Session: FSI-02-01 Tube Arrays - 1

Paper Number: 107312

107312 - Experimental Investigation of Combined Axial Flow and Jet Cross-Flow on PWR Mock-Up Array 

Some pressurized water reactors (PWRs) are designed to relieve the pressure increase in the barrel-baffle region associated with a loss of coolant accident (LOCA).  Flow holes, called LOCA holes, are introduced in the baffle plates to equalize the pressure difference between the core side and the barrel-baffle region. However, it was found that emanating jet flow from LOCA holes during normal operation induces fretting wear of the fuel rods at the spacer grid position. The effect of jet in transverse flow (JITF) on a PWR mock-up array should be investigated in order to determine the rod array response and, as a result, to set safe operating conditions for these reactors.

This research looks at the effect of axial flow velocity on the stability of a single-span 6x5 square rod bundle having a prototypical fuel assembly dimensions in some designs of pressurized water reactor cores. The axisymmetric flexible rods in the highly compact array are instrumented with four strain gauges to measure the two-dimensional rod displacements. Then, the responses of the rod bundle under combined flows (i.e. JITF) are measured at three test axial flow velocities, 1 m/s, 1.5 m/s, and 2.0 m/s. The experimental results show that the critical jet cross-flow velocity increases with the axial flow velocity. This could be due to the bending effect of axial flow on the jet flow (i.e. jet trajectory). The stability limits are collected to provide a stability map of the arrays subjected to the jet in transverse flow.

Presenting Author: Ibrahim Gad-el-Hak Polytechnique Montreal

Presenting Author Biography: Ibrahim is a research associate at Polytechnique Montreal. His area of specialization is dynamics and flow induced
vibrations of reactor components.

Authors:

Ibrahim Gad-el-Hak Polytechnique Montreal
Njuki Mureithi Polytechnique Montréal
Kostas Karazis Framatome Inc.