The TRACER Center at Argonne National Laboratory: Advancements in Radiokrypton Dating

The new Trace Radioisotope Analysis Center (TRACER) at Argonne National Laboratory is now offering state-of-the-art radiokrypton dating to the earth science community at-large. Due to its simple production and transport in the terrestrial environment, ⁸¹Kr (half-life = 230,000 yr) is an ideal tracer for old water and ice with mean residence times in the range of 10⁵-10⁶ years. Likewise, the anthropogenic isotope ⁸⁵Kr (half-life = 10.8 yr) is a valuable tracer of young groundwater. In recent years, Atom Trap Trace Analysis (ATTA) of both isotopes has made radiokrypton dating available thanks to significant advances in the ATTA technique developed at Argonne National Laboratory (ANL). ATTA is a laser-based atom counting method that is both efficient and isotopically selective. The TRACER Center at ANL features a new high-throughput ATTA instrument that can measure up to 250 ⁸¹Kr or 1500 ⁸⁵Kr samples per year, a second ATTA instrument dedicated to research and development, and a dedicated gas purification system for separating krypton from the degassed samples. Both ATTA instruments can currently handle samples as small as 1μL of Kr gas (STP), which can be extracted from 10 L of water or 5 kg of ice. At TRACER, we also continue to investigate parameters crucial to new and existing applications of radiokrypton dating. In this light, we will report on progress toward measuring the absolute abundance of ⁸¹Kr in the atmosphere, as well as determining natural sources of ⁸¹Kr subsurface production. This work is supported by the U.S. Department of Energy, Office of Science, under Contract No. DEAC02-06CH11357.