Simultaneous measurement of tritium and radiocarbon by ultra-low-background proportional counting

Abstract

Use of ultra-low-background capabilities at Pacific Northwest National Laboratory provide enhanced sensitivity for measurement of low-activity sources of tritium and radiocarbon using proportional counters. Tritium levels are nearly back to pre-nuclear test backgrounds (~2-8 TU in rainwater), which can complicate their dual measurement with radiocarbon due to overlap in the beta decay spectra. We present results of single-isotope proportional counter measurements used to analyze a dual-isotope methane sample synthesized from ~120mg of H₂O and present sensitivity results.

Keywords: Dual-isotope measurements; Proportional counting; Radiocarbon; Tritium; Ultra-low-background.