Qualification of Mechanised Ultrasonic Inspection of Pipings in Finnish Nuclear Power Plants
R. Paussu, Fortum, Finland; J. Pitkänen, P. Kauppinen, VTT, Finland
ABSTRACT
Finnish national qualification strategy is based on ENIQ Methodology and published Recommended Practices. The qualification of mechanised ultrasonic inspection for piping welds is one of pilot cases implemented in Finland. The qualification approach, experiences, difficulties and lessons learned are described in the paper. Ultrasonic inspection of critical sections of pipelines will be mechanised in the future to improve the reliability of inservice inspections and to reduce the radiation dose of inspection personnel. For this purpose, a new inspection system with robust scanner and probe holders was developed. The qualification performed covers mechanised ultrasonic inspection of pipelines for both BWR and VVER plants in Finland. Definition of input data and qualification levels are playing an important role in the qualification process. The purpose of qualification was to demonstrate the capability of inspection system to detect and discriminate the defined defects. The results of open trial proved that circumferential worst case defects are detected also by scanning only from one side of the weld joint. The inspection procedure was optimised during the qualification process. Technical justification forms a very important part of qualification. In this pilot case, the technical justification was implemented on the basis of physical reasoning and evidence gained from laboratory trials, other qualifications and results of relevant field inspections. This pilot case was used for practising co-operation between qualification body and vendor. Model reports, images of findings, summaries of results, the structure of qualification dossier and the qualification rules for mechanised UT inspections are established based on this pilot case. Those documents will complete the Finnish strategy document for qualification.
Publication Source: 3nd International Conference on NDE in Relation to Structural Integrity for Nuclear and Pressurized Components, November 14-16, 2001, Seville Spain. Publisher: Tecnatom s.a. - [Homepage]
