Natural attentuation of tritium in vadose zone moisture and ground water at a Lawrence Livermore site in Northern California, USA
Tritium used in explosives experiments and buried in unlined landfills at a remote Lawrence Livermore National Laboratory (LLNL) site has resulted in three ground water tritium plumes. Using an innovative approach, we determined that despite ground water tritium activities of up to 1.5 million picoCuries per liter (pCi/L) in some locations, natural attenuation processes are significantly limiting the migration of tritium to environmental receptors. We used soil vapor and moisture tritium activity measurements to calculate the source inventory of tritium in the vadose zone. We determined the 12 year annual inventory of tritium in ground water, using objective tritium activity contours and the highly variable saturated thickness of the aquifer. Our analysis indicates that despite seasonal slug releases of tritium, the two plumes emanating from two landfills are stable, with the 1,000 and 20,000 pCi/L contours essentially fixed in space. The third plume emanates continuously from an explosives testing platform; the 1,000 pCi/L contour is translating slightly, but the 20,000 pCi/L contour is retreating upgradient towards the source. Additionally, the long-term trend in total tritium activity for each plume is decreasing. Three processes account for the attenuation of tritium observed: 1) radioactive decay, 2) hydrodynamic dispersion, and 3) dwindling tritium sources. In preparation for the possibility that remediation may be required anyway, we have evaluated innovative remediation technologies for tritium at this site.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Defense Programs (DP)
- DOE Contract Number:
- W-7405-Eng-48
- OSTI ID:
- 8839
- Report Number(s):
- UCRL-JC-133579; EW04F6030; ON: DE00008839
- Resource Relation:
- Conference: Scientific Advisory Committee Global Interest Issues Seminar, Large Scale Area Remediation, Snezhinsk, Russia, June 21-25, 1999
- Country of Publication:
- United States
- Language:
- English
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