Fuel configurations

The asymptotic burning rate behavior under saturated flame radiation conditions is a useful fact. It provides an upper limit, at pool-like fuel configurations of typically 1-2 m diameter, for the burning flux. Experimental values exist in the burning literature for liquids as well as solids. They should be thoughtfully used for design and analysis purposes. Some maximum values are listed in Table 9.3. 

The test conditions should be in steady-state operation at fixed low return boiler water temperature or steady-state operation at fixed outlet and inlet boiler water temperatures. Boilers are classified based on 10 criteria output function, capacity and configuration storage, fuel configuration, boiler flue gas/intake air system technology, power, boiler/bumer configuration, boiler water temperature control, burner combustion control, and installation. 

Fuel forms. The three alternative fuel forms for an LS-VHTR have very different characteristics and different refueling strategies. Trade studies will be required to determine the optimum reactor core and fuel configuration. Our preliminary assessment suggests that both pebble bed and stringer-type cores would be easier and faster to refuel than the Fort St. Vrain prismatic cores. 

Calculated and Experimental Keff for Close-Packed Fuel Configuration... 

Two concurrent evaluations were made for all probable (and a few improbable) fliel configurations that could be identified. One was made by reactor physics personnel using mactor design codes, while the other was made by nuclear criticality safety specialists using criticality safety codes. In addition to evaluating specific fuel configurations, basic data Such as K-infinite vs fuel-to-water ratios were tabulated for different enrichments, fuel particle sizes, water temperatures, boron levels, etc. 

Fuel configurations were separated into two states undamaged and damaged. For Ae undamaged state, the reactivity of an infinite array of mtact TMI-2 fuel assemblies was calculated for various coolant pressures, moderator temperatures, moderator densities, boron concentrations, and fuel pin pitchies. These and all infinite media calculations were performed using the cemiputer code XPOSE, an Exxon Nuclear revised version of LEOPARD. 

The drop of a heavy load on to the reactor or spent fuel pool could lead to a damage of the spent fuel or to a loss of the cooling capabilities and to a consequential release of radioactive materials. Additionally, if fuel is of sufficient enrichment, the normal boron concentrations that are maintained may not be sufficient to prevent a load drop from causing the fuel configuration to be crushed and result in criticality. 

What fuel configuration is specified by Technical Specifications to prevent flux peaking in a... 

A landmark series of experiments was successfully completed in ANL-Idaho s Experimental Breeder Reactor-II (EBR-II) to demonstrate the capability of a metal-fueled reactor to accommodate severe accidents without scram with very benign consequences, i.e., no failure of fuel assemblies or core structures. In earlier designs, such event sequences were considered as potential, extremely low-probability initiating events leading to core disruption. Similar tests were performed in the Fast Flux Test Facility (FFTF) with an oxide fuel configuration. 

Although certainly not conclusive, these results indicate it is probably feasible to design Pu Al fueled configurations with aluminum clad and relatively low europium content that exhibit both negative prompt temperature coefficients and negative moderator temperature coefficients over a wide range of exposures. 

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