RETRAN-3D results and one-dimensional analytical model for the critical power of a rod bundle with cosine-shape heating

The critical power of a rod bundle with BWR parameters is assessed. Therefore we apply the RETRAN-3D code [Peterson et al., 1998] and derive an analytical model for cosine-shaped heating. The value of the model and the numerical results is assessed by comparison with an experimental investigation, which was presented by [Mitsutake et al., 1997] together with a numerical sub-channel analysis using the COBRA/BWR code. The experiment we compare with considers a single full sized BWR fuel assembly of length L that is typical of the GE-10 fuel and is referred as ''high-burnup 8 x 8 fuel''; see figure 5b in [Inoue et al., 1995]. This type of fuel consists of 60 fuel rods and one large water rod in the centre. In the experiment electrical heaters in the individual fuel rods simulate the heat production, which varies axially and horizontally. (orig.)