ca9UD6B9 - ca9110708 AECL-9923 CSNI-149 ATOMIC ENERGY W£& ENERGIE ATOMIQUE OF CANADA LIMITED YfijF DU CANADA LIMITEE PROCEEDINGS OF THE SECOND CSNI WORKSHOP ON IODINE CHEMISTRY IN REACTOR SAFETY Organized under the auspices of the OECD Nuclear Energy Agency, Committee on the Safety of Nuclear Installations and Hosted by Atomic Energy of Canada Limited and Ontario Hydro Toronto, Canada 1988 June 2-3 Edited by A. C. Vikis 1989 March Copyright Atomic Energy of Canada Limited, 1989. AECL-9923/CSNI-149 PROCEEDINGS OF THE SECOND CSNI WORKSHOP ON IODINE CHEMISTRY IN REACTOR SAFETY Organized under the auspices of the OECD Nuclear Energy Agency, Committee on the Safety of Nuclear Installations and Hosted by Atomic Energy of Canada Limited and Ontario Hydro Toronto, Canada 1988 June 2-3 Edited by A.C. Vikis LEGAL NOTICE Atomic Energy of Canada and the Organization for Economic Co-Operation and Development assume no liability concerning information published in these proceedings. EDITORIAL NOTE In preparing these proceedings, the original manuscripts, as submitted by the authors, were used without further editorial changes. FOREWORD The Second CSNI Workshop on Iodine Chemistry in Reactor Safety was held in Toronto, Canada, on 1988 June 2 and 3. The Workshop was hosted by Atomic Energy of Canada Limited (AECL) and Ontario Hydro, and was attended by about forty iodine experts from ten OECD countries. Nineteen research papers were presented on various aspects of iodine chemistry, ranging form the most fundamental to the most applied. These papers and the ensuing discussions indicate that substantial progress was made in understanding the chemistry of iodine in water-cooled power-reactor accidents. The Workshop was a most effective forum for exchanging information on new progress and for delineating problems requiring resolution. As Chairman of the Workshop, I wish to thank the authors who have made this Workshop possible with their excellent contributions; the Program Committee, namely Dr. E.C. Beahm (USA), Dr. P.N. Clough (UK), Dr. W. Morell (FRG), Dr. P.E. Potter (UK) and Dr. J. Royen (OECD) for preparing the program; and the session Chairmen for running the Workshop. Also, I would like to acknowledge Mr. R.J. Fluke (Ontario Hydro) for his assistance with local arrangements and Dr. W. Kupferschmidt (AECL), Mr. A. Melnyk (AECL) and Mrs. C.J. Rohrig (AECL) for their assistance in organizing the Workshop and preparing these proceedings. A.C. VIKIS Chairman, Second CSNI Workshop on Iodine Chemistry in Reactor Safety CONTENTS Page FOREWORD - A.C. Vikis INTRODUCTION AND BRIEF DESCRIPTION OF CSNI - J. Royen 1 WORKSHOP SUMMARY/RECOMMENDATIONS 3 I. KINETICS AND MECHANISMS 5 Chairman: P.E. Potter and K. Ishigure KINETICS OF IODINE HYDROLYSIS IN UNBUFFERED SOLUTIONS, 7 Donald A. Palmer and L.J. Lyons, Oak Ridge National Laboratory, U.S.A. RADIOLYTIC AND SURFACE REACTIONS OF DILUTE IODINE 19 SOLUTIONS, W.G. Burns, M.C. Kent, W.R. Marsh, P.E. Potter and H.E. Sims, Harwell Laboratory, U.K. FACTORS AFFECTING RADIOLYSIS OF DILUTE IODINE 39 SOLUTIONS, K. Ishigure and H. Shiraishi, University of Tokyo, JAPAN. THE RADIATION-INDUCED FORMATION OF IODOALKANES AND 48 THE RADIOLYSIS OF IODOMETHANE, J. Paquette and B.L. Ford, Atomic Energy Of Canada, CANADA AQUEOUS IODINE AT LOW CONCENTRATIONS AND HIGH 74 TEMPERATURES, S.R. Daish, E.C. Beahm and W.E. Shockley, Oak Ridge National Laboratory, U.S.A. AN EXPERIMENTAL STUDY OF RADIOIODINE VOLATILITY, 96 G.J. Evans and R.E. Jervis and S.M. Mirbod, University of Toronto, CANADA. THE INFLUENCE OF RADIATION ON THE STABILITY OF CSI 114 IN FLOWING STEAM, D.J. Wren, R.K. Rondeau and M.C. Pellow, Atomic Energy Of Canada Limited, CANADA DISCUSSION ON SESSION I 131 continued... CONTENTS (continued) Page II. THERMODYNAMIC MEASUREMENTS 133 Chairman: E.C. Beahm ON THE EXISTENCE OF IODIDE BORATE COMPLEXES IN SATURATED 135 STEAM, D.J. Turner, Central Electricity Research Laboratory, U.K. IODINE DISPROPORTIONATE EQUILIBRIA UP TO 300°C, 151 P.P.S. Saluja, Atomic Energy Of Canada Limited, CANADA. III. REVOLATILIZATION STUDIES 171 Chairman: E.C. Beahm IODINE VOLATILITY FROM EVAPORATING PRIMARY COOLANT 173 FILMS IN STEAM ATMOSPHERES, B.J. Handy, and D.G. Jones, National Nuclear Corporation Limited, U.K. REVOLATILISATION OF FISSION PRODUCTS, ESPECIALLY 185 IODINE, FROM VATER PHASES EVAPORATING TO DRYNESS. M. Furrer and T. Buhler-Gloor, Paul Scherre Institute, Switzerland DISCUSSIONS ON SESSIONS II AND III 194 IV. MODEL/CODE DEVELOPMENT 195 Chairman: V. Morell COMPUTER MODELLING OF THE RADIATION CHEMISTRY OF 197 AQUEOUS IODIDE SOLUTIONS IN LABORATORY CONDITIONS AND IN A PVR LOCA USING THE FACSIMILE COMPUTER PROGRAM, W.G. Burns and H.E. Sims, Harwell Laboratory, U.K. continued... CONTENTS (concluded) MODELLING THE CHEMISTRY OF IODINE, J. Paquette, 216 Atomic Energy of Canada Limited, CANADA. RADIOLYSIS OF IODINE IN MOIST AIR: A COMPUTER STUDY, 235 N.H. Sagert, Atomic Energy of Canada Limited, CANADA. CHEMISTRY AND MASS TRANSPORT OF IODINE BEHAVIOR 251 IN CONTAINMENT, E.C. Beahm, C.F. Weber, T.S. Kress, W.E. Shockley and