ML18187A373
| ML18187A373 | |
| Person / Time | |
|---|---|
| Site: | PROJ0734 |
| Issue date: | 07/10/2018 |
| From: | Ridge A Division of Decommissioning, Uranium Recovery and Waste Programs |
| To: | |
| C RIDGE NMSS DUWP | |
| References | |
| Download: ML18187A373 (29) | |
Text
Summary of NRC Staff Recommendations to Modify 2013 NRC Saltstone Disposal Facility Monitoring Plan Based on NRC Staff Technical Review Reports July 10, 2018 Saltstone Disposal Facility Onsite Observation Visit Division of Decommissioning, Uranium Recovery and Waste Programs U.S. Nuclear Regulatory Commission
Framework for Modifying Monitoring Plan
- NRC staff may recommend modifications to monitoring plan in technical review report (TRR)
- See NRC staff recommendations to modify 2013 NRC Saltstone Disposal Facility (SDF) Monitoring Plan on Slides #6 though #28
- If NRC implements all those recommendations, then see Slide #29 for the Status and Prioritization of SDF Monitoring Factors
- NRC may send letter to U.S. Department of Energy (DOE) that supplements monitoring plan
- NRC letters to DOE supplementing 2013 SDF Monitoring Plan
- June 5, 2017 - ML17097A351: Closed Monitoring Factors (MF) 3.01, MF 3.02, and MF 3.04 under both 10 CFR 61.41 and 10 CFR 61.42 performance objectives
- March 1, 2018 - ML18033A071: Clarified Number of Monitoring Factors in DOE Savannah River Site Monitoring Plans
- June 29, 2018 - ML18107A161: Increased Priority of MF 2.01 to Medium and Added New MF 10.14 (Medium Priority)
- Future NRC letter(s) to DOE expected based on other NRC staff TRRs 2
Technical Review Reports Related to the Saltstone Disposal Facility (1 of 3)
Title Date Accession No.
Solubility of Technetium Dioxides in Reducing Cementitious Material Leachates, a Thermodynamic 11/7/2013 ML13304B159 Calculation Oxidation of Reducing Cementitious Waste Forms 6/4/2015 ML15098A031 Quality Assurance Documentation for the 8/1/2016 ML16196A179 Cementitious Barriers Partnership Toolbox Dose Calculation Methodology for Liquid Waste 12/23/2016 ML16277A060 Performance Assessments at the Savannah River Site Iodine Sorption Coefficients for Use in Performance 1/5/2017 ML16342C575 Assessments for the Saltstone Disposal Facility Saltstone Waste Form Hydraulic Performance 3/23/2017 ML17018A137 3
Technical Review Reports Related to the Saltstone Disposal Facility (2 of 3)
Title Date Accession No.
Performance of the High Density Polyethylene, High Density Polyethylene/Geosynthetic Clay Liner, and the 4/12/2017 ML17081A187 Lower Lateral Drainage Layer Hydraulic Performance and Erosion Control of the Planned Saltstone Disposal Facility Closure Cap and 1/31/2018 ML18002A545 Adjacent Area Groundwater Monitoring at and Near the Planned 5/17/2018 ML18117A494 Saltstone Disposal Facility Update on Projected Technetium Release from Saltstone 5/22/2018 ML18095A122 Summary Of Activities Related to the Review of the U.S.
Department of Energy Savannah River Site Fiscal Year 6/29/2018 ML18158A172 2013 and Fiscal Year 2014 Special Analysis Documents for the Saltstone Disposal Facility 4
Technical Review Reports Related to the Saltstone Disposal Facility (3 of 3)
Title Date Accession No.
