Commercial generation of energy via nuclear power plants in the United States (U.S.) has generated thousands of metric tons of spent nuclear fuel (SNF), the disposal of which is the responsibility of the U.S. Department of Energy (DOE) (Nuclear Waste Policy Act of 1982). Any repository licensed to dispose of the SNF must meet requirements regarding the long-term performance of the repository. In evaluating the long-term performance of the repository, one of the events that may need to be considered is the SNF achieving a critical configuration. Of particular interest is the potential behavior of SNF in dual-purpose canisters (DPCs), which are currently being used to store the SNF but were not designed for permanent disposal. As part of a multiyear plan that is currently being developed for the DOE, a two-phase study has been initiated to examine the potential consequences, with respect to long-term repository performance, of criticality events that might occur during the postclosure period in a hypothetical repository containing DPCs. Phase I, a scoping phase, consists of generating an approach intended to be a starting point for the development of the modeling tools and techniques that may eventually be required either to exclude criticality from or include criticality in a performance assessment (PA) as appropriate. The Phase I approach will be used to guide the analyses and simulations done in Phase II to further the development of these modeling tools and techniques as well as the overall knowledge base. The purpose of this report is to document the approach created during Phase I. The study discussed herein focuses on the consequences of criticality in a DPC; it does not address the probability of occurrence of a criticality event. This approach examines two types of criticality events for SNF disposed of in a single type of DPC: a steady-state criticality and a transient criticality. The steady-state critical event is characterized by a relatively low constant power output over 10,000 years, while the transient critical event is characterized by a power spike that lasts on the order of seconds. Possible effects of the criticality are an increase in the radionuclide inventory; an increase in temperature; and a change in the chemistry inside the waste package, along with a change in radionuclide solubilities, fuel degradation rates, and steel corrosion rates. Additionally, for transient criticality the possibility of mechanical damage to the engineered and natural barriers also exists.
This report describes the current status of the safety case for the deep borehole disposal (DBD) concept. It builds on the safety case presented in Freeze et al. (2016), presenting new information and identifying additional information needs for specific safety case elements. At this preliminary phase of development, the DBD safety case focuses on the generic feasibility of the DBD concept. It is based on potential system designs, waste forms, engineering, and geologic conditions; however, no specific site or regulatory framework exists. Updated information is provided for the following safety case elements: (1) pre-closure basis and safety analysis, (2) post-closure basis and performance assessment, and (3) confidence enhancement. This research was performed as part of the deep borehole field test (DBFT). Based on revised U.S. Department of Energy (DOE) priorities in mid-2017, the DBFT and other research related to a DBD option was discontinued; ongoing work and documentation were closed out by the end of fiscal year (FY) 2017. This report was initiated as part of the DBFT and documented as an incomplete draft at the end of FY 2017. The report was finalized by Sandia National Laboratories in FY2018 without DOE funding, subsequent to the termination of the DBFT, and published in FY2019.
Post-closure performance assessment (PA) calculations suggest that deep borehole disposal of cesium (Cs)/strontium (Sr) capsules, a U.S. Department of Energy (DOE) waste form (WF), is safe, resulting in no releases to the biosphere over 10,000,000 years when the waste is placed in a 3-5 km deep waste disposal zone. The same is true when a hypothetical breach of a stuck waste package (WP) is assumed to occur at much shallower depths penetrated by through-going fractures. Cs and Sr retardation in the host rock is a key control over movement. Calculated borehole performance would be even stronger if credit was taken for the presence of the WP.
Various versions of deep borehole nuclear waste disposal have been proposed in the past in which effective sealing of a borehole after waste emplacement is generally required. In a high temperature disposal mode, the sealing function will be fulfilled by melting the ambient granitic rock with waste decay heat or an external heating source, creating a melt that will encapsulate waste containers or plug a portion of the borehole above a stack of the containers. However, there are certain drawbacks associated with natural materials, such as high melting temperatures, inefficient consolidation, slow crystallization kinetics, the resulting sealing materials generally being porous with low mechanical strength, insufficient adhesion to waste container surface, and lack of flexibility for engineering controls. In this study, we showed that natural granitic materials can be purposefully engineered through chemical modifications to enhance the sealing capability of the materials for deep borehole disposal. The present work systematically explores the effect of chemical modification and crystallinity (amorphous vs. crystalline) on the melting and crystallization processes of a granitic rock system. The approach can be applied to modify granites excavated from different geological sites. Several engineered granitic materials have been explored which possess significantly lower processing and densification temperatures than natural granites. Those new materials consolidate more efficiently by viscous flow and accelerated recrystallization without compromising their mechanical integrity and properties.
