ML23228A015
| ML23228A015 | |
| Person / Time | |
|---|---|
| Site: | PROJ0734 |
| Issue date: | 08/21/2023 |
| From: | George Alexander NRC/NMSS/DDUWP/RTAB |
| To: | Stephen Koenick NRC/NMSS/DDUWP/LLWPB |
| References | |
| Download: ML23228A015 (3) | |
Text
MEMORANDUM TO:
Steve S. Koenick, Chief Low-Level Waste and Projects Branch Division of Decommissioning, Uranium Recovery, and Waste Programs Office of Nuclear Material Safety and Safeguards THRU:
Chris A. McKenney, Chief Risk and Technical Analysis Branch Division of Decommissioning, Uranium Recovery, and Waste Programs Office of Nuclear Material Safety and Safeguards FROM:
George W. Alexander, Risk Analyst Risk and Technical Analysis Branch Division of Decommissioning, Uranium Recovery, and Waste Programs Office of Nuclear Material Safety and Safeguards
SUBJECT:
TELECONFERENCE
SUMMARY
- Z-AREA SALTSTONE DISPOSAL FACILITY GROUNDWATER MONITORING On March 17, 2023, the U.S. Nuclear Regulatory Commission (NRC) staff held a teleconference with staff from the South Carolina Department of Health and Environmental Control (SCDHEC) to discuss the U.S. Department of Energy (DOE) groundwater monitoring program for the Saltstone Disposal Facility (SDF) at the DOE Savannah River Site (SRS). The NRC staff held the call to support the staffs monitoring of the SDF in coordination with the State of South Carolina, as described in the NRC staffs plan for monitoring the SDF (accessible with the NRCs Agencywide Documents Access and Management System under Accession No. ML13100A113), as supplemented by the six NRC letters from June 5, 2017 to October 18, 2021 (ML17097A351, ML18033A071, ML18107A161, ML18219B035, ML19150A295, and ML21279A173).
The NRC and SCDHEC staffs discussed NRC staff observations about the DOE groundwater monitoring program and sump pump data from Saltstone Disposal Structure (SDS) 6. The groundwater monitoring program discussion addressed both monitoring well placement and trends in early indicator species (e.g., nitrate, specific conductance) in wells downgradient of the cylindrical disposal structures based on data from the DOE Z-Area SDF Groundwater Monitoring Report for 2022 (SRNS-TR-2022-00691 [ML23038A017]) and previous DOE annual groundwater monitoring reports.
CONTACT: George W. Alexander, NMSS 301-415-6755 August 21, 2023 Signed by McKenney, Christepher on 08/21/23 Signed by Alexander, George on 08/21/23
S. Koenick 2
The NRC staff observed that several wells downgradient of the cylindrical disposal structures have increasing trends in nitrate and specific conductance, based on a Mann-Kendall trend analysis, or exceed background values for those analytes. Although the nitrate and specific conductance do not present a hazard, the NRC staff expressed concern that the trends and analytes exceeding background could be indicators of the performance of the disposal structures because the salt waste sequestered in saltstone has high nitrate concentrations.
Additionally, the elevated specific conductance values could be related to leakage of water during disposal structure hydrotesting. Water pumped from SDS 6 sumps provided an additional indicator of disposal structure performance. The SCDHEC staff acknowledged the NRC staff concerns and indicated that groundwater contaminant concentrations in Z-Area were within SCDHEC regulatory limits.
The SCDHEC staff also indicated that the DOE released uncontaminated water from hydrotesting of the new disposal structures to the Z-Area sedimentation basin, and infiltrating water from the sedimentation basin could affect the nitrate and specific conductance in Z-Area groundwater. The NRC staff questioned the effect groundwater infiltrating into the sedimentation basin could have on the wells closer to the cylindrical disposal structures because the sedimentation basin is downgradient of the disposal structures.
The NRC staff then indicated that the availability of groundwater monitoring data to support disposal structure hydraulic performance was somewhat limited by issues related to monitoring well placement in Z-area that the NRC staff described in two Technical Review Reports (TRRs)
(ML18117A494; ML23017A084). In those TRRs, the NRC staff expressed concern that the DOE monitoring program for Z-Area at SRS does not include sufficient wells in the Upper Three Runs Aquifer (UTRA) Upper Aquifer Zone (UAZ) to detect lateral transport of contaminants along the tan clay confining zone (TCCZ), which separates the UTRA-UAZ from the UTRA lower aquifer zone (LAZ). Therefore, apparent trends in nitrate concentrations and specific conductance that the NRC staff discussed during the call were based on groundwater data obtained from monitoring wells below the TCCZ. No data were available to assess the quality of water that may have been present in the UTRA-UAZ closer to SDS 6 because the DOE groundwater monitoring wells are not screened in the UTRA-UAZ in that area. In addition, the NRC staff expressed concern that there are no background wells screened in the UTRA-LAZ.
The SCDHEC staff indicated that SCDHEC expected to issue its review of the DOE 2022 Annual Groundwater Monitoring Report for Z-Area within a few weeks. The SCDHEC staff subsequently provided that review on May 25, 2023 (ML23176A009).
Meeting Participants U.S. NRC SCDHEC George Alexander John Abernathy Hans Arlt Justin Koon Harry Felsher Sheila Watts Gianni Nelson A. Christianne Ridge cc: WIR ListServ
ML23228A015 OFFICE NMSS/DUWP/RTAB NMSS/DUWP
/LLWPB*
NMSS/DUWP/RTAB NMSS/DUWP/RTAB NAME GAlexander HFelsher CMcKenney GAlexander DATE Aug 17, 2023 Aug 21, 2023 Aug 21, 2023 Aug 21, 2023