Characterization of the Contaminated Soil Under the Hanford 324 Building B Cell, Washington, USA - 12182
- Worley Parsons Polestar, 601 Williams Boulevard, Suite 4A, Richland WA 99352 (United States)
The 324 Building on the Hanford site played a key role in radiochemical and metallurgical research programs conducted by DOE. The B hot cell in the 324 Building was the site of high-level waste vitrification research. During clean-out operations in November 2009, a tear was noted in the stainless steel liner on the floor of B Cell. Exposure rate readings taken at various locations in the soil about 0.5 meters below B Cell reached 8,900 Roentgen (R) per hour, confirming the existence of a significant soil contamination field. The source of the radioactive material was likely a 510 L spill from the Canister Fabrication Project, consisting of purified, concentrated Cs-137 and Sr-90 solutions totaling 48,000 TBq (1.3 MCi). MCNP modeling was used to estimate that the measured exposure rates were caused by 5,900 TBq (160 kCi) of Sr- 90 and Cs-137, although additional contamination was thought to exist deeper in the soil column. Two physical soil samples were obtained at different depths, which helped verify the contamination estimates. A detailed exposure rate survey inside B Cell was combined with additional MCNP modeling to estimate that an additional 1,700 TBq (460 kCi) is present just below the floor. Based on the results of the sampling campaign, it is likely that the radioactive material below B Cell is primarily consists of feed solutions from the FRG Canister Fabrication Project, and that it contains purified Sr-90 and Cs-137 with enough actinide carryover to make some of the soil transuranic. The close agreement between the Geoprobe calculations and the physical samples adds confidence that there are more than 3700 TBq (100,000 Ci) of Sr-90 and Cs-137 in the soil approximately 1 meter below the cell floor. The majority of the Cs-137 is contained in the first meter of soil, while significant Sr-90 contamination extends to 10 meters below the cell floor. It is also likely that an additional 15,000 TBq (400,000 Ci) of Cs-137 and Sr-90 activity is present directly below the floor of the cell, and that the residual activity inside the cell is only half of the previous estimates. However, the partitioning of activity between residuals in the cell and in the soil below the floor is much more uncertain than the activity calculations associated with the Geoprobe measurements. Taken together, the calculated soil activities represent about half of the spill associated with the FRG Canister Fabrication project. The remainder of the spill is believed to have remained in the cell, where the majority has been removed as part of cell cleanup activities. The magnitude of the soil contamination below 324 B Cell is sobering, and it represents one of the most challenging remediation activities in the DOE complex. Of course, safe remediation begins with a good understanding of the magnitude of the problem. As a result, additional modeling and cross-comparison efforts are planned for 2012. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9-332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 22293481
- Report Number(s):
- INIS-US-14-WM-12182; TRN: US14V1135115005
- Resource Relation:
- Conference: WM2012: Waste Management 2012 conference on improving the future in waste management, Phoenix, AZ (United States), 26 Feb - 1 Mar 2012; Other Information: Country of input: France; 12 refs.
- Country of Publication:
- United States
- Language:
- English
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