05000387/LER-2017-006

From kanterella
Jump to: navigation, search
LER-2017-006, Control Room Envelope In-leakage Exceeded the Technical Specification Limit
Susquehanna Steam Electric Station Unit 1
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications

10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
Initial Reporting
ENS 53003 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
3872017006R01 - NRC Website
LER 17-006-00 for Susquehanna, Unit 2, Regarding Secondary Containment Declared Inoperable Due to Trip of Zone II Exhaust Fan
ML17249A538
Person / Time
Site: Susquehanna Talen Energy icon.png
Issue date: 09/06/2017
From: Berryman B
Susquehanna, Talen Energy
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-7633
Download: ML17249A538 (4)


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 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.

CONDITIONS PRIOR TO EVENT

Unit 1 — Mode 1, approximately 100 percent Rated Thermal Power Unit 2 — Mode 1, approximately 100 percent Rated Thermal Power

EVENT DESCRIPTION

On October 6, 2017 at

1945 hours
0.0225 days
0.54 hours
0.00322 weeks
7.400725e-4 months

, a loss of Control Room Habitability Envelope (CRHE) [EllS System Identifier: NA] was declared due to failing to meet Technical Specification (TS) 3.7.3, Surveillance Requirement (SR) 3.7.3.4 during surveillance testing. Specifically, during testing of the "A" Control Room Emergency Outside Air Supply (CREOAS) train [EIIS System Identifier: VI], the unfiltered inleakage was determined to be 222 cubic feet per minute (cfm) plus a test uncertainty of 458 cfm for a total of 680 cfm. This value exceeded the allowable inleakage value of 500 cfm. The CRHE is required to be maintained such that occupants can control the reactor safely under normal conditions and maintain it in a safe condition following a radiological event, hazardous chemical release, or a smoke challenge. Technical Specification (TS) 3.7.3, Required Action B.1, required immediate initiation of action to implement mitigating actions. The mitigating actions included the ability to issue potassium iodide (KI) to the control room staff and Emergency Plan responders. An adequate supply was verified to be available. Required Action B.2 required that, within

24 hours
2.777778e-4 days
0.00667 hours
3.968254e-5 weeks
9.132e-6 months

, the mitigating actions be verified to ensure CRE occupant exposures to radiological, chemical, and smoke hazards will not exceed limits. Toxic chemical analysis and smoke infiltration analysis assume normal ventilation operation and are not invalidated by the failed SR 3.7.3.4 results for the CRE. Analyses of dose impact determined that, with issuance of KI in accordance with procedures and an unfiltered inleakage of 800 cfm, the dose consequence to the control room operators and affected Emergency Plan personnel is substantially less than the regulatory limit of 5 Rem Total Effective Dose Equivalent (TEDE) for event duration.

Smoke testing was completed to identify sources of leakage. Leakage was identified from the filter train and fan plenum doors of the "A" CREOAS filter train. The door gaskets were found to be out of position.

The gaskets had been replaced in 2012 and 2013 (between November 26, 2012 and November 27, 2013) as part of a preventive maintenance activity. The gaskets on the filter train and the fan plenum door were repaired.

On November 30, 2017, a re-test was performed that resulted in acceptable results (165 cfm ± 328 cfm).

On October 6, 2017, at

2146 hours
0.0248 days
0.596 hours
0.00355 weeks
8.16553e-4 months

, this condition was reported (ENS #53003) in accordance with 10 CFR 50.72(b)(3)(v)(D) as an event or condition that, at the time of discovery, could have prevented the fulfillment of the safety function needed to mitigate the consequences of an accident. This is also reportable in accordance with the corresponding criteria of 10 CFR 50.73(a)(2)(v)(D). In addition, since the gaskets are assumed to have been out of position since installation in 2012/2013, this condition is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by TS 3.7.3 due to not meeting SR 3.7.3.4.

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 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.

CAUSE OF EVENT

The direct cause was the door gaskets being out of position on the "A" CREOAS filter train. During removal, the gaskets were not flush with the door and were glued to a single spot on the top, middle and bottom section of the gasket strip. The gaskets likely rolled out of position due to not being completely glued onto the surface of the channel. The exact point in time of when the gaskets rolled out of position cannot be determined. Since there is no evidence that the personnel opened the filter train doors causing the gaskets to roll out of position after installation of the gaskets in 2012 and 2013, it is conservatively assumed that the gasket rolled out of position during the gasket replacement.

ANALYSIS/SAFETY SIGNIFICANCE

During the October 2017 tracer gas testing of the CREOAS trains, the unfiltered inleakage with the 'A' CREOAS train in operation was determined to be 680 cfm (including measurement uncertainty). Operation of CREOAS is assumed in two Final Safety Analysis Report (FSAR) Chapter 15 dose consequence analyses (Fuel Handling Accident and Design Basis Accident — Loss of Coolant Accident (DBA-LOCA)).

The Fuel Handling Accident calculation was performed using 700 cfm of unfiltered inleakage to bound the October 2017 testing results. The results of this analysis showed dose consequence to the control room operator remained less than the regulatory limit of 5 Rem TEDE.

The DBA-LOCA analysis was also performed using 700 cfm of unidentified inleakage to bound the October 2017 testing results. In the analysis, a bounding measured value from 2011 through 2017 was used for the Engineered Safety Features (ESF) recirculation leakage while other assumptions (e.g. secondary containment bypass leakage, containment leakage) were maintained at the design values in order to preserve the conservatism of the calculation. The results of this analysis showed dose consequence to the control room operator remained less than the regulatory limit of 5 Rem TEDE.

Based on engineering analysis of the event, the limiting dose consequences remained within the regulatory limit of 5 Rem TEDE and the Control Room Habitability Envelope (CRHE) remained capable of performing its safety function. 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.

CORRECTIVE ACTIONS

The key corrective action is as follows:

1. The gaskets on the filter train and the fan plenum door were repaired.

2. A re-test was performed that resulted in acceptable results.

3. A step in the work scope of the preventive maintenance activity for replacing the gaskets will be added to state, "Ensure gasket is entirely glued into the channel such that the gasket is in contact with the entire channel.

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 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.

2017

COMPONENT FAILURE INFORMATION

Information for gasket:

Manufacturer: Farr Company Model: N-228 - 006 - 01

PREVIOUS SIMILAR EVENTS

dated March 3, 2017 was similar in that the cause was related to a gasket issue.