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Mesoscale to plant-scale models of nuclear waste reprocessing

Rao, Rekha R.; Pawlowski, Roger P.; Brotherton, Christopher M.; Cipiti, Benjamin B.; Domino, Stefan P.; Jove Colon, Carlos F.; Moffat, Harry K.; Nemer, Martin N.; Noble, David R.; O'Hern, Timothy J.

Imported oil exacerabates our trade deficit and funds anti-American regimes. Nuclear Energy (NE) is a demonstrated technology with high efficiency. NE's two biggest political detriments are possible accidents and nuclear waste disposal. For NE policy, proliferation is the biggest obstacle. Nuclear waste can be reduced through reprocessing, where fuel rods are separated into various streams, some of which can be reused in reactors. Current process developed in the 1950s is dirty and expensive, U/Pu separation is the most critical. Fuel rods are sheared and dissolved in acid to extract fissile material in a centrifugal contactor. Plants have many contacts in series with other separations. We have taken a science and simulation-based approach to develop a modern reprocessing plant. Models of reprocessing plants are needed to support nuclear materials accountancy, nonproliferation, plant design, and plant scale-up.

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TYPE Conference YEAR 2010
OSTI

A conformal decomposition finite element method for modeling stationary fluid interface problems

Proposed for publication in the International Journal for Numerical Methods in Fluids.

Noble, David R.; Newren, Elijah N.; Lechman, Jeremy B.

A method is developed for modeling fluid transport in domains that do not conform to the finite element mesh. One or more level set functions are used to describe the fluid domain. A background, non-conformal mesh is decomposed into elements that conform to the level set interfaces. Enrichment takes place by adding nodes that lie on the interfaces. Unlike other enriched finite element methods, the proposed technique requires no changes to the underlying element assembly, element interpolation, or element quadrature. The complexity is entirely contained within the element decomposition routines. It is argued that the accuracy of the method is no less than that for eXtended Finite Element Methods (XFEM) with Heaviside enrichment. The accuracy is demonstrated using multiple numerical tests. In all cases, optimal rates of convergence are obtained for both volume and surface quantities. Jacobi preconditioning is shown to remove the ill-conditioning that may result from the nearly degenerate conformal elements.

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TYPE Journal Article YEAR 2008
OSTI

Foam process models

Rao, Rekha R.; Mondy, L.A.; Moffat, Harry K.; Noble, David R.; Notz, Patrick N.; Adolf, Douglas B.

In this report, we summarize our work on developing a production level foam processing computational model suitable for predicting the self-expansion of foam in complex geometries. The model is based on a finite element representation of the equations of motion, with the movement of the free surface represented using the level set method, and has been implemented in SIERRA/ARIA. An empirically based time- and temperature-dependent density model is used to encapsulate the complex physics of foam nucleation and growth in a numerically tractable model. The change in density with time is at the heart of the foam self-expansion as it creates the motion of the foam. This continuum-level model uses an homogenized description of foam, which does not include the gas explicitly. Results from the model are compared to temperature-instrumented flow visualization experiments giving the location of the foam front as a function of time for our EFAR model system.

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TYPE SAND Report YEAR 2008
OSTIDOI
Results 126–150 of 181
Results 126–150 of 181