Leak-Before-Break criteria and strength monitoring implementation impact on in-service inspection of RBMK primary circuit components

Abstract Major scientific and technical tasks of strength monitoring and surveillance in NPP RBMK operation are considered proceeding from the present-day requirements to safety insurance based on the circuit integrity concept. The application of the “Leak-Before-Break” Concept in the most complete and systematic definition corresponding to the approaches adopted in the U.S.A. will permit, in the case of success, to assess the compliance of RBMK primary circuit components with still more rigid requirements to the integrity and safety in comparison with the regulatory requirements acting at present in the R.F. nuclear industry. Procedures for evaluation of allowable size defects in pipelines with Dy800 depending on the loading levels are viewed. It is shown that the application of the LBB Concept criteria and the implementation of a strength monitoring system as a means of continuous operation quality control permit to assess the requirements to the sensitivity of metal control devices and to support NPP utilities to optimize ISI schedule.