• Intercalibration of Environmental Isotope Measurements: The Program of the International Atomic Energy Agency

      Gonfiantini, Roberto; Rozanski, Kazimierz; Stichler, Willibald (Department of Geosciences, The University of Arizona, 1990-01-01)
      We briefly present here the environmental isotope intercalibration programs of the International Atomic Energy Agency (IAEA). In fact, the IAEA has implemented two parallel programs during the last 20 years: for stable isotopes of light elements and for a radioactive isotope of hydrogen, tritium. This IAEA activity resulted in the preparation of a number of reference and intercomparison materials of various types, now stored in the Agency and available upon request.
    • Radiocarbon Dating Reproducibility at the Museo de la Plata Radiocarbon Laboratory

      Figini, Anibal J.; Huarte, Roberto; Carbonari, Jorge (Department of Geosciences, The University of Arizona, 1990-01-01)
      We discuss here the variability, for our laboratory, in counting for radiocarbon dating of replicate measurements of background and secondary modern standard, duplicate measurements of samples provided by the International Collaborative Study, and replicate measurements of the dilution of the 14C-labeled benzene standard. The variability in the measurements of the International Collaborative Study samples suggest the existence of systematic bias.
    • Routine Checks in the Uppsala Conventional 14C Laboratory to Achieve Reliable Results

      Olsson, Ingrid U. (Department of Geosciences, The University of Arizona, 1990-01-01)
      I describe here a series of routine self-checks that the Uppsala 14C laboratory performs with all measurements. We estimate all uncertainties in the physical measurement of a sample. We study long-term stability, calculate mean values for oxalic acid and background and compare expected and real statistical distributions of uncertainties. To reduce the risk of bias, the samples from each series are almost exclusively run on the same counter. Some samples are, however, run on two or more counters to check the possible bias to achieve reliable activity comparisons with other laboratories. It is always possible to trace which counter is used, since different number series are used for different counters.
    • Sources of Random Error in the Debrecen Radiocarbon Laboratory

      Hertelendi, Ede (Department of Geosciences, The University of Arizona, 1990-01-01)
      A new high-pressure methane-filled counter system for 14C dating was installed in 1986 when the first stage of the International Collaborative Study (ICS) started. Random errors in the new measuring system and in the process of chemical pretreatment and preparation were checked during the three years of intercomparison. Results show that the most important source of error in our laboratory is gas contamination. This causes variation of the count rate to exceed the statistically expected variability. Other sources of error are also discussed and limits of their contributions are given.
    • Time-Resolved Liquid Scintillation Counting

      Kessler, Michael (Department of Geosciences, The University of Arizona, 1990-01-01)
      Historically, scientists who perform low-level measurements of 14C for age dating, and 3H2O for environmental contamination, have purchased or constructed highly specialized instruments to quantitate low-level radionuclides using a general-purpose liquid-scintillation analyzer (LSA). The LSA uses special time-resolved 3-D spectrum analysis (TR-LSC) to reduce background without substantially affecting sample counting efficiency. This technique, in combination with a special slow fluor scintillating plastic, further reduces the minimal detectable limit for the TR-LSC liquid scintillation counter.