A Handbook of Radioactivity Measurements Procedures NCRP Reports 58

634 Pages·1985·23.578 MB·English

NCRP REPORT No. 58
Second Edition
A HANDBOOK OF
RADIOACTIVITY
MEASUREMENTS
PROCEDURES
With Nuclear Data for Some Biomedically
Important Radionuclides, Reevaluated between
August, 1983 and April, 1984
Recommendations of the
NATIONAL COUNCIL ON RADIATION
PROTECTION AND MEASUREMENTS
Issued February 1,1985
Second Reprinting May 15, 1989
Third Reprinting February 28,1994
National Council on Radiation Protection and Measurements
7910 WOODMONT AVENUE / BETHESDA, MD. 20814
LEGAL NOTICE
This report was prepared by the National Council on Radiation Protection and Meas-
urements (NCRP). The Council strives to provide accurate, complete and useful infor-
mation on its reports. However, neither the NCRP, the members of NCRP, other
persons contributing to or assisting in the preparation of this report, nor any person
acting on the behalf of any of these parties (a) makes any warranty or representation,
express or implied, with respect to the accuracy, completeness or usefulness of the
information contained in this report, or that the use of any information, method or
process disclosed in this report may not infringe on privately owned rights; or (b)
assumes any liability with respect to the use of, or for damages resulting from the use
of, any information, method or process disclosed in this report.
Library of Congress Cataloging in Publication Data
National Council on Radiation Protection and Measurements.
Main entry under title:
A Handbook of radioactivity measurements procedures.
(NCRP report ; no. 58)
'Recommendations of the National Council on Radiation Protection and Measure-
ments."
'Febmary 1,1985"
Bibliography: p.
Includes index.
1. Radioactivity-Measurement. 2. Radioactivity-Instruments. I. National Council
on Radiation Protection and Measurements. 11. Series.
QC795.42.H36 1985 539.7'7 84-25423
ISBN 0.913392-71-5
Copyright (O National Council on Radiation
Protection and Measuremenu 1985
All rights resewed. This publication isprotectedby copyright. No part of this publication
may be reproduced in any form or by any meane, including photocopying, or utilized by
any information storage and retrieval system without written permission from the
copyright owner, except for brief quotation in critical articles or reviews.
Preface to the First Edition
In 1961 the NCRP issued NCRP Report No. 28, A Manual of
Radioactivity Procedures, which was published as the National Bureau
of Standards Handbook 80. The report came to be one of the definitive
works in the area of radioactivity measurements. As the development
of new techniques, procedures, and equipment made parts of the
Report obsolescent, the NCRP recognized the need to update and
extend the document. The report consisted essentially of three parts:
Part One being "Radioactivity Standardization Procedures"; Part
Two, "Measurement of Radioactivity for Clinical and Biological Pur-
poses"; and Part Three, "Disposal of Radioactive Material". Since the
disposal of radioactive material constitutes a subject in itself, the
NCRP, in preparing the revision of Report No. 28, decided to concen-
trate on the first two parts of the Report.
Because of the projected bulk of the revised report, it was decided
to divide the task of preparation into two parts. NCRP Scientific
Committee 18A was given the task of drafting the material on general
measurement and standardization procedures; and Scientific Commit-
tee 18B was charged with drafting the material on those measurement
procedures specifically concerned with medical and biological appli-
cations. This report is the result of Committee 18A's work. As such,
it follows, to a high degree, the general format of the original report.
Thus, the physics of detectors is discussed in Section 2.0 and then the
uses to which these detectors may be put are discussed in those sections
dealing with direct and indirect measurerr~ents.A t the same time, each
of the sections has been developed in much more detail than previously
and it is therefore inevitable that some duplication occurs. In fact,
some duplication has been deliberately included so that individuals
may utilize given sections of the Report without having to refer back
to earlier sections where similar material may have been covered. In
almost every case, it is believed that the repetition will not only
emphasize the suitability of a detector for a particular application, but
will also add detail to the information already given.
In a report of this length it is inevitable that the supply of unique
symbols would be exhausted. Where, however, there may have been
...
111
iv / PREFACE
some duplications in the use of symbols, every effort has been made
to keep them consistent within the short section in which they appear.
