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PAC AE News - Bravo (B) steam generator

Loose Parts Monitoring System Performs Flawlessly


An acoustic measurement from the LPMS that indicates metal-to-metal impact.

In nuclear power plants the Loose Parts Monitoring System (LPMS) “listens” for metal to metal impact in the reactor cooling system to prevent the dangerous escape of irradiated water in to the environment.

While these events do not happen often, public and plant safety is a primary concern, potentially saving the plant millions of dollars in repairs and damages.

In 2005, MISTRAS installed a Loose Parts Monitoring System at a regional power company’s nuclear power plant in the Southeastern U.S. For nine years it sat quietly, hardly noticed in the back corner of the control room. That all changed in the early morning hours of April 8.

MISTRAS’ Power Generation group received a call at 3 a.m. requesting support for sounding alarms coming from the LPMS. The plant's automated notifications were occurring at 5-10 times per-second during the critical heating stages and causing great concern in its return to normal power generation. A small team of MISTRAS employees including our Manager of Research Contracts and Applications, our Director of Custom Automation and our Director of Acoustic Emission Products, comprised a response team to evaluate the events.

Over the next three days, the team worked around the clock, alternating responsibilities, analyzing thousands of data files, maintaining constant communications with the plant to determine the locations of movement, size of the loose parts, and their next course of action. Working in part of the plant’s response team, the three oversaw the LPMS through changes in flow conditions and plant shutdown procedures in order to stabilize the reactor, retrieving the loose part and allowing repairs to occur.

Three days later, plant personnel retrieved a metallic part from the Bravo (B) steam generator, repeatedly impacting the heat exchanger's tube sheet. The stainless steel part (weighing .5 lbs.) went undetected, potentially causing considerably more damage, like a radioactive coolant leak or an environmental hazard.

The waveform above is one of the many impacts effecting the steam generator wall, detected by the MISTRAS Loose Parts Monitoring System, which represents the sophisticated monitoring, diagnostics and analysis MISTRAS Products and Systems division provides to the power industry. Read More...

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