ML21026A012
| ML21026A012 | |
| Person / Time | |
|---|---|
| Site: | PROJ0734 |
| Issue date: | 01/27/2021 |
| From: | Cynthia Barr Division of Decommissioning, Uranium Recovery and Waste Programs |
| To: | |
| Barr C | |
| Shared Package | |
| ML21026A013 | List: |
| References | |
| Download: ML21026A012 (11) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 January 26, 2021 NOTE TO: File PROJ0734 FROM: Cynthia Barr, Sr. Risk Analyst Risk and Technical Analysis Branch Division of Decommissioning, Uranium Recovery, And Waste Programs Signed by Barr, Cynthia Office of Nuclear Material Safety and Safeguards on 01/26/21
SUBJECT:
SUMMARY
OF DECEMBER 9, 2020, WEBINAR CALL RELATED TO EXPERIMENTS CONDUCTED BY THE SAVANNAH RIVER ECOLOGY LABORATORY AND THE CENTER FOR NUCLEAR WASTE REGULATORY ANALYSES TO SUPPORT TANK FARM CLOSURE AT THE SAVANNAH RIVER SITE On December 9, 2020, the U.S. Nuclear Regulatory Commission (NRC) and U.S. Department of Energy (DOE) held a webinar on research related to the closure of high-level waste tanks at the Savannah River Site (SRS) in Aiken, SC. The webinar included NRC contractors from the Center for Nuclear Waste Regulatory Analyses (CNWRA) and DOE contractors from Savannah River Remediation (SRR) and Savannah River Ecology Laboratory (SREL). The purpose of the webinar was for NRC and DOE contractors to discuss experimental details related to ongoing research conducted by the CNWRA and SREL related to aqueous and solid phase characterization of tank grout and in particular the ability of reducing tank grout to condition infiltrating groundwater to maintain low solubility of key radionuclides in the tank waste. Additional details regarding the webinar are provided below.
Docket No.: PROJ0734
Enclosure:
Meeting Summary CONTACT: Cynthia Barr, NMSS/DUWP (301) 415-4015
SUBJECT:
SUMMARY
OF DECEMBER 9, 2020, WEBINAR CALL RELATED TO EXPERIMENTS CONDUCTED BY THE SAVANNAH RIVER ECOLOGY LABORATORY AND THE CENTER FOR NUCLEAR WASTE REGULATORY ANALYSES TO SUPPORT TANK FARM CLOSURE AT THE SAVANNAH RIVER SITE Distribution:
GAlexander DPickett (CNWRA)
LParks CDinwidddie (SwRI)
SDembek GWalter (CNWRA)
MHeath SKoenick ADAMS Accession No.: ML17352A059 OFFICE NMSS NMSS:BC NAME C. Barrr C. McKenney DATE 1/25/21 01/26/21
Meeting Summary Meeting Background Prior to the webinar, the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE) exchanged the following draft technical reports related to the experiments conducted by the Center for Nuclear Waste Regulatory Analyses (CNWRA) and Savannah River Ecology Laboratory (SREL).
- 1. SREL Doc.: R-21-0001, Aqueous and Solid Phase Characterization of Potential Tank Fill Materials, ML20303A339, Savanah River Ecology Laboratory, Aiken, SC, August 2020.
- 2. SRR-CWDA-2020-00061 Application of Characterization of the Aqueous and Solid Phase Chemistry of Closure Grouts, Savannah River Remediation, Aiken, SC, August 25, 2020.
- 3. Walter. G.R., C.L. Dinwidddie, Tank Grout Water-Conditioning TestsFiscal Year 2019 Status Report, ML20126G298, Center for Nuclear Waste Regulatory Analyses, San Antonio, Texas, April 2020.
Additionally, DOE provided two presentations
- 1. SRR-CWDA-2020-00085, Rev. 1, Tank Grout Bulk Chemistry Experiments, Savannah River Remediation, Aiken, SC, December 9, 2020.
- 2. SRR-CWDA-2020-00088, Long Term Radiological Lysimeter Program, Savannah River Remediation, Aiken, SC, December 9, 2020.
CNWRA also provided a presentation, which is attached to this meeting summary.
List of
Participants:
NRC Steve Dembek Cynthia Barr George Alexander Mark Fuhrman CNWRA/SwRI David Pickett Cynthia Dinwiddie Gary Walter DOE-SR Chuck Comeau
SREL John Seaman Christina Logan SRR Larry Romanowski Steve Thomas Kent Rosenberger Mark Layton Greg Flach Jerry Mangold Tim Coffield Bre Cantrell Larry Romanowski (SRR) opened the meeting. A roll call and brief introductions were conducted. Cynthia Barr (NRC) provided the welcome and discussed the purpose of the meeting, which was to share information on similar research performed by CNWRA and SREL.
Research was related to conditioning of infiltrating groundwater by reducing tank grout. Free flowing discussion and questions were encouraged so that the research staffs could learn from each other and help inform future experiments in this area.
Discussions on SRS Grout Experiments Cynthia Barr provided a summary of tank grout experiments conducted by CNWRA over the last several years including an intermediate-scale grout monolith experiment conducted to study flow through the system, as well as experiments to study the ability of SRS tank grout to condition infiltrating groundwater to favorable chemical conditions necessary to maintain low solubility of key radionuclides in the tank waste. The intermediate-scale (20 ft diameter) tank grout monolith test showed that water could flow through shrinkage gaps between the grout and tank wall, around in-tank components, and even between grout lifts. With regard to the groundwater conditioning experiments, column or flow through experiments were initially conducted to study the ability of the tank grout to condition the groundwater to high pH and low Eh. However, it was difficult to keep oxygen out of the system and achieve the low Eh conditions assumed in the performance assessments (PA) in these tests. Next, batch experiments were performed using tank grout of different particle sizes (i.e., both cubed and crushed grout). Additionally, individual cementitious grout components and simple mixtures of cementitious grout components were also tested in batch experiments to see if lower Eh conditions could be achieved.
