05000391/LER-2019-002, Breach Due to Penetration Boot Seal Separation Results in Shield Building Inoperability
| ML19231A035 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 08/19/2019 |
| From: | Anthony Williams Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| WBL-19-040 LER 2019-002-00 | |
| Download: ML19231A035 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3912019002R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 August 19, 2019 WBL-19-040 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391 10 CFR 50.73
Subject:
Licensee Event Report 391/2019-002-00, Breach Due to Penetration Boot Seal Separation Results in Shield Building lnoperability This submittal provides Licensee Event Report (LER) 391/2019-002-00. This LER provides details concerning a breach in the Watts Bar Nuclear Plant (WBN) Unit 2 Shield Building annulus in excess of allowable margin, due to a penetration boot seal that had pulled away from the shield building wall. This event is being reported to the Nuclear Regulatory Commission (NRC) as an event or condition that could have prevented fulfillment of a safety function of structures or systems that are needed to control the release of radioactive material in accordance with 10 CFR 50.73(a)(2)(v)(C).
There are no regulatory commitments contained in this letter. Please direct any questions concerning this matter to Tony Brown, WBN Licensing Manager, at (423) 365-7720.
nthony L. Williams I Site Vice President Watts Bar Nuclear Plant Enclosure cc: See Page 2
U.S. Nuclear Regulatory Commission WBL-19-040 Page2 August 19, 2019 cc (Enclosure):
NRG Regional Administrator - Region II NRG Senior Resident Inspector - Watts Bar Nuclear Plant
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3160-0104 EXPIRES: 03/31/2020 (04-2018)
Eslimatad bu-den per response to comply with this mandatory collec1ion request 80 hOI.IS.
Reported lessons lellll8d ae incaporatsd into the icensing process and fed bad< to indumy. Send comments regll'ding burden estima1B to the Information Se!vic:es Branch LICENSEE EVENT REPORT (LER)
(T-2 F43). U.S. Nuclea Regulatory Convnisslon, Washington, DC 20555--0001,or by e-mail i
to lnfocollects. Resolll>t@rvc.gov, and to the Desk Officer, Office of lnlcnnation and
~ r; Regulatory Atlai's, NEOB-10202, (3150-0104), Office of M1rNQement and Budget Washington, DC 20503. W a means used 1o Impose an Information collection does nc1 display a aJnenUy vald OIi.i! contol number, the NRC may nc1 conduct or sponsor, and a person is nc1 requred to respond t>, the infonnmon collection.
3.Page Watts Bar Nuclear Plant. Unit 2
- 05000391 1 OF 5
- 4. Title Breach Due to Penetration Boot Seal Separation Results in Shield Building lnoperability
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facllltles Involved I
Sequential I Rev Facility Name Dockal Number Month Day YHr Year Number No.
Month Day Year NIA 05000 Facility Name Dockel-r 06 20 2019 2019 - 002
- - 00 08 19 2019 NA 05000
- 9. Operating Mode
- 11. This Report Is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)
D 20.2201(b>
D 20.22oa<a><3>
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2201(d>
D 20.2203(a><3><n>
D 50.73(a)(2)(ii)(B)
D 50.73(8)(2)(vili)(B) 1 D 20.2203(8)(1>
D 20.2203(a)(4>
D 5o.73(8)(2)<m>
D 50.73(8)(2)(ix)(A)
D 20.2203(8)(2>
D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. Power Level D 20.2203(8)<2><n>
D 50.36(c)(1)(ii)(A)
D 50. 73(8)(2)(v)(A)
D 13.71(8)(4>
D 20.2203(8)(2><m>
D so.3a(c)(2>
D 50.73(a)(2)(v)(B)
D 73. 71 (a)(5)
D 20.2203(a)(2)(iv)
D 5o.46(8)(3)(n>
t8] 50. 73(8)(2)(v)(C)
D 13.11(a><1>
100 D 20.2203(8)(2)(v)
D 50.73(8)(2)(i)(A)
D 50. 73(8)(2)(v)(D)
D 13.11<a><2>
D 20.2203(8)(2)(vi)
D 50.73(a)(2)(i)(B)
D 50.73(8)(2)(vii)
D 13.77(a><2><n>
D 5o. 13<aH2><C)
D OTHER Specify in Abstract below or in NRC Fonn 366A