Selenium Sorption TBD TBD Saltstone Degradation TBD TBD Disposal Structure Concrete Degradation TBD TBD Revised General Separations Area (GSA) (Groundwater)
TBD TBD Model Subsurface Flow and Transport TBD TBD 5
MF 2.01: Hydraulic Performance of Closure Cap
- Change: increase priority from low to medium
- Recent DOE Tc-99 and I-129 research results indicate greater risk-significance than previously assumed
- More information needed to support assumptions related to
- Hydrologic Evaluation of Landfill Performance (HELP) code
- Hydraulic conductivity of the High Density Polyethylene/Geosynthetic Clay Liner composite layer
- As built cover properties
- Infiltration calculations associated with recent larger disposal structures 6
MF 2.02: Erosion Control of the SDF Engineered Surface Cover and Adjacent Area
- No change to priority (low) or status
- Change title and description to clarify that areas adjacent to the future SDF closure cap are covered under the NRC monitoring activities at the SDF because of risk-significance of controlling erosion in those areas
- More information is needed to address previous concerns from the NRC 2012 SDF TER, support assumptions related to the closure cap and silting-in of cover layers, and calculations associated with the soil loss equation 7
MF 3.01: Hydraulic Conductivity of Field-Emplaced Saltstone
- Change: close under both 10 CFR 61.41 and §61.42
- Research is adequate to support the assumed initial hydraulic conductivity of field-emplaced saltstone
- Testing on cores of field-emplaced saltstone from Saltstone Disposal Structure (SDS) 2A supports DOE assumptions about the initial hydraulic conductivity of saltstone
- Additional laboratory studies and analyses provided explanations for previously-observed results that did not support modeling assumptions 8
MF 3.02: Variability of Field-Emplaced Saltstone
- Change: close under both §61.41 and §61.42
- Properties of saltstone core samples provided significant insight into variability in field-emplaced saltstone
- The production, placement, and curing conditions that could cause significant variability in saltstone performance are well-controlled by the DOE
- The DOE process to evaluate variability due to potential future changes is an adequate basis for the DOE to use to assess and control saltstone variability 9
MF 3.03: Applicability of Laboratory Data to Field-Emplaced Saltstone
- No change to priority (high) or status
- Narrow scope to understanding differences between the short-term changes in hydraulic conductivity in laboratory-prepared and field-emplaced saltstone
- Results of physical and hydraulic properties of core samples provide support for use of laboratory data in representing the initial properties of field-emplaced saltstone
- Differences in the evolution of observed leaching behavior between laboratory-prepared and field-emplaced samples may be due to differences in the evolution of hydraulic properties 10
MF 3.04: Effect of Curing Temperature on Saltstone Hydraulic Properties
- Change: close under both §61.41 and §61.42
- Measurements of cores from SDS 2A demonstrated that the effects of curing conditions were adequately accounted for in the assumed initial hydraulic conductivity and effective diffusivity values
- Additional laboratory studies and analyses provided explanations for previously-observed results that did not support modeling assumptions 11
MF 5.01: Radionuclide Release from Field-Emplaced Saltstone
- No change to priority (high) or status
- Tc solubility limits the DOE used to model Tc release from chemically reduced saltstone in the 2014 Evaluation Case are not supported by recent data from dynamic leaching of cores of field-emplaced saltstone
- Projected SDF performance is sensitive to Tc solubility in reduced saltstone
- Models of SDF performance should account for data from SDS 2A cores, including a technical justification for the projected duration of young cementitious material conditions 12
MF 5.02: Chemical Reduction of Tc by Saltstone
- Change: reduce priority from high to medium
- NRC staff reinterpretation of three studies that led to concern
- Observed insensitivity of Tc release to leachate dissolved oxygen
- Greater-than-assumed Tc concentration in releases from cores of field-emplaced saltstone expected to be reducing
- Results of DOE sensitivity analyses
- More information needed to support assumptions about re-reduction and projected duration of reducing conditions 13
MF 5.03: Reducing Capacity of Saltstone
- Change: reduce priority from medium to low
- Greater than expected Tc releases from reduced saltstone reduce gap between releases from oxidized and reduced saltstone
- NRC review of sensitivity analyses that the DOE provided in response to Questions SP-2 and SP-8 of the NRC Request for Additional Information on the FY14 Special Analysis Document confirmed low risk-significance of reducing capacity of saltstone
- More information needed to address sulfur dissolution and the applicability of the Ce (i.e., Angus-Glasser) method 14
MF 5.04: Certain Risk-Significant Kd Values for Saltstone MF 10.04: Kd Values for Saltstone
- Change: Move monitoring of sorption of iodine on saltstone from MF 10.04 to MF 5.04
- Kd value of iodine for saltstone appears to be risk-significant based on recent data and analyses
- Preliminary leaching data from saltstone cores indicate that iodine is not significantly retained by field-emplaced saltstone
- Kd values assumed for iodine for saltstone in the FY14 Special Analysis Document appear to be higher than is justified based on available data
- More information is needed to support assumed iodine Kd values for saltstone. Alternatively, an analysis with more justified Kd values for iodine in saltstone could be provided.
15
MF 5.05: Potential for Short-Term Rinse-Release from Saltstone
- Change: close under both §61.41 and §61.42
- NRC staff reinterpretation of two studies that led to concern
- Surficial phenomena: Scaling of data from a study of intact laboratory samples led to projected peak fractional releases less than 1 mrem/yr
- Volumetric phenomena: Release from core samples consistent with solubility of TcO2*1.6 H2O or TcO2*2 H2O.
Additional release mechanisms (e.g., first flush or release from persistent oxidized fraction) not needed to represent initial Tc release
- The importance of chemical conditions to Tc release will be monitored under MF 5.01 16
MF 6.01: Certain Risk-Significant Kd Values in Disposal Structure Concrete MF 10.06: Kd Values for Disposal Structure Concrete
- Change: Move monitoring of sorption of iodine on disposal structure concrete from MF 10.06 to MF 6.01
- Kd values assumed for iodine for disposal structure concrete in the FY14 Special Analysis Document may be higher than is justified based on available data
- Recent research results indicate less sorption of iodine in saltstone than represented in the 2014 Evaluation Case, increasing its risk-significance
- More information is needed to support assumptions about sorption of iodine on disposal structure concrete. Alternatively, an analysis with more justified Kd values for iodine for disposal structure concrete could be provided.
