Theoretical analysis of fuel vibration in fast burst reactors

The fuel of a fast burst reactor is subject to vibrations occasioned by rapid temperature rise when the reactivity in the core is suddenly increased. This paper covers an analysis of such fuel vibration in the fast neutron source reactor ''YAYOI'' under pulsed operation, with use made of the finite element method, and adopting as parameters the rate of temperature rise and the spatial temperature distribution. An analytical solution is also obtained assuming that the fuel is under plane stress, for comparison with the results derived by the finite element method. Agreement between the two results is very good within the bounds of the plane stress condition. The results indicate that the amplitudes of dynamic displacement and stress increase with rising rate of energy release. The relation between these quantities is presented. (auth.)