Eerikäinen, Lauri

Keskinen, Rauli

Saarenheimo, Arja

A dynamic post-analysis is presented for a sudden pipe break which occurTed in the main feed water ~ystem of the VVER 440 type PWR plant Loviisa 2 on February 25, 1993. A thermal hydraulic code TMOC, based on the method of characteristics, is first used to determine the induced rapid two phase fluid transients. The resulting pressure and momentum flux histories are then applied as an excitation in a nonlinear structural dynamic analysis which makes use of the general purpose finite element code ABAQUS. The permanent relative displacement of the broken pipe ends is finally compared with the value observed after the event. An underestimate of some 30% may for the most part be attributed to scant experimental data and uncertainties in boundary conditions. Assumptions regarding impact against a nearby beam structure and the dynamic stress-strain curve of the fenitic pipe material strongly affect this comparison

Dynamic post-analysis of a feed water pipe at the Loviisa nuclear power plant

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