Initial Single-Shell Tank System Performance Assessment for the Hanford Site

Conference · Sun Jul 01 04:00:00 EDT 2007

OSTI ID:21294717

Jaraysi, M N; Kristofzski, J G; Connelly, M P ^[1]; Wood, M I ^[2]; Knepp, A J ^[3]; Quintero, R A ^[4]

---

1. CH2M HILL Hanford Group, Inc., Richland, WA (United States)
2. Fluor Hanford Inc., Richland WA (United States)
3. YAHSGS LLC, Richland WA (United States)
4. Office of River Protection, United States Department of Energy, Richland, WA (United States)

The Initial Single-Shell Tank System Performance Assessment for the Hanford Site (SST PA) presents the analysis of the long-term impacts of residual wastes assumed to remain after retrieval of tank wastes and closure of the SST farms at the U.S. Department of Energy (DOE) Hanford Site. The SST PA supports key elements of the closure process agreed upon in 2004 by DOE, the Washington State Department of Ecology (Ecology), and the U.S. Environmental Protection Agency (EPA). The SST PA element is defined in Appendix I of the Hanford Federal Facility Agreement and Consent Order (HFFACO) (Ecology et al. 1989), the document that establishes the overall closure process for the SST and double-shell tank (DST) systems. The approach incorporated in the SST PA integrates substantive features of both hazardous and radioactive waste management regulations into a single analysis. The defense-in-depth approach used in this analysis defined two major engineering barriers (a surface barrier and the grouted tank structure) and one natural barrier (the vadose zone) that will be relied on to control waste release into the accessible environment and attain expected performance metrics. The analysis evaluates specific barrier characteristics and other site features that influence contaminant migration by the various pathways. A 'reference' case and a suite of sensitivity/uncertainty cases are considered. The 'reference case' evaluates environmental impacts assuming central tendency estimates of site conditions. 'Reference' case analysis results show residual tank waste impacts on nearby groundwater, air resources; or inadvertent intruders to be well below most important performance objectives. Conversely, past releases to the soil, from previous tank farm operations, are shown to have groundwater impacts that are significantly above most performance objectives. Sensitivity/uncertainty cases examine single and multiple parameter variability along with plausible alternatives to 'reference' cases to judge how well the proposed closure system performs when changes to important assumptions are made to the hydrogeologic and engineered systems. The estimated impacts from these cases are generally consistent with 'reference' case results (i.e., performance objectives are exceeded by contaminants from past releases but not tank residuals). This document and its future iterations will play a critical role in the decision making process for the closure of the Hanford Tank Farms. It will support interim decisions related to tank retrievals and interim corrective measures, in addition to supporting the major closure decisions of tanks and tank farms. Hence, it is imperative that the review process of this document is inclusive of the decision makers as well as the Hanford Stakeholders. (authors)

• Research Organization: WM Symposia, 1628 E. Southern Avenue, Suite 9 - 332, Tempe, AZ 85282 (United States)
• OSTI ID: 21294717
• Report Number(s): INIS-US--09-WM-07359
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ENVIRONMENTAL IMPACTS
GROUND WATER
HANFORD RESERVATION
PERFORMANCE
RADIOACTIVE WASTE MANAGEMENT
RADIOACTIVE WASTES
SHUTDOWN
STORAGE FACILITIES
TANKS
US EPA