Acknowledgments are made to Dr. Ayres who acted as secretary to
the Committee, and to Dr. Hoppes who, while making no specific
written contribution, served invaluably by spending many hours in
valuable discussion with the Chairman of the Scientific Committee
during the course of editing and clarifying the original text. The
assistance of Miss P. A. Mullen in the work of coordinating the
references is also gratefully acknowledged.
The Council has noted the adoption by the 15th General Conference
of Weights and Measures of special names for some units of the
Systcme International d'Unit6s (SI) used in the field of ionizing
radiation. The gray (symbol Gy) has been adopted as the special name
for the SI unit of absorbed dose, absorbed dose index, kerma, and specific
energy imparted. The becquerel (symbol Bq) has been adopted as the
special name for the SI unit of activity (of a radionuclide). One gray
equals one joule per kilogram; and one becquerel is equal to one second
to the power of minus one. Since the transition from the special units
currently employed-rad and curie-to the new special names is
expected to take some time, the Council has determined to continue,
for the time being, the use of rad and curie. To convert from one set
of units to the other, the following relationships pertain:
1 rad = 0.01 Jkg-' = 0.01 Gy,
1 curie = 3.7 x 10'' s-I = 3.7 x 10'' Bq (exactly).
Serving on Scientific Committee 18A during the preparation of this
report were:
WILFRIDB . MANN.,C hairman
Members
ABRAHAMP . BAERC BERNDK AHN
J. CALVINB RANTLEY HARRYH . KU
RUSSELLL . HEATH A. ALANM OCHISSI
WILLIAMJ . MAC~NTRYEE,x officio (Chairman, Scientific Committee 18B)
NCRP Secretmiat, CONSTANTINJE. MALETSKOS
PREFACE / v
The Council wishes to express its appreciation to the members and
consultants for the time and effort they devoted to the preparation of
this report.
WARRENK . SINCLAIR
President, NCRP
Bethesda, Maryland
February 15, 1978
Preface to the Second Edition
By 1983 supplies of NCRP Report No. 58, A Handbook of Radioac-
tivity Measurements Procedures, which was issued in 1978, were ex-
hausted. In view of the progress which continues to be made in the
field of radionuclide metrology it was decided to reissue it, not just by
reprinting, but as a substantially revised edition, that now constitutes
the present text.
Many of the individuals who participated in the earlier work of
Scientific Committee 18A and a few others have contributed to this
revision. The chairman of the Committee has asked that the contri-
bution of several new pages of extensively revised text by A. P. Baerg,
R. L. Heath, J. G. V. Taylor, and J. A. B. Gibson, mostly to Sections
2, 3 and 4 be especially acknowledged. He also wishes to thank R.
Colle, E. H. Eisenhower, H. H. Ku with K. Eberhardt, D. D. Hoppes
and R. Loevinger for countless and lively discussions of as many drafts
of the new Sections 8.3 and 8.4 before a consensus was almost achieved;
and to acknowledge very valuable discussions with B. M. Coursey and
A. Grau Malonda when writing the new sub-section 4.3.9. Very grateful
acknowledgement is due to M. J. Martin for organizing a special
printing of nuclear data for selected radionuclides for this edition from
the ENSD File of the Oak Ridge Nuclear Data Project. Contributions
ranging from suggestions to references and discussions have been
welcomed from W. C. Eckleman, T. G. Hobbs, J. M. R. Hutchison, B.
Kahn, J. R. Noyce, C. T. Peng, L. A. Slaback, B. N. Taylor and M. P.
Unterweger.
Especial thanks are due to D. D. Hoppes for very many cogent and
fruitful discussions that were grossly intrusive on his time that was so
graciously spared; and to Commander J. A. Spahn (U.S.N., Ret.) who
substituted at short notice for C. J. Maletskos to represent the NCRP
Secretariat and who has given weeks to meticulous and devoted editing
of this new edition.
The NCRP wishes to acknowledge the deep debt of gratitude owed
to Dr. Wilfrid B. Mann for the extensive effort he devoted to the
scientific editing of this revised second edition and for his dedication
to the never ending task of updating important technical information
in this edition of the report.
Warren K. Sinclair
President, NCRP
Bethesda, Maryland
September 12, 1984
Contents
Preface .................................................
Preface to the Second Edition ...........................
.
1 Introduction ........................................
1.1 General ........................................
1.2 Radiations Emitted From Radioactive Atoms ........
1.3 The Half/Life. Decay Constant. and Activity of A Ra-
dioactive Element ...............................
