TECHNICAL REPORTS SERIES No. 84 Radiation Chemistry and its Applications ?J INTERNATIONAL ATOMIC ENERGY AGENCY, VIENNA, 1968 RADIATION CHEMISTRY AND ITS APPLICATIONS The following States are Members of the International Atomic Energy Agency: AFGHANISTAN GERMANY, FEDERAL NORWAY ALBANIA REPUBLIC OF PAKISTAN ALGERIA GHANA PANAMA ARGENTINA GREECE PARAGUAY AUSTRALIA GUATEMALA PERU AUSTRIA HAITI PHILIPPINES BELGIUM HOLY SEE POLAND BOLIVIA HUNGARY PORTUGAL BRAZIL ICELAND ROMANIA BULGARIA INDIA SAUDI ARABIA BURMA INDONESIA SENEGAL BYELORUSSIAN SOVIET IRAN SIERRA LEONE SOCIALIST REPUBLIC IRAQ SINGAPORE CAMBODIA ISRAEL SOUTH AFRICA CAMEROON ITALY SPAIN CANADA IVORY COAST SUDAN CEYLON JAMAICA SWEDEN CHILE JAPAN SWITZERLAND CHINA JORDAN SYRIAN ARAB REPUBLIC COLOMBIA KENYA THAILAND CONGO, DEMOCRATIC KOREA, REPUBLIC OF TUNISIA REPUBLIC OF KUWAIT TURKEY COSTA RICA LEBANON UGANDA CUBA LIBERIA UKRAINIAN SOVIET SOCIALIST CYPRUS LIBYA REPUBLIC CZECHOSLOVAK SOCIALIST LUXEMBOURG UNION OF SOVIET SOCIALIST REPUBLIC MADAGASCAR REPUBLICS DENMARK MALI UNITED ARAB REPUBLIC DOMINICAN REPUBLIC MEXICO UNITED KINGDOM OF GREAT ECUADOR MONACO BRITAIN AND NORTHERN EL SALVADOR MOROCCO IRELAND ETHIOPIA NETHERLANDS UNITED STATES OF AMERICA FINLAND NEW ZEALAND URUGUAY FRANCE NICARAGUA VENEZUELA GABON NIGERIA VIET-NAM YUGOSLAVIA 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". Printed by the IAEA in Austria April 1968 TECHNICAL REPORTS SERIES No. 84 RADIATION CHEMISTRY AND ITS APPLICATIONS REPORT OF A PANEL ON RADIATION CHEMISTRY: RECENT DEVELOPMENT AND REVIEW OF RANGE OF APPLICABILITY OF EXISTING SOURCES, HELD IN VIENNA, 17-21 APRIL 1967 INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 1968 RADIATION CHEMISTRY AND ITS APPLICATIONS (Technical Reports Series, No. 84) ABSTRACT. The report of a panel convened by the IAEA and held in Vienna, 17-21 April 1967. The meeting was attended by 15 specialists from ten countries. Contents: Introduction: Summary of discussions; General observations and recommendations; Reports; Communications and comments. The ten reports cover such subjects as application of ionizing radiation to polymer chemistry, the status of chemonuclear reactors and radiation chemical processing, synthesis and decomposition induced by ionizing radiation, and the use of low-energy electron accelerators for the curing of paints and thin films. Each report is in its original language (9 English and 1 French) and is preceded by an abstract in English with a second one in the original language if this is not English. The rest of the publication is in English. (182 pp., 16 X 24 cm, paper-bound, 23 figures) (1968) Price: US S4.00; £1.13.4 RADIATION CHEMISTRY AND ITS APPLICATIONS IAEA, VIENNA, 1968 STI/DOC/ 10/84 FOREWORD In recent years considerable progress has been made in understanding the fundamental chemical reactions that occur when materials are irradiated. This has followed from the development of new techniques for studying these reactions. There have also been significant advances in source technology and in the design of accelerators for carrying out irradiations. Parallel to these developments there has been an increasing interest in the industrial application of chemical effects of radiation, particularly in work on polymers. The International Atomic Energy Agency held a Panel on Radiation Chemistry in Vienna on 17 - 21 April 1967 to review the current status of various sources, new techniques in radiation chemistry, and their appli- cations. Fifteen specialists attended from 10 countries. The main sources mentioned by the Panel were isotope sources, electron accelerators, and chemonuclear reactors. Among the basic techniques dis- cussed were pulsed radiolysis, flash photolysis, fast ESR methods, irradi- ation at liquid helium temperatures, electric discharge methods and far ultra-violet methods. Interesting industrial applications were discussed, such as the development of wood-plastic combinations, and a paper was given on the curing of paints and thin films. Summaries of the presentations and discussions, together with the re- commendations and the written contributions, are given in this report. It is hoped that the publication will be useful to radiation chemists and to those responsible for establishing and operating programmes based on radiation chemical processes. CONTENTS I. INTRODUCTION 1 II. SUMMARY OF DISCUSSIONS 1 III. GENERAL OBSERVATIONS AND RECOMMENDATIONS 17 IV. REPORTS 23 Application of ionizing radiation to polymer chemistry (PL- 236/1) 23 A . Danno Characteristics and range of applicability of accelerators for radiation chemical processes (PL-236/10) 