14 research outputs found
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Performance assessment in support of compliance certification application for the WIPP project
The Waste Isolation Pilot Plant (WIPP) is being developed by the US Department of Energy for the geologic (deep underground) disposal of transuranic (TRU) waste. A Compliance Certification Application (CCA) of the WIPP (1) for such disposal was submitted to the US Environmental Protection Agency (EPA) in October, 1996, and is currently under review, with a decision anticipated in late 1997. An important component of the CCA is a performance assessment (PA) for the WIPP carried out by Sandia National Laboratories. The final outcome of the PA is a complementary cumulative distribution function (CCDF) for radionuclide releases from the WIPP to the accessible environment and an assessment of the confidence with which this CCDF can be estimated. This paper describes the computational process used to develop the CCDF. The results of uncertainty and sensitivity analysis are also presented
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Optimization and control of the plasma shape and current profile in noncircular cross-section tokamaks
High-..beta.. equilibria which are stable to all ideal MHD modes are found by optimizing the plasma shape and current profile for doublets, up-down asymmetric dees, and symmetric dees. The ideal MHD stability of these equilibria for low toroidal mode number n is analyzed with a global MHD stability code, GATO. The stability to high-n modes is analyzed with a localized ballooning code, BLOON. The attainment of high ..beta.. is facilitated by an automated optimization search on shape and current parameters. The equilibria are calculated with a free-boundary equilibrium code using coils appropriate for the Doublet III experimental device. The optimal equilibria are characterized by broad current profiles with values of ..beta../sub poloidal/ approx. =1. Experimental realization of the shapes and current profiles giving the highest ..beta.. limits is explored with a 1 1/2-D transport code, which simulates the time evolution of the 2-D MHD equilibrium while calculating consistent current profiles from a 1-D transport model. Transport simulations indicate that nearly optimal shapes may be obtained provided that the currents in the field-shaping coils are appropriately programmed and the plasma current profile is sufficiently broad. Obtaining broad current profiles is possible by current ramping, neutral beam heating, and electron cyclotron heating. With combinations of these techniques it is possible to approach the optimum ..beta.. predicted by the MHD theory