05000327/LER-1917-001, Regarding Breached Door Renders Both Trains of the Auxiliary Building Gas Treatment System Inoperable

Regarding Breached Door Renders Both Trains of the Auxiliary Building Gas Treatment System Inoperable

ML17117A495
Person / Time
Site:	Sequoyah
Issue date:	04/26/2017
From:	Anthony Williams Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 17-001-00
Download: ML17117A495 (8)

LER-1917-001, Regarding Breached Door Renders Both Trains of the Auxiliary Building Gas Treatment System Inoperable

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 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)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
3271917001R00 - NRC Website

text

Tennessee Valley Authority, Sequoyah Nuclear Plant, P.O. Box 2000, Soddy Daisy, Tennessee 37384 April 26, 2017 10 CFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-77 and DPR-79 NRC Docket Nos. 50-327 and 50-328

Subject:

Licensee Event Report 50-327 and 50-328/2017-001-00, Breached Door Renders Both Trains of the Auxiliary Building Gas Treatment System Inoperable The enclosed licensee event report provides details concerning discovery of a breached door associated with the auxiliary building secondary containment enclosure (ABSCE) boundary that resulted in both trains of the Auxiliary Building Gas Treatment System being declared inoperable. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plant's Technical Specifications and in accordance with 10 CFR 50.73(a)(2)(v), as an event or condition that could have prevented the fulfillment of a safety function of structures or systems that are needed to: (C) control the release of radioactive material and (D) mitigate the consequences of an accident.

There are no regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Michael McBrearty, Site Licensing Manager, at (423)843-7170.

Anthony L. Williams Site Vice President Sequoyah Nuclear Plant Enclosure: Licensee Event Report 50-327 and 50-328/2017-001-00 cc:

NRC Regional Administrator - Region II NRC Senior Resident Inspector-Sequoyah Nuclear Plant printed on recycled paper

NRC FORM 366 (04-2017)

NRC FORM 366 (04-2017)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

LICENSEE EVENT REPORT (LER)

1. FACILITY NAME Sequoyah Nuclear Plant Unit 1

2. DOCKET NUMBER 05000327

3. PAGE 1 OF 6

4. TITLE Breached Door Renders Both Trains of the Auxiliary Building Gas Treatment System Inoperable

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 Sequoyah Nuclear Plant Unit 2 DOCKET NUMBER 05000328 03 03 17 2017

- 001

- 00 04 26 17 FACILITY NAME DOCKET NUMBER NA 05000

9. OPERATING MODE 1

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)

10. POWER LEVEL 100 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C) 73.77(a)(1) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 73.77(a)(2)(i) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(ii) 50.73(a)(2)(i)(C)

OTHER Specify in Abstract below or in NRC Form 366A

12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TELEPHONE NUMBER (Include Area Code)

Scott T Bowman 423-843-6910 CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX

CAUSE

SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX N/A

14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED SUBMISSION DATE MONTH DAY YEAR YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

NO ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On March 3, 2017, at 2232 eastern standard time (EST), Door A212 was improperly breached to facilitate a continuous fire watch. On March 7, 2017, at 0830 EST, a senior reactor operator discovered Door A212 blocked open during a walk down of the Auxiliary Building. The open door created a breach of the auxiliary building secondary containment enclosure (ABSCE) boundary. The identified breach exceeded the allowed ABSCE breach margin. As a result, both units entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3.7.12, Condition B for two trains of the Auxiliary Building Gas Treatment System (ABGTS) inoperable due to an inoperable ABSCE boundary in Mode 1, 2, 3, or 4. At 0949 EST, on March 7, the door was closed and both units exited LCO 3.7.12, Condition B. Both trains of ABGTS were inoperable longer than allowed by TS. There were no actual safety consequences as a result of this event.

An evaluation determined the cause to be a less than adequate single barrier breaching standard exists at Sequoyah Nuclear Plant. A contributing cause was an inconsistent approach to entry into the barrier breaching process. Corrective actions include revising the breaching procedure to address all possible breaches and include a matrix for doors and their associated impacts, and addressing potential knowledge deficiencies.

