KindE1893 157X2. DETECTION OF LOW-LEVEL RESIDUAL ACTIVITYX2.1 The ability to evaluate the existence and amount oflow-level residual activity in the presence of natural radioac-tive background is dependent on both the electromechanicalcharacteristics of the detector system and upon the pro
47、tocols bywhich the detector system is employed. For assessing theresidual radioactive condition of a surface to support anunrestricted release determination, the accepted protocol is toemploy a detector, coupled to a scaler, to obtain measurementson a fixed set of grid locations. For this type of me
48、asurement,one must know the minimum sensitivity of the detector systemfor comparison to guidelines that must be met. However, thistechnique is only representative for uniformly distributedactivity. It will not be effective for “hot” spot activity, particu-larly beta or alpha. For example, five measu
49、rements using a100 cm2probe to characterizea1m1marea will cover 5percent of the surface being assessed. Even when applied atpredetermined systematic or biased locations, it will onlydetect hot spots in a hit or miss fashion. Scanning, using thedetector coupled to a ratemeter is the most effective method forlocating “hot” spot activity. This technique however, is limitedby the transient response characteristics of the detector and theratemeter. The effects of scanning protocol on hot spot detec-tion has been quantified for several commo
