05000327/LER-2018-001, Inadequate Post Maintenance Testing Results in Condition Prohibited by Technical Specifications

Inadequate Post Maintenance Testing Results in Condition Prohibited by Technical Specifications

ML18261A290
Person / Time
Site:	Sequoyah
Issue date:	09/18/2018
From:	Anthony Williams Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 2018-001-00
Download: ML18261A290 (8)

LER-2018-001, Inadequate Post Maintenance Testing Results in Condition Prohibited by Technical Specifications

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
3272018001R00 - NRC Website

text

Tennessee Valley Authority, Sequoyah Nuclear Plant, P.O. Box 2000, Soddy Daisy, Tennessee 37384 September 18, 2018 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 50-328/2018-001-00, Inadequate Post Maintenance Testing Results in Condition Prohibited by Technical Specifications The enclosed licensee event report provides details concerning a situation in which inadequate post maintenance testing resulted in one train of the Emergency Gas Treatment System being inoperable for longer than allowed by Technical Specifications. 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 Mr. Jonathan Johnson, Site Licensing Manager, at (423)843-8129.

ibny L. Williams Site Vice President Sequoyah Nuclear Plant Enclosure: Licensee Event Report 50-327 and 50-328/2018-001-00 cc:

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

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)

, the NRC may not conduct or sponsor,and a personis notrequired to respondto,the informationcollection.

1. FACILITY NAME 2

DOCKETNUMBER Sequoyah Nuclear Plant Unit 1 05000-327 YEAR 2018 a

LER NUMBER SEQUENTIAL NUMBER

- 001 REV NO.

- 00 transitioned to Mode 3 within 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. This constitutes another event of an operation or condition which was prohibited by the plant's TSs. This event is also reportable 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.

B.

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

An operability test of the EGTS Air Cleanup Subsystem was not performed after maintenance. This allowed the B-trainof EGTS to be inoperable longer than allowed by TSs without being detected.

C.

Dates and approximate times of occurrences

Date/Time (EDT)

February 2018 06/26/18, 0902 06/26/18, 1443 07/10/18, 0211 07/10/18,2200Description The work order for replacing the flow switch electronic circuit board was prepared and reviewed. The only post maintenance test (PMT) specified in the work order was to complete a calibration on the replaced board. The work planner and senior reactor operator who reviewed the work order failed to identify the need to functionally test the B-train EGTS AirCleanup Subsystem after board replacement.

Both units enter TS 3.6.10 Condition A due to removing B-train EGTS from service for relative humidity heaters flowswitch circuit board replacement and calibration.

Both units exit TS 3.6.10 Condition A after circuit board replacement and calibration. B-train EGTS was returned to service and placed in a standby condition. The B-train relative humidity heaters were not verified to be able to energize following circuit board replacement. The B-train of EGTS was still inoperable.

Both units enter TS 3.6.10 Condition A due to tagging the A-train of EGTS out of service for a maintenance outage.

Both units exit TS 3.6.10 Condition A due to A-train of EGTS being restored to operable status.

Page 3 of 7(04-2018)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020

, the NRC may not conduct or sponsor,and a personis notrequired to respondto, the informationcollection.

1. FACILITY NAME Sequoyah Nuclear Plant Unit 1 Date/Time (EDT) 07/22/18, 1008 07/24/18,0115

2. DOCKET NUMBER 05000-327 YEAR 2018

Description

3. LER NUMBER SEQUENTIAL NUMBER 001 Both units enter TS 3.6.10 Condition A due to removing B-train of EGTS from service to perform a B-train EGTS flow test associated with SR 3.6.10.1. Main Control Room operators discovered that the B-train relative humidity heaters were not energized.

Following replacement of the B-train EGTS relative humidity heaters flow switch circuit board, with the board removed on June 26, the B-train of EGTS was able to pass the flow test associated with SR 3.6.10.1. Both units exited TS 3.6.10 Condition A due to the EGTS Air Cleanup Subsystem being restored to operable status.

REV NO.

- 00 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 other systems or secondary functions affected by this event.

F.

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

Operations personnel performed an SI for SR 3.6.10.1 (operate each EGTS Air Cleanup Subsystem train for greater than or equal to 15 continuous minutes with heaters operating) and identified that the B-train relative humidity heaters did not energize.

G.

Failure mode, mechanism, and effect of each failed component:

There was no component that failed during the event.

H.

Operator actions

Upon failure to meet SR 3.6.10.1, Operators declared LCO 3.6.10, EGTS AirCleanup Subsystem, not met and entered TS 3.6.10 Condition A for one EGTS Air Cleanup Subsystem train being inoperable.

I.

