Impact of restrained thermal expansion on NPP Krško

Koc, Halilovič, Štok
2013

A goal of the analysis is the influence of the improper pipe shimming installation on the mechanical state of the primary loop piping.

Mechanical analyses of the Krško NPP primary system piping subjected to the restrained thermal expansion due to insufficient pipe shim clearances are addressed in the paper. Reduction of clearance between a pipe and respective pipe restraints preclude free thermal expansion of the pipe system during the heat-up, thus causing a rise of excessive contact forces in the pipe - pipe restraint pairs. This results in a development of unfavourable strains and stresses both in pipes and restraints. A series of numerical simulations was performed which demonstrate sufficient strength resistance of the Krško NPP primary piping, while supports are much more susceptible and need careful engineering consideration.