NUCLEAR POWER PLANT COMPONENT RELIABILITY UNDER FLOODING CONDITIONS (INL)

Working with Idaho National Laboratory, Dr. Pope is engaged research focusing on nuclear power plant component reliability under flooding conditions. This research includes smoothed particle hydrodynamic (SPH) modeling, small scale component testing, wave system generation design, mathematical reliability modeling, and full scale component testing design work. In 2016 full scale component testing commenced. Additionally, renovation of existing lab space was completed in 2016 that will include the addition of a 2,000 gallon capacity reservoir and testing bay for full component testing. The research team decided that non-loadbearing structural components should be tested first so that methodologies can be developed before more complex components, such as electrical and mechanical components, are tested. A non-loadbearing structure found in Nuclear Power Plants (NPPs) are doorways. Doorways play a significant role in determining the overall flooding risk because they provide an easy point of access for water to enter a room and cause subsequent damage.  To be able to better understand when and how doorways fail a Portal Evaluation Tank (PET) (Fig. 1) was designed and built to allow for testing of doors under flooding conditions. A perforated center column (Fig. 2) with perforations to evenly distribute water to all the walls of the tank and thus avoid applying additional water jet force to the door was also designed and utilized.

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Dr. Pope and his team approached the analysis and use of the data from the flooding experiments through fragility models.  While traditional fragility models are often limited by simplistic design and excess conservatism, Dr. Pope and his team avoid those limitation by using a data-informed and flexible approach called Bayesian fragility modelling through event-driven regression modelling.

Based on the experiments conducted, door failure during rising water events depends on water depth, flow rate into the area, door orientation (opening into or out of the room), door material, and the door hardware.  Two types of doors were tested to failure: hollow core and steel.  Hollow core doors tended to fail by breaking (Fig 3) while steel doors failed due to hardware failing (Fig 4) or bending (Fig 5).

From the six hollow core door experiments, the lowest failure depth was 0.71 m (28 in.) and the highest failure depth was 0.99 m (39 in.). From the twelve steel door experiments, the average failure depth was 0.89 m (35 in.) regardless of flow rate while the highest failure depth for steel doors occurred at 1.07 m (42.1 in.) when a new latch handle was used.