Cynthia Dinwiddie and Gary Walter of the CNWRA discussed the tank grout water conditioning test results in more detail including grout formulations, experimental setup, and a summary of the test results. CNWRAs presentation slides are provided in an attachment to this meeting summary. The lowest Eh observed for tank grout was significantly higher (300 mV) using grade 120 slag and a pulverized grout sample. In general, the tank grout experiments showed Eh values significantly higher than assumed in the PA (i.e., around 470 mV in the PAs).
Gregory Flach (SRR) presented results of SREL research that showed that the Eh endpoints 2
assumed in PA modeling were not achieved (high and low Eh values). The impact of Eh on solubility of key radionuclides and thoughts on future work were also discussed. Gregory Flach mentioned that updated geochemical modeling would be pursued to better understand radionuclide solubility.
Finally, Jerry Mangold (SRR) provided an update on lysimeter testing. Jerry Mangold provided information about lysimeter tests including those with Pu and Ra. Estimated Kds for Pu were significantly higher than previously assumed values. These values will be recommended to Dan Kaplan for the next update to the geochemical data package used to support the tank farm PAs.
SRR indicated that lysimeter reports were transmitted to NRC via the Box site at the end of October 2020.
Detailed Technical Discussions Discussion topics during the presentations included the following:
CNWRA inquired about tap water SREL used to mix the grout for the experiments (CNWRA used water from Strom and Kaback). Municipal water was used to mix grout at the Argos batch plant, which was later found out to be groundwater1. Because SRS groundwater has low dissolved solids content, SREL determined that tap water should be okay. John Seaman indicated that the real difference is how groundwater was modeled versus what was actually being used as mix water (the groundwater should be equilibrated with kaolinite).
CNWRA inquired about the contents of SRR-CWDA-2019-00038 (Table 2) cited in the SREL report, which was not available for review. DOE explained that it was just a 2-page document cited by SREL by which DOE provided paste and water formulations to SREL for testing.
CNWRA discussed differences in how environmental conditions were controlled in the tests. CNWRA initially sparged reaction vessels with N2/CO2 gas to remove dissolved oxygen. This is in contrast to SREL using hydrogen gas or a Coy Chamber to control oxygen.
CNWRA discussed potential problems with degradation of septa used to seal water sampling ports in each reaction vessel. Septa were occasionally replaced, but the impact on oxygen ingress was unclear.
CNWRA recorded ORP, pH, and DO measurements at 2- to 5-minute intervals with automated data recorders, and also recorded these parameters by hand in a scientific notebook at least once per business day.
NRC inquired about the results of the SREL testing, including increases in Eh over time that suggested potential oxidation as the experiments continued. CNWRA inquired about dilution due to loss of water and inclusion of makeup water. SREL indicated that this would be similar to what is expected in the field.
NRC inquired about sulfide content and use of XANES or other methods to determine sulfide content. John Seaman indicated that they only looked at total sulfur in XRF and 1
Following the webinar, CNWRA confirmed that municipal water in Jackson, SC is sourced by groundwater. CNWRA also confirmed that the batch plant had changed ownership from Argos to Smyrna Ready Mix.
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did not look at speciation.
XRD analysis results were similar between CNWRA and SREL. NRC noted amorphous hump in Grade 120 slag (80 percent was in an amorphous phase).
CNWRA confirmed that Grades 100 or 120 slag from any manufacturer may be used to mix SRS tank grout, because the specification for tank grout is not highly prescriptive.
CNWRA also inquired about SRELs use of Ottawa sand rather than the sand from DOEs vendor.
Sand was not used in the grout formulation for SREL experiments because the quartz peak associated with sand would overwhelm XRF results (quartz peak interference),
although sand was added to the columns in the experiments to homogenize flow.
NRC inquired if there were any pressure anomalies that would suggest channeling or blockage. There was also discussion of residence time and its impact on grout water conditioning. SRELs 5 mL/day flow rate was discussed and characterized as very low (and potentially leading to longer residence times for reaction compared to higher flow rates).
CNWRA inquired if DOEs remaining compressive-strength grout cylinders could be used for grout water-conditioning testing. DOE indicated that these were not available.
NRC indicated that it would be important to update geochemical modeling for solubility, as well as for Eh evolution, because even if the Eh were known, the solubility-limiting phases in the pH/ Eh diagrams from PA modeling may not be correct based on high-level waste leaching experiments. For example, solubility of key radionuclides such as Pu, Tc, and U were orders of magnitude higher than assumed in PA modeling. DOE agreed it planned to update the geochemical modeling, including an update of minerology and potentially using a new thermodynamic database. DOE invited NRC to provide recommendations for additional research and updated PA modeling.
With regard to SRRs calculations of Kd for Pu, NRC inquired if SRR thought about calculating the Kd based on the retardation factor and how far Pu had traveled. Earlier research showed that a small fraction of Pu could travel much further and a Kd of 3 L/kg would be appropriate for this fraction.
SRR indicated that a routine environmental monitoring report (Eastern and Western Groundwater Operable Unit scoping) was completed. The report was provided to NRC for review following the webinar.
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Attachment CNWRA Presentation Slides
A-2 A-3 A-4 A-5