Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Roughness of the nuclear reactor piping inner surface depending on operating time

9/30/2019 2019 - #03 Global safety, reliability and diagnostics of nuclear power installations

Trofimov M.A. Globa R.A.

DOI: https://doi.org/10.26583/npe.2019.3.08

UDC: 621.644, 621.9.08

During operation of nuclear reactors, there are various factors that affect the NPP piping leading to erosion of the pipe inner surface and its increased microrelief (roughness). Metal corrosion occurs and propagates faster on the surface having a higher value of the roughness parameter. Failures through erosive wear of the parent metal take place predominantly in the pipe bending area. The roughness of the pipe inner surface has a sizeable effect on the signal attenuation in the process of the pipe wall ultrasonic inspection. Defective main pipeline segments were cut out as part of preventive maintenance from which samples having different operating times were taken. Five defective pipe segments of the austenitic 12Kh18N10T-grade steel cut out from a high-pressure preheater’s piping and defective pipe segments of the perlite-class grade 20 steel with different operating times were used to determine experimentally the actual value of the pipe inner surface roughness. In addition, one piece of a new ∅273×12 pipe of 12Kh18N10T steel and one piece of a ∅159×6 pipe of grade 20 steel were cut out. The inner surface roughness in different segments was measured. Dependences of the roughness value on the operating time and the pipe segment type were obtained. As the result of the study, company specimens were obtained the insides of which had the surface roughness being in accordance with the different pipe operating times. This made it possible to take into account the effects of the pipe inner surface roughness on the signal attenuation in the process of the weld integrity ultrasonic testing and during ultrasonic measurements of the weld adjacent zone grain size value following the weld repair.

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life extension surface roughness metal corrosion operating conditions Elcometer 7061 Marsurf PS1 roughness meter parent metal preventive maintenance