17
MF 6.02: Tc Sorption in Disposal Structure Concrete
- Change: close under both §61.41 and §61.42
- Major changes in DOE model of Tc migration through disposal structure concrete resolved NRC staff concern
- Discontinued average-Kd approach
- Included fast pathways through disposal structure concrete in Evaluation Case
- DOE sensitivity analyses show assumed oxidation state of disposal structure concrete had little impact on magnitude or timing of projected peak dose 18
MF 6.03: Performance of Disposal Structure Roofs and HDPE/GCL Layers
- No Change to priority (medium) or status
- NRC staff recognizes the importance of the Lower Lateral Drainage Layer (LLDL), the HDPE geomembrane also in combination with a GCL
- Contrast between the high hydraulic conductivity of the LLDL and the low hydraulic conductivity of the HDPE/GCL composite layer has a significant impact on projected performance
- Clarification on potential revisions to DOEs conceptual model of bottom-up deposition of clay particles in the LLDL is needed
- Clarification of potential revisions to DOEs technical basis for HDPE performance due to the potential breach of the SDS 3A HDPE is needed
- Additional support is needed for assumptions relating to the initial parameters used to develop the sampling set of flow cases 19
MF 7.01: Certain Risk-Significant Kd Values in Site Sand and Clay MF 10.09: Kd Values for SRS Soil
- Change: Move monitoring of sorption of iodine in SRS subsurface soil from MF 10.09 to MF 7.01, including the sorption on both leachate impacted and non-leachate impacted soils
- Kd values for subsurface soil not adequately supported
- Basis for the leachate impact factors was not provided
- Recent research results indicate less sorption of iodine in saltstone than represented in the 2014 Evaluation Case, increasing its risk-significance
- More information is needed to support assumptions about subsurface Kd values for iodine, particularly the leachate-impacted Kd values. Alternatively, an analysis with more justified Kd values for iodine in subsurface soils could be provided.
20
MF 8.02: Groundwater Monitoring
- No Change made to priority (periodic) or status
- MF 8.02 is a periodic monitoring factor where the groundwater data will be monitored in perpetuity at the SDF
- No changes have been made to MF 8.02; however, this monitoring factor is directly associated with the new MF 8.03 21
MF 8.03: Identification and Monitoring of Groundwater Plumes in the Z Area
- Change: add new MF 8.03 as a high-priority factor under
§61.41 and §61.42
- Periodic nature of MF 8.02 does not address newly identified NRC staff concerns, which will be monitored under MF 8.03
- Monitoring wells should detect saltstone disposal structure leaks or any unintentional release to the subsurface relatively early
- Monitoring wells should be able to delineate the plume within the Z-Area
- Background concentration values from the Upper Three Runs AquiferLower Aquifer Zone (UTRA-LAZ) are needed
- Recommend simulating past and current SDS 4 plume concentrations in the Z-Area to obtain site-specific parameter values 22
MF 10.02: Defensibility of Conceptual Models (1 of 3)
- No Change to priority (high) or status
- Addresses the uncertainty of conceptual models and analysis of potential alternative conceptual models under the assumption that present natural and environmental processes will remain unchanged over time
- MF 10.02 is cross-cutting and certain aspects of the MF are discussed in three TRRs:
- Tc release update (ML18095A122)
- Groundwater monitoring (ML18117A494)
- HDPE and Lower Lateral Drainage Layer Performance (ML17081A187) 23
MF 10.02: Defensibility of Conceptual Models (2 of 3)
- Tc release:
- Shift from prioritizing potential exposure to trace quantities of oxygen to focusing on releases from reduced saltstone
- Far-field flow:
- Lengthy flow and transport along the surface of the TCCZ as an alternative conceptual model 24
MF 10.02: Defensibility of Conceptual Models (3 of 3)
- Near field:
- Unlike the PORFLOW model from the DOE 2009 SDF Performance Assessment, the DOE SDF FY 2014 Special Analysis Document represents a conceptual model involving sudden and complete failure of the HDPE layer and HDPE/GCL composite layer performance as evaluation case
- NRC recommends that the evaluation case and the DOE expected or best estimate case both be carried forward; the latter as a possible sensitivity case
- DOE provided NRC the document Conceptual Model Development for the Saltstone Disposal Facility Performance Assessment in May 2018 25
