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Title: Assessment of Tritium Activities in Bailed versus Pumped Samples from Wells at the Nevada National Security Site

Abstract

The Underground Test Area (UGTA) Activity uses a variety of methods to collect groundwater samples to identify radionuclide migration from underground nuclear tests. These include depth-discrete bailing, pumping with low-volume rod pumps, and pumping with electrical submersible pumps. The Nevada National Security Site (NNSS) Integrated Groundwater Sampling Plan specifies that when sampling with a pump, a minimum of three effective well volumes are withdrawn and then samples are collected after water-quality parameters have stabilized. In locations where pumping is not feasible, depth-discrete bailing is used and purging prior to sampling is usually not required. A recent study evaluated three sampling technologies and recommended that historical tritium results be evaluated where both pumped and bailed samples are available to identify preferred sampling protocols for the collection of tritium samples. The tritium ( 3H) activities were obtained from the UGTA chemistry data base. Wells were identified with known 3H activities above method detection limits, and then evaluated if both bailed and pumped samples had been collected. Twenty two wells and piezometers with bailed samples, pumped samples, and 3H activities above background were identified for further consideration. The conclusions from this analysis are: Bailed samples collected for 3H analysis near the water surfacemore » in a well are lower in 3H activity than bailed samples from within screened intervals and pumped samples. Depth-discrete bailed samples from within the screened intervals are generally in good agreement with pumped samples from developed wells and piezometers. Depth-discrete bailed samples from undeveloped wells and piezometers are in good agreement with the first pumped samples. However, the next pumped samples increased in 3H activity, resulting in a greater percent difference between the undeveloped bailed samples and later pumped samples. Continuous pumping over extended periods removing large purge volumes from wells can perturbate the surrounding groundwater system for long periods of time. These perturbations can cause large changes in 3H activities in the aquifer near the well because of the mixing of groundwater with variable 3H activities. Recommendations include: Bailed samples for 3H should not be collected near the water surface in the well. Bailed samples should be collected from within the well screen. Logs of temperature, chemistry, and thermal flow should be evaluated to identify optimal depths within the well screen to collect depth-discrete bailer samples. Purging of large volumes of water from the well over extended periods of time should be avoided when collecting 3H samples. Sufficient time should be allowed after pumping large volumes of water from the well (e.g., after well development) for the surrounding aquifer and 3H activities to return to ambient conditions« less

Authors:
 [1]
  1. Nevada System of Higher Education, Reno, NV (United States). Desert Research Institute (DRI)
Publication Date:
Research Org.:
Nevada Univ., Reno, NV (United States). Desert Research Institute; Nevada System of Higher Education, Reno, NV (United States). Desert Research Institute (DRI)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); USDOE Environmental Management Nevada Program, Las Vegas, NV (United States)
OSTI Identifier:
1483945
Report Number(s):
DOE/NV/0003590-28; 45285
DOE/NV/0003590-28; TRN: US1902683
DOE Contract Number:  
NA0003590; NA0000939
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Underground Test Are; UGTA; groundwater samples; radionuclide migration; depth-discrete bailing; pumping; low-volume rod pumps; electrical submersible pumps; NNSS; sampling; water quality parameters; purging; tritium; sampling protocols; piezometers; perturbate; aquifer; temperature; thermal flow; chemistry; optimal depths; ambient conditions

Citation Formats

Hershey, Ronald L. Assessment of Tritium Activities in Bailed versus Pumped Samples from Wells at the Nevada National Security Site. United States: N. p., 2018. Web. doi:10.2172/1483945.
Hershey, Ronald L. Assessment of Tritium Activities in Bailed versus Pumped Samples from Wells at the Nevada National Security Site. United States. doi:10.2172/1483945.
Hershey, Ronald L. Thu . "Assessment of Tritium Activities in Bailed versus Pumped Samples from Wells at the Nevada National Security Site". United States. doi:10.2172/1483945. https://www.osti.gov/servlets/purl/1483945.
@article{osti_1483945,
title = {Assessment of Tritium Activities in Bailed versus Pumped Samples from Wells at the Nevada National Security Site},
author = {Hershey, Ronald L.},
abstractNote = {The Underground Test Area (UGTA) Activity uses a variety of methods to collect groundwater samples to identify radionuclide migration from underground nuclear tests. These include depth-discrete bailing, pumping with low-volume rod pumps, and pumping with electrical submersible pumps. The Nevada National Security Site (NNSS) Integrated Groundwater Sampling Plan specifies that when sampling with a pump, a minimum of three effective well volumes are withdrawn and then samples are collected after water-quality parameters have stabilized. In locations where pumping is not feasible, depth-discrete bailing is used and purging prior to sampling is usually not required. A recent study evaluated three sampling technologies and recommended that historical tritium results be evaluated where both pumped and bailed samples are available to identify preferred sampling protocols for the collection of tritium samples. The tritium (3H) activities were obtained from the UGTA chemistry data base. Wells were identified with known 3H activities above method detection limits, and then evaluated if both bailed and pumped samples had been collected. Twenty two wells and piezometers with bailed samples, pumped samples, and 3H activities above background were identified for further consideration. The conclusions from this analysis are: Bailed samples collected for 3H analysis near the water surface in a well are lower in 3H activity than bailed samples from within screened intervals and pumped samples. Depth-discrete bailed samples from within the screened intervals are generally in good agreement with pumped samples from developed wells and piezometers. Depth-discrete bailed samples from undeveloped wells and piezometers are in good agreement with the first pumped samples. However, the next pumped samples increased in 3H activity, resulting in a greater percent difference between the undeveloped bailed samples and later pumped samples. Continuous pumping over extended periods removing large purge volumes from wells can perturbate the surrounding groundwater system for long periods of time. These perturbations can cause large changes in 3H activities in the aquifer near the well because of the mixing of groundwater with variable 3H activities. Recommendations include: Bailed samples for 3H should not be collected near the water surface in the well. Bailed samples should be collected from within the well screen. Logs of temperature, chemistry, and thermal flow should be evaluated to identify optimal depths within the well screen to collect depth-discrete bailer samples. Purging of large volumes of water from the well over extended periods of time should be avoided when collecting 3H samples. Sufficient time should be allowed after pumping large volumes of water from the well (e.g., after well development) for the surrounding aquifer and 3H activities to return to ambient conditions},
doi = {10.2172/1483945},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {11}
}