1.4 The Interaction of Radiation with Matter ...........
1.4.1 Interactions of Charged Particles with Matter .
1.4.2 Interactions of Energetic Photons with Matter
1.4.3 Other Interactions .........................
1.5 Fundamental or Direct Methods of Radioactivity Stan-
dardization ....................... .. ..........
1.5.1 Introduction; Terminology ..................
1.5.2 Direct Methods of Measurement ............
1.5.3 "Near-Direct" Methods of Measurement ......
1.5.3.1 Weighing of a Radioactive Element of
Known Isotopic Abundance ...........
1.5.3.2 Calorimetry ........................
1.5.3.3 Ionization Measurements ............
1.5.3.4 Loss-of-Charge Method ..............
1.5.3.5 Activity from Produdion Data ........
1.6 Indir.e ct .o r Relative Methods of Radioactivity Stan-
dardlzation .....................................
.
2 Physics of Some Radiation Detectors ................
2.1 Ionization Chambers .............................
2.1.1 Current Ionization Chamber ................
2.1.2 Pulse Ionization Chamber ..................
2.2 Proportional Counters ...........................
2.2.1 Shape of the Output Pulse ..................
2.2.2 Choice of Counting Gas ....................
2.2.3 Characteristics of Proportional Counters .....
2.3 Geiger-Miiller Counters ..........................
2.4 Scintillation Detectors ...........................
2.4.1 Introduction ......... ........................
Vlll
CONTENTS / ix
2.4.2 The Scintillation Process ................... 33
2.4.3 Conversion of Fluorescent Radiation to Elec-
trone (Phototube) ......................... 36
2.4.4 Output-Pulse Processing ................... 39
2.4.5 Liquid-Scintillation Counting ............... 42
2.4.5.1 Counting ........................... 42
2.4.5.2 Quenching ......................... 44
2.4.6 Gas-Scintillation Counting ................. 48
2.4.6.1 Gas-Scintillation Counters ........... 48
2.4.6.2 Gas-Proportional-Scintillation Counters 49
2.5 Semiconductor Detectors ......................... 50
2.5.1 Lntroduction .............................. 50
2.5.2 Energy Resolution ......................... 55
-
2.5.3 Characterizing Detector Performance ........ 57
2.6 Cerenkov Counting .............................. 58
2.7 Dead.Time, Decay, and Background Corrections ..... 60
2.7.1 Introduction .............................. 60
2.7.2 Dead-Time Corrections .................... 60
2.7.2.1 Introduction ........................ 60
2.7.2.2 Statistics of Dead-Time Distorted Pro-
cesses ............................. 63
2.7.2.3 Dead Times of Practical Systems ...... 64
2.7.2.4 Measuring Dead Times .............. 65
2.7.2.4.1 Oscilloscope Method ......... 65
2.7.2.4.2 Double-Pulse Method ........ 65
2.7.2.4.3 Two-Source Method ......... 65
2.7.2.4.4 Source-Pulser Method ....... 67
2.7.2.4.5 Two-Pulser Method ......... 67
2.7.2.4.6 Decaying-Source Method ..... 68
2.7.2.4.7 Proportional-Sources Method . 68
2.7.2.4.8 Reference-Peak Method ...... 69
2.7.2.5 Dead Times in Series ................ 70
2.7.2.6 Further Reading .................... 71
2.7.3 Background and Decay Corrections .......... 71
3. Fundamental or Direct Measurements of Activity in
Radioactive Decay .................................. 74
3.1 General ........................................ 74
3.2 Beta-Gamma Coincidence Counting ................ 75
3.2.1 General .................................. 75
3.2.2 Coincidence Counting ...................... 76
3.2.3 Anticoincidence Counting .................. 79
3.2.4 Correlation Counting ...................... 82
3.2.5 Count-Rate-Dependent Corrections .......... 85
3.2.6 Efficiency- Dependent Effects ............... 86
x / CONTENTS
3.2.7 Complex Beta-Gamma Decay ............... 87
3.2.8 Experimental Techniques for Complex Beta-
Gamma Decay ............................ 89
3.2.8.1 Efficiency Variation ................. 89
3.2.8.2 Gamma-Channel Energy Response .... 90
3.2.8.3 Multiple-Channel 4 r 8-7 Counting .... 91
3.2.8.4 Data Analysis ...................... 92
3.2.9 Applications of Coincidence Counting ........ 93
3.3 Sum-Peak Coincidence Counting .................. 94
