The scraping operation should satisfy the following requirements:

1. A component should be reusable, i. e. scraping operation should not lead to loss of integrity and reduction in service life of a component,
2. the dimensions and volume of the removed samples should be sufficient for carrying out required destructive as well as nondestructive examination of the samples, and
3. the scraped samples should be free from unwanted contaminants.

A scraping technique has been developed to obtain sliver samples from specified locations within the bore of sagged pressure tubes of Pressurised Heavy Water Reactor (PHWR) meeting all the three aforementioned requirements.

These sliver samples have been used for measurement of equivalent hydrogen concentration. Characteristics of sliver samples, i. e., weight, shape and number of chips, are very sensitive to inside diameter, ovality, straightness and material properties of the pressure tube. Hence once scraping tool is qualified on the basis of a pressure tube of standard dimensions and material properties, characteristics of sliver samples may reveal deviations in dimensional and material properties. Tubes subjected to scraping have been qualified for continued fitness for operation on the basis of visual examination, liquid penetrant examination, ultrasonic examination, microhardness measurement, microscopic examination, contour graph, cast impression and surface finish assessments carried out on prototypes. Profile of the scraped area has been noted to merge smoothly with internal profile of the pressure tube and does not lead to any ultrasonic indications which can be interpreted as flaw.

In order to save radiation dose to operating personnel, a remotised driving system has been developed for axial positioning of scraping tool in the pressure tube of coolant channel.

In principle, scraping technique can be extended for the direct evaluation of critical material conditions of tubular products in other industries.

This paper describes different stages in qualification of the technique, typical profile of sliver samples, evaluation of scraped region of pressure tube for reusability and features for remote operation.