Event Notification Report for February 25, 2010

INVALID ACTUATION OF CONTAINMENT ISOLATION VALVES

"This 60-day notification is being made in accordance with 10 CFR 50.73(a)(1), which states that in case of an invalid actuation reported under 10 CFR 50.73(a)(2)(iv)(A), other than the actuation of the Reactor Protection System (RPS) when the reactor is critical, the licensee may provide a telephone notification to the NRC within 60 days after discovery of the event instead of submitting a written LER. Because plant conditions necessary to prompt a containment isolation were not present, this event constitutes an invalid system actuation under 10 CFR 50.73(a)(2)(iv)(A). The condition meets the criteria of 10 CFR 50.73(a)(2)(iv)(B)(2) because the loss of the Unit 1 'B' RPS bus affected containment isolation valves in more than one system.

"On 1/4/2010 at 1418 hours, the Unit 1 'B' RPS bus was lost. This event resulted in a half scram and primary containment isolations. By design, when the RPS MG set output breaker trips, all EPA breakers downstream of the MG set also trip resulting in a half scram and primary containment isolation signals.

"An event investigation found the Unit 1 'B' RPS MG set running with its output breaker tripped. The output voltage was indicating 120VAC, which indicates that the voltage regulator was operating properly. Upon removal of the MG set cover, the underfrequency relay (UFR) contacts were found to be chattering, with frequency steady at approximately 60 Hz. A review of plant drawings indicated that a chattering UFR could cause the MG set output breaker to trip. Voltage readings were taken and no additional electrical problems (other than the UFR) were identified. The affected RPS loads were subsequently powered from their alternate source and all actuations and isolations were reset.

"Inspection and test of the failed UFR found that one leg of a capacitor on the UFR electronic board had broken adjacent to its solder joint connection on the board. It is suspected that the capacitor lead may have been flawed during manufacture of the board. The failure was accelerated by the constant vibration that the connection is subjected to, as the UFR is mounted on the MG set.

"The failed UFR electronic board was subsequently replaced and successfully passed all functional tests.

"There were no actual safety consequences associated with this event. Valves affected by the invalid signal fulfilled their isolation function by successfully closing. The RPS loads were transferred to their alternate power supply and the trips and isolations were reset. In addition, the Unit 1 'B' RPS bus did not experience an underfrequency condition."

The licensee has notified the NRC Resident Inspector.

TECHNICAL SPECIFICATION REQUIRED SHUTDOWN DUE TO RHR INOPERABILITY

"At 1840 on 2/25/10, Unit 2 RHR Division II became inoperable due to exceeding 260 degrees F on the injection line. The temperature is elevated due to leakage past the injection line check valve (2-CKV-74-68) and the inboard injection valve (2-FCV-74-67). The 260 degree F value is based on engineering calculations to ensure the injection line does not become steam voided. RHR Division I was already inoperable for scheduled maintenance when this condition occurred. Entered TS LCO 3.0.3 based on TS LCO 3.5.1 Condition H - Two or more Low pressure ECCS injection/spray subsystems inoperable for reasons other than Condition A.

"Action was taken to lower power at 1935 when the conditions requiring entry into LCO 3.0.3 could not be corrected.

"Tech Spec LCO 3.0.3 was exited at 2000 when RHR Loop II system pressure was raised using an alternate keep fill flow path to ensure that the injection line would remain filled. Power will be returned to 100%.

"This event requires a 4 hour report in accordance with 10 CFR 50.72(b)(2)(i)."

The licensee informed the NRC Resident Inspector.

DISCOVERY OF AN AFTER-THE-FACT UNUSUAL EVENT

"This is a one-hour report for the discovery of a condition that briefly met the emergency action level (EAL) for an Unusual Event but did not warrant declaration of an emergency classification. A detailed review of the conditions that existed at approximately 2315 EST on February 25 during a winter storm determined that the winds reached a speed of approximately 94 miles per hour for approximately four seconds. This wind speed exceeded the EAL value of greater than or equal to 90 miles per hour. However, because the condition cleared within approximately four seconds, a declaration of an Unusual Event would not have been warranted. The information examined during this detailed review was not the wind speed indication displayed in the control room and used by the operators for evaluating Emergency Action Levels. The additional analysis, which was performed following the winter storm, used data obtained by Engineering. The control room indication remained below 90 miles per hour at all times. This event is a one-hour report based on the guidance in NUREG-1022 for a condition that met an emergency plan EAL and the basis for the emergency classification no longer existed at the time of discovery. The [NRC] Resident Inspector has been informed of this notification and good neighbor notifications will be made to [the State of] New Hampshire and Massachusetts."