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Isotopic Neutron Sources for Neutron Activation Analysis

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Isotopic Neutron Sources for Neutron Activation Analysis IAEA-TECDOC-465 ISOTOPIC NEUTRON SOURCES FOR NEUTRON ACTIVATION ANALYSIS USER'S MANUAL PREPARE . HOSTJ Y DB E UNIVERSITY OF GHENT A TECHNICAL DOCUMENT ISSUED BY THE INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1988 IAEe Th A doe t normallsno y maintain stock f reportso thin si s series. However, microfiche copies of these reports can be obtained from INIS Clearinghouse International Atomic Energy Agency Wagramerstrasse5 P.O.Bo0 10 x A-1400 Vienna, Austria Orders shoul accompaniee db prepaymeny db f Austriao t n Schillings 100, in the form of a cheque or in the form of IAEA microfiche service coupons which may be ordered separately from the INIS Clearinghouse. PLEAS AWARE EB E THAT MISSINE TH AL F LO G PAGE THIN SI S DOCUMENT WERE ORIGINALLY BLANK ISOTOPIC NEUTRON SOURCES FOR NEUTRON ACTIVATION ANALYSIS IAEA, VIENNA, 1988 IAEA-TECDOC-465 Printed by the IAEA in Austria June 1988 FOREWORD Neutron activation analysis (NAA) is a well established analytical techniqu countrien i e s wher nucleaea r reacto s availablei r . However, manf o y the developing countries have neither a nuclear reactor nor other sources of neutrons, but have still a strong interest in this technique. Throug Technicas it h l Co-operation Programme Agence ,th bees yha n promoting the use of nuclear analytical techniques such as Neutron Activation Analysi X-rad san y Fluorescence Analysi mann i s y governmenta universitd an l y laboratorie developinn i s g Member States. Instrumentatio s oftei n n provided for such purposes, e.g., gamma spectrometry systems and other radioactivity counting equipment. mann I y developing majoe countriesth rf o drawback e ,on e lac th f o ks i s appropriate neutron sources, eithe nucleaa r r research reacto neutroa r o r n generator. Wit purpose th h asseso t e feasibilite sth usinf o y g other alternative neutron sources, a Consultants' Meeting on Isotopic Neutron Sources for Neutron Activation Analysis was organized in May 1985. It was concluded that Isotopic Neutron Sources of an appropriate design and characteristics in terms of neutron flux and spectra, could allow small research center universitd san y laboratorie o carr t st interestin ou y d an g meaningful training and research oriented projects based on neutron activation and radiochemistry. The present User's Manual is an attempt to provide with a series of well thought demonstrative experiment utilizatioe baseA th NA n o dn n i sa f no isotopic neutron source, for teaching and training purposes. In some cases, these ideas can be applied to the solution of practical analytical problems. The Agency wishes to thank all scientists who participated in the Consultants' Meeting, and particularly Professor Dr. J. Hoste, who undertook tase writo th kt presene eth t manual. EDITORIAL NOTE In preparing this material for the press, staff of the International Atomic Energy Agency have mounted and paginated the original manuscripts and given some attention to presentation. The views expressed necessarilynot do reflect governmentsthosethe of Memberthe of States or organizations under whose auspices the manuscripts were produced. The use in this book of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries. The mention of specific companies or of their products or brand names does not imply any endorsement recommendationor IAEA. partthe the of on CONTENTS INTRODUCTION ............................................................................................9 . 1. ISOTOPIC NEUTRON SOURCES ................................................................. 12 1.1. Alpha (a,n)-sources .............................................................................. 12 1.1.1e (a,n)-reactioTh . n .....................................................................2 1 . 1.1.2. Typ f alpha-sourceo e s ................................................................3 1 . 1.1.3. Neutron yield energd an s y ...........................................................3 1 . 1.1.4. Source choice ..........................................................................7 1 . 1.1.5. Source arrangement .................................................................... 18 1.1.6. Transport container .................................................................... 24 1.1.7. Safety aspects ..........................................................................5 2 . 1.1.8. Source installation .....................................................................5 2 . 1.1.9. General safety ........................................................................... 28 1.2. Spontaneous fission sources ...................................................................9 2 . 1.3. Photoneutron sources ............................................................................ 31 1.4. Neutron multipliers .............................................................................. 33 . 2 PRINCIPLE ACTIVATIOF SO N ANALYSIS ..................................................5 3 . 2.1. General equation .................................................................................. 35 2.2. Activatio isotopin a n ni c neutron source ....................................................8 3 . 2.2.1. Fast flux .................................................................................. 39 2.2.2. Thermal flux ............................................................................. 40 2.2.3. Epithermal neutron flux ..............................................................1 4 . 2.2.4. Reaction rate for (n,7) reactions .................................................... 41 2.3. Standardization .................................................................................... 42 2.3.1. Absolute method ........................................................................ 42 2.3.2. Relative method ......................................................................... 42 2.3.3. Single comparator ...................................................................... 44 2.3.4. ko-standardization ....................................................................... 44 2.4. Source f erroo s r .................................................................................6 4 . 2.4.1. Flux gradients ........................................................................... 46 2.4.2. Neutron shielding ....................................................................... 47 2.4.3. Nuclear interference ..................................................................8 4 . 2.4.3.1. Threshold reactions .........................................................8 4 . 2.4.3.2. Fission reactions ............................................................. 48 3. PROMPT GAMMA NEUTRON ACTIVATION ANALYSIS (PGNAA) ..................0 5 . 4. THERMAL NEUTRON ABSORPTION ANALYSIS ........................................... 52 4.1. Principle ...........................................................................................2 5 . 4.2. Detectio e thermath f no l flux .................................................................4 5 . 4.3. Standardization .................................................................................... 54 4.4. Other applications ................................................................................ 55 . 5 TRANSPORT SYSTEMS ............................................................................7 5 . 6. MEASURING EQUIPMENT ........................................................................ 59 6.1. General ............................................................................................9 5 . 6.2. Sodium iodide detectors ........................................................................9 5 . 6.3. Germanium semi-conductor detectors ........................................................ 64 6.4. Detector calibration .............................................................................. 65 6.4.1. Resolutio d efficiencan n y ............................................................6 6 . 6.4.2. Energy calibration .....................................................................8 6 . 6.4.3. Evaluatio gamme th f no a spectra ...................................................9 6 . 7. SAMPLE PREPARATION ........................................................................... 72 8. APPLICATIONS ........................................................................................ 74 8.1. Determination of silver in lead ................................................................ 74 8.1.1. Introduction .............................................................................4 7 . 8.1.2. Nuclear data ............................................................................5 7 . 8.1.3. Equipment ................................................................................ 76 8.1.4. Sample and standard preparation .................................................... 76 8.1.5. Irradiation and counting conditions ................................................. 76 8.2. Determinatio f manganesno pyrolusitn i e ferromanganesd an e e .......................7 7 . 8.2.1. Introduction .............................................................................7 7 . 8.2.2. Nuclear data ............................................................................. 78 8.2.3. Interferences ............................................................................
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