Thermal-hydraulic verification of SVEA 5x5 fuel

A full-scale thermal-hydraulic verification program of SVEA 5x5 BWR fuel was carried out in the ABB Atom FRIGG loop. The test sections consisted of 25-rod and 24-rod bundles, simulating sub-bundles of two fuel assembly versions, SVEA-100 and SVEA-96, respectively. Indirectly heated rods connected to several individual rectifier units made it possible to control the local power distribution in a simple way. The measurements covered single- and two-phase pressure drop, dryout and stability. For a number of different local power distributions extensive variations were made in mass flux, subcooling and pressure. The pressure drop measurements confirm that the two-phase multiplier correlation, originally developed for 8x8 fuel and verified for SVEA 4x4 bundles, remains valid also for the new lattice. The large dryout data base shows improvements over 4x4, dependent on mass flux and local power distribution. The loop stability testing supports the favourable in-core stability experience. (orig.)