I.

Plant Operating Conditions Before the Event

At the time of the event, Sequoyah Nuclear Plant (SQN) Unit 1 and Unit 2 were in Mode 1 at 100 percent rated thermal power.

II.

Description of Event

A.

Event Summary

As a result of fire protection [EIIS: KF] piping inspections, the fire protection for the Fuel Handling Exhaust Fan (FHEF) [EIIS: FAN] Filter [EIIS: FLT] Enclosure was authorized to be isolated under a clearance. The isolation required a continuous fire watch to inspect the inside of the FHEF Filter Enclosure. With the FHEF in service, excessive differential pressure across Auxiliary Building [EIIS: NF] Door [EIIS: DR] A212 hindered opening the door for the inspection. Therefore, a fire protection impairment permit was generated to breach Door A212; however, the door was not evaluated as a breach of the auxiliary building secondary containment enclosure (ABSCE) boundary. On March 3, 2017, at 2232 eastern standard time (EST), Door A212 was breached to facilitate the continuous fire watch.

On March 7, 2017, at 0830 EST, a senior reactor operator (SRO) discovered Door A212 blocked open during a walk down of the Auxiliary Building. The open door created a breach of the ABSCE boundary. The identified breach exceeded the allowed ABSCE breach margin. As a result, both units entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3.7.12, Condition B for two trains of the Auxiliary Building Gas Treatment System (ABGTS) [EIIS: VF] inoperable due to an inoperable ABSCE boundary in Mode 1, 2, 3, or 4. At 0949 EST, on March 7, the door was closed and both units exited LCO 3.7.12, Condition B.

An 8-hour non-emergency event notification (EN 52597) was made to the 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: (C) control the release of radioactive material and (D) mitigate the consequences of an accident. This LER documents the reportable event under 10 CFR 50.73(a)(2)(v)(C) and 10 CFR 50.73(a)(2)(v)(D).

Additionally, it was determined that both trains of ABGTS were inoperable from March 3, 2017, at 2232 to March 7, 2017, at 0949. LCO 3.7.12, Condition B requires restoration of the ABSCE boundary within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Upon failure to meet the Required Action and associated Completion Time of Condition B, LCO 3.7.12, Condition C requires the unit to be in Mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. Because both trains of ABGTS were inoperable for approximately 83.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and remained in Mode 1, this is a condition prohibited by TS and is therefore being reported in accordance with 10 CFR 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plants TS.

Page 3 of 6 (04-2017)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

3. LER NUMBER Sequoyah Nuclear Plant Unit 1 05000-327 YEAR SEQUENTIAL NUMBER REV NO.

2017

- 001

- 00 B.

Status of structures, components, or systems that were inoperable at the start of the event and contributed to the event:

No inoperable structures, components, or systems contributed to this event.

C. Dates and approximate times of occurrences

Date/Time (EST) Description 03/03/17, 2232 Door A212 was breached to facilitate a continuous fire watch.

03/07/17, 0830 An SRO discovered Door A212 breached. The identified breach exceeded the allowed ABSCE breach margin. Both units entered LCO 3.7.12, Condition B.

03/07/17, 0949 Door A212 was closed. This restored both the ABSCE boundary and both trains of the ABGTS to operable status. Both units exited LCO 3.7.12, Condition B.

D. Manufacturer and model number of each component that failed during the event

There was no component that failed during the event.

E.

Other systems or secondary functions affected

There were no systems or secondary functions affected by this event.

F.

Method of discovery of each component or system failure or procedural error

While performing a walk down of the Auxiliary Building, an SRO discovered Door A212 blocked open.

G. The failure mode, mechanism, and effect of each failed component, if known:

There was no component that failed during the event.

H. Operator actions

Both trains of ABGTS were declared inoperable due to the identified breach exceeding the allowed ABSCE breach margin. Both units entered LCO 3.7.12, Condition B.

I.

Automatically and manually initiated safety system responses

There were no automatic or manual system responses associated with this event.

Page 4 of 6 (04-2017)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

3. LER NUMBER Sequoyah Nuclear Plant Unit 1 05000-327 YEAR SEQUENTIAL NUMBER REV NO.

2017

- 001

- 00 III.

