Spacer Grid Thermal Hydraulics Program

Through the joint efforts of the Pennsylvania State University and the United States Nuclear Regulatory Commission, an experimental Rod Bundle Heat Transfer (RBHT) facility was designed and built. The purpose of the facility is to collect fundamental rod bundle thermal-hydraulic data that can be used to develop and validate models for system codes used by the nuclear industry.

The facility is a once through electrically heated 7x7 rod bundle with prototypical PWR geometry. Spacer grids with mixing vanes are present and the instrumentation is specifically located such that the effect of the spacer grids on thermal-hydraulic phenomena such as pressure drop and heat transfer can be captured.

To date, constant reflood, steam cooling, steam cooling with droplet injection and level swell experiments have been conducted under the supervision of the late Dr. Lawrence Hochreiter. Currently, the facility is being utilized under the Spacer Grid Thermal-Hydraulics (SGTH) program to study the effect of spacer grids under post CHF steady and oscillatory reflood conditions. Preliminary results show that for the same nominal reflood rate, oscillations in the flow decrease peak clad temperature but delay quench time.