Evaluation of the single-pass flow-through test to support a low-activity waste specification

A series of single-pass flow-through (SPFT) tests was performed on five reference low-activity waste glasses and a reference glass from the National Institute of Standards and Technology to support a product specification for low-activity waste (LAW) forms. The results showed that the SPFT test provides a means to quantitatively distinguish among LAW glass forms in terms of their forward reaction rate at a given temperature and solution pH. Two of the test glasses were also subjected to SPFT testing at Argonne National Laboratory (ANL). Forward reaction rate constants calculated from the ANL test data were 100 to over 1,000 times larger than the values obtained from the SPFT tests conducted at PNL. An analysis of the ANL results showed that they were inconsistent with independent measurements done on glasses of similar composition, the known pH-dependence of the forward rate, and with the results from low surface-area-to-volume, short duration product consistency tests. Because the data set obtained from the SPFT tests done at PNL was consistent with each of these same factors, a detailed examination of the test procedures used at both laboratories was performed to determine the cause(s) of the discrepancy. The omission of background subtraction in the data analysis procedure and the short-duration (on the order of hours) of the ANL tests are factors that may have significantly affected the calculated rates

Selection of a computer code for Hanford low-level waste engineered-system performance assessment. Revision 1

Planned performance assessments for the proposed disposal of low-activity waste (LAW) glass produced from remediation of wastes stored in underground tanks at Hanford, Washington will require calculations of radionuclide release rates from the subsurface disposal facility. These calculations will be done with the aid of computer codes. The available computer codes with suitable capabilities at the time Revision 0 of this document was prepared were ranked in terms of the feature sets implemented in the code that match a set of physical, chemical, numerical, and functional capabilities needed to assess release rates from the engineered system. The needed capabilities were identified from an analysis of the important physical and chemical processes expected to affect LAW glass corrosion and the mobility of radionuclides. This analysis was repeated in this report but updated to include additional processes that have been found to be important since Revision 0 was issued and to include additional codes that have been released. The highest ranked computer code was found to be the STORM code developed at PNNL for the US Department of Energy for evaluation of arid land disposal sites

Selection of a computer code for Hanford low-level waste engineered-system performance assessment

Planned performance assessments for the proposed disposal of low-level waste (LLW) glass produced from remediation of wastes stored in underground tanks at Hanford, Washington will require calculations of radionuclide release rates from the subsurface disposal facility. These calculations will be done with the aid of computer codes. Currently available computer codes were ranked in terms of the feature sets implemented in the code that match a set of physical, chemical, numerical, and functional capabilities needed to assess release rates from the engineered system. The needed capabilities were identified from an analysis of the important physical and chemical process expected to affect LLW glass corrosion and the mobility of radionuclides. The highest ranked computer code was found to be the ARES-CT code developed at PNL for the US Department of Energy for evaluation of and land disposal sites

Breakthroughs in seismic and borehole characterization of Basalt sequestration targets

AbstractMafic continental flood basalts form a globally important, but under-characterized CO2 sequestration target. The Columbia River Basalt Group (CRBG) in the northwestern U.S. is up to 5 km thick and covers over 168,000 km2. In India, flood basalts are 3 km thick and cover greater than 500,000 km2. Laboratory experiments demonstrate that the CRBG and other basalts react with formation water and super critical (sc) CO2 to precipitate carbonates, thus adding a potential mineral trapping mechanism to the standard trapping mechanisms of most other types of CO2 sequestration reservoirs.Brecciated tops of individual basalt flows in the CRBG form regional aquifers that locally have greater than 30% porosity and three Darcies of permeability. Porous flow tops are potential sites for sequestration of gigatons of sc CO2 in areas where the basalts contain unpotable water and are at depths greater than 800 m. In this paper we report on the U.S. DOE Big Sky Regional Carbon Sequestration Partnership surface seismic and borehole geophysical characterization that supports a field test of capacity, integrity, and geochemical reactivity of CRBG reservoirs in eastern Washington, U.S.A.Traditional surface seismic methods have had little success in imaging basalt features in on-shore areas where the basalt is thinly covered by sediment. Processing of the experimental 6.5 km, 5 line 3C seismic swath included constructing an elastic wavefield model, identifying and separating seismic wave modes, and processing the swath as a single 2D line. Important findings include: (1) a wide variety of shear wave energy modes swamp the P-wave seismic records; (2) except at very short geophone offsets, ground roll overprints P-wave signal; and (3) because of extreme velocity contrasts, P-wave events are refracted at incidence angles greater than 7–15 degrees. Subsequent removal of S-wave and other noise during processing resulted in tremendous improvement in image quality.The application of wireline logging to onshore basalts is underexploited. Full waveform sonic logs and resistivity-based image logs acquired in the 1250 m basalt pilot borehole provide powerful tools for evaluating geomechanics and lithofacies. The azimuth of the fast shear wave is parallel to SH and records the changes through geologic time in basalt flow and tectonic stress tensors. Combined with image log data, azimuthal S-wave data provide a borehole technique for assessing basalt emplacement and cooling history that is related to the development of reservoirs and seals, as well as the orientation of tectonic stresses and fracture systems that could affect CO2 transport or containment. Reservoir and seal properties are controlled by basalt lithofacies, and rescaled P- and S-wave slowness curves, integrated with image logs, provide a tool for improved recognition of subsurface lithofacies

The Wallula basalt sequestration pilot project

AbstractThe U.S. Department of Energy Big Sky Regional Carbon Sequestration Partnership completed drilling the world’s first continental flood basalt sequestration pilot borehole to a total depth (TD) of 1253 m at a paper mill site near the town of Wallula located in Southeastern Washington State. Site suitability was assessed prior to drilling by acquisition, processing and analysis of a four-mile, five-line, three component seismic swath, which was processed as a single data-dense line. Analysis of the seismic survey data indicated absence of major geologic structures that would preclude CO2 injection at the site. Drilling of Wallula pilot borehole was initiated on January 13, 2009 and reached TD on April 6, 2009. Hydrogeologic information was obtained primarily during borehole drilling/advancement utilizing a progressive drill-and-test characterization strategy. A general decreasing transmissivity trend with depth pattern was observed, which is consistent with results exhibited for Columbia River basalt interflow zones at a number of other deep wells in the region. Based on the comparative results from 10 test intervals, a candidate injection test zone was identified between the general depth interval of ∼828 and 875 m bgs. Over this interval, three brecciated interflow zones were intersected and isolated for CO2 injection. The flow tops have moderate permeability (75 to 150 millidarcies) and are bounded by thick flow interiors that have extremely low (microdarcy) permeability. The borehole configuration established at the Wallula pilot site provides a unique opportunity to scientifically study the reservoir behaviour of three connected reservoir intervals confined between primary and secondary caprock zones. The permitting process for the CO2 injection has proceeded in accordance with formal rules for geologic sequestration projects enacted in June 2008 into the underground injection control program administered by the Washington State Department of Ecology. The permitting process is expected to conclude in October 2010 and injection would begin soon thereafter. Post-injection monitoring includes long-term sampling of water retrieved from the injection zone, shallow groundwater and soil gas monitoring, and PSInSAR