Fukushima event reconstruction using modelling and isotope relationships
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Fukushima event reconstruction using modelling and isotope relationships Ian Hoffman • Ed Korpach • Pawel Mekarski • Kurt Ungar • Jing Yi Weihua Zhang • Mikael Moring • Vladimir Khotylev • Ali El-Jaby
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Received: 28 July 2012 / Published online: 24 August 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract Using particulate and noble gas raw data analysed from Comprehensive Nuclear Test-Ban-Treaty (CTBT) monitoring sites, Canadian National Surveillance networks and atmospheric transport modelling, it is possible to associate some of the main events in the Fukushima accident timeline with observations, and perturbations in isotopic ratios in Japan, through the Pacific and into North America. Additional sources identified during the accident period will be commented upon in the context of CTBT treaty verification. Keywords Fukushima reactor accident Noble gas Xenon Environmental radioactivity monitoring Accident reconstruction Comprehensive Nuclear Test-Ban-Treaty (CTBT)
Introduction The Fukushima reactor accident caused by catastrophic damage to systems designed to remove decay heat from the Tohoku earthquake and tsunami off the coast of Japan on March 11, 2011 led to large releases of radioactive materials both in particulates and gaseous form that were I. Hoffman (&) E. Korpach P. Mekarski K. Ungar J. Yi W. Zhang Radiation Protection Bureau, Health Canada, 775 Brookfield Rd, Ottawa, ON K1A 1C1, Canada e-mail: [email protected] M. Moring Radiation and Safety Authority (STUK), Laippatie 4, 1400881 Helsinki, Finland V. Khotylev A. El-Jaby Canadian Nuclear Safety Commission, 280 Slater St, Ottawa, ON K1P 5S9, Canada
observed worldwide [1–3, 5, 6, 8, 10]. Using data collected at both Canadian and international radioactivity monitoring sites, further analysis and examination was performed to see if a relationship between isotopic observations could provide an indication of accident processes occurring at the Fukushima reactor site in Japan. The primary data sources in Canada were the four CTBT International Monitoring System (IMS) stations locations in Sidney, BC, Yellowknife, NWT, Resolute Bay, NU, and St. John’s, NFLD, and an additional national monitoring station located in Ottawa, ON. In addition to the Canadian data available, data was also used from monitoring stations operated by Japan, the USA, Germany, Iceland, and Sweden. The plan for the global CTBT network is the eventual construction of 80 high volume (over 20,000 m3/d) aerosol samplers and 40 noble gas analysers. The network is nearly complete for both particulate and noble gas monitoring systems. The systems in the network are a mixture of fully automated and manual (human operated) samplers. Within each technology type, there are some important variations on how each system operates. Each CTBT particulate sampler nominally operates according to an (approximate) schedule described by: aerosol collection for a period of 24 h, sample cool-down for 24 h to let short-lived natural radionuclides and progeny decay, followed
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