Nuclear Geophysics and its Applications Geophysics Nuclear TECHNICAL REPORTS SERIES No. 393 Technical Reports Series No.Technical 393 Nuclear Geophysics and its Applications ISBN 92–0–100699–3 INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1999 ISSN 0074–1914 NUCLEAR GEOPHYSICS AND ITS APPLICATIONS The following States are Members of the International Atomic Energy Agency: AFGHANISTAN HAITI PARAGUAY ALBANIA HOLY SEE PERU ALGERIA HUNGARY PHILIPPINES ARGENTINA ICELAND POLAND ARMENIA INDIA PORTUGAL AUSTRALIA INDONESIA QATAR AUSTRIA IRAN, ISLAMIC REPUBLIC OF REPUBLIC OF MOLDOVA BANGLADESH IRAQ ROMANIA BELARUS IRELAND RUSSIAN FEDERATION BELGIUM ISRAEL SAUDI ARABIA BOLIVIA ITALY SENEGAL BOSNIA AND JAMAICA SIERRA LEONE HERZEGOVINA JAPAN SINGAPORE BRAZIL JORDAN SLOVAKIA BULGARIA KAZAKHSTAN SLOVENIA BURKINA FASO KENYA SOUTH AFRICA CAMBODIA KOREA, REPUBLIC OF SPAIN CAMEROON KUWAIT SRI LANKA CANADA LATVIA SUDAN CHILE LEBANON SWEDEN CHINA LIBERIA SWITZERLAND COLOMBIA LIBYAN ARAB JAMAHIRIYA SYRIAN ARAB REPUBLIC COSTA RICA LIECHTENSTEIN THAILAND COTE D’IVOIRE LITHUANIA THE FORMER YUGOSLAV CROATIA LUXEMBOURG REPUBLIC OF MACEDONIA CUBA MADAGASCAR TUNISIA CYPRUS MALAYSIA TURKEY CZECH REPUBLIC MALI UGANDA DEMOCRATIC REPUBLIC MALTA UKRAINE OF THE CONGO MARSHALL ISLANDS UNITED ARAB EMIRATES DENMARK MAURITIUS UNITED KINGDOM OF DOMINICAN REPUBLIC MEXICO GREAT BRITAIN AND ECUADOR MONACO NORTHERN IRELAND EGYPT MONGOLIA UNITED REPUBLIC EL SALVADOR MOROCCO OF TANZANIA ESTONIA MYANMAR UNITED STATES ETHIOPIA NAMIBIA OF AMERICA FINLAND NETHERLANDS URUGUAY FRANCE NEW ZEALAND UZBEKISTAN GABON NICARAGUA VENEZUELA GEORGIA NIGER VIET NAM GERMANY NIGERIA YEMEN GHANA NORWAY YUGOSLAVIA GREECE PAKISTAN ZAMBIA GUATEMALA PANAMA ZIMBABWE The Agency’s Statute was approved on 23 October 1956 by the Conference on the Statute of the IAEA held at United Nations Headquarters, New York; it entered into force on 29 July 1957. The Headquarters of the Agency are situated in Vienna. Its principal objective is “to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world’’. © IAEA, 1999 Permission to reproduce or translate the information contained in this publication may be obtained by writing to the International Atomic Energy Agency, Wagramer Strasse 5, P.O. Box 100, A-1400 Vienna, Austria. Printed by the IAEA in Austria March 1999 STI/DOC/010/393 TECHNICAL REPORTS SERIES No. 393 NUCLEAR GEOPHYSICS AND ITS APPLICATIONS INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 1999 VIC Library Cataloguing in Publication Data Nuclear geophysics and its applications. — Vienna : International Atomic Energy Agency, 1999. p. ; 24 cm. — (Technical reports series, ISSN 0074–1914 ; no. 393) STI/DOC/010/393 ISBN 92–0–100699–3 Includes bibliographical references. 1. Isotope geology. 2. Radiation well logging. I. International Atomic Energy Agency. II. Series: Technical reports series (International Atomic Energy Agency); 393. VICL 98–00215 FOREWORD Nuclear geophysics is the study and practice of nuclear physics as applied to geology. Examples of different materials dealt with by nuclear geophysics include raw materials such as petroleum, water, metalliferous minerals and coal as well as processed materials such as glass, purified minerals and ceramics. The methodology of nuclear geophysics started with the discovery, by Henry Becquerel in 1896, of the radioactivity in uranium sulphate. Since then it has evolved up to contemporary measurement technology which includes electronically actuated radiation sources and high resolution detectors interfaced with miniaturized, user friendly computers. The past fifty years have witnessed an enormous development in nuclear geophysics enabled by the progress in other physical disciplines, mathematics, geology itself and information science. Nuclear geophysics depends on the interaction of nuclear radiation with geological materials. The effects detected or measured are also radiations. What provides the practical basis for nuclear geophysics is the fact that the geological properties of the materials are factors determining the characteristics of these detected radiations. To start with, the report discusses the essence and the development of nuclear geophysics as well as the nature and methods of carrying out nuclear geophysical measurements. It deals with translating the results of measurements that have only a physical meaning into results with a tangible significance in the context of the properties of the materials measured. Borehole logging and dynamic or static bulk analysis are the main measurement applications of