05000416/LER-2021-001, Primary Containment Outer Airlock Door Inoperable Due to Unacceptable Leak Rate
| ML21137A090 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 05/14/2021 |
| From: | Franssen R Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GNRO-2021/00016 LER 2021-001-00 | |
| Download: ML21137A090 (6) | |
| 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), Loss of Safety Function |
| 4162021001R00 - NRC Website | |
text
GNRO-2021/00016 May 14, 2021 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
SUBJECT:
Grand Gulf Nuclear Station, Unit 1 Licensee Event Report 2021-001-00, Primary Containment Outer Airlock Door Inoperable Due To Unacceptable Leak Rate Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 Renewed License No. NPF-29 Attached is Licensee Event Report 2021-001-00, Primary Containment Outer Airlock Door Inoperable Due To Unacceptable Leak Rate. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(i)(B), as an operation or condition which was prohibited by the plants Technical Specifications, and under 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented the fulfillment of a safety function.
This letter contains no new Regulatory Commitments. Should you have any questions concerning the content of this letter, please contact Jeff Hardy, Regulatory Assurance Manager at 269-764-2011.
Sincerely, Robert Franssen RF/fas Attachments: Licensee Event Report 2021-001-00 Robert Franssen Site Vice President Grand Gulf Nuclear Station Tel: 601-437-7500 Entergy Operations, Inc.
P.O. Box 756 Port Gibson, Mississippi 39150 10 CFR 50.73
GNRO-2021/00016 Page 2 of 3 cc:
NRC Senior Resident Inspector Grand Gulf Nuclear Station Port Gibson, MS 39150 U.S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
GNRO-2021/00016 Page 3 of 3 Attachment Licensee Event Report 2021-001-00
NRC FORM 366 (08-2020)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2023 LICENSEE EVENT REPORT (LER)
(See Page 3 for required number of digits/characters for each block)
(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 1. Facility Name Grand Gulf Nuclear Station, Unit 1
- 2. Docket Number 05000416
- 3. Page 1 OF 3
- 4. Title Primary Containment Outer Airlock Door Inoperable Due To Unacceptable Leak Rate
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Month Day Year Year Sequential Number Rev No.
Month Day Year Facility Name N/A Docket Number 05000 N/A 02 22 2021 2021 - 001 -
00 5
14 2021 Facility Name Docket Number N/A 05000 N/A
- 9. Operating Mode
- 10. Power Level 1
100
)
No N/A N/A N/A Abstract (Limit to 1560 spaces, i.e., approximately 15 single-spaced typewritten lines)
On February 22, 2021, Grand Gulf Nuclear Stations Primary Containment Outer Airlock located on 208 elevation exceeded the Technical Specification (TS) Surveillance Requirements 3.6.1.2.1 leakage rate during the pre-maintenance barrel test due to gross leakage of the equalizing valve associated with the outer airlock door. Analysis determined that the inner and outer airlock equalizing valves were leaking - caused by lack of lubrication during valve installation.
This event is reportable under 10 CFR 50.73(a)(2)(i)(B), as an operation or condition which was prohibited by the plants Technical Specifications. The event is also being reported under 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented the fulfillment of a safety function.
Actions taken were the lubrication and replacement of the equalizing valve on the outer door. The equalizing valve on the inner door was rebuilt with new O-rings and lubricated prior to reinstallation. Following replacement of the outer door and rebuild of the inner door, the local leak rate test (LLRT) was tested satisfactorily.
There were no consequences to the general safety of the public, nuclear safety, industrial safety or radiological safety. No radiological releases occurred due to this event.
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Plant Conditions
Grand Gulf Nuclear Station (GGNS) Unit 1 was operating at 100 percent power in MODE 1. There were no Structures, Systems, or Components that were inoperable that contributed to this event.
Event Description
On February 22, 2021, GGNSs Primary Containment [NH] Airlock [AL] outer door located on 208 elevation exceeded the Technical Specification (TS) Surveillance Requirements (SR) 3.6.1.2.1 leakage rate during the pre-maintenance barrel test due to gross leakage of the 1M23F018D equalizing valve [V] associated with the outer airlock door, resulting in a condition that could have prevented the fulfillment of a safety function during times when the inner airlock door was open.
A maintenance work window for the 208 Containment Personnel Airlock outer door was scheduled for February 22, 2021. As part of the maintenance evolution, the airlock barrel local leak rate test (LLRT) was performed to identify any leaking components needing to be repaired during the maintenance window. Technical Specification 3.6.1.2, Primary Containment Airlocks, was entered on February 22, 2021, at 0530 hrs. for the maintenance window.
Per calculation MC-Q1M23-16001, the maximum allowable primary containment leakage rate (La) for the calculated maximum peak containment pressure (Pa) 12.1psig is 337,617 SCCM. Per SR 3.6.1.2.1 overall airlock leakage rate is less than or equal to 0.05 times La which is 16,880 SCCM.
Analysis determined that the equalizing valves had failed prior to February 22 due to lack of lubrication during installation. The Containment Airlock outer door was declared inoperable due to excessive leakage. In accordance with TS 3.6.1.2 Condition (One or more primary containment airlocks with one primary containment airlock door inoperable), the OPERABLE door should be closed and locked in the affected airlock. The required actions were not met in the required completion time. This event is reportable under 10 CFR 50.73(a)(2)(i)(B), any operation or condition which was prohibited by the plants Technical Specifications.
This also resulted in a condition that could have prevented the fulfillment of a safety function to mitigate the consequences of an accident, during times when the inner airlock door was open, and is reportable under 10 CFR 50.73(a)(2)(v)(D).
During the periods when the outer airlock door was inoperable, the inner airlock door either remained closed (Operable) or was opened for passage and under the control of site personnel. As a result, Entergy has determined that it did not result in a safety system functional failure. Therefore, in accordance with the guidance provided in NEI 99-02, Revision 7, Regulatory Assessment Performance Indicator Guideline, Section 2.2, Mitigating Systems Cornerstone, Sub-Section, Safety System Functional Failures, Page 30, Lines 27 through 30; this condition will not be counted as a safety system functional failure against Performance Indicator MS05, Safety System Functional Failures.
Safety Assessment
There were no actual consequences for this event. Primary Containment Inner Door was either closed and OPERABLE or under the direct control of site personnel during the identified condition. There was no radiological release from the primary containment as a result of this event. There were no other actual consequences to safety of the general public, nuclear safety, industrial safety, or radiological safety.
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Page 3 of 3 (08-2020)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2023 LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)
- 3. LER NUMBER Grand Gulf Nuclear Station, Unit 1 05000-416 YEAR SEQUENTIAL NUMBER REV NO.
2021
- - 001
- - 00 Event Cause(s):
The direct cause of the event was that the Primary Containment inner and outer airlock doors equalizing valves were leaking.
The inner and outer airlock equalizing valves were not lubricated prior to installation causing premature failure of the O-rings to be the contributor to this event.
Corrective Actions
Actions taken were the lubrication and replacement of the equalizing valve on the outer door. The equalizing valve on the inner door was rebuilt with new O-rings and lubricated prior to reinstallation. Following replacement of the outer door and rebuild of the inner door, the local leak rate test (LLRT) was conducted with satisfactorily results. Additionally, the valve replacement instructions will be updated to include lubricating the equalizing valve prior to installation to prevent future premature failure of the O-rings.
Previous Similar Events
None.
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