Characterization of Direct-Push Vadose Zone Sediments from the 241-B and 241-BX Tank Farms

Brown, Christopher F. ; Icenhower, Jonathan P. ; Um, Wooyong ; Bjornstad, Bruce N. ; Valenta, Michelle M. ; Iovin, Cristian ; Lanigan, David C. ; Clayton, Ray E. ; Geiszler, Keith N. ; Clayton, Eric T. ; Kutnyakov, Igor V. ; Baum, Steven R. ; Lindberg, Michael J. ; Or

关键词: AR FACILITIES;    HANFORD RESERVATION;    STORAGE FACILITIES;    RADIOACTIVE WASTE STORAGE;    SOILS;    SEDIMENTS;    GEOCHEMISTRY;    PLUMES;    RADIONUCLIDE MIG;   

DOI  :  10.2172/925726
RP-ID  :  PNNL-17162
PID  :  OSTI ID: 925726
Others  :  Other: 830403000
Others  :  TRN: US0802443

学科分类：核能源与工程

美国|英语

来源: SciTech Connect

【 摘 要 】

Geochemical tests provide evidence for the transit of a plume of caustic waste solution through the sediment column at the Hanford 241-B and -BX Tank Farms. Direct-push samples recovered from boreholes surrounding Tanks 241-B-110 and 241-BX-102 and related waste transfer lines and diversion boxes included sediments typical of those previously recovered from other localities on the Hanford Site. The Hanford formation sediments are dominantly quartzo-feldspathic sands strewn with lithic fragments, displaying a range of particle size distributions and sorting characteristics. Some moderately well-sorted, fine-grained lithologies are interpreted as lenticular bodies irregularly dispersed in coarser-grained, more poorly sorted sediments. Tier I tests conducted on the vadose zone sediments revealed an inverse correlation between moisture content and sediment size fraction (i.e., there is greater moisture content in finer-grained sediments). The Tier I tests also showed that the pore water solutions were likely sodium-rich, moderately saline, and possessed higher pH values than background (untainted) sediments. These data are characteristic of sediments that have encountered sodium-rich, saline, caustic waste solution, as documented in other reports at other suspect contamination sites around Hanford. Analyses of solutions from 1:1 water extracts reveal relatively balanced cation and anion concentrations, indicating that most of the geochemical species have been accounted for. The water extract data for affected sediments also indicate unusually high concentrations of aluminum, iron, and phosphorus. The relatively high concentrations of aluminum and iron may be the result of dissolution of secondary amorphous phases that precipitated after a reactive plume partially dissolved aluminum- and iron-bearing phases as it migrated through the sediment column. On the other hand, the presence of elevated concentrations of phosphorous may be the tell-tale signature of wastes derived from the bismuth phosphate separation process. Elements typically mobile in the geosphere, such as technetium-99, are present at either low concentrations or are below the analytical detection limit. However, we expect that the mobile elements would be present mainly along a narrow plume front, and if this front had passed deeper into the sediment profile than depths sampled, the retention of these elements would be minor. On the other hand for the direct push sediments from around BX Tank Farm, uranium-238 was detected in nearly all sediment specimens (by acid extract experiments) at concentrations above the natural crustal average (0.763 pCi/g), and we also detected the presence of several anthropogenic radioisotopes, such as cobalt-60, cesium-137, europium-154, and europium-155 (by gamma energy analysis). These data are direct confirmation of contamination of the sediments.