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Title: Hydrogeologic performance assessment analysis of the low-level radioactive waste disposal facility near Sheffield, Illinois

Technical Report ·
OSTI ID:6019842

A hydrogeologic performance assessment was conducted for the commercial low-level radioactive waste disposal site located about 3 miles southwest of the town of Sheffield, in Bureau County, northwestern Illinois. The site has 21 trenches, which contain about 900,000 meters{sup 3}, of buried waste and about 60,000 curies of nuclear by-product material. The disposal trenches cut through a complex series of Quaternary deposits, and are composed primarily of silts, clays, and sands. Ground water beneath the site, which ranges in depth from 1.5 to 14 meters, generally moves in two directions: northeast to east toward a strip-mine lake and south to southeast towards small tributary channels belonging to Lawson Creek, which eventually drains into the strip-mine lake southeast of the site. The results in the performance assessment, which focused on the site ground-water pathway, suggest that tritium, strontium 90, and carbon 14 would be the only radionuclides released from the Sheffield site in any significant concentrations. A comparison of simulated tritium concentrations east of the site in the time frame of the burial history would suggest that model results are greater than the highest measured values by a factor of 2 or 3. The discrepancy between actual and predicted concentrations likely reflects errors in the assumed tritium inventory estimates, availability in the inventory, and/or the actual release from the multitude of waste forms considered in the performance assessment. A comparison of transport results for strontium 90 and carbon 14 is not possible since neither has been detected in ground water near the site. 30 refs., 44 figs., 47 tabs.

Research Organization:
Nuclear Regulatory Commission, Washington, DC (USA). Div. of Low-Level Waste Management and Decommissioning; Pacific Northwest Lab., Richland, WA (USA)
Sponsoring Organization:
USNRC; Nuclear Regulatory Commission, Washington, DC (USA)
DOE Contract Number:
AC06-76RL01830
OSTI ID:
6019842
Report Number(s):
NUREG/CR-5714; PNL-7633; ON: TI91012193
Country of Publication:
United States
Language:
English