Behavior of nuclear fuel during a reactor accident

This page describes how uranium dioxide nuclear fuel behaves during both normal nuclear reactor operation and under reactor accident conditions, such as overheating. Work in this area is often very expensive to conduct, and so has often been performed on a collaborative basis between groups of countries, usually under the aegis of the Organisation for Economic Co-operation and Development's Committee on the Safety of Nuclear Installations (CSNI).

This is a false colour tomography picture of a bundle (FPT1) of 18 irradiated fuel rods (23 GWd/tU mean burn-up) degraded under steam as part of the PHEBUS set of experiments. The black and blue is for areas of low density while red is an area of high density. It can be seen that the fuel has failed mechanically and has formed a pool near the bottom of the bundle. The bottom of the bundle did not melt.

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