Abstract
An analysis of a data set consisting of 3 years of high time resolution radioxenon stack measurements from the three nuclear reactors at the Forsmark nuclear power plant in Sweden, as well as measurements of atmospheric radioxenon in Stockholm air, 110 km away, is presented. The main causes for the stack releases, such as the function of the xenon mitigation systems, presence of leaking fuel elements, and reactor operations such as shutdown and startup, are discussed in relation to the stack data. The relation between radioxenon releases and reactor operation is clearly illustrated by the correlation between the stack measurements and thermal reactor power. In general, the isotopic ratios of the Stockholm measurements, which are shown to mainly originate from Forsmark releases, agree well with stack measurements, and with a modeled reactor operational sequence. Results from a forward atmospheric dispersion calculation agree very well with observed plume arrival times and widths, and with some exceptions, also with absolute activity concentrations. The results illustrates the importance of detailed knowledge of radioxenon emissions from nuclear power plants when interpreting radioxenon measurements for nuclear test ban verification, and provide new input to this kind of analysis. Furthermore, it demonstrates the possibility to use sensitive radioxenon detection systems to remotely detect and verify reactor operation.
Highlights
The dominating release source for the radioactive xenon routinely found in the atmosphere are medical isotope production facilities (IPFs) (Saey et al 2010), which are estimated to contribute to 95% of the global133Xe-activity of about 50 TBq released daily (Achim et al 2016)
Nuclear reactors are typically weak radioxenon sources compared to IPFs, they still can be very important to take into account when interpreting potential nuclear explosion signals detected in the radioxenon network of the International Monitoring System (IMS) used for verification of the Comprehensive Nuclear-Test–Ban Treaty (CTBT)(CTBTO 2019)
Surprisingly many atypical releases from power reactors, both with respect to isotopic ratios and released activities, have been detected through the years. It is important for the CTBT verification regime to gain as much knowledge as possible on the radioxenon signatures from nuclear power plants
Summary
The dominating release source for the radioactive xenon (radioxenon) routinely found in the atmosphere are medical isotope production facilities (IPFs) (Saey et al 2010), which are estimated to contribute to 95% of the global133Xe-activity of about 50 TBq released daily (Achim et al 2016). Surprisingly many atypical releases from power reactors, both with respect to isotopic ratios and released activities, have been detected through the years It is important for the CTBT verification regime to gain as much knowledge as possible on the radioxenon signatures from nuclear power plants. In this paper we present an analysis on an extensive set of measurements of radioxenon releases from a nuclear power plant Data consists both of stack measurements performed by the plant operator, as well as high-time resolution atmospheric measurements performed by The Swedish Defence Research Agency (FOI) in Stockholm, 110 km south of the plant, during the same time period. 2 the stack data set is reported, along with an analysis of activities and isotopic ratios compared to reported reactor operation and simulations.
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