This paper describes resolving an operational vibration problem of a feed-water (RL) piping located in the Turbine Hall of Kola Nuclear Power Plant (Units 3 and 4) with the help of high viscous dampers technology. Intensive vibration of these lines raised concerns in actual operation state of the plant and piping safety especially prior to power capacity upgrading of the Kola 3 and 4. Power upgrading is associated with an increase of working media flow in piping and corresponding increase of piping vibration might lead to exceeding recommended and threshold levels.

The investigation covers the following items:

- 3D vibration measurement and walkdown of all vibrating RL-lines;

- Piping finite element models development;

- Simulation of dynamic excitation causing piping vibration close to measured one;

- Development and implementation of protective measures.

As a result of this work the minimal optimum number of high viscous dampers and their location along the lines were determined and the dampers were installed at the piping. VD type dampers of different size and construction were used.

Finally, the substantial reduction of RL piping vibration has been achieved providing more safety and extending service life for pipelines and their support systems.