The licensee identified a finding of very low safety significance (Green) and associated
NCV of
TS 3.7.1,
Residual Heat Removal Service Water [RHRSW] System; which requires, in part, that two
RHRSW subsystems shall be
operable in Modes 1, 2, and 3 or per Condition A, One
RHRSW subsystem
inoperable; the
RHRSW subsystem must be restored to
OPERABLE status within 7 days or the applicable conditions and required actions of Limiting Condition forOperations 3.4.7,
Residual Heat Removal Shutdown Cooling System Hot Shutdown, for
RHR shutdown cooling made
inoperable by
RHRSW System must be entered. Contrary to the above, on March 27, 2017, the licensee exited the requirements in
TS 3.7.1, with a Tag Section still hanging, rendering B
RHRSW subsystem
inoperable, while in Mode 1. This was identified by the licensee when the maintenance organization notified operations that work was complete, and the Tag Section was released. The licensee reentered
TS 3.7.1, Condition A, entered the issue as
CAP 1554105 and assigned a Human Performance Event Investigation. A crew clock reset was also taken as well as communicating lessons learned to the entire plant organization.This finding was more-than minor because the performance deficiency wasassociated with the equipment performance attribute of the
Mitigating Systems Cornerstone and adversely affected its objective to ensure the availability and capability of systems that respond to
initiating events to prevent undesirable consequences. Specifically,
RHRSW System is designed to provide cooling water for the
RHR System heat exchangers, required for a safe reactor shutdown following a Design Basis Accident or
transient. Two
RHRSW subsystems are required to be
OPERABLE to provide the required redundancy to ensure that the system functions to remove post-accident heat loads, assuming the worst case single active failure occurs coincident with the loos of offsite power. The finding was of very low safety significance (Green) because it was not a design or qualification deficiency, did not involve an actual loss of safety system, did not represent actual loss of a safety function of a single train for greater than its TS allowed outage time, and did not represent an actual loss of function of one or more non-Tech Spec Trains of equipment designated as high safety-significant in accordance with the licensees
maintenance rule program for >24 hours.