Cause of the Event

A.

Cause of each component or system failure or personnel error

There was no component or system failure associated with the event.

An evaluation determined the cause to be a less than adequate single barrier breaching standard exists at SQN. A contributing cause was an inconsistent approach to entry into the barrier breaching process. Individuals enter into the barrier breaching process using the applicable standard that they are most familiar with rather than using the barrier breaching governing procedure.

B.

Cause(s) and circumstances for each human performance related root cause

There was no identified human performance related root cause.

IV.

Analysis of the Event

The ABGTS filters airborne radioactive particulates from the area of the fuel pool following a fuel handling accident or loss of coolant accident (LOCA). In Mode 1, 2, 3, or 4, the ABGTS is required to be operable to provide fission product removal associated with Emergency Core Cooling System leaks due to a LOCA and leakage from containment and annulus.

The ABGTS is a standby system that consists of two independent and redundant trains. Each train consists of a heater, a prefilter, a high efficiency particulate air filter, an activated charcoal adsorber section for removal of gaseous activity, and a fan. The system initiates filtered ventilation of the auxiliary building following receipt of a high radiation signal from the fuel handling area radiation monitors, a high radiation signal from the train-specific Auxiliary Building exhaust vent monitor, a Phase A containment isolation signal from either reactor, or a high temperature signal from the Auxiliary Building air intakes.

The breached door exceeded the allowed ABSCE breach margin rendering the ABSCE inoperable. This configuration could have prevented the ABGTS from maintaining a pressure greater than or equal to -0.25 inches water gauge with respect to atmospheric pressure during the post accident mode of operation.

V.

Assessment of Safety Consequences

There were no actual safety consequences as a result of this event. The SQN probabilistic risk assessment model does not specifically credit the use of the ABGTS when calculating the probability of core damage or large early release. Accordingly, the risk associated with this event is considered to be very small.

Page 5 of 6 (04-2017)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

3. LER NUMBER Sequoyah Nuclear Plant Unit 1 05000-327 YEAR SEQUENTIAL NUMBER REV NO.

2017

- 001

- 00 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 components or systems 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:

The event did not occur when the reactor was shutdown.

C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from discovery of the failure until the train was returned to service:

Both trains of ABGTS were inoperable for approximately 83.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The elapsed time from discovery of both trains of ABGTS being inoperable until both trains were restored to operable status was approximately 79 minutes.

VI.

Corrective Actions

Corrective Actions are being managed by the Tennessee Valley Authority (TVA) corrective action program under Condition Report 1269767.

A.

Immediate Corrective Actions

Door A212 was closed and both units exited LCO 3.7.12, Condition B.

B.

Corrective Actions to Prevent Recurrence or to reduce probability of similar events occurring in the future:

Corrective actions include revising the breaching procedure to address all possible breaches and include a matrix for doors and their associated impacts. Additionally, a performance analysis worksheet will be performed to identify knowledge deficiencies associated with the ABSCE and door postings.

Page 6 of 6 (04-2017)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

3. LER NUMBER Sequoyah Nuclear Plant Unit 1 05000-327 YEAR SEQUENTIAL NUMBER REV NO.

2017

- 001

- 00 VII. Previous similar events at the same plant:

A review of SQN LERs identified an event in which a penetration affecting the ABSCE was breached without required compensatory measures. LER 327/2013-01, associated with the event, identified the root cause as ineffective procedures for controlling containment penetration breaches during Modes 5 and 6. A corrective action was to develop and implement a governing procedure for controlling breaches of the shield building, ABSCE, control room boundaries, and design basis flood barriers.

VIII. Additional Information

None.

IX.

Commitments

None.

Page 7 of 7 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 3/31/2020

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

LICENSEE EVENT REPORT (LER)

FAILURE CONTINUATION

2. DOCKET NUMBER

3. LER NUMBER 05000-YEAR SEQUENTIAL NUMBER REV NO.

SYSTEM COMPONENT MANUFACTURER REPORTABLETO EPIX