This report represents completion of milestone deliverable M2SF-18SNO10309013 "Inventory and Waste Characterization Status Report and OWL Update that reports on FY2018 activities for the work package (WP) SF-18SNO1030901. This report provides the detailed final information for completed FY2018 work activities for WP SF-18SN01030901, and a summary of priorities for FY2019. This status report on FY2018 activities includes evaluations of waste form characteristics and waste form performance models, updates to the OWL development, and descriptions of the two planned management processes for the OWL. Updates to the OWL include an updated user's guide, additions to the OWL database content for wastes and waste forms, results of the Beta testing and changes implemented from it. There are two processes being planned in FY2018, which will be implemented in FY2019. One process covers methods for interfacing with the DOE SNF DB (DOE 2007) at INL on the numerous entries for DOE managed SNF, and the other process covers the management of updates to, and version control/archiving of, the OWL database. In FY2018, we have pursued three studies to evaluate/redefine waste form characteristics and/or performance models. First characteristic isotopic ratios for various waste forms included in postclosure performance studies are being evaluated to delineate isotope ratio tags that quantitatively identify each particular waste form. This evaluation arose due to questions regarding the relative contributions of radionuclides from disparate waste forms in GDSA results, particularly, radionuclide contributions of DOE-managed SNF vs HLW glass. In our second study we are evaluating the bases of glass waste degradation rate models to the HIP calcine waste form. The HIP calcine may likely be a ceramic matrix material, with multiple ceramic phases with/without a glass phase. The ceramic phases are likely to have different degradation performance from the glass portion. The distribution of radionuclides among those various phases may also be a factor in the radionuclide release rates. Additionally, we have an ongoing investigation of the performance behavior of TRISO particle fuels and are developing a stochastic model for the degradation of those fuels that accounts for simultaneous corrosion of the silicon carbide (SiC) layer and radionuclide diffusion through it. The detailed model of the TRISO particles themselves, will be merged with models of the degradation behavior(s) of the graphite matrix (either prismatic compacts or spherical "pebbles") containing the particles and the hexagonal graphite elements holding the compacts.
Mwangi, Paulina; Brady, Patrick V.; Radonjic, Mileva; Thyne, Geoffrey
This paper examines the role of crude oil's organic acid surface active compounds (SAC) in determining the reservoir wettability over a range of salinities and temperatures. To isolate the effects of individual SACs, this project used model oil mixtures of pure decane and single SACs to represent the oleic phase. Due to the large number of experiments in this study, we used wettability measurement method by the modified flotation technique (MFT) to produce fast, reliable, and quantitative results. The results showed that oil wetting by decane increased with temperature for carbonate rocks. Sandstones oil wetting showed little temperature dependency. The presence of long-chained acids in decane increased oil wetting in sandstone and carbonate rocks as salinity was lowered, while the short-chained acid increased water wetting under the same conditions. The effect of organic acids on wettability was slightly enhanced with increasing temperature for all rock types.
Chen, Yongqiang; Xie, Quan; Sari, Ahmad; Brady, Patrick V.; Saeedi, Ali
Wettability of the oil/brine/rock system is an essential petro-physical parameter which governs subsurface multiphase flow behaviour and the distribution of fluids, thus directly affecting oil recovery. Recent studies [1–3] show that manipulation of injected brine composition can enhance oil recovery by shifting wettability from oil-wet to water-wet. However, what factor(s) control system wettability has not been completely elucidated due to incomplete understanding of the geochemical system. To isolate and identify the key factors at play we used SO42—free solutions to examine the effect of salinity (formation brine/FB, 10 times diluted formation brine/10 dFB, and 100 times diluted formation brine/100 dFB) on the contact angle of oil droplets at the surface of calcite. We then compared contact angle results with predictions of surface complexation by low salinity water using PHREEQC software. We demonstrate that the conventional dilution approach likely triggers an oil-wet system at low pH, which may explain why the low salinity water EOR-effect is not always observed by injecting low salinity water in carbonated reservoirs. pH plays a fundamental role in the surface chemistry of oil/brine interfaces, and wettability. Our contact angle results show that formation brine triggered a strong water-wet system (35°) at pH 2.55, yet 100 times diluted formation brine led to a strongly oil-wet system (contact angle = 175°) at pH 5.68. Surface complexation modelling correctly predicted the wettability trend with salinity; the bond product sum ([>CaOH2+][–COO−] + [>CO3−][–NH+] + [>CO3−][–COOCa+]) increased with decreasing salinity. At pH < 6 dilution likely makes the calcite surface oil-wet, particularly for crude oils with high base number. Yet, dilution probably causes water wetness at pH > 7 for crude oils with high acid number.
This report supplements Joint Workplan on Filler Investigations for DPCs (SNL 2017) providing new and some corrected information for use in planning Phase 1 laboratory testing of slurry cements as possible DPC fillers. The scope description is to "Describe a complete laboratory testing program for filler composition, delivery, emplacement in surrogate canisters, and post-test examination. To the extent possible specify filler material and equipment sources." This report includes results from an independent expert review (Dr. Arun Wagh, retired from Argonne National Laboratory and contracted by Sandia) that helped to narrow the range of cement types for consideration, and to provide further guidance on mix variations to optimize injectability, durability, and other aspects of filler performance.
Society of Petroleum Engineers - SPE EOR Conference at Oil and Gas West Asia 2018
Al-Saedi, Hasan N.; Alhuraishawy, Ali K.; Flori, R.E.; Brady, Patrick V.; Heidari, P.
