Effectiveness of an in-situ permeable reactive barrier in removing strontium-90 from groundwater - 15418

Conference · Wed Jul 01 04:00:00 EDT 2015

OSTI ID:22824325

Lee, Art; Rohay, Virginia; Williams, Bruce; Hulstrom, Larry; Faught, Bill ^[1]; Vermeul, Vince; Williams, Mark; Szecsody, Jim ^[2]; Thompson, Michael ^[3]

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1. CH2M HILL Plateau Remediation Company (United States)
2. Pacific Northwest National Laboratory (United States)
3. US DOE (United States)

An in-situ permeable reactive barrier (PRB) is being used to remove strontium-90 from groundwater along the 100-N Area shoreline at the U.S. Department of Energy Hanford Site in southeastern Washington. The PRB was formed by emplacing apatite, a calcium phosphate mineral, in the subsurface sediments via injection of calcium-citrate and sodium-phosphate solution into the aquifer through a network of vertical wells. The relatively slow biodegradation of citrate allowed sufficient time for the injected solution to disperse in the PRB treatment zone as the free calcium and phosphate combined to form apatite. Substitution of strontium for calcium in the apatite crystal structure is thermodynamically favorable. As groundwater flows through the PRB toward the Columbia River, strontium-90 is sequestered into the apatite crystal matrix. The sequestered strontium-90 undergoes radioactive decay in place within the PRB. Groundwater monitoring wells installed between the PRB and the Columbia River are used to monitor the PRB effectiveness. The concentration of strontium-90 in the monitoring wells following apatite emplacement are compared to the pre-injection concentrations. The performance goal of the PRB is to reduce the concentration of strontium-90 in groundwater down gradient of the PRB by 90 percent, compared to the pre-injection concentrations. Groundwater samples in Fall 2013 show the percent reduction in strontium-90 concentrations ranged from 71 to 98 percent in eleven of the twelve monitoring wells. The data indicate that the PRB is effective in reducing the flux of strontium-90 toward the Columbia River and is thereby instrumental in protection of the Columbia River. (authors)

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 22824325
• Report Number(s): INIS-US--19-WM-15418
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
54 ENVIRONMENTAL SCIENCES
APATITES
AQUIFERS
BIODEGRADATION
CALCIUM
CALCIUM PHOSPHATES
CITRATES
COLUMBIA RIVER
CONCENTRATION RATIO
CRYSTAL STRUCTURE
DIFFUSION BARRIERS
GROUND WATER
MONITORING
NUCLEAR DECAY
SEDIMENTS
SODIUM PHOSPHATES
STRONTIUM 90