43 N. W. Holm Status report on chemonuclear reactors and radiation chemical processing (PL-236/4) : 53 M. Steinberg Safety for large irradiation facilities (PL-236/2) 63 A. Danno Low-temperature irradiations (PL-236/5) 67 Z. P. Zagorski and S. Mine Pulse radiolysis (PL-236/6) 89 D. F. Sangster Le développement de la radiochimie: quelques aspects de la conjoncture (PL-236/8) 93 P. Lévêque et J.R. Puig Synthesis and decomposition induced by ionizing radiation (PL-236/7) 97 Silvia Ionescu Radiation-induced polymerization: mechanisms and industrial aspects (PL-236/9) 125 D. O. Hummel, Christel Schneider, R. C. Potter, G. Ley, J. Denaxas, D. Widdershoven and M. Ryska The use of low-energy electron accelerators for the curing of paints and thin films (PL-236/3) 165 F.L. Dalton V. COMMUNICATIONS AND COMMENTS 171 List of participants 181 I. INTRODUCTION The use of radiation in industry has increased greatly during the last few years. Of importance has been the use of radiation to modify polymers giving cross-linked and shrinkable plastic film and tubing. It has also been demonstrated that chemicals can be manufactured by radiation chemical processes. More recently radiation grafting of polymers on to various substrates and the manufacture of copolymers have both been under investigation. In these cases, to obtain optimum conditions, research is directed to maximize yields. In any atomic energy programme there will be many examples of materials exposed to ionizing radiation. Reactor moderator, coolant, chemical reprocessing solutions and radioisotopes may be instanced. In these cases it is necessary to minimize the deleterious effects of radiation. Fundamental investigations in the field of radiation chemistry have been directed towards elucidating the reaction mechanisms obtained in systems subjected to radiation, and measurements of the reaction parameters. This has led to a better understanding of chemical reactions, in general, as well as of those particularly associated with radiolysis. The field covered by the Panel was broad in its scope ranging from fundamental studies through research and development of processes of potential industrial importance to commercial enterprises. Because of this wide scope, this report cannot claim to have covered each area exhaustively. Rather, an attempt has been made to define the field and to put each part into perspective in relation to each other part. At the same time it has been possible on some subjects to comment in some detail where the expert knowledge of Panel members made this possible. The report of the Panel comprises four parts: summary of presentations and discussions on each topic discussed at the Panel; general observations that reflect the view of the participants on each topic, and recommendations regarding the Agency1 s activities; the ten written contributions to the Panel; finally, comments on various selected topics. II. SUMMARY OF DISCUSSIONS 1. Sources 1.1. Various existing sources Steinberg (United States of America) reviewed chemonuclear fission- fragment energy sources1. Uranium containing glass fibre and U02-coated platinum sources has the disadvantages of low melting point and radiation damage. Uranium-palladium solid solutions have been developed to the point where reliable fission-fragment radiation chemistry experiments 1 STEINBERG, M., "Status report on chemonuclear reactors and radiation chemical processing", this Report, PL-236/4. 1 2 DISCUSSIONS can be performed. Platinum-coated U-Pd improves the resistance to radiation damage and should prevent spallation of uranium atoms. Nitrous oxide and carbon dioxide gas dosimetry allows the determination of fission- fragment energy deposition efficiency which is in conformity with analytical range-geometrical calculations. The 0.1 mil (2.5 /urn) foil has been fabricated into honeycomb arrays for insertion into the in-pile chemo- nuclear loop. Brookhaven is continuing to develop bonded coextruded 60Co sources. 137Cs sources of caesium chloride in stainless-steel envelopes are being tested. 90Sr sources of microspheres in stainless-steel needles are being used in small-scale experiments. Larger multicurie sources of 90Sr which would have high integrity have yet to be developed. 137Cs has the advantage of long half-life and availability, but large-scale application depends primarily on the development of a high integrity source. Holm (Denmark) reviewed his work on d. c. and linear accelerators2. The main points included increased technological development of machine radiation sources based on continued development of accelerators for research purposes.