Numerous quantitative and qualitative methods have been presented to measure wettability. The most well-known methods are Amott-Harvey and U.S. Bureau of Mines. The Amott method describes how the wetting phase displaces the nonwetting phase spontaneously; the main problem with this method insensitivity near neutral wettability. Another problem with this method is that imbibition can take several hours to more than two months to complete. The most important benefit of USBM that differs from the Amott method is the sensitivity close to neutral wettability, but the disadvantage is that USBM cannot recognize if the reservoir has mixed wettability or not, though Amott can. We come up with a method to measure sandstone wettability only by Ca2+ and Br− chromatographic separation according to the method described by Strand et al. (2006) on a chalk core. Three sister cores were pre-aged in formation water without Ca2+ and Br−, and the cores were then aged in oil for three weeks at 95°C. The cores were then flooded with the same formation water until Sor was established. Core#1 was flooded with high salinity water (~117,000 ppm) containing identical concentrations of Ca2+ and Br− (89 μmole). Core#2 was flooded with low salinity water d30HSW. Core#3 was sequentially flooded with HS and LS water to investigate the wettability alteration in the same core. All experiments were conducted at 25 and 70°C to examine the effect of temperature on wettability alteration by the new method. The effluents were collected by a fraction collector for chemical analysis for Ca2+ and Br−, divided by the inlet concentration of Ca2+ and Br−, and then plotted with injected pore volume (PV). The area between the Ca2+ and Br− curves was calculated (Ao). Core#4 was pre-aged in heptane in order to establish water-wet sandstone. The heptane was displaced from the core by the same formation water until residual heptane saturation was reached. The same HS water was injected into Core#3. The effluents were analyzed using the same method as for Core#1, 2. The area between the two curves was also determined using the same method as for Core#1, 2 (AH). The wettability index was then calculated by dividing Ao by AH. The wettability index ranged from 0 for strongly oil-wet to 1 for strongly water-wet and 0.5 for intermediate wettability. Another core was sequentially flooded by HS and LS water to further investigate the wettability alteration by LS water and to verify our new method. The divalent cation Ca2+ was considered as the most potential ion towards sandstone when injecting low salinity water to sandstone. An ion exchange occurred between Ca2+ and H+ during flooding which is the key point for wettability alteration, and in turn, increases oil recovery. Bromine is a tracer that has no potential to the sandstone surface area. Thus, the area between Ca2+ and Br− is proportional directly to the water-wet surface site in sandstone (i.e., both Ca2+ and Br− contact the same water-wet surface area).
Proceedings - SPE Symposium on Improved Oil Recovery
Al-Saedi, Hasan N.; Brady, Patrick V.; Flori, Ralph; Heidari, Peyman
The ever-growing global energy demand and natural decline in oil production from mature oil fields over the last several decades have been the main incentives to search for methods to increase recovery efficiency. This paper quantifies the clay role and the important role of pH in the water flooding of low salinity water in sandstone with and without clays as a function of temperature. Four chromatography columns containing different amounts of sand, illite, and kaolinite (100% sand; 5% Illite, 95% sand; 5% kaolinite, 95% sand; 2.5% Illite, 2.5% kaolinite, 95% sand) were water flooded with various salinities at four different temperatures 25, 70, 90 and 120 °C. Effluent concentrations of Ca2+ and CH3COO−, and pH were measured. The system was pre-aged for a week at 70 °C with 0.01 molar (M) sodium acetate to simulate the bonding of oil-bound carboxylic acids with the reservoir. Desorption of carboxylic groups from reservoir clay surfaces is thought to be an important control over low salinity EOR water injection and its extent should depend on pH. To quantify the impact of the presence of the clay, a clay-free sample was also used, the acetate release and Ca2+ desorption were in some cases higher than those observed in non-clay free samples. Typically, cores with higher clay content saw a great rise in pH, but the clay-free samples also saw a rise in pH, as great as that of the clay-containing cores.
This workplan addresses filler attributes (i.e., possible requirements), assumptions needed for analysis, selection of filler materials, testing needs, and a long-range perspective on R&D activities leading to filler demonstration and a safety basis for implementation.
The removal of silica, ubiquitous in produced and industrial waters, by novel mixed oxides is investigated in this present study. We have combined the advantage of high selectivity hydrotalcite (HTC, (Mg6Al2(OH)16(CO3)·4H2O)), with large surface area of active alumina (AA, (Al2O3)) for effective removing of the dissolved silica from cooling tower water. The batch test results indicated the combined HTC/AA is a more effective method for removing silica from CTW than using each of HTC or AA separately. The silica uptake was confirmed by Fourier transform infrared (FTIR), and Energy dispersive spectroscopy (EDS). Results indicate HTC/AA effectively removes silica from cooling tower water (CTW), even in the presence of large concentrations of competing anions, such as Cl−, NO3− HCO3−, CO32− and SO42−. The Single Path Flow Through (SPFT) tests confirmed to rapid uptake of silica by combined HTC/AA during column filtration. The experimental data of silica adsorption fit best to Freundlich isotherm model.