Event Notification Report for October 09, 2018

UNPLANNED LOSS OF EMERGENCY RESPONSE EQUIPMENT

"At 2115 CST on October 9, 2018, South Texas Project Electric Generating Station (STPEGS) experienced an unplanned loss of the Integrated Computer System (ICS) to the Emergency Operations Facility (EOF). The loss of ICS resulted in a major loss of emergency assessment capability to the STPEGS Emergency Operations Facility (EOF) for greater than 75 minutes. Assessment capability has been verified to be available in the Unit 1 and Unit 2 Technical Support Centers (TSC) and the Unit 1 and Unit 2 Control Rooms.

"This report is being made pursuant to 10 CFR 50.72(b)(3)(xiii), any event that results in a major loss of emergency assessment capability, off site response capability, or off site communications ability.

"The NRC Resident Inspector has been informed."

The cause of the unplanned loss is currently being investigated and compensatory measures are in place.


* * * UPDATE ON 10/10/18 AT 0951 EDT FROM RICK NANCE TO PHIL NATIVIDAD * * *

Integrated Computer System was returned to service as of 0810 CDT on October 10, 2018.

Notified R4DO (Gepford) and CAT via email.

CONTROL ROOM EMERGENCY VENTILATION AC SYSTEM INOPERABLE

"On October 9, 2018 at 2002 CDT the Control Room Emergency Ventilation Air Condition (CREV AC) system was in the process of being returned to service following maintenance. During the return to service, the end bell on the CREV AC Condenser developed a significant leak requiring isolation. No work was performed on the CREV AC Condenser during the work window.

"The CREV AC system maintains a habitable control room environment and ensures the operability of components in the control room emergency zone during accident conditions.

"This notification is being made in accordance with 10CFR50.72(b)(3)(v)(D), "Event or Condition That Could Have Prevented Fulfillment of a Safety Function " because the CREV system is a single train system required to mitigate the consequences of an accident."

The NRC Resident Inspector has been notified.

* * * RETRACTION AT 1714 EST ON 11/14/2018 FROM JASON SWAIN TO JEFF HERRERA * * *

"The purpose of this notification today (November 14, 2018) is to retract the ENS Report made on October 10, 2018 at 0326 EDT (ENS Report #53657).

"Upon further investigation, it was determined that while the CREV AC system was out of service for planned maintenance and inoperable, the return to service valve sequencing caused an in-rush of residual heat removal service water (RHRSW) at 300 psig dead-heading into the refrigeration condensing unit (RCU). Previous normal sequencing had refilled the RCU with service water which is supplied at 100 psig. This unexpected higher than normal pressure on the RCU end bell gasket (rated at 150 psig) caused the gasket to be pushed from its normally seated position to allow a leak path. The gasket was not previously leaking; upon removal was inspected and no evidence of premature cracks or tears were found.

"The CREV AC system leak was induced by an improper coordination of return to service activities at the time of discovery, and the leak path was not previously present. This was not a latent failure. As such, a pre-exiting condition that could have prevented the fulfillment of a safety function did not exist, and based on this information, ENS Report# 53657 is being retracted.

"Note: On October 11, 2018 at 1330 hours CDT, the CREV RCU System gaskets were replaced and the system was returned to service under the properly sequenced tagout and was returned to Operable status.

"The NRC Resident Inspector has been notified. "

Notified the R3DO (Peterson).

60-DAY OPTIONAL TELEPHONIC NOTIFICATION OF INVALID SPECIFIED SYSTEM ACTUATION

"This 60-day telephone notification is being made in accordance with 10 CFR 50.73(a)(1) and 10 CFR 50.73(a)(2)(iv)(A) to provide information pertaining to an invalid Engineered Safety Feature actuation signal.

"On October 9, 2018, Arkansas Nuclear One, Unit 2 was in refueling Mode 6, when a vital inverter failed while aligned from its alternate power source causing a loss of one of four vital instrument buses. The loss of the instrument bus resulted in one of the four engineered safety feature protection channels to enter a tripped state. Because one of the other four channels was already in a tripped state in support of a channel power supply replacement activity, two out of four protection channels were now in the tripped state resulting in a Safety Injection Actuation Signal, Containment Spray Actuation Signal, Containment Cooling Actuation Signal, Recirculation Actuation Signal, Emergency Feed Actuation Signal, and Containment Isolation Actuation Signal.

"In general, only one train of equipment is protected and assumed to be available during Mode 6 operations. Due to the defense-in-depth plant configuration in Mode 6, which is intended to avoid inadvertent start of emergency systems, the resulting actuations caused no adverse impact to Shutdown Cooling or Spent Fuel Pool cooling operations. At least one train of the following systems was aligned for automatic actuation:

"Service Water
Emergency Diesel Generator
Containment Penetration Room Exhaust Fan
Other non-essential components which are shed or realigned upon safeguards actuation

"The few systems and components that were aligned for automatic operation responded as designed, including containment isolation valves and valves associated with the above systems (if aligned for automatic operation). The Service Water system was already in operation and, therefore, no Service Water pumps actuated. All systems and components which were capable of automatic operation performed as designed.

"The Emergency Diesel Generator started but did not synchronize to the bus. No safety injection occurred to the core.

"This actuation was caused by equipment failure and was not an actual signal resulting from parameter inputs. The affected actuation signals do not perform a safety function in Mode 6 and are not required to be available or operable. Therefore, this actuation is considered invalid.

"This event was entered into ANO's corrective action program for resolution. This event did not result in any adverse impact to the health and safety of the public.

"In accordance with 10 CFR 50.73(a)(i) a telephone notification is being made in lieu of submitting a written Licensee Event Report. The licensee has notified the NRC Resident Inspector."

PART-21 - RHR SHAFT SEAL O-RING SHEARED DUE TO MANUFACTURER DEFECT

The following is a synopsis from the Part 21 report received via e-mail:

During an outage at Prairie Island Nuclear Generating Plant, the licensee replaced the mechanical shaft seal on the 11 Residual Heat Removal (RHR) pump. During subsequent post maintenance testing, it was found that there was significant seal leakage on the pump. An evaluation was completed on December 4, 2018, which determined that it was a substantial safety hazard. The licensee has shipped back six seals to Framatome to be tested. It was determined that the cause of the failure was improper O-ring installation by the manufacturer. Discussions with Framatome indicate that only Prairie Island Nuclear Generating Plant is effected by this defect, but investigations are still ongoing.

Affected Plant:
Region 3: Prairie Island Nuclear Generating Plant

NUCLEAR GAUGE SHUTTER STUCK OPEN

The following is a summary from a phone call with the licensee:

The licensee decided to remove seven nuclear gauges from service. Ronan Engineering performed the removal. During the device removal on October 9, 2018, one device was found to have a stuck shutter in the open position. The gauge was removed and repaired.