Results of the QUENCH-12 reflood experiment with a VVER-type bundle

The QUENCH-12 experiment investigated the effects of VVER materials and bundle geometry on core reflood, in comparison with test QUENCH-06 (ISP-45) with western PWR geometry. While the PWR bundle simulator is made of a single unheated rod, 20 heated rods, and 4 corner rods arranged on a square lattice, the VVER bundle uses 13 unheated rods, 18 heated rods and 6 corner rods, arranged on a hexagonal lattice. The test was conducted with broadly the same protocol as QUENCH-06, so that the effects of VVER characteristics could be more easily observed. Ths involved pre-oxidation to a maximum of about 200 μm oxide thickness at a temperature of about 1200degC, followed by a power ramp until a temperature of 1800degC was reached, then reflood with water at room temperature was initiated. The test was successfully conducted at the Karlsruhe Research Center on 27 September 2006 in the frame of ISTC project 1648.2. The determination of the test protocol was based on numerous calculations with SCDAP/RELAP5, SCDAPSIM and ICARE/CATHARE. The amount of hydrogen released in the quench phase (24 g) is six times higher than in QUENCH-06. This may be attributed to the longer excursion time, damaging of the cladding surfaces due to the breakaway oxidation and oxidation of locally formed melt. (author)