PORFLOW Implementation of Special Waste from Models for Slit and Engineered Trenches in the E-Area Low Level Waste Facility Performance Assessment

et al. 2023

SWM commissioned this SA to determine the effects of placing operational stormwater runoff covers over ST DUs ST01 through ST07 at about years 5, 10, and 15 of the 30-year operational period. Covering changed the movement of contaminants to the water table and the hypothetical well. Early movements typically decreased because the cover decreased the flow of water from the surface through the contaminants. Later movements typically increased because less of the inventory had been released than for the uncovered cases analyzed in the PA. These effects on contaminant movement translated into higher SA-calculated limits relative to PA limits in the early years and some lower SA-calculated limits relative to PA limits in the later years. Because the lower of the two sets of limits was always selected as the operational limit, the net effect was to lower limits in the later years (typically 100 years and later). Earlier covers at 5 years magnified the changes.

“…In the aquifer model, SWFs in trenches with known disposal locations are placed only at aquifer source nodes corresponding to the disposal location in the DU footprint (Danielson, 2021).…”

Section: E13mentioning

confidence: 99%

“…In the aquifer model, SWFs in trenches with no known disposal location (or future disposals) are distributed uniformly across the aquifer source nodes (Danielson, 2021).…”

Section: E13mentioning

confidence: 99%

Performance Assessment for the E-Area Low-Level Radioactive Waste Disposal Facility at the Savannah River Site: Appendix A

et al. 2023

“…The conceptual model assumption was that after 750 years, water will enter the disposal casks via small holes due to corrosion in the welds. This estimate was based on communication from the Pittsburgh Naval Reactors Office (Datovech, 1994). Datovech performed a literature review to determine the time it will take to corrode through the cask welds (having a minimum 1.25-inch thickness) resulting in hydraulic failure of the cask and subsequent inventory release.…”

Section: Concrete Degradationmentioning

confidence: 99%

“…Datovech performed a literature review to determine the time it will take to corrode through the cask welds (having a minimum 1.25-inch thickness) resulting in hydraulic failure of the cask and subsequent inventory release. The main reference used by Datovech (1994) in determining the puncture time is a condensed summary of the National Bureau of Standards (NBS) seminal investigation on the corrosion of metals in soils by Romanoff (1957).…”

Section: Concrete Degradationmentioning

confidence: 99%

“…Of the soil types included in the NBS investigation, a Cecil clay loam from Atlanta is most representative of the soil at SRS. Although Datovech (1994) does not provide specifics on the calculation employed to arrive at a time-to-puncture of 750 years, he does cite computations by Logan (1939), one of the NBS investigators involved in generating the data reported by Romanoff (1957). Logan (1939) Romanoff, 1957).…”

Section: Concrete Degradationmentioning

confidence: 99%

See 1 more Smart Citation

Performance Assessment for the E-Area Low-Level Radioactive Waste Disposal Facility at the Savannah River Site: Chapter 4

et al. 2023

air, and radon. This section describes the development and implementation of conceptual models for STs and ETs for the GW protection pathway. The ST and ET conceptual models for the IHI exposure pathway are described in Section 3.7.3 and Section 7.3. ST and ET conceptual models for the air and radon pathways are described in Section 3.6. STs and ETs are considered together in this section because the similarities in their facility design; waste characterization; and physical, hydraulic, and chemical properties result in the same (or nearly the same) GW conceptual model.A GW transport analysis is conducted to determine maximum radionuclide concentrations as a function of time within the 100-meter POA buffer zone. PORFLOW (ACRi, 2018), which models both steady-state and transient flow and transport of radionuclide chains (parents and daughters) in porous media, is the primary analysis tool used. Two-and three-dimensional flow and transport analyses are performed to describe, in detail, the migration of species from the trench waste zones downward through the VZ to the underlying water table . VZ simulations (treated as source terms) results are input into a 3-D aquifer transport model to compute maximum GW concentrations of radionuclides within the 100-meter POA. Preliminary GW protection and all-pathways disposal limits for STs and ETs over the 1,000-year period of performance are developed from the computed maximum GW concentrations using the PA/CA Performance Assessment for the Implementation of Groundwater Modeling E-Area Low-Level Radioactive Waste Disposal Facility at the Savannah River Site SRNS-RP-2022-00270 / SRNL-STI-2021-00388 Revision A 4-5completed stack of boxes using a bulldozer. This step brings the trench up to grade and fills in voids between the individual boxes and between the stacks of boxes and the trench sidewalls.Based on this conceptual model, Phifer (2010) developed, and Nichols and Butcher (2020) later refined, a recommended set of blended material and hydraulic property values for containerized waste disposal in STs before and after dynamic compaction (see Table 4-1). This conceptual model also applies to containerized waste in ETs as discussed in Section 4.1.1.2.Inputs and assumptions for the blending calculations are as follows (SRNL, 2020):• The outside dimensions of a B-25 box are 6.0182-foot long, 3.8482-foot wide, and 3.9353-foot high, equating to an average exterior volume of 91.1380 ft 3 (2,580,742 cm 3 ).• The inside dimensions of a B-25 box are 6.0000-foot long, 3.8300-foot wide, and 3.9170-foot high, equating to an average interior volume of 90.0127 ft 3 (2,548,875 cm 3 ).• The volume of waste in a B-25 box is equal to the interior volume 90.0127 ft 3 (2,548,875 cm 3 ); the total waste volume in a stack of four B-25 boxes is 360.0506 ft 3 (10,195,499 cm 3 ).• The average density of uncompacted waste within a B-25 box is 0.1785 g cm -3 (Phifer and Wilhite, 2001).• The total waste mass in a four-high stack of B-25 boxes is 1,819,897 grams (10,195,499 cm 3 × 0.1785 g cm -3 ).• Th...

Performance Assessment for the E-Area Low-Level Radioactive Waste Disposal Facility at the Savannah River Site: Chapter 2

et al. 2023

According to U.S. Census Bureau's annual estimates of resident population, based on 2010 census data, the estimated 2019 population in the eight-county region of influence (ROI) is 610,073 (Table 2-2). Four counties each are in South Carolina (Aiken, Allendale, Bamberg, and Barnwell) and Georgia (Burke, Columbia, Richmond, and Screven). The ROI includes counties within and immediately adjacent to SRS (see Figure 2-2) where most SRS workers reside. Approximately 87% of the eight-county 2019 estimated population lived in three counties: Aiken County, SC (28.0%), Columbia County, GA (25.7%), and Richmond County, GA (33.2%). The balance of the eight-county 2019 estimated population (~13%) lived in Allendale, Barnwell and Bamberg counties in South Carolina and Burke and Screven counties in Georgia. Table 2-2. Population Distribution and Percent of Region of Influence for Counties and Selected Communities Jurisdiction 2019 Population Estimate 1 2019 %ROI SOUTH CAROLINA