05000251/LER-2018-001, Inoperable Auxiliary Feedwater Steam Supply Flowpath

Inoperable Auxiliary Feedwater Steam Supply Flowpath

ML18191B126
Person / Time
Site:	Turkey Point
Issue date:	06/27/2018
From:	Stamp B Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2018-127 LER 2018-001-00
Download: ML18191B126 (4)

LER-2018-001, Inoperable Auxiliary Feedwater Steam Supply Flowpath

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2512018001R00 - NRC Website

text

U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555-0001 Re:

Turkey Point Unit 4 Docket No. 50-251 Licensee Event Report: 2018-001-00 Date of Event: May 7, 2018 Inoperable Auxiliary Feedwater Steam Supply Flowpath JUN 2 7 2018 L-2018-127 10 CFR § 50.73 The attached Licensee Event Report 05000251/2018-001-00 is submitted pursuant to 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by the Turkey Point Unit 4 Technical Specifications.

If there are any questions, please call Mr. Robert J. Hess, Licensing Manager at 305-246-4112.

Sincerely, p..~

Brian Stamp Plant General Manager Turkey Point Nuclear Plant Attachment cc:

Regional Administrator, USNRC, Region II Senior Resident Inspector, USNRC, Turkey Point Nuclear Plant Florida Power & Light Company 9760 SW 344th St., Homestead, FL 33035

NRC FORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)

, the NRC may not conduct or sponsor, and a oerson is not reauired to resoond to, the information collection.

,3. Page Turkey Point Unit 4 05000251 1 OF3

4. Title Inoperable Auxiliary Feedwater Steam Supply Flowpath

5. Event Date

6. LER Number

7. Report Date

8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Month Day Year Number No.

05000 05 07 2018 2018

- 001 06 27 2018 Facility Name Docket Number

- 0 05000 Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)

On May 7, 2018 at 0049 while operating in Mode 1 at 100% power, Turkey Point Unit 4 experienced a failure of the steam generator A auxiliary feedwater (AFW) steam supply valve during preplanned surveillance testing. A review of the failure identified that it likely existed since the prior surveillance test on April 11, 2018. The resulting inoperability period of 26 days exceeded the seven-day allowed out of service time for an inoperable steam supply flowpath in Turkey Point Unit 4 Technical Specification (TS) 3.7.1.2, Auxiliary Feedwater System, resulting in a condition prohibited by TS. No adverse consequences resulted from this event.

The cause of the failure of the steam supply valve was disengagement of the torque arm from the stem key. With the torque arm disengaged from the key, the valve stem rotated and caused the geared limit switch settings for the motor operator to become out of sync with the valve travel. As a result, the limit switches did not actuate at the expected set points. Corrective actions included repairing the torque arm, overhauling the motor-operator, resetting the limit switches, installing a set screw as a secondary restraint on the torque arm, and revising maintenance procedures to verify position and tightness of the torque arm or anti-rotation device during preventative maintenance activities.

NRG FORM 366 (04-2018)

Description of Event

SEQUENTIAL NUMBER

- 001 REV NO.

- 0 On May 7, 2018 at 0049 while operating in Mode 1 at 100% power, Turkey Point Unit 4 experienced a failure of the steam generator (SG) [SG] A auxiliary feedwater (AFW) steam supply valve [BA, 20] during preplanned surveillance testing. A review of the failure identified that it likely existed since the prior surveillance test on April 11, 2018. The resulting inoperability period of 26 days exceeded the seven-day allowed out of service time for an inoperable steam supply flowpath in Turkey Point Unit 4 Technical Specification (TS) 3.7.1.2, Auxiliary Feedwater System, resulting in a condition prohibited by TS.

Cause of the Event

The direct cause of the event was that the torque arm on MOV-4-1403, SG-A AFW steam supply valve, was disengaged from the stem key. With the torque arm disengaged from the key, the valve stem rotated causing the geared limit switch [BA, ZIS] settings for the motor operator to become out of sync with the valve travel. The most likely cause of the torque arm being loose was that preventive maintenance procedures did not include steps to verify the torque arm is properly positioned and correctly tightened on the valve stem.

Analysis of Event

The AFW system includes three steam turbine-driven pumps [BA, P] for Turkey Point Units 3 and 4. The three pumps are installed such that each pump supplies AFW to either Unit 3 or 4, with any single pump supplying the total feedwater requirement of either unit. Two pumps are normally aligned to AFW Train 2 and the third pump is normally aligned to AFW Train 1. Upon initiation of the AFW system, the turbine steam supply isolation valves automatically open and actuate position switches, which in turn actuate opening of the AFW flow control valves [BA, FCV].

During surveillance testing on May 7, 2018, the limit switches associated with MOV-4-1403, SG-A AFW steam supply valve, did not actuate as required when the valve was opened. As a result, the AFW flow control valves did not open automatically.

Troubleshooting found the MOV-4-1403 torque arm (anti-rotation device) out of position and disengaged from the stem key. With the torque arm disengaged from the key, the valve stem was able to rotate causing the geared limit switch settings on the motor operator to become out of sync with the valve travel. As a result, the limit switches did not actuate at the expected set points.

Investigation determined that the limit switch misalignment occurred during surveillance testing on April 11, 2018 when the valve was last closed. Technical Specification (TS) 3.7.1.2, Auxiliary Feedwater System, allows seven days to restore an inoperable steam supply flow path to operable status. Since the flow path was inoperable for approximately 26 days, this event is reportable in accordance with 10 CFR 50. 73(a)(2)(i)(B) as a condition prohibited by the TS.

Turkey Point TS 3.7.1.2 requires two independent AFW trains with three steam supply flow paths and three pumps to be operable in Modes 1, 2 and 3. With the single AFW steam supply flow inoperable, two redundant flow paths were available to support operation of the AFW system. Therefore, this event did not involve a safety system functional failure. No adverse consequences resulted from this event, and the event had no adverse impact on the health and safety of the public or the plant and its personnel.

NRG FORM 3668 (02-2018)

Page 2 of 3 (04-2018)

U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 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/)

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

3. LERNUMBER YEAR Turkey Point Unit 4 05000-251 2018

Corrective Actions

SEQUENTIAL NUMBER

- 001 REV NO.

- 0 Corrective actions to repair the torque arm, overhaul the motor-operator, and reset the limit switches during static diagnostic testing were completed on AFW steam supply valve MOV-4-1403. Additionally, the torque arm key was replaced and a modification was implemented to install a set screw as a secondary restraint on the torque arm.

Corrective actions are planned to revise maintenance procedures to verify the position and tightness of the torque arm or anti-rotation device during preventative maintenance activities.

Actions to address extent of condition verified that the torque arm and valve stem key of the remaining AFW valves susceptible to the same condition were properly positioned and tighten. Additionally, set screws were installed in the AFW steam supply valve torque arms as a secondary restraint on the torque arm.

Additional Information

The Energy Industry Identification System (EIIS) codes are included in this LER in the following format: [EIIS system identifier, Ells component identifier].

Turkey Point Condition Report AR 2262955.

Similar Events

A review of the LERs issued over the last five years related to the AFW system revealed no similar occurrences at Turkey Point. Page 3 of 3