Liquid-metal Fast Breeder Reactor Safety Research Articles

Modeling of Bubbly and Annular Two-Phase Flow in Subchannel Geometries with BACCHUS-3D/TP

The theoretical and computational bases of the BACCHUS-3D/TP computer program are reviewed. The computer program has been developed in the frame of the liquid-metal fast breeder reactor safety project at the Kerforschungszentrum Karlsruhe and is used for thermal-hydraulic analysis of nuclear fuel bundles under normal and accident conditions. The present program combines two models and solution procedures previously used separately, namely, an improved slip model and a separated-phase model. The first model uses mixture equations and accounts for slip between the phases, whereas the latter uses separate continuity and momentum equations. At the present stage of development, both assume thermodynamic equilibrium. Techniques used to affect smooth transitions between the two models are described, including treatment of frictional pressure drop and solution of the Poisson pressure and momentum equations. A detailed derivation of the computation of mass transfer between the phases is given because it is a central and novel feature of the model. A summary of validations performed to date, together with the quantities measured and compared with computations is given in tabular form.

Experimental and Numerical Investigations of Sodium Boiling Experiments in Pin Bundle Geometry

In the framework of the liquid-metal fast breeder reactor safety analysis program, out-of-pile sodium boiling experiments have been run at Kernforschungszentrum Karlsruhe in a 37-pin bundle simulating a fast reactor subassembly. Three representative runs are analyzed in detail in terms of experimental evaluation and numerical simulation. The latter is performed with the three-dimensional, two-phase flow computer code BACCHUS-3D/TP, which describes coolant behavior in bundle geometry. The comparison between computed and experimental results has helped in correlating data from different instruments, thus allowing deeper insight into the details of the boiling behavior. Experimental data also provided a valuable code verification. By modifying the drift-flux model, the code validity range has been enlarged.

Thermocapillary-Induced Breakup of Molten Cladding Films

The fragmentation of molten cladding films into rivulets and single waves is investigated. This problem is especially relevant to liquid-metal fast breeder reactor safety analysis because of its impact on the flow regime of the clad melt. Among other effects, various instabilities may contribute to film breakup. In the axial direction, the Kelvin-Helmholtz instability can arise. As the Sandia transient axial relocation experiments frequently exhibit, an azimuthal fragmentation process also occurs. Consequently, another instability due to thermocapillarity is proposed.

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Boiling and Dryout Behavior in a Liquid-Metal Fast Breeder Reactor Subassembly Bundle Under Low Heat Flux and Low Flow Conditions

For certain postulated severe accident conditions such as a loss of piping integrity and a loss of heat sink in connection with liquid-metal fast breeder reactor safety analysis, the process of dec...

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An Evaluation of Fuel Motion in Recent TREAT Experiments with Liquid-Metal Fast Breeder Reactor Fuel

In the past few years since the introduction of the 1.2-m-high Hodoscope Collimator, a number of TREAT experiments have been conducted with liquid-metal fast breeder reactor (LMFBR) fuel having 864- to 914-mm-long active fuel columns. The purpose of this study was to examine the fuel-motion results obtained from the hodoscope for some of these tests by relating the importance of the fuel motion to the associated LMFBR safety issues. The experiments discussed here represent the current limit in the state-of-the-art in LMFBR safety testing in the TREAT reactor. 8 refs.

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Progress in liquid-metal fast breeder reactor safety research and development—An overview of the issues

The safety of Liquid-Metal Fast Breeder Reactors has been the subject of massive world-wide research and development. This paper attempts to give a brief overview of the R & D directed toward an understanding of those events that could contribute to the release and transport of fission products and transuranic elements up to the boundary of the reactor secondary containment system.

Progress in Liquid-Metal Fast Breeder Reactor safety research and development—An overview of the issues : M. H. Fontana. Prog. Nucl. Energy2, 199 (1978)

Progress in Liquid-Metal Fast Breeder Reactor safety research and development—An overview of the issues : M. H. Fontana. Prog. Nucl. Energy2, 199 (1978)

The Production of Molten UO2Pools by Internal Heating: Apparatus and Preliminary Experimental Heat Transfer Results

The capability for removal of heat from a pool of molten fuel under postaccident conditions is an important consideration in liquid-metal fast breeder reactor safety analysis. No experimental data for pool heat transfer from molten UO/sub 2/ under conditions simulating internal heat generation by fission product decay have been reported previously in the literature. An apparatus to provide such data was developed and used to investigate heat transfer from pools containing up to 7.5 kg of UO/sub 2/; the internal heat generation rates and pool depths attained cover most of the ranges of interest for postaccident heat removal analysis. It was also observed in these studies that the presence of simulated fission products corresponding to approximately 150,000 kW-day/kg burnup had no significant effect on the observed heat transfer.

Mathematical and Computational Techniques Employed in the Deterministic Approach to Liquid-Metal Fast Breeder Reactor Safety

This paper reviews major computer code packages presently utilized or under active development in the U.S. for deterministic liquid-metal fast breeder reactor safety analysis. Although the review covers the very large accident domain from intact predisassembly geometry through radiological consequences, an attempt was made to categorize code systems according to the physical problems solved to provide a working orientation for those not intimately involved in the field. Mathematical and computational aspects were given particular focus in the hope of stimulating development of more efficient numerical approaches in those areas of greatest need.

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