NOTE 1: FCT Document Cover Sheet should be filled out and submitted with the deliverable. Or, if the PICS:NE system permits, completely enter all applicable information in the PICS:NE Deliverable Form. The requirement is to ensure that all applicable information is entered either in the PICS:NE system or by using the FCT Document Cover Sheet. NOTE 2: In some cases there may be a milestone where an item is being fabricated, maintenance is being performed on a facility, or a document is being issued through a formal document control process where it specifically calls out a formal review of the document. In these cases, documentation (e.g., inspection report, maintenance request, work planning package documentation or the documented review of the issued document through the document control process) of the completion of the activity, along with the Document Cover Sheet, is sufficient to demonstrate achieving the milestone. If QRL 1, 2, or 3 is not assigned, then the Lab / Participant QA Program (no additional FCT QA requirements) box must be checked, and the work is understood to be performed and any deliverable developed in conformance with the respective National Laboratory / Participant, DOE or NNSA-approved QA Program.

The safety case for deep borehole disposal of nuclear wastes contains a safety strategy, an assessment basis, and a safety assessment. The safety strategy includes strategies for management, siting and design, and assessment. The assessment basis considers site selection, pre-closure, and post-closure, which includes waste and engineered barriers, the geosphere/natural barriers, and the biosphere and surface environment. The safety assessment entails a pre-closure safety analysis, a post-closure performance assessment, and confidence enhancement analyses. This paper outlines the assessment basis and safety assessment aspects of a deep borehole disposal safety case. The safety case presented here is specific to deep borehole disposal of Cs and Sr capsules, but is generally applicable to other waste forms, such as spent nuclear fuel. The safety assessments for pre-closure and post-closure are briefly summarized from other sources; key issues for confidence enhancement are described in greater detail. These confidence enhancement analyses require building the technical basis for geologically old, reducing, highly saline brines at the depth of waste emplacement, and using reactive-transport codes to predict their movement in post-closure. The development and emplacement of borehole seals above the waste emplacement zone is also important to confidence enhancement.

No abstract

A long-term assessment of the Waste Isolation Pilot Plant (WIPP) repository performance must consider the impact of gas generation resulting from the corrosion and microbial degradation of the emplaced waste. A multiphase fluid flow code, TOUGH2/EOS8, was adapted to model the processes of gas generation, disposal room creep closure, and multiphase (brine and gas) fluid flow, as well as the coupling between the three processes. System response to gas generation was simulated with a single, isolated disposal room surrounded by homogeneous halite containing two anhydrite interbeds, one above and one below the room. The interbeds were assumed to have flow connections to the room through high-permeability, excavation-induced fractures.System behavior was evaluated by tracking four performance measures: (1) peak room pressure; (2) maximum brine volume in the room; (3) total mass of gas expelled from the room; and (4) the maximum gas migration distance in an interbed. A deterministic approach, including baseline and sensitivity simulations, was used. Baseline simulations used current best estimates of system parameters, selected through an evaluation of available data, to predict system response to gas generation under best-estimate conditions. Sensitivity simulations quantified the effects of parameter uncertainty by evaluating the change in the performance measures in response to parameter variations. In the sensitivity simulations, a single parameter value was varied to its minimum and maximum values, representative of the extreme expected values, with all other parameters held at best-estimate values.Simulation results indicated that (1) in the absence of interbed fracturing, disposal room pressures will exceed, lithostatic, even at gas-generation rates representative of vapor-limited conditions, (2) under best-estimate conditions, brine availability was insufficient to fully exhaust the brine-dependent gas-generation potential, (3) the mass of gas expelled from the room and the gas migration distance are much more sensitive to the total mass of gas generated than to the gas-generation rate, and (4) the halite properties are important to gas migration because gas movement in the interbeds is limited by the displacement of interbed brine into the surrounding halite.Sensitivity simulations identified the following parameters as important to gas expulsion and migration away from a disposal room: interbed porosity; interbed permeability; gas-generation potential; halite permeability; and interbed threshold pressure. The uncertainty in multiphase flow parameters was not adequately characterized because of the lack of WIPP-specific data. Simulations also showed that the inclusion of interbed fracturing and a disturbed rock zone had a significant impact on system performance.The TOUGH2/EOS8 deterministic simulation and sensitivity results were similar to stochastic results obtained by WIPP Performance Assessment from a repository-scale model. Because the deterministic approach allows conceptual models to be quanti...

A hydrologic modeling study was performed to gain insight into the flow mechanisms around Room Q. A summary of hydrologic and structural data and of predictive fluid flow models from Room Q are provided. Six years of measured data are available from the time of excavation. No brine accumulation in Room Q was measured in the first two years following excavation. However, there is considerable uncertainty associated with this early-time data due to inadequate sealing of the room. Brine may have been lost to evaporation or it may have flowed into newly created disturbed rock zone (DRZ) porosity resulting from excavation. Non-zero brine accumulation rates were measured from 2-5 years, but brine accumulation within the room dropped to zero after 5.5 years. A conceptual model for brine inflow to Room Q was developed which assumes far-field Darcy flow combined with an increasing DRZ pore volume. Numerical simulations employed TOUGH28W and used predictive DRZ porosity increase with time from SPECTROM-32 rock deformation simulations. Simulated brine inflow showed good agreement with measured brine accumulation rates for the first five years. Two important conclusions were drawn fiom the simulation results: (1) early-time brine inflow to the room can be reduced to zero if the DRZ pore volume increases with time, and (2) brine accumulation (inflow) rates fiom 2 to 5 years suggest a far-field permeability of 5 x m2 with a bulk rock compressibility of 5.4 x 10-I2 Pa-I. The early-time brine inflow to the DISCLAIMER This report was prepared as a n account of work sponsored by a n agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disdased, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or sern'ce by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necesSarily state or reflect those of the United States Government or any agency thereof.. Greg Ruskauff of INTERA Inc. for performing many of the TOUGH28W numerical simulations; Kerry DeVries of RE/SPEC Inc. for his time and efforts providing results from SPECTROM-32 simulations; Rick Bower of TechReps Inc. for providing Room Q data;

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.

No abstract

The safety case for deep borehole disposal of nuclear wastes contains a safety strategy, an assessment basis, and a safety assessment. The safety strategy includes strategies for management, siting and design, and assessment. The assessment basis considers site selection, pre-closure, and post-closure, which includes waste and engineered barriers, the geosphere/natural barriers, and the biosphere and surface environment. The safety assessment entails a pre-closure safety analysis, a post-closure performance assessment, and confidence enhancement analyses. This paper outlines the assessment basis and safety assessment aspects of a deep borehole disposal safety case. The safety case presented here is specific to deep borehole disposal of Cs and Sr capsules, but is generally applicable to other waste forms, such as spent nuclear fuel. The safety assessments for pre-closure and post-closure are briefly summarized from other sources; key issues for confidence enhancement are described in greater detail. These confidence enhancement analyses require building the technical basis for geologically old, reducing, highly saline brines at the depth of waste emplacement, and using reactive-transport codes to predict their movement in post-closure. The development and emplacement of borehole seals above the waste emplacement zone is also important to confidence enhancement.