Törnquist Per, Eriksson Mats, Olszewski Grzegorz, Carlsson Marie, López-Lora Mercedes, Pettersson Håkan B L
Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences, 581 83 Linköping, Sweden.
Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences, 581 83 Linköping, Sweden.
Mar Pollut Bull. 2023 Mar;188:114637. doi: 10.1016/j.marpolbul.2023.114637. Epub 2023 Feb 1.
Studsvik, a Swedish nuclear research facility, has been releasing aquatic radioactive discharges in the Baltic Sea, through the bay Tvären, since 1959. The permissible discharge levels are regulated by the Swedish Radiation Safety Authority (SSM) but only information about Co, Cs, Eu, total alpha and beta activities were reported up to 2002. Since then, the reports cover most a more comprehensive set of radionuclides. In this context, the seabed can be utilized as a chronological archive to investigate historical Studsvik releases. To this end, 23 sediment cores covering the whole area of the bay were studied and 5 of them were dated using Pb-dating methods. Since the discharges from Studsvik contain both plutonium and caesium, neither can be used to validate the Pb-dating method. Instead, stable lead with maximum deposition, known to be dated to 1970, was used. Cobalt-60, Cs, and Eu depth distributions were studied from the dated sediment cores and compared with reported levels of aquatic discharges. The expected sediment Cs-peak from the fallout from the Chornobyl accident was however smeared out, indicating an ongoing inflow of Cs with the Baltic seawater. Our findings show that reported releases of aquatic discharges of Co and Eu are consistent with measured sediment activity distribution. The sediments from the deepest parts of Tvären, with intact chronology and with a high time resolution, are ideal for investigating historical nuclear discharges and can be a tool to investigate unreported radionuclide releases. Dated sediment can in this way be a tool for nuclear safeguards to evaluate past and present activities in nuclear facilities.
自1959年以来，瑞典核研究机构Studsvik一直通过特瓦伦湾向波罗的海排放含放射性物质的废水。瑞典辐射安全管理局（SSM）对允许的排放水平进行监管，但直到2002年，仅报告了有关钴、铯、铕、总阿尔法和贝塔活度的信息。从那时起，报告涵盖了更全面的一组放射性核素。在这种情况下，海床可作为一个年代序列档案，用于调查Studsvik过去的排放情况。为此，研究了覆盖该湾整个区域的23个沉积物岩芯，其中5个采用铅测年法进行了年代测定。由于Studsvik的排放物中同时含有钚和铯，因此两者都不能用于验证铅测年法。取而代之的是，使用已知可追溯到1970年的具有最大沉积量的稳定铅。从测年的沉积物岩芯中研究了钴 - 60、铯和铕的深度分布，并与报告的废水排放水平进行了比较。然而，切尔诺贝利事故沉降物预期的沉积物铯峰值被抹平，这表明铯随着波罗的海海水持续流入。我们的研究结果表明，报告的钴和铕的废水排放量与测量的沉积物活度分布一致。特瓦伦湾最深处具有完整年代序列和高时间分辨率的沉积物，是调查历史核排放的理想选择，并且可以作为调查未报告的放射性核素排放的工具。通过这种方式，测年的沉积物可以成为核保障措施评估核设施过去和当前活动的工具。
