Direct Sampling from NPP Components

A quick method to determine the current state of materials is a direct sampling of the primary circuit components and evaluation of the removed samples. Removing materials from operated devices using classical techniques represents an inappropriate interference with the integrity of assessed part. These “classical” destructive methods require subsequent repair of removed parts, including welding, heat treatment and a range of non-destructive testing.

To avoid such complications it is proposed to use a special quasi “non-destructive” sampling system. For this purpose it is planned to apply a special Rolls Royce equipment SSamTM-2. This device is designed as a universal system for the sampling of different devices without significantly affecting of the component surface and without necessity to repair or modify the component. The SSamTM-2 sampling system provides a remotely operated material sampling capability. The machine’s unique hemispherical cutter is able to remove a sample without mechanical distortion or thermal degradation of the material. The sampling procedure produces a depression in the base material approximately 0.8 mm deeper than the sample thickness.

SSamTM-2 machine by Rolls-Royce Company removes small slices of material using a cylindrical machine that has a diameter of approximately 70 mm and is 400 mm long.  Samples are removed using a hemispherically-shaped cutter, rotating at 10,000 rpm, mounted at one end of the machine. The cutter “scoops” through the material to remove the samples, which are approximately 25 mm in diameter and 2.5 mm in thickness. The resulting depression in the component is smooth and typically requires no post-sampling repair.

The first sampling of the main primary circulation pipeline at Bohunice Unit 3 was performed during the regular outage in 2013. Up to now, it has already been performed the surface sampling of primary piping, steam generator shells, compensator shell and reactor pressure vessels at Bohunice and Mochovce NPPs (2013-2017).

Removed samples are analysed to determine the components actual state. Due to a small amount of removed materials it is applied the SPT technique for determination of mechanical properties. After cutting and testing the remains of the samples are used for chemical analysis, micro hardness measurement, microstructure and sub-microstructure analysis.

 

Contact
Jana Petzová, VUJE, a.s., Slovakia,
Division for Diagnostic of Nuclear Power Components
jana.petzova@vuje.sk