Critical Reflections about Doel3 & Tihange2

Integrity reactor vessels Doel 3 and Tihange 2

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Figure 18: Effect of unequal distributed flaws on the roundness of the reactor vessel.

2. Boundary conditions for flaw simulation in shell segment. As far as the authors could understand the modelling of the flaws, a small segment from the reactor vessel shell has been selected for finite element simulation. The boundary conditions are the stresses resulting from the internal pressure in the reactor and the top of the segment can move parallel with the bottom. The latter boundary condition holds in the case the rest of the shell is solid, however due to the high flaw density, this can be an underestimation of the resulting stresses. [ 18 ] p77-81. Also the fact that only a segment is selected can lead to an underestimation of the resulting stresses. The hoop stress in the vessel wall is only pure tensile in the case that the vessel is perfectly cylindrical and the material is homogeneous. Due to the flaws, the material isn’t homogeneous any more, which has the same effect as unroundness, and additional bending stresses are introduced. This effect is demonstrated in figure 18. 3. Vibration levels are unknown. 4. Opinion of Westinghouse. The reactor is designed by Westinghouse, however the author has not found any opinion of Westinghouse about the implications of the flaws found in the reactor vessels in the reports available at the FANC website.

R.Boonen & J.Peirs

May 18, 2017