S.R. Daish, Oak. Ridge National Laboratory, U.S.A. DISCUSSIONS ON SESSION IV 270 V. LARGE-SCALE TESTS/OTHER 273 Chairman: M. Furrer MEASUREMENTS OF RADIOIOIDINE SPECIES IN SAMPLES OF 275 PRESSURIZED WATER REACTOR COOLANT, Paul G. Violleque, Science Applications International Corporation, U.S.A. A DESCRIPTION OF THE RADIOIODINE TEST FACILITY (RTF) 292 AND RESULTS OF INITIAL RTF FULL-SYSTEM TESTS, W.C.H. Kupferschmidt, R. Portman and G.G. Sanipelli, Atomic Energy of Canada Limited, CANADA. SHORT PRESENTATION OF PHEBUS-FP, C. Huber, 314 Centre d'Etudes Nucleaires de Cadarache, FRANCE. PLANKED WORK AT JAERI FOR IODINE CHEMISTRY DURING 317 REACTOR ACCIDENT, M. Saeki, Japan Atomic Energy Research Institute, JAPAN. LIST OF PARTICIPANTS 321 - 1 - INTRODUCTION It is my pleasure to welcome you, on behalf of the OECD and its Nuclear Energy Agency, to this Second CSNI Workshop on the Chemistry of Iodine in Reactor Safety, organized in collaboration with Atomic Energy of Canada Limited and Ontario Hydro. Iodine chemistry continues to enjoy high priority in the CSNI programs of work as part of severe accident source term studies. Following the Three Mile Island accident, considerable interest was generated in the chemical form of iodine in severe accidents. Because of the apparent small release of iodine to the containment, it was suggested that the chemical form of iodine must have hindered its release from the reactor coolant system; it was concluded tentatively that a low-volatility iodide compound, namely cesium iodide, had been formed, and that it had been transported as such within the plant instead of molecular iodine as previously assumed. In fact, there was very little direct evidence from the TMI accident that indicated what the chemical form of .he iodine was during reactor coolant system transport or in the containment. Thermodynamic analyses conducted for NUREG-0772 (published in 1981) showed the formation of cesium iodide during transport in the reactor coolant system, but its formation was not favoured in the reactor core. Since the publication of NUREG-0772, additional experimental evidence indicates that other factors may also affect cesium iodide stability in the reactor coolant system. The environment created during a reactor accident contains a large number of chemical species and this results in a complex chemistry. Factors affecting the chemical form of iodine in the reactor coolant system - and therefore its volatility - include the cesium-to-iodine ratio, boron compounds, hydrogen-to-steam ratio, temperature, pH and redox potential of the aqueous medium, and possibly others such as radiation. They will thus depend on the type of accident. If iodine is transported through the reactor coolant system as cesium iodide, because of its lower volatility, a significant fraction of iodine would be retained by aerosol deposition or condensation. In this case, iodine release to the containment is reduced, which is particularly important in accident analyses involving early containment failures. On the other hand, volatile iodides such as I2 and HI are more readily transported in the reactor coolant system. In this case, the major parameter affecting the release of iodine is the amount of volatile iodide generated in the reactor coolant system. A detailed understanding of the chemistry of iodine in aqueous solutions is an essential step in the prediction of the magnitude of possible releases of volatile iodine to the environment in water reactor accidents. The key issues, therefore, are: 1. what are the chemical forms of iodine in the reactor coolant system over the range of severe accident conditions, and 2. how would they affect severe accident iodine source terms. These issues affect all types of plants and neeidrnt sequences. They are Important components of t lie mandate of Principal Working Group No. A on the Confinement of Accidental Radioactive ! .-leases ot the NEA's Committee on the Safety of Nuclear Installations (CSNI). They have been included in the 1989-1991 programme of work of the Group. It is my pleasure to thank, on behalf of NEA, Atomic Energy of Canada Limited and Ontario Hydro for the hospitality generously offered to this Workshop. We also would like to thank the members of the Programme Committee, Dr. Beahm, Dr. Clough, Dr. Neeb (represented by Dr. Morell), Dr. Potter and more particularly Dr. Vikis who has taken charge of the Canadian part of the organization of the Workshop. Thanks to their efforts and advice, the meeting will be fruitful and very interesting. We would also like to thank Ontario Hydro, in particular Mr. Fluke, for organizing yesterday a very informative visit to the Darlington nuclear power plant. Few of us had seen a CANDU reactor before that; the visit and the explanations were most interesting. J. ROYEN CSNI SECRETARY - 3 - SECOND CSNI WORKSHOP ON IODINE CHEMISTRY IN REACTOR SAFETY SUMMARY/RECOMMENDATIONS The second CSNI Workshop on Iodine Chemistry in Reactor Safety vas held in Toronto, on 1988 June 2 & 3, and was attended by about forty iodine experts from ten OECD countries.