Measurement of Helium-3/Helium-4 Ratios in Soil Gas at the 618-11 Burial Ground

Olsen, Khris B. ; Dresel, P Evan ; Evans, John C.

Pacific Northwest National Laboratory (U.S.)

关键词: Helium-3;    Helium-4;    Helium-3/Helium-4 Ratio, Tritium, Soil Gas, Groundwater;   

DOI  :  10.2172/965713
RP-ID  :  PNNL-13675
RP-ID  :  AC05-76RL01830
RP-ID  :  965713

美国|英语

来源: UNT Digital Library

【 摘 要 】

Seventy soil gas-sampling points were installed around the perimeter of the 618-11 Burial Ground, approximately 400 feet downgradient of well 699-13-3A, and in four transects downgradient of the burial ground to a maximum distance of 3,100 feet. Soil gas samples were collected and analyzed for helium-3/helium-4 ratios from these 70 points. Helium-3/helium-4 ratios determined from the soil gas sampling points showed significant enrichments, relative to ambient air helium-3 concentrations. The highest concentrations were located along the northern perimeter of the burial ground. Helium-3/helium-4 ratios (normalized to the abundances in ambient air) ranged from 1.0 to 62 around the burial ground. The helium-3/helium-4 ratios from the 4 transect downgradient of the burial ground ranged from 0.988 to 1.68. The helium-3/helium-4 ratios from around the burial ground suggest there is a vadose zone source of tritium along the north side of the burial ground. This vadose zone source is likely the source of tritium in the groundwater. The helium-3/helium-4 ratios also suggest the groundwater plume is traveling east-northeast from the burial ground and the highest groundwater tritium value may be to the north of well 699-13-3A. Finally, there appears to be no immediately upgradient sources of tritium impacting the burial ground since all the upgradient helium-3/helium-4 ratios are approximately 1.0.