Feasibility of Improving BWR Performance Using Hydride Fuel

Neutronic and thermal-hydraulic analyses have been performed for U-ZrH{sub 1.6} hydride fueled BWR cores considering a wide range of core design variables: (1) Fuel rod outer diameter in the range from 0.6 to 1.6 cm; (2) Lattice pitch-to-diameter ratio, P/D: 1.1 to 1.6; (3) Several uranium enrichment levels. The design constraints considered include minimum excess reactivity, negative Doppler coefficient, negative void coefficient, MCPR, peak and average fuel temperatures, peak clad surface temperature, coolant inlet temperature, coolant exit quality, coolant pressure drop, as well as constraints imposed by vibrations and structural considerations. It was found that U-ZrH1.6 fuel can significantly simplify the BWR fuel bundle design by eliminating water rods, partial-length fuel rods and wide water channels and by using a single radial enrichment. A 10 x 10 hydride fuel bundle having the volume of the reference 9 x 9 oxide fuel bundle can be loaded with 35% more fuel rods having a similar diameter and lattice pitch. As a result of this along with flatter pin-by-pin power distribution the hydride fuel bundle can deliver {approx} 40% higher power density than the reference oxide fuel bundle, provided the core coolant pressure drop could be increased by {approx} 50%. Alternatively, the hydridemore » fuelled core can be designed not to exceed the reference BWR core pressure drop and to deliver the reference power while using {approx} 40% shorter fuel bundles. The hydride fuelled core has a more negative fuel temperature coefficient of reactivity and a less negative void coefficient of reactivity. These trends are expected to enhance the safety and improve the stability of hydride fueled BWRs. A thorough evaluation of hydride fuel and its implementation possibilities in BWRs is recommended. (authors)« less