Automatically and manually initiated safety system responses

There were no automatic or manually initiated safety system responses associated with this event.Page 4 of 7(04-2018)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

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, the NRC may not conductor sponsor,and a personis notrequired to respondto,the informationcoilection.

3. LER NUMBER Sequoyah Nuclear Plant Unit 1 05000-327 YEAR 2018 SEQUENTIAL NUMBER

- 001 REV NO.

- 00 III.

Cause of the Event

A.

Cause of each component or system failure or personnel error

The cause of the event was the lack of formality in determining PMTs and return to operability (RTO) tests even though the procedure provides adequate guidance for this determination. PMTs may include RTOs and other maintenance tests. Work planners assumed that if no SR for a maintenance task could be found then no RTO test is required.

Operations personnel did not provide enough vigor and challenge in their reviews of PMTs for work orders associated with safety related equipment. The extent of required review of RTO testing by Operation personnel was not fully understood leading to assumptions, in which for PMTs, may not be adequate to verify operability of equipment being tested.

B.

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

There was a lack of formality in determining required testing following maintenance by the Work Management and Operations organizations.

The personnel involved were SQN employees. They were performing work associated with the replacement of the B-train EGTS Air Cleanup Subsystem flow switch electronic circuit card. There were no time or situational pressures present.

IV.

Analysis of the Event

The design bases for the EGTS are (1) to keep the air pressure within each Shield Building annulus below atmospheric at all times in which the integrity of that particular containment is required, and (2) to reduce the concentration of radioactive nuclides in annulus air that is released to the environs during a loss of coolant accident (LOCA) in either reactor unit to levels sufficiently low to keep the exclusion area boundary dose rate below the 10 CFR 100 guideline values.

The specified function of the relative humidity heaters is to reduce the relative humidity of the air stream to 70 percent relative humidity to prevent degradation of charcoal adsorber media efficiency.

An engineering calculation determined the maximum relative humidity in the annulus resulting from a loss of coolant accident or a high energy line break would conservatively not exceed 61 percent relative humidity. Therefore, the Updated Final Safety Analysis Report specified function of the relative humidity heaters would be maintained with the heaters de-energized.Page 5 of 7(04-2018)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020

, the NRC may not conduct or sponsor,and a personis notrequiredto respondto, the informationcollection.

1. FACILITY NAME 2

DOCKET NUMBER a

LER NUMBER Sequoyah Nuclear Plant Unit 1 05000-327 YEAR 2018 SEQUENTIAL NUMBER 001 REV NO.

- 00 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 credit the use of the EGTS when calculating the probability of core damage or large early release. Accordingly, the risk associated with this event is considered to be very small.

A.

Availability of systems or components that could have performed the same function as the components and systems that failed during the event:

Although B-train relative humidity heaters failed to energize, an engineering evaluation determined the B-train of EGTS was fully capable of meeting its specified function with the heaters not energized. Additionally, the A-train of EGTS was operable for the majority of the time the B-train was inoperable.

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 shut down.

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:

Operators identified a failure of B-train EGTS to meet SR 3.6.10.1 on July 22 at 1008. B-train EGTS was declared operable approximately 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> later on July 24 at 0115.

VI.

Corrective Actions

This event was entered into the Tennessee Valley Authority Corrective Action Program under Condition Reports 1433166 and 1436225.

A.

Immediate Corrective Actions

None.Page 6 of 7(04-2018)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020

, the NRC may not conduct or sponsor,and a personis notrequired torespondto,the infbrmatjoncoilectjon.

1. FACILITY NAME Z

DOCKET NUMBER Sequoyah Nuclear Plant Unit 1 05000-327 YEAR 2018

3. LER NUMBER SEQUENTIAL NUMBER

- 001 B.

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

The corrective action is to conduct information sharing with each Operations Crew and the Work Planners to determine PMT and RTO requirements in accordance with the maintenance procedure.

Additionally, the preventive maintenance instruction associated with the work order was revised to ensure the requirements of the SI are met when performing future maintenance.

VII.

Previous Similar Events at the Same Site

A review of SQN LERs identified two previous events associated with human errors.

LER 327/2016-005-00 reports a condition prohibited by TSs associated with the Hydrogen Mitigation System caused most likely by human error. LER 327/2016-006-00 reports a condition prohibited by TSs associated with the improper calibration of reactor trip instrumentation caused by Instrumentation &Controls Maintenance Personnel not being trained for operation of a digital multi-meter which resulted in an incorrect impedance setting being used during calibration.

VIII.

Additional Information

There is no additional information.

IX.

Commitments

There are no commitments.

REV NO.

- 00Page 7 of 7