05000341/LER-2022-004, Containment Isolation Valve Actuator Found Disconnected from Its Bonnet Resulting in Condition Prohibited by Technical Specifications
| ML22304A009 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 10/31/2022 |
| From: | Peter Dietrich DTE Electric Company |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NRC-22-0043 LER 2022-004-00 | |
| Download: ML22304A009 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3412022004R00 - NRC Website | |
text
October 31, 2022 NRC-22-0043 U.S. Nuclear Regulat01y Commission Attention: Document Control Desk Washington, DC 20555-0001 Fenni 2 Power Plant NRC Docket No. 50-341 NRC License No. NPF-43
Subject:
Licensee Event Repo1i (LER) No. 2022-004 Peter Diehich Senior Yice Pl'esident and Chief Nuclear Officer DTE Electric Company 6400 N. Dixie Highway, Newport, l\\Il 48166 Tel: 734.586.4153 Email: peter.dietrich@dteenergy.com DTE 10 CFR 50.73 Pursuant to 10 CFR 50.73(a)(2)(i)(B), DTE Electric Company (DTE) is submitting LER No. 2022-004, Contaillillent Isolation Valve Actuator Found Disconnected from its Bonnet Resulting in Condition Prohibited by Technical Specifications.
No new commitments are being made in this submittal.
Should you have any questions or require additional info1mation, please contact Mr. Eric Frank, Manager - Nuclear Licensing, at (734) 586-4772.
Sincerely, Peter Dietrich Senior Vice President and Chief Nuclear Officer
Enclosure:
Licensee Event Repo1i No. 2022-004, Containment Isolation Valve Actuator Found Disconnected from its Bonnet Resulting in Condition Prohibited by Technical Specifications.
cc:
NRC Project Manager NRC Resident Office Regional Administrator, Region III
Enclosure to NRC-22-0043 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2022-004 Containment Isolation Valve Actuator Found Disconnected from its Bonnet Resulting in Condition Prohibited by Technical Specifications
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: 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, R3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/}
- 1. Facility Name Fermi 2
- 4. Title Eslinaled
- 2. Docket Number
- 3. Page 05000 341 1 OF 4
Containment Isolation Valve Actuator Found Disconnected from its Bonnet Resulting in Condition Prohibited by Technical
~n..c.r-ifir-~+innc
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Month Day Year Year Sequential Revision Month Day Year
+----+----lf----+--N_um_be
_ r_--+-_N_o_. ---t---+-----+----1 N/A Facility Name Docket Number 05000 06 27 2022 2022
- 004 00 10 31 2022 Facility Name Docket Number N/A 05000
- 9. Operating Mode 1
110. Power Level 9
Abstract
On 06/27/2022 during start up walkdowns for Forced Outage 22-01, engineering personnel discovered the B2103F019 (Main Steam Outboard Drain Isolation valve) motor operator separated from the valve bonnet yoke arm flange. The motor operator was energized (motor and gear train freely running) and agitating on the end of the vertically oriented valve stem. The inboard isolation valve (B2103F016) was capable to isolate during the entire time the B2103F019 was inoperable. Upon identification, the Containment Isolation Valve was declared inoperable per Technical Specification 3.6.1.3. The cause was determined to be improper thread engagement, due to personnel error of installing the incorrect bolts following testing using an installed testing device. B2103F019 was secured and is planned to be reworked during the next availability (refueling outage). The cycle schedule was reviewed for the impact of B2103F016 and 82103F019 isolated with no issues identified. An extent of condition was performed on the other motor operated valves tested during the previous refueling outage.
This event is being reported under 10 CFR 50.73(a)(2)(i)(B) for operation or condition prohibited by TS.
INITIAL PLANT CONDITIONS
Mode-1 Reactor Power - 9 Percent There were no structures, systems, or components (SSCs) that were inoperable at the start of this event that contributed to his event.
DESCRIPTION OF THE EVENT On 06/27/2022 during start up walkdowns for Forced Outage 22-01, engineering personnel discovered the B2103F019 (Main Steam Outboard Drain Isolation valve) [SBJ[ISV] motor operator [84] separated from the valve bonnet yoke arm flange [V]. The motor operator was energized (motor and gear train freely running) and agitating on the end of the vertically oriented valve stem. Having run out of stem threads, the actuator was being restrained on the end of the valve stem by the unthreaded portion of the stem nut counterbore and by the electrical conduit that serves the motor operated valve (MOV).
The MOV was de-energized by shutting off the actuator power supply at the Motor Control Center.
During the initial investigation, the (4) actuator mounting bolts had pulled out of the actuator housing, with visible damage to he threaded actuator mounting holes. After inspection it was identified that the removed bolts were 1 in long 5/16 inch cap bolts that, when fully tightened, only had 2 or 3 threads of engagement into the actuator.
