Flow Accelerated Corrosion Monitoring of Safety Related Components in Ukrainian NPPs

Authors : Yu. Grebenyuk, S. Kostenko             

Company : State Nuclear Regulatory Committee of Ukraine
                   

Country : Ukraine

Topics

Flow Accelerated Corrosion
FAC management

Operation feedback

ABSTRACT :

One of the main requirement for NPP nuclear and radiation safety is to ensure the boundary integrity of operating medium circulation loop. The problem of provision on flow accelerated corrosion of NPP condensate-feed and vapor-and-steam paths piping and equipment is one of more important.

Normative documents establishing necessity of inspection: PNAEG-7-010-89 «Components and pipelines of nuclear facilities. Welds and surfacing. Rules of inspection», PNAEG-7-031-91 «Unified methods of measurement for base metal (semiproduct), weld and surfacing of nuclear facility components and pipelines. Ultrasonic inspection. Thickness measurement of monometal, bimetal and anti-corrosion surfaces», AIEU-10-09, AIEU-9-04 «Standard programs for operating inspections».

Corrosion monitoring of piping and equipment for VVER-1000 running the «Standard programs for operating inspections» (AIEU-9-04) and carry out by ultrasonic inspection. There are turbine extraction steam system, reheat steam system, MSR drain system, high pressure heater drain system and high pressure feed water pump outlet pipe. Serious accidents by reason of flow accelerated corrosion do not suffer on Ukrainian NPP in life time.

But the State Nuclear Regulatory Committee of Ukraine remains concerned about effects resulting in feeder failures in life time extension. This concern is based on current limitations in both understanding of degradation mechanisms and capability of in-service inspection technique.   It is the regulator's view that reliable assessment of integrity of NPP condensate-feed and vapor-and-steam paths piping and equipment requires the integration of different aspects from a mechanistic understanding of degradation, material behavior, modeling of physical-chemical processes, creation of software and execution of numerical-experimental works, development and introduction of in-service inspection methods.