Main Steam Line Break Loads on BWR and ABWR Steam Dryer

Abstract

In a boiling water reactor (BWR) and advanced boiling water reactor (ABWR) a main steam line pipe rupture in the main steam piping system, hereafter called main steam (MS) line, will create a decompression wave and a pressure disturbance that moves through the MS line toward the reactor pressure vessel (RPV). It expands into a large region transmitting a compression wave at acoustic speed and spreads as an acoustic wave over the adjacent dryer plate. The initial acoustic pressure force on the dryer is expected to spread from an origin at the steam line attachment. It reflects back toward the RPV wall and again to the dryer until it dissipates. This is expected in a space that is not of uniform spacing because the dryer surface is nearly flat and the vessel wall is a curved surface. The acoustic load region is bounded by the steam dryer outer surface and RPV inner wall surfaces. In this paper, simplified, conservative modeling is applied in this approach to obtain reasonable bounding loads. The method is compared against the result of a detailed fine-structure Computation Fluid Dynamic (CFD) analysis using the same input data. Therefore, the simplified method may be used to quickly estimate conservative decompression forces on a dryer surface.