Irregular results of the thickness measurements on the low pressure regeneration piping of NPP Dukovany

Topic :

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ABSTRACT :

Regular thickness measurements within the scope of a standard FAC program have been made on the low pressure regeneration piping of NPP Dukovany. The segmented elbow on this line exhibited highly irregular pattern of measurement results. Majority of the data points have shown reduction of thickness up to 1/4 of the nominal wall thickness. However, there was about one third of the data points randomly scattered within the matrix with wall thickness close to the nominal values. The measurement equipment has been repeatedly tested for defects with negative results. Since this situation has been evaluated as unsafe for the line operation, the elbow has been replaced. No significant FAC damage has been observed on the inner surface of the piping. Subsequent X-ray and metallographic analysis has shown that there is plenty of large inclusions present in the material of the elbow. Those inclusions act as material discontinuity and have adverse effect on the thickness measurement precision.

Speaker Biographical Information

M. Postler.

Working in the Nuclear Research Institute Rez, Czech Republic since 1995. Active mostly in the field of failure analysis, material studies and flow accelerated corrosion. Participation on numerous national and international projects.