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Widening concrete cracks in Seabrook Nuclear Station

Nuke Plant Cited Over Widening Concrete Cracks, The Town Common by Stewart Lytle, Thursday August 1
2, 2021  REGIONAL – The Nuclear Regulatory Commission (NRC) slapped the wrist of Seabrook Station Thursday for not projecting the likely deterioration of its structural concrete caused by alkali-silica reaction (ASR).

In a 20-page quarterly inspection report, the NRC issued a Green finding, its lowest level of citation, to NextEra. It found that the staff of the New Hampshire nuclear plant “did not adequately account for the future progression of ASR in their prompt operability determination for several Seabrook structures. 

“Specifically, NextEra staff did not trend and project the periodic threshold monitoring data for the affected structural elements to ensure the structures would remain capable of performing their safety functions to the next scheduled inspection.”

Starting last fall, the NRC conducts inspections at Seabrook Station every six months. 

During their walk-through of the plant, the inspectors also found that three structures – the emergency feedwater pumphouse, service water cooling tower and control and diesel generator building – had widening cracks that exceeded the design limits. The mechanical penetration area also has cracks that are approaching the limits. 

Once a threshold limit is exceeded, more frequent inspections are required and may result in corrective action such as a structural modification to alleviate the condition, the report stated.

The 30-year-old atomic reactor has concrete infected by ASR, an irreversible type of concrete degradation, caused by water reacting with the concrete. It has been called “concrete cancer.” 

The inspectors were also concerned with the degradation of the steel rebar in the concrete structures. …………….

relative to Seabrook’s ASR testing and monitoring program.  While the Board ultimately approved the plant’s concrete management program, it did so with four new license conditions that direct NextEra Seabrook to conduct much more frequent and stringent monitoring and engineering evaluations in a number of situations. They were:

  • NextEra must increase the frequency of monitoring from 10 years to six months.
  • NextEra must develop a monitoring program to anticipate or monitor rebar failures.
  • If the cracks in the concrete get worse, NextEra must monitor the concrete more often. 
  • Each concrete core extracted from Seabrook must undergo a detailed microscopic petrographic evaluation to detect microcracks. 

“It’s frightening to think that were it not for C-10’s challenge, the inspection interval referenced in this report may have been as long as a decade,” Treat said. “Now NextEra has to perform them every six months. But collecting data without using it to model future trends in concrete degradation is of little use.”

August 16, 2021 - Posted by | safety, USA

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