- 12. Licensee Contact for this LER Licensee Contact relephone Number (Include Area Code)
Amber Aboulfaida, Licensing Engineer (423) 365-1818 Cause Syetem Component Manufacturer Reportable to ICES
cause
System Component Manufacturer Reportable to ICES N/A N/A N/A N/A NIA
- 14. Supplemental Report Expected Month Day YHr D Yes (If yes, complete 15. Expected Submission Date)
[8l No
- 15. Expected Submission Date NIA N/A N/A Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
On June 20, 2019, at 1340 Eastern Daylight Time (EDT), a breach in excess of allowable margin was identified in the Watts Bar Nuclear Plant (WBN) Unit 2 Shield Building annulus. The breach consisted of a penetration boot seal that had pulled away from the shield building wall, creating a gap between the boot seal and the annulus wall. As a result, WBN U2 entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3.6.15, Condition A. for the shield building being inoperable. On June 21, 2019, at 0036, the boot seal was repaired. and WBN U2 exited LCO 3.6.15, Condition A.
There were no human performance errors identified that contributed to this event. Corrective actions included repairing the boot seal, and modifying permanent scaffolding.
lfhis event is being reported to the Nuclear Regulatory Commission (NRC) under 10 CFR 50.73(a)(2)(v)(C) as an event or condition that could have prevented fulfillment of a safety function of structures or systems that are needed to control the release of radioactive material.
NRC FORM 366 (04-2018)
I.
Plant Operating Conditions Before the Event
Watts Bar Nuclear Plant (WBN) Unit 2 was at 100 percent rated thermal power (RTP). Unit 1 was unaffected by this event.
II.
Description of Event
A. Event Summary On June 20, 2019, at 1340 Eastern Daylight Time (EDT), while performing a Radiological Protection (RP) walkdown, a breach in excess of allowable margin was identified in the Watts Bar Nuclear Plant (WBN) Unit 2 Shield Building [EIIS: NH] annulus. The breach consisted of a penetration boot seal [EIIS: SEAL] that had pulled away from the shield building wall, creating a gap approximately 10 inches square between the boot seal and the annulus wall. As a result, WBN U2 entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3.6.15, Condition A, for the shield building being inoperable. On June 21, 2019, at 0036, the boot seal was repaired, and WBN U2 exited LCO 3.6.15, Condition A.
An 8-hour non-emergency event notification (EN 54127) was made to the Nuclear Regulatory Commission (NRC) in accordance with 10 CFR 50.72(b)(3)(v) as an event or condition that could have prevented fulfillment of a safety function of structures or systems that are needed to control the release of radioactive material. This Licensee Event Report (LER) documents the reportable event under 10 CFR 50.73(a)(2)(v)(C).
B. Status of structures, components, or systems that were inoperable at the start of the event and that contributed to the event No inoperable structures, systems, or components contributed to this condition.
C. Dates and approximate times of occurrences
Date Time
~
05/02/19 -
06/20/19 1340 06/20/19 1641 06/20/19 1759 06/21/19 0036 NRC FORM 386A (04-2018)
Quality Control (QC) acceptance check on Boot Seal Installation during U2R2 (Work Order (WO) 120237990)
Entered TS LCO 3.6.15, Condition A, Shield Building inoperable.
Authorized performance of WO 120536836 to repair R2S065 boot seal 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> report made to the NRC (EN 54127)
Post Maintenance Test (PMT) performed satisfactorily following boot seal repair. Exited TS LCO 3.6.15, Condition A Page _2_ of _s_
2019 -
002 00
D. Manufacturer and model number of each component that failed during the event
There were no components that failed during the event. The R2S065 penetration boot seal pulled away from the shield building wall.
