2002 Initial Assessments for B-BX-BY Field Investigation Report (FIR): Numerical Simulations
IIn support of CH2M HILL Hanford Group, Inc.'s (CHG) preparation of a Field Investigative Report (FIR) for the Hanford Site Single-Shell Tank (SST) Waste Management Area (WMA) B-BX-BY, a set of numerical simulations of flow and solute transport was executed to predict the performance of surface barriers for reducing long-term risks from potential groundwater contamination at the B-BX-BY WMA. This report documents the simulation of 14 cases involving two-dimensional cross sections through the B-BX-BY WMA. Two cross-sections were used for this analysis, one through the BX WMA from tanks BX-108 to BX-102, and another through the trench B-38 for simulating B trench discharges. The simulations were used to investigate the impact of surface barriers, water-line leaks, inventory placement, meteoric recharge and partitioning between the aqueous and sorbed phases. Three transported solutes were considered: uranium-238 (U-238), technetium-99 (Tc-99), and nitrate (NO3). For the BX tank simulations, results showed that simulations investigating water-line leaks demonstrated the highest peak concentrations. Interim barriers had a significant impact on peak concentrations in later times, but not in early times due to a high concentration zone of contaminants near the water table. Overall, simulation results for the BX WMA showed that only a small fraction of the U-238 inventory migrated from the vadose zone in most of the test cases. In general, similar peak WMA concentrations occurred for all of the simulations (<800 pCi/L for Tc-99 and <800 mg/L for NO3), with the exception of the water-line leak cases. In the B trench cases, simulations predicted that the U-238 would not migrate from the vadose zone to the aquifer in the thousand years that were simulated. The simulations also predicted that Tc-99 would appear quickly in the aquifer following the trench discharge in 1954, with peak concentrations occurring around 2020 to 2030.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15002644
- Report Number(s):
- PNNL-13949; 820201000; TRN: US200418%%37
- Country of Publication:
- United States
- Language:
- English
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