Development of Thermally Formed Plugs for Deep Borehole Waste Disposal Applications
- Olympic Research, Inc., Port Townsend, WA (United States)
- South Dakota School of Mines and Technology, Rapid City, SD (United States)
- Arnold Hydrogeology Consulting
In deep borehole disposal of nuclear waste where waste packages are emplaced in deep boreholes in crystalline rock formations, improved well seals and plugs are needed to ensure performance over the long durations of nuclear waste isolation. Similar needs exist in the oil and gas, CO2 injection, and geothermal energy extraction fields as wells are set deeper into harsh geochemical and thermal environments. Conventional well sealing cements are challenged by the conditions at depth, due to their vulnerability to chemical degradation and limited service temperature. High performance plug and seal components can be formed in place using self-propagating high-temperature synthesis (SHS) processes. Solid phase metal/oxide reactions, supplemented by engineered mixtures of minerals and oxides, form ceramic-like sealing features in wells. The plugs are developed by lowering sealed packages of reactive material into the well, and reacting the charges to form molten material which fills and solidifies in the target region of the well. The reaction produces strong, low permeability, high corrosion resistant plug material. The initial viability assessment demonstrated formulations capable of achieving high compressive strength (over three times that of cement), low permeability with the inherent corrosion resistance and service temperature characteristics of ceramics. The Phase II effort refined the plug formulations to optimize reaction product properties, simulated the thermal/mechanical response of the surrounding material to the plug formation process, designed and fabricated a prototype emplacement system, and performed a field test of the system in a cased commercial test well. This sequential Phase IIa project focused on the application to deep borehole nuclear waste disposal in uncased granite boreholes. Mineralogic analysis and material testing evaluated candidate SHS systems, and demonstrated the ability to form aluminosilicate, feldspar, and iron-dominated ceramic plugs, each with unique characteristics. Enhanced numerical simulations predicted the thermal, hydrologic, and mechanical effects of the plug on its surroundings. Plug formation experiments in small granite block samples measured thermal responses that compared favorably with simulations. Mechanical responses were complicated by imperfections in the granite materials, but in some cases did show good agreement. A revised emplacement tool and package design addressed shortcomings of the system identified in the prior phase, with a much-simplified emplacement process and more robust reactant packaging. Due to changes in the DOE nuclear waste program, this Phase IIa project was terminated after the first of two years in the project plan. This report documents the technical progress through that period.
- Research Organization:
- Olympic Research, Inc., Port Townsend, WA (United States)
- Sponsoring Organization:
- USDOE Office of Nuclear Energy (NE)
- DOE Contract Number:
- SC0010135
- OSTI ID:
- 1422211
- Type / Phase:
- SBIR (Phase IIA)
- Report Number(s):
- DOE-ORI-0010135-IIa
- Country of Publication:
- United States
- Language:
- English
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