|Perry Nuclear Power Plant|
|Reporting criterion:||10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material|
10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
10 CFR 50.73(a)(2)(v), Loss of Safety Function
|4402017003R00 - NRC Website|
|Person / Time|
|From:||Hamilton D B|
FirstEnergy Nuclear Operating Co
Document Control Desk, Office of Nuclear Reactor Regulation
|Download: ML17177A350 (4)|
Estimated buten per response to comply with this mandatory collection request: 80 hojrs. Reportec lessons earned are incorporated into the licensing process and fed back to industry. Sena comments regarding burden estimate to the Informaton Services Branch (T-2 F43;. U.S. Nucear Regulatory Commission. Washington. DC 20555-0001. or by e-mail to !nfocollects.Resource@nrc.gov. and to the Desk Offce
- . Office of Information and Regulatory Affairs.
NEOB-10202. (31500104). Office of Management anc Budget Washington. DC 20503. If a means urea to impose an information collection does no: display a currently valid OMB control number. the NRC may rot conduct o
- sponsor and a person is not reamed to resocrd :le information collecion.
- 003 - 00 Perry Nuclear Power Plant 05000- 440 YEAR 2017 Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
On April 27. 2017. at0545 hours
, with the plant in Mode 1 at 100 percent rated thermal power, while shifting Annulus Exhaust Gas Treatment System (AEGTS) [BH] from sub-system B to sub-system A, annulus differential pressure could not be maintained within the required system operating band. which caused an unplanned entry into technical specification limiting conditions of operation and a momentary loss of safety function. Sub-system B was inoperable while being shutdown to standby readiness in accordance with plant operating procedures and would not have automatically started in response to an actuation signal. Investigation determined that sub-system A was inoperable due to a failed recirculation damper [DMP]. Sub-system B was restarted at0550 hours
, to maintain annulus differential pressure. Annulus differential pressure was maintained above the minimum differential pressure throughout the event and technical specification limiting conditions for operation were not exceeded. The recirculation damper was repaired and AEGTS sub-system A was restored to operable status on April 28, 2017, at2208 hours
DESCRIPTION OF EVENT
AEGTS consists of two 100 percent sub-systems. AEGTS processes the ambient air in the annular space between the shield building and the containment vessel to limit a release to the environment of radioisotopes which may leak from the primary containment under accident conditions. The AEGTS is a recirculation type system with split flow. Some of the filtered air extracted from the annulus space is recirculated and some is discharged to the unit vent. AEGTS is designed to continuously maintain a negative pressure differential of 0.25 inches of water gauge minimum between the containment vessel annulus and the outside environment and direct the exhaust flow from the annulus through a charcoal filter plenum to ensure that the release of radioactivity to the environment is below permissible discharge limits. During normal operation the expected discharge to the unit vent is approximately 700 cfm, at a negative pressure differential of 0.66 inches of water gauge. The 0.66 inches of water gauge pressure differential is provided to maintain the 0.25 inches of water gauge minimum pressure differential required due to instrument location, to meet plant post-LOCA conditions, and to adjust for all environmental conditions. Operating parameters in accordance with plant procedures require annulus pressure to be maintained between 0.75 inches and 1.0 inches water gauge negative pressure differential.
AEGTS sub-system A was inoperable from April 24, 2017, at0427 hours
, until April 26, 2017, at1453 hours
. for planned maintenance which included replacement of the actuator on the recirculation damper. On April 27. 2017. while shifting AEGTS from sub-system B to sub-system A, annulus differential pressure could not be maintained within the required system operational band. During the shifting operation the off going AEGTS sub-system (in this event, B) exhaust fan's switch is held in STOP prior to being placed in STANDBY, which interrupts current flow to a seal-in circuit and stops the exhaust fan. If an actuation signal is received while holding exhaust fan switch in the STOP position, the actuation signal is overridden. and another seal-in circuit will continue to override the actuation signal when the switch is placed in STANDBY. Therefore: the off going AEGTS subsystem is declared inoperable while holding the exhaust fan switch in STOP. in accordance with plant operating procedures. AEGIS sub-system B was declared inoperable at0544 hours
while the exhaust fan switch was held in STOP and declared operable at0545 hours
following release of the switch. Control room operators recognized that annulus differential pressure was outside of the operating band (0.7 inches water gauge negative differential pressure) and not improving. Control room operators started AEGTS sub-system B at0550 hours
, and stopped AEGTS sub-system A at0556 hours
. AEGTS sub-system A was declared inoperable at0545 hours
. Investigation determined that sub-system A was inoperable due to a failed recirculation damper. Estimated Carden per response to comply with this rnardatn collection request.80 hours
. Reportec comments regarding burden estimate to the information Services Branch (T-2 F43) U S. Nuclear Regu atory Commission. Washington. DC 20555-0001. or by e-mail Is Infocollects Resource@nrc gov and to tne Desk Officer, Office of Information and Regulatory Affairs.
- (3150-0104): OFce o' 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. arid a person is not reap red to respond to: the information collection.
CAUSE OF EVENT
The cause for the AEGTS sub-system A recirculation damper failure was a failure to follow procedure by electrical, and instrument and controls technicians which resulted in the split coupling that connects the actuator to the damper not being properly tightened.
ANALYSIS OF EVENT
Since AEGTS is not a core damage mitigation system and does not mitigate large and early containment releases, the inoperability of the AEGIS is determined to be of small safety significance. This event is being reported in accordance with 10CFR50.73(a)(2)(v)(C) and 10CFR50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfilment of a safety function.
The failure to follow procedure was addressed by the FENOC performance management process.
PREVIOUS SIMILAR EVENTS
A review of LERs and the corrective action database for the past three years identified that no previous similar events occurred involving AEGTS.
There are no regulatory commitments contained in this report. Actions described in this document represent intended or planned actions. are described for the NRC's information. and are not regulatory commitments.