|Susquehanna Steam Electric Station Unit 2|
|Reporting criterion:||10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material|
|ENS 52826||10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material|
|3882017005R00 - NRC Website|
comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov. and to the Desk Officer, Office of Information and Regulatory Affairs.
NEON-10202, (3150-0104), Office of Management and Budget. Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number. the NRC may not conduct or sponsor, and a person is not required to respond lo, the information collection.
i YEAR 2017 - 005 - 00
CONDITIONS PRIOR TO EVENT
Unit 1 — Mode 1, approximately 100 percent Rated Thermal Power Unit 2 — Mode 1, approximately 100 percent Rated Thermal Power There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.
On June 24, 2017, at approximately1028 hours
, Unit 2 Reactor Building [EllS System Code: NG] secondary containment Zone Ill differential pressure was not maintained above the Technical Specification (TS) limit of 0.25 in w.g. A Nuclear Plant Operator (NPO) reported Filtered Exhaust System Fan A [EIIS Code: FAN] had tripped. The NPO then placed Filtered Exhaust System Fan B [EllS Code: Fan] in START and Filtered Exhaust System Fan A in STANDBY. Zone Ill differential pressure was restored at approximately1042 hours
. On June 24, 2017, at1542 hours
, this condition was reported (ENS #52826) in accordance with 10 CFR 50.72(b)(3)(v)(C) as an event or condition that, at the time of discovery, could have prevented the fulfillment of the safety function. SSES has no redundant Secondary Containment System.
The cause of the trip was due to a failed solenoid valve [EIIS Code: SOL] on the discharge damper [EIIS Code: DMP]. Upon failure of the solenoid valve, the discharge damper failed closed and Filtered Exhaust System Fan A tripped on low flow.
CAUSE OF EVENT
The cause of the event was the failure of the ASCO solenoid valve. Based on further review, the ASCO solenoid valve has been determined to be less than adequate for its application in Reactor Building HVAC.
Technical Specification 220.127.116.11 Surveillance Requirement 18.104.22.168.1 requires that secondary containment vacuum is maintained greater than or equal to 0.25 in. w.g. This event is being reported pursuant to 10 CFR 50.73(a)(2)(v)(C), as a loss of Secondary Containment differential pressure results in a condition that could have prevented fulfillment of a safety function to mitigate the consequences of an accident by controlling the release of radioactive material.
Based on engineering analysis of the event, secondary containment could have performed its safety function of isolating as assumed in the accident analysis and of re-establishing 0.25 in w.g. vacuum (drawdown) within the assumed accident analysis time (10 minutes).
This event will not be counted as a safety system functional failure (SSFF) for the NRC performance indicator based on the engineering analysis supporting the system's ability to fulfill the safety function.
comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, 'Washington, DC 20555-0001, or by e-mail to NEOB-10202, (3150-0104). Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
3. LER NUMBER
NO Susquehanna Steam Electric Station Unit 2 05000388
Key corrective actions include replacement of the failed solenoid valve with a more robust model.
COMPONENT FAILURE INFORMATION
ASCO Services 3-way electrical solenoid valve Air ASCO 8320 Solenoid Valve, General Use Model 8320G003 120 VAC
PREVIOUS SIMILAR EVENTS
The following are recent LERs involving loss of secondary containment due to component failures:
Supply Plenum Screens," dated February 2, 2016.
June 10, 2015.