nuclear geophysics and, consequently, their performance underlies much of the discussion of the report on its benefits to society. Various nuclear techniques available that are based on the use of isotopic and, where applicable, electronic sources of neutrons, gamma and X rays are discussed in these applications. One example of an important trend in borehole logging discusses the use of spectrometric backscatter gamma ray technique for quantitative logging, based on the use of radioactive sources of very low radioactivity, combining the features of effective quantitative analysis, low cost and safety. The report aims at providing background information on the nature of nuclear geophysics, its objectives, its tools for investigation and its wide range of applications benefiting society and industry. It gives a comprehensive account of the fundamentals of nuclear geophysics and its applications to society. The report also contains additional scientific material on the interaction of nuclear radiation with geological samples, on data processing and interpretation. It concentrates on the more traditional and well established applications which are mainly related to economic progress and to methods increasing the output yield of the desired products of industrial processes and, thereby, minimizing wastage in the resources used by these processes. The report reviews the achievements and performance of nuclear geophysical measurements, particularly in applications to mining, industry and agriculture. It also analyses many of these important applications for their economic impact. It updates the available information on nuclear geophysics by giving an account of the most relevant achievements and concepts introduced during recent years. Also, it provides references to many of the significant recent publications in this field. The report contains material relevant not only to scientists and technologists active in the various branches of mineral industry but, even more importantly, aims at informing both managers and people generally educated in areas outside the specialized discipline of nuclear geophysics. It seeks to inform both the general reader and the non-specialist scientist on the application and impact of nuclear geophysics in modern society. The IAEA acknowledges the work of all those who were involved in the drafting and review and is particularly grateful to P.L. Eisler for his major contribution. EDITORIAL NOTE Although great care has been taken to maintain the accuracy of information contained in this publication, neither the IAEA nor its Member States assume any responsibility for consequences which may arise from its use. The use 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 names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA. CONTENTS 1. INTRODUCTION . 1 1.1. Substance and nature of nuclear geophysics . 1 1.2. History of nuclear geophysical methods . 2 2. FUNDAMENTALS OF NUCLEAR PHYSICS . 7 2.1. What do we measure? . 7 2.1.1. Types of sample measures . 8 2.1.2. Natural and artificial fields . 10 2.1.3. Radiation transport . 14 2.2. How do we make measurements? . 20 2.2.1. Nuclear geophysical measuring instruments and their configurations . 20 2.2.2. Physics of nuclear radiation detection . 21 2.2.3. Radiation detection and signal processing . 24 2.2.4. Sources of radiation for nuclear applications . 35 2.3. Basic interpretation models . 39 2.3.1. Introduction . 39 2.3.2. Models . 41 2.4. Summary . 54 Reference . 55 3. PARAMETERS OBTAINED BY NUCLEAR TECHNIQUES . 56 3.1. Material parameters . 59 3.2. Primary parameters measured . 62 3.3. Types of measurement . 77 3.4 Summary . 82 References . 84 4. MEASUREMENT METHODS . 87 4.1. Introduction . 87 4.2. Scale of the methods . 87 4.3. Environment of the methods . 88 4.3.1. The subsurface . 88 4.3.2. Tracer techniques . 92 4.3.3. X rays and mineral processing . 96 4.4. Reliability of the measurements . 98 4.5. Relevance of the measurements . 99 4.6. Emerging trends . 100 4.7. Summary . 108 References . 110 5. INTERPRETATION . 111 5.1. Relevance of the environment to interpretation . 111 5.2. Scale of interpretation . 112 5.2.1. General considerations . 112 5.2.2. Relevance of technique to scale of interpretational procedures . 112 5.3. Further strategies for solving the inverse problem . 113 5.3.1. Spectral interpretation . 114 5.3.2. Interpretational relationships and statistical models . 118 5.4. Reliability . 124 5.5. Emerging trends in interpretation and measurement . 126 5.5.1. Petrophysical filtration and cyclometry . 126 5.5.2. Other forms