Today’s NRC Event Reports include a problem with safety-related electrical equipment at the FitzPatrick nuclear power plant in New York. On Wednesday, plant operators discovered during pre-installation testing that three of four Rosemount model 710 trip units would not turn on. The units were returned to Rosemount, where it was discovered that resistors in the start up units had failed.
The safety significance of the failed units, according to the Event Report: “…some of the applications for the trip unit require it to energize to perform the associated safety functions. Therefore, the identified failure mechanism could have represented a substantial safety hazard if the components had been installed….”
FitzPatrick attempted to minimize the potential impact of the defect, saying: “The condition had no actual safety consequences as the deficiency was identified during pre-installation testing and if installed without pre-installation testing, the system could not have passed post maintenance testing.”
What is wrong with that is, first, that a crucial safety system left the manufacturer with a significant defect that the maker failed to identify, and, second, that we don’t know how many of the potentially defective parts may have been sent to other nuclear power plants. Rosemount Nuclear Instruments identifies itself on its website as “the world leader in the design and manufacture of process instrumentation” and includes the tagline: “Make Every Nuclear Facility in the World Safer by Using Our Instruments.”