05000317/LER-2024-001, Condition Prohibited by Technical Specifications Due to Safety Injection Check Valve Not Full Closed
| ML24075A103 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/13/2024 |
| From: | Simpson A Constellation Energy Group |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| LER 2024-001-00 | |
| Download: ML24075A103 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3172024001R00 - NRC Website | |
text
Constellationy.
March 13, 2024 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Subject:
Calvert Cliffs Nuclear Power Plant, Unit No. 1 Renewed Facility Operating License Nos. DPR-53 NRC Docket No. 50-317 Licensee Event Report 2024-001, Revision 00 Peter F. Moodie Plant Manager Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657 410-495-5205 Office 603-548-7775 Mobile www.constellat1on.com peter.moodie@constellation.com 10 CFR 50.73 Condition Prohibited by Technical Specifications due to Safety Injection Check Valve Not Full Closed The attached report is being sent to you as required by 10 CFR 50. 73.
There are no regulatory commitments contained in this correspondence.
Should you have questions regarding this report, please contact Mr. Larry D. Smith at (410) 495-5219.
Respectfully,
~
Peter F. Moodie Plant Manager PFM/ALS/aj Attachment:
LER 317-2024-001, Rev 00 cc:
NRC Project Manager, Calvert Cliffs NRC Regional Administrator, Region I NRC Resident Inspector, Calvert Cliffs S. Seaman, DNR
Abstract
In January 2024, it was discovered that a check valve in the safety injection system was not full shut and was therefore leaking by its seat. This check valve is also a containment isolation valve. Operations personnel declared the valve inoperable and immediately entered the applicable technical specification limiting condition for operation as required. However, because the condition existed for a time longer than allowed by the plant's technical specifications, this event is considered a condition prohibited by the plant's technical specifications and a licensee event report is required. The cause of the issue was due to a valve packing leak that allowed boric acid to build up and increase friction preventing the valve from going shut. To correct the issue, the valve was cleaned, disassembled, inspected and repaired during the scheduled Unit 1 refueling outage in February 2024.
PLANT AND SYSTEM IDENTIFICATION
- 2. DOCKET NUMBER YEAR 05000317 2024
- 3. LER NUMBER SEQUENTIAL NUMBER 001 REV NO.
00 Calvert Cliffs Nuclear Power Plant, Unit 1, is a Combustion Engineering Pressurized Water Reactor with a licensed maximum power level of 2737 megawatts thermal. The Energy Industry Identification System code used in the text is identified as [SQ].
A. CONDITION PRIOR TO EVENT Unit: 1 Date: January 13, 2024 Power level: 100 Mode: Unit 1 was in Mode 1 when the condition was discovered.
B. DESCRIPTION OF EVENT On January 13, 2024, Operations performed a partial technical specifications surveillance test to determine if a check valve in the safety injection system, that is located in the Unit 1 containment building and is classified as a containment isolation valve, was leaking by. This was in response to a condition identified on January 11, 2024, when a review of the main control room logs identified that the 128 Safety Injection Tank (SIT) level had lowered one inch (approximately 40 gallons) and system pressure had lowered 1.5 psig in approximately six hours. It was unclear what caused the issue due to the number of components and flow paths in the system.
However, maintenance on the system performed during that time could explain the drop in SIT level and pressure assuming a safety injection check valve in the system was leaking by. Operations initiated an issue report (IR04730811) documenting the issue with the 128 SIT on January 11, 2024. Troubleshooting was performed to assist Operations in determining the cause for 128 SIT's drop in level and pressure. On January 13, 2024, an unsatisfactory result was obtained during performance of the partial technical specifications surveillance test due to the inability to lower test pressure to at least 40 psig, as required to perform the test (Test pressure could not be lowered below 250 psig which was approximately the pressure of the associated 128 SIT). Therefore, Operations declared the check valve, 1CKVSl-148 inoperable and entered Technical Specification (TS) Limiting Condition for Operation (LCO) 3.6.3.A, for one or more penetration flow paths with one containment isolation valve inoperable. IR04730916 was initiated. On January 16, 2024, a Unit 1 containment entry was performed to verify the actual position of the check valve. After manually cycling the check valve, it was left in the shut position.
C. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES January 11, 2024: 12:00: Operations discovered 128 SIT level had lowered one inch (approximately 40 gallons) and pressure had lowered 1.5 psig in about six hours.
January 13, 2024:16:35: Technical Specification 3.6.3.A was entered due to 1CKVSl-148 out of service due to leak-by observed during partial performance of STP O-065J-1.
