ASTM_E_1297_-_08_2013.pdf

Designation:E129708(Reapproved 2013)Standard Test Method forMeasuring Fast-Neutron Reaction Rates by Radioactivationof Niobium1This standard is issued under the fixed designation E1297;the number immediately following 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 test method describes procedures for measuringreaction rates by the activation reaction93Nb(n,n)93mNb.1.2 This activation reaction is useful for monitoring neu-trons with energies above approximately 0.5 MeV and forirradiation times up to about 30 years.1.3 With suitable techniques,fast-neutron reaction rates forneutrons with energy distribution similar to fission neutronscan be determined in fast-neutron fluences above about 1016cm2.In the presence of high thermal-neutron fluence rates(1012cm2s1),the transmutation of93mNb due to neutroncapture should be investigated.In the presence of high-energyneutron spectra such as are associated with fusion and spalla-tion sources,the transmutation of93mNb by reactions such as(n,2n)may occur and should be investigated.1.4 Procedures for other fast-neutron monitors are refer-enced in Practice E261.1.5 Fast-neutron fluence rates can be determined from thereaction rates provided that the appropriate cross sectioninformation is available to meet the accuracy requirements.1.6 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.7 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 limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE170 Terminology Relating to Radiation Measurements andDosimetryE181 Test Methods for Detector Calibration and Analysis ofRadionuclidesE185 Practice for Design of Surveillance Programs forLight-Water Moderated Nuclear Power Reactor VesselsE261 Practice for Determining Neutron Fluence,FluenceRate,and Spectra by Radioactivation TechniquesE262 Test Method for Determining Thermal Neutron Reac-tion Rates and Thermal Neutron Fluence Rates by Radio-activation TechniquesE844 Guide for Sensor Set Design and Irradiation forReactor Surveillance,E 706(IIC)E944 Guide for Application of Neutron Spectrum Adjust-ment Methods in Reactor Surveillance,E 706(IIA)E1005 Test Method for Application and Analysis of Radio-metric Monitors for Reactor Vessel Surveillance,E 706(IIIA)E1006 Practice for Analysis and Interpretation of PhysicsDosimetry Results from Test Reactor ExperimentsE1018 Guide for Application of ASTM Evaluated CrossSection Data File,Matrix E706(IIB)3.Terminology3.1 DefinitionsThe definitions stated in TerminologyE170 are applicable to this test method.4.Summary of Test Method4.1 High purity niobium is irradiated in a neutron fieldproducing radioactive93mNb from the93Nb(n,n)93mNb reac-tion.The metastable state decays to the ground state by thevirtual emission of 30 keV gamma rays that are all internallyconverted giving rise to the actual emission of orbital electronsfollowed by X rays.4.2 Sources of the irradiated niobium are prepared for X rayor liquid scintillation counting.4.3 The X rays emitted as a result of the decay of93mNb arecounted,and the reaction rate,as defined in Practice E261,iscalculated from the decay rate and irradiation conditions.4.4 The neutron fluence rate may then be calculated fromthe appropriate spectral-weighted neutron activation crosssection as defined by Practice E261.1This test method is under the jurisdiction of ASTM Committee E10 on NuclearTechnology and Applicationsand is the direct responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved Jan.1,2013.Published January 2013.Originallyapproved in 1989.Last previous edition approved in 2008 as E1297 08.DOI:10.1520/E1297-08R13.2For 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 ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Significance and Use5.1 Refer to Practice E261 for a general discussion of thedetermination of decay rates,reaction rates,and neutronfluence rates with threshold detectors(1-29).3Refer to PracticeE1006,Practice E185 and Guide E1018 for the use andapplication of results obtained by this test method.(30-32)5.2 The half-life of93mNb is 5730 6 220 days(33)and hasa K X-ray emission probability of 0.1099 6 0.0025 per decay(33).The Kand KX-rays of niobium are at 16.521316.152and 18.61818