Abstract'[hi.,, rep_rt describe.,, an assessment of the hmg-term performance of a repository system that c, mtains deeply buried highly radi_mctive waste; the system is assumed tc) be located at the potential >lte at Yucca Mountain, Nevada.
An equation is derived by which advective groundwater velocity in a confined aquifer may be estimated by a single‐well tracer test in which a single tracer pulse is allowed to drift from the well and then pumped back to the well and sampled to obtain a breakthrough curve. Although similar in methodology to preexisting methods, this method differs in that it takes into account ambient groundwater movement during the pumpback phase. Using sodium chloride as a tracer solution, a series of small‐scale tests were run in a laboratory sand tank model to test the theory. Results of linear flow tracer tests through the model, simulating unperturbed regional advective flow at known velocities, were compared to results of single‐well drift‐and‐pumpback tests conducted during linear flow through the model. Advective velocities computed by both types of tests were identical, thus proving the validity of the equation.
A new mathematical model is presented for determining the time histories of impact forces on horizontal circular members and flat deck structures of offshore platforms. Comparison with characteristics of measured data allows explanation of various anomalies, as well as further insight into the effects of measurement system dynamics. Extensions of the analysis are described for application to problems of impact on vertical cylinders, as well as overhanging decks or jacket structure legs during platform transport. INTRODUCTION The problem of wave impact forces on offshore platforms has primarily been concentrated (in the past) on the case of horizontal members in the splash zone, where these support members experience impact forces due to contact with the crests of incident waves. A number of publications related to this problem area have appeared in OTC and related publications ([1]-[5]), where both theoretical analyses and experimental results have been presented and discussed. The results have been primarily concerned with vertical impact forces on the cylinder structure, but some consideration was also given to horizontal forces. While most of the experimental data in these papers was that from model tests, data on a large Ocean Test Structure (OTS) in the Gulf of Mexico together with an associated theoretical analysis-correlation study were presented in [5]. Although these results have arrived as some generally accepted value for the peak vertical impact force, there were a number of questions related to the nature of the load time history. Various effects associated with the measurement procedures; the influence of inertial reactions; effects of measurement system dynamics; influence of filters used in data acquisition and analysis processes; etc. have an influence on the measurements that must be considered when determining the nature of the impact forces and their magnitudes. Such aspects were not uniformly considered in all of the prior publications. Another important problem area, of more recent concern, involves impact forces on platform deck structures (particularly for older platform installations). Large impact forces occur due to extreme waves whose crests can inundate the deck structure due to insufficient air gaps. These reduced air gaps occur as a consequence of subsidence of the local seabed region (or settlement of the platform over time), as well as the increased extreme wave heights that were not forecast as well when these earlier platforms were installed. A particular illustrative case is that of the the Ekofisk platform. The Ekofisk platform deck is composed of flat plating, for which type of structure there are large loads possible. Other platforms have their deck composed of a finite number of beams on which grating is places, so that a reduced "hard structure" region is present. For such cases the horizontal deck loads are then usually the dominant loads on the deck structure. The nature of the loads on flat plate decks differs from that on horizontal cylinders, and the theoretical methods used for each type of structural element are describes in the present paper. The approach used in this paper is similar to techniques used in analysis of ship slamming phenomena.
Yucca Mountain, Nevada is a potential site for a high-level radioactive-waste repository. Uncertainty and sensitivity analyses were performed to estimate critical factors in the performance of the site with respect to a criterion in terms of pre-wasteemplacement ground-water travel time. The degree of failure in the analytical model to meet the criterion is sensitive to the estimate of fracture porosity in the upper welded unit of the problem domain. Fracture porosity is derived from a number of more fundamental measurements including fracture frequency, fracture orientation, and the moistureretention characteristic inferred for the fracture domain. Yucca Mountain, Nevada i_ he potential site of a repository for high-level radioactive waste. To be chosen for development as a repository, the site would be required to meet sets of legal, technical, and political criteria. Performance assessment is the probabilistic assessment of the likelihood that a system will meet the technical criteria governing its performance for a specified period of time (Hart, !987). Performance assessment is used to determine the circumstances under which the site may fail to meet the compliance criteria, to prioritize information needs for further study and from site characterization, and, eventually, to provide an estimate of the degree of compliance with the criteria. Performance assessment is an iterative process that builds on existing technological capabilities and current understanding of the site and the processes at the site that may be of importance to compliance. With each iteration, needs for more information and better analytical capabilities may be identified. This iterative process continues until confidence in the performance of the system is achieved. I ASTEilThe analyses in this document have a specific purpose. That purpose is to provide an analytical basis for prioritizing certain kinds of information needs and data required from a program of site characterizatiGn within the framework of performance assessment. No claim is made that the assumptions in the models used for the analyses are valid. The claim is made, however, that the assumptions are reasonable given our current understanding of the site and the constraints of today's technology. The analyses suggest what information might be important, and they also suggest ways in which future analyses couid be improved for the next iteration. The analyses in this document should not be interprete_l as an attempt to estimate compliance with a legal criterion for groundwater travel time such as 10 CFR 60.113B(2) (Nuclear Regulatory Commission). Sections 2, 3, and 4 di_uss the elements of the conceptual model used in the analyses that follow. Section 2 describes the geologic model, primarily in terms of the geometric relationships among its components. Section 3 describes the process model, the computer program that is used to implement it, and the model input. Section 4 defines the criterion for pre-waste-emplacement ground-water travel time. The uncertainty anal...
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