E. Other systems or secondary functions affected
There were no other systems or secondary functions affected by this event.
F. Method of discovery of each component or system failure or procedural error
An RP technician identified the breach while performing a walkdown in the WBN Unit 2 annulus.
G. Failure mode, mechanism, and effect of each failed component There were no components that failed during the event.
H. Operator actions
The Shield Building was declared inoperable due to the breach associated with the R2S065 penetration boot seal exceeding the allowed Unit 2 annulus breach margin. Unit 2 entered TS LCO 3.6.15, Condition A I.
Automatically and manually initiated safety system responses
There were no automatic or manually initiated safety system responses associated with this event.
Ill.
Cause of the Event
A Cause of each component or system failure or personnel error There were no components that failed during the event. The R2S065 penetration boot seal pulled away from the shield building wall. An investigation into the event did not identify any workmanship causes. The boot seal was installed during the previous spring refueling outage (U2R2) with a Quality Control (QC) acceptance check on May 2, 2019.
Inadvertent contact with the boot seal is a potential cause of the annulus breach; however, no human performance causes were identified. Annulus access records were reviewed and all personnel were interviewed regarding activities conducted in the 2019
- 002 00 annulus. No activity could be identified that would have had the potential to impact the boot seal.
IV.
Analysis of the Event
The shield building is a concrete structure that surrounds the steel containment vessel. Between the containment vessel and the shield building inner wall is an annular space that collects containment leakage that may occur following a loss of coolant accident (LOCA) as well as other design basis accidents (DBAs) that release radioactive material. The shield building is required to be operable in Modes 1, 2, 3, and 4.
During normal operations when containment integrity is required, annulus vacuum is established and maintained by the annulus vacuum control subsystem. During an emergency, the Emergency Gas Treatment System (EGTS) [EIIS: BH] establishes a negative pressure in the annulus between the shield building and the steel containment vessel.
The R2S065 penetration boot seal pulled away from the shield building wall, which created a 10 inch by 1 inch gap between the boot seal and the annulus wall. The 10 square inch breach exceeded the Unit 2 annulus breach margin. With this leakage the EGTS could not maintain a pressure equal to or more negative than -0.50 inches water gauge in the annulus at an elevation equivalent to the top of the Auxiliary Building, as required by Surveillance Requirement (SR) 3.6.15.4.
V.
Assessment of Safety Consequences
There were no actual safety consequences as a result of this event. The WBN probabilistic risk assessment model does not specifically credit the use of EGTS when calculating the probability of core damage or large early release. Accordingly, the risk associated with this event is considered to be negligible.
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event There were no systems or components that failed during the event.
B. For events that occurred when the reactor was shut down, availability of systems or components needed to shutdown the reactor and maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident Not applicable.
YEAR 2019 -
- 3. LER NUMBER SEQUENTIAL NUMBER 002 REV NO.
00 C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from the discovery of the failure until the train was returned to service Approximately 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br /> elapsed from the time the breach was discovered until Unit 2 exited TS LCO 3.6.15.
VI.
Corrective Actions
These events were entered into the Tennessee Valley Authority (TVA) Corrective Action Program and are being tracked under Condition Report (CR) 1526540.
A. Immediate Corrective Actions
The R2S065 penetration boot seal was repaired, a PMT was performed, and WBN Unit 2 exited LCO 3.6.15, Condition A.
- 8. Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future No workmanship or human performance errors were identified. However, learnings were shared regarding the failure, and care and attention for sensitive plant components and configuration control was emphasized. Also, permanent scaffolding was modified to preclude a similar event from occurring.
VII.
Previous Similar Events at the Same Site
LER 390/2018-002-00 submitted on March 19, 2018, documents an event where the shield building was declared inoperable due to spurious equipment operation which resulted in the shield building pressure limits exceeding TS allowed values.
The cause of the previous similar event has a different direct cause than this event.
VIII.
Additional Information
There is no additional information.
IX.
Commitments
There are no new commitments. Page _s_ of _s_