- 2. DOCKET NUMBER
- 3. LER NUMBER YEAR SEQUENTIAL REV NUMBER NO.
05000317 2024 -
001 00 January 16, 2024: During a Unit 1 containment entry, station personnel found the check valve in the open position. The check valve would not shut without assistance from operations personnel. Operations personnel utilized the weighted arm of the check valve and left the check valve in the shut position.
February 12, 2024: 12:35: Unit 1 entered Mode 5 (Cold Shutdown).
February-March 2024: During a scheduled Unit 1 refueling outage, the check valve was disassembled, inspected and repaired. Repairs included removal of boric acid that had accumulated on the valve, replacing packing rings and replacing the packing bushing, to resolve the leak. Upon reassembly and successful post maintenance operational testing, the valve was returned to Operable status and the associated TS LCO was exited.
D. CAUSE OF EVENT The method of discovery for this event was self-revealing and is documented in the site's Corrective Action Program (CAP) under IR04730916. The valve was inspected during the Unit 1 refueling outage in February 2024. It was determined that the initial failure of 1CKVSl-148 was caused by a packing leak that allowed boric acid to come out of solution, dry and increase the friction between the check valve swing arm and packing gland preventing the valve from going full shut and thus causing the valve to leak by its seat. The CAP investigation is ongoing, therefore additional actions may be determined.
E. SAFETY ANALYSIS The subject event satisfies the criteria in NUREG-1022, Revision 3, for any event or condition that was prohibited by the plant's Technical Specifications. A Licensee Event Report (LER) is required if a condition existed for a time longer than permitted by the TS (i.e., greater than the total allowed restoration and shutdown outage time or completion time in the STS), even if the condition was not discovered until after the allowable time had elapsed and the condition was rectified immediately upon discovery. It is assumed that there was firm evidence that a condition prohibited by TS existed before discovery, for a time longer than permitted by the TS.
Specifically, for this event, the condition was discovered on January 13, 2024 at 16:35 when the partial surveillance test failed. There is firm evidence that the condition existed on January 11, 2024, when Operations personnel identified that the 128 SIT level and pressure had decreased. The cause of the lowered level and decreased pressure was confirmed when the partial surveillance test failed on January 13, 2024, and further verified via the Unit 1 containment entry on January 16, 2024 when the check valve was found in the open position. The degraded condition affected the close function of the valve, such that the containment isolation function could not be satisfied. Technical Specification 3.6.3 "Containment Isolation Valves" Limiting Condition for Operation states "Each Containment Isolation Valve Shall be Operable", and is applicable in Modes 1, 2, 3 and 4. With one or more penetration flow paths with one containment isolation valve inoperable (Condition A), the required action is to isolate the affected penetration flow path by use of at least one closed and de-activated automatic valve, closed manual valve, blind flange, or check valve with flow through the valve secured within four (4) hours or in accordance with the risk informed completion time (RICT) program.
Required action also requires verification that the affected penetration flow path is isolated once per 31 days following isolation for isolation devices outside Containment AND prior to entering MODE 4 from MODE 5 if not performed within the previous 92 days for isolation devices inside containment. With Required Action and
- 2. DOCKET NUMBER
- 3. LER NUMBER YEAR SEQUENTIAL REV NUMBER NO.
05000317 2024 -
001 00 associated Completion Time not met (Condition D), required action is to be in Mode 3 within six (6) hours and Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. As noted above, there is firm evidence that the condition (check valve open) existed from January 11, 2024 at 12:00 until February 12, 2024 when Unit 1 entered Mode 5 at 12:35. Therefore, this event is reportable pursuant to 1 0CFR50.73(a)(2)(i)(B). There were no safety consequences as a result of the event.
F. CORRECTIVE ACTIONS During the 2024 Unit 1 refueling outage, the check valve was cleaned, disassembled, inspected and repaired.
Valve packing rings and the packing bushing were removed and replaced. The valve body and internals were cleaned and inspected with no evidence of damage identified. The surveillance test was subsequently performed satisfactorily. The Corrective Action Program investigation is ongoing, therefore additional actions may be determined.
G. PREVIOUS OCCURRENCES A review of Calvert Cliffs' events was performed. There were no previous occurrences of a safety injection check valve failing to close due to increased friction from an accumulation of boric acid.
H. COMPONENT FAILURE DATA Component 1CKVSl-148 128 Safety Injection Header Check Valve IEEE 803 FUNCTION ID CKV IEEE805 SYSTEM ID BQ Page_4_ of _4_