3.4 Photon-Photon Coincidence Counting .............. 97
3.5 4r Proportional Counting ........................ 100
3.5.1 General .................................. 100
3.5.2 Dead Time ............................... 104
3.5.3 Background ..............................1 04
3.5.4 Source-Mount Absorption .................. 105
3.5.5 Source Self-Absorption Correction ........... 105
3.5.6 Applications .............................. 105
3.5.6.1 47ra Proportional Counting ........... 106
3.5.6.2 478 Proportional Counting ........... 106
3.5.6.3 4rx Proportional Counting ........... 107
3.5.6.4 47re- Proportional Counting .......... 108
3.5.7 Further Reading .......................... 109
3.6 Internal Gas Counting ........................... 109
3.7 Alpha-Particle Counting .......................... 113
3.7.1 Introduction .............................. 113
3.7.2 Standardization by 2ra Proportional Counting 113
3.7.3 Backscattering ............................ 114
3.7.4 Source Self-Absorption ..................... 115
3.7.5 Calculation of Scattering and Source Self-
Absorption ...............................1 16
3.7.6 The Robinson Counter ..................... 117
3.7.7 Low-Geometry Solid-Angle Counters ......... 120
3.8 Liquid-Scintillation Counting .....................1 20
3.8.1 Detection Sensitivity ...................... 120
3.8.2 Zero-Detection Probability ................. 121
3.8.3 Double- and Triple-Coincidence Methods ..... 124
3.8.4 Beta .g amma Coincidence -Counting Tech-
niques ................................... 125
3.9 Calorimetry .................................... 125
3.10 Mass and Resonant-Ionization Spectrometry ........ 128
3.11 Standardization of Gamma-Ray Emitters by Dosimetry
Measurements .................................. 130
3.11.1 Measurements by Ionization Chambers and
Sources Calibrated in Terms of Exposure ..... 130
CONTENTS / xi
3.11.2 Measurement by Ionization Chamber of Known
Volume .................................. 136
3.12 Loss-of-Charge Method .......................... 138
3.13 Calculation of Activity of Artificially Produced
. Radionuclides from Irradiation Data ............... 138
4 Indirect or Comparative Measurements of Activity in
Radioactive Decay .................................. 140
4.1 General ........................................ 140
4.2 Radionuclide Identification and Assay by Energy
Spectrometry ................................... 140
4.2.1 General .................................. 140
4.2.2 Interaction of Photons with Matter .......... 141
4.2.2.1 Photoelectric Effect ................. 142
4.2.2.2 Compton-Scattering Process .......... 142
4.2.2.3 Pair Production ..................... 144
4.2.3 The Pulse-Height Spectrum ................ 145
4.2.4 Pulse-Height Spectrometers ................ 148
4.2.4.1 Detector ........................... 150
4.2.4.2 Pulse Amplifier ..................... 151
4.2.4.3 Multichannel Pulse-Height Analyzer ... 154
4.2.4.4 Instrument Dead Time ............... 158
4.2.5 Experimental Effects in Photon Spectrometry . 159
4.2.5.1 Effect of Environment on Detector
Response .......................... 159
4.2.5.2 Summation Effects .................. 162
4.2.5.3 Problems at High Counting Rates ..... 165
4.2.6 Quantitative Analysis of Gamma-Ray Spectra . 167
4.2.6.1 Detector Efficiency .................. 167
4.2.6.2 Photopeak. or Full.Energy.Peak. Effi-
ciency ............................. 169
4.2.6.3 Peak-to-Total Ratio ................. 169
4.2.6.4 Emission-Rate and Energy Measure-
ments ............................. 169
4.2.6.5 Efficiencies of Semiconductor Detectors 171
4.2.7 Methods of Spectral Analysis-NaI(T1) Detec-
tors ..................................... 175
4.2.7.1 Graphical Analysis by Subtraction ..... 175
4.2.7.2 Linear Least-Squares-Fitting Method . . 175
4.2.8 Methods of Spectral Analysis-Ge Detectors . . 177
4.2.8.1 Energy us. Pulse-Height Scale ........ 181
4.2.8.2 Computer-Based Data Systems ....... 185
4.3 Liquid-Scintillation Counting ..................... 188
4.3.1 Composition of Liquid Scintillator ........... 188
4.3.2 Measurement of Aqueous Samples ........... 189