MF 10.05: Moisture Characteristic Curves (MCCs)
- No Change to priority (low) or status
- Evaluation Case in the FY 2013 and FY 2014 Special Analysis Documents relied on MCCs
- Effect of the MCCs was limited in these cases due to the high assumed saturation of saltstone
- Accordingly, the support was determined to be sufficient
- MCCs could become more risk-significant if future modeling projects lower saturation levels 26
MF 10.08: Consumption Factors and Uncertainty Distributions for Transfer Factors
- Change: Expand MF 10.08
- Include items documented in Technical Review of the Dose Calculation Methodology for Liquid Waste Performance Assessments at the Savannah River Site (ML16277A060)
- Items identified by the NRC that should be addressed in future SRS Performance Assessment model revisions include:
- Human receptor definition
- Certain behavioral parameters (e.g., consumption rates of water and certain foods, breathing rate, fractions of foods produced locally, exposure and inhalation parameters, and crop and gardening parameters)
- Transparency and traceability of assumed parameter values 27
MF 10.14: Scenario Development and Defensibility
- Change: add new MF 10.14 as a medium-priority factor under §61.41 and §61.42
- MF added to distinguish more clearly between conceptual model uncertainty (MF 10.02) and future scenario uncertainty (MF 10.14)
- More information is needed about the potential importance of future plausible alternative scenarios to dose projections
- More information is needed about the development and defensibility of the central scenario 28
Expected Future Status and Prioritization of MA 1 MA 2 MA 3 SDF Monitoring Factors MA 4 MA 5 MA 6 MA 7 Subsurface MA 8 Environmental MA 9 Site Stability MA 10 Performance MA 11 Radiation Inventory Infiltration Waste Form Waste Form Waste Form Disposal Transport Monitoring Assessment Model Protection and Erosion Hydraulic Physical Chemical Structure Revisions Program Control Performance Degradation Degradation Performance - 7.01 - - 8.01 - - 9.01 - - 10.01 - - 11.01 -
- 1.01 - - 2.01 - - 3.01 - - 4.01 - - 5.01 - - 6.01 - Certain Risk- Leak Detection § Settlement Due Implementation of Conceptual Dose to Significant Kd to Increased Models +/- Individuals Inventory in Hydraulic Hydraulic Waste Form Radionuclide Certain Risk-Values in Site Overburden During Disposal Performance of Conductivity of Matrix Release from Significant Kd Sand and Clay Operations Structures § Closure Cap Field-Emplaced Degradation +/- Field-Emplaced Values in - 8.02 - - 9.02 - - 10.02 - - 11.02 -
Saltstone +/- Saltstone +/- Disposal Groundwater Settlement Due Defensibility of Conceptual Air Monitorin Monitoring § to Dissolution of Models +/-
Structure Calcareous - 10.03 -
Concrete Sediment Diffusivity in Degraded
- 1.02 - - 2.02 - - 3.02 - - 4.02 - - 5.02 - - 6.02 - Saltstone Methods Used Erosion Control Variability of Waste Form Chemical Tc Sorption in - 8.03 - - 10.04 -
of the SDF Identification and Kd Values for Saltstone to Assess Field-Emplaced Macroscopic Reduction of Tc Disposal Monitoring of Inventory Engineered Saltstone +/- Fracturing +/- by Saltstone +/- Structure Groundwater - 10.05 -
Surface Cover Concrete +/- Plumes in the Z Moisture Characteristic and Adjacent Area +/- Curves
- 10.06 -
Area.
Kd Values for Disposal
- 3.03 - - 5.03 - - 6.03 - Structure Concrete Applicability of Reducing Performance of - 10.07 -
Laboratory Data Capacity of Disposal Calculation of Build-Up in Biosphere Soil to Saltstone Structure Roofs
- 10.08 -
Field-Emplaced and HDPE/GCL Consumption Factors and Saltstone +/- Layers Uncertainty Distributions for
- 3.04 - - 5.04 - - 6.04 - Transfer Factors Effect of Curing Certain Risk- Disposal - 10.09 -
Kd Values for SRS Soil Temperature on Significant Kd Structure
- 10.10 -
Saltstone Values for Concrete Far-Field Model Calibration Hydraulic Saltstone Fracturing - 10.11 -
Properties +/- Far-Field Model Source Loading Approach
- 5.05 - - 6.05 -
- 10.12 -
Potential for Integrity of Far-Field Model Dispersion Short-Term Non- - 10.13 -
Rinse-Release cementitious Impact of Calcareous Zones from Saltstone Materials on Contaminant Flow and Transport
§ Periodic Monitoring Factors (i.e., MFs related to data that NRC staff expects to review on a periodic basis)
- 10.14 -
Low Priority Scenario Development and Medium Priority Defensibility
+/- High Priority
§ Periodic Monitoring Factors (i.e., MFs related to data that NRC staff expects to review on a periodic basis)
Closed Low Priority 29