Based on the sequence of events, as noted per plant computer data, during the 06/27/2022 closing stroke the actuator-to-bonnet yoke flange-threaded connections failed. This allowed the unrestrained actuator to traverse up the valve stem as the stem nut rotated about the valve-stem threads.
SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS
There were no safety consequences or radiological releases associated with this event. At no time during this event was here a potential for endangering the public health and safety.
B2103F019 is a normally closed Primary Containment Isolation Valve (PCIV) [JM] and has a safety function to automatically close on a Reactor Vessel Low Level 1, and on Accident Isolation Signals E-Main Steam Line High Flow, F-Main Steam Line Tunnel High Temperature, G-Main Steam Line Low Pressure, J-Low Condenser Vacuum, P-Turbine Building High Temperatures to provide primary containment isolation of penetration, X-8. B2103F019 does not have a safety function in he open position. It is opened to provide a drain path for Main Steam line moisture to the turbine drain system during plant start-up or similar conditions. It is an 1ST Appendix Ill (formerly NRC GL 96-05) MOV with an active safety function to close within a design basis stroke time of 23 seconds per TRM 3.6.3 Table TR3.6.3-1 Group 1 Main Steam Automatic Isolation Valves. It is Type C Leak Tested and Bypass Leakage Tested under the Appendix J program. It is classified as Seismic Class I.
Based on physical condition of valve B2103F019, it would not have been able to close and fulfill its function o isolate primary containment. For penetration X-8, the inboard containment isolation valve (B2103F016) was Operable hroughout the entire period, where B2103F019 was not. While redundancy of the primary containment isolation function was compromised, penetration X-8 was able to be isolated.
Although the penetration isolation of the Main Steam drain line safety function was maintained operable (based on the B2103F016 being capable and operable to isolate during the entire time B2103F019 was inoperable), TS 3.6.1.3 states that each PCIV (except vacuum breakers) shall be operable in Modes 1, 2, and 3. Condition A identifies that if the penetration flow path with one inoperable PCIV, then the flow path shall be isolated by closing and deactivating at least one automatic or manual valve in the flow path within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The initial past operability for the initial discovery of the issue on 6/27/2022 determined the condition was not reportable based on the Safety Function of the flow path was maintained by B2103F016 being operable. The past operability failed to identify that this condition is prohibited by Technical Specifications and B2103F019 was not operable as an isolation valve since the startup of the Refueling outage.
Probabilistic Risk Analysis was performed on the inoperable B2103F019, and it was determined that there was no change in Core Damage Frequency (CDF), and minimal change in Large Early Release Frequency (LERF).
CAUSE OF THE EVENT
The cause was determined to be improper thread engagement, due to personnel error (utility employees) of installing the incorrect bolts following testing using an installed testing device. Thread engagement was not achievable due to bolt length. The WO review concluded that bolting was ordered to perform thrust test utilizing a Torque-Thrust Cell (TTC). Per Crane Nuclear documentation, (4) 5/1 6-18 x 1-inch cap screws are required to mount a RA TTC to an SMB-000 actuator and the final installed bolting for the yolk/actuator is 5/16-18 x 1-1 /2-inch. Maintenance activities during the refueling outage used shorter testing bolts during final assembly to secure the actuator to the valve yoke flange which resulted in improper thread engagement (as found actuator bolting was confirmed to be 5/16-18 x 1-inch cap screws).
CORRECTIVE ACTIONS
B2103F019 was secured and is planned to be reworked during the next availability (forced or refueling outage). The cycle schedule was reviewed for the impact of B2103F016 and B2103F019 isolated for the remainder of the cycle with no issues identified.
Seven additional Motor Operated Valves were identified as being in a potential similar condition due to the mounting bolts being removed during the previous refueling outage for maintenance. On six of the seven, a visual inspection determined hat the correct bolting is present, and no separation exists between the actuator and bonnet as described in the condition
description
The seventh valve (B2103F016) is located in the drywell and is inaccessible. As described above, B2103F016 is the inboard isolation valve in series with B2103F019, B2103F016 has operated a minimum of six times since the previous refueling outage and has not shown any indication of a similar issue. B2103F016 has been deenergized in the closed position to isolate the containment penetration X-8.
PREVIOUS OCCURRENCES
A review of the Corrective Action Program for additional Containment Isolation Valves that may have been inappropriately classified as not reportable as the safety function was not challenged due to the subsequent in series valve was operable was performed. Three issues were correctly identified at time of discovery during the surveillance requirement and repaired. Another issue identified by a similar surveillance requirement (but was monitored at an increased surveillance requency) was previously identified by the NRC under Green NCV 05000341/2022001-02. This issue was an NRC violation as the subsequent increased frequency was not performed as stated. Page 4
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