05000277/LER-2002-003-05, Re Loss of High Pressure Coolant Injection System Function as a Result of Less than Adequate Check Valve Condition
| ML040440310 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 01/30/2004 |
| From: | Stone J Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CCN 04-14007 LER 02-003-05 | |
| Download: ML040440310 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| 2772002003R05 - NRC Website | |
text
Exelkni.
Exelon Nuclear Telephone 717.456.7014 Nuclear Peach Bottom Atomic Power Station www.exeloncorp.com 1848 Lay Road Delta, PA 17314-9032 1 OCFR 50.73 January 30, 2004 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station (PBAPS) Unit 2 Facility Operating License Nos. DPR-44 NRC Docket No. 50-277
Subject:
Licensee Event Report (LER) 2-03-05 This LER reports a loss of safety function involving the High Pressure Coolant Injection System (HPCI) resulting from less than adequate materiel condition of a suction flow path check valve. In accordance with NEI 99-04, the regulatory commitment contained in this correspondence is to restore compliance with the regulations. The specific methods that are planned to restore and maintain compliance are discussed in the LER.
If you have any questions or require additional information, please do not hesitate to contact us.
Sincerely, J hn A. Stone lant Manager each Bottom Atomic Power Station JAS/djf/CR 189956 Attachment cc:
PSE&G, Financial Controls and Co-owner Affairs R. R. Janati, Commonwealth of Pennsylvania INPO Records Center H. J. Miller, US NRC, Administrator, Region I R.. McLean, State of Maryland C. W. Smith, US NRC, Senior Resident Inspector CCN 04-14007
SUMMARY OF EXELON NUCLEAR COMMITMENTS The following table identifies commitments made in this document by Exelon Nuclear.
(Any other actions discussed in the submittal represent intended or planned actions by Exelon Nuclear. They are described to the NRC for the NRC's information and are not regulatory commitments.)
Commitment
Committed Date or "Outage" In accordance with NEI 99-04, the In accordance with the Corrective Action regulatory commitment contained in this Program correspondence is to restore compliance with the regulations. The specific methods that are planned to restore and maintain compliance are discussed in the LER.
Abstract
approximately 15 single-spaced typewritten lines)
On 12/10/03, at approximately 1040 hours0.012 days <br />0.289 hours <br />0.00172 weeks <br />3.9572e-4 months <br />, during the performance of a routine Logic System Functional Test for the High Pressure Coolant Injection (HPCI) system, Operations personnel detected an unexpected condition when a Suppression Pool high water level alarm was received. Based on engineering reviews, it was subsequently determined at approximately 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> that the HPCI check valve 61 in the system suction path from the Suppression Pool was not properly closed.
This resulted in the HPCI system possibly not being capable of performing its intended restart design function for certain design bases events. For these events, with HPCI aligned to the Suppression Pool, the HPCI system piping could be voided while the system is not operating resulting in water hammer conditions if the HPCI system would need to restart after performing its design function.
There were no actual safety consequences or water hammer events associated with this event. The cause of the HPCI suction check valve 61 not closing properly was attributed to the valve disc not seating properly. This was caused by excessive clearances of certain check valve internal components due to maintenance procedures not containing adequate criteria concerning component clearances and alignment of the valve disc to the seat. In body repairs were made to the HPCI Suction Check Valve 61 and HPCI was returned to a fully operable condition by approximately 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> on 12/12/03. Maintenance procedures will be upgraded.
NRC FORM 366 (7-2001)
(If more space Is required, use additional copies of NRC Forn 366A) (17)
Unit Conditions Prior to the Event Unit 2 was in Mode 1 and operating at approximately 100% rated thermal power when the event occurred. There were no structures, systems or components out of service that contributed to this event. At the time of discovery, the High Pressure Coolant Injection (HPCI) System was considered inoperable to support a routine Logic System Functional Test (LFST). The inoperability had been declared on 12/10/03, at approximately 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br />. The HPCI system was not in operation at the time of discovery.
Description of the Event On 12/10/03, at approximately 1040 hours0.012 days <br />0.289 hours <br />0.00172 weeks <br />3.9572e-4 months <br />, during the performance of a routine Logic System Functional Test for the High Pressure Coolant Injection (HPCI) (EIIS:
BJ) system, Operations personnel detected an unexpected condition when a Suppression Pool high water level alarm was received. Based on engineering reviews, it was subsequently determined at approximately 1800 hours0.0208 days <br />0.5 hours <br />0.00298 weeks <br />6.849e-4 months <br /> that the HPCI check valve 61 (EIIS: V) in the system suction path from the Suppression Pool (EIIS: TK) was not properly closed. This allowed water from the Condensate Storage Tank (CST) (EIIS: TK) suction source to flow to the Suppression Pool when the HPCI system suction valve swapover function was being tested. The check valve condition resulted in the HPCI system possibly not being capable of performing its intended restart design function for certain design bases events. For limited design events where HPCI suction would need to swap over from the normal Condensate Storage Tank (CST) suction source to the Suppression Pool, HPCI pump discharge piping could be voided as a result of water draining back to the Suppression Pool through the open check valve 61 while the HPCI system is not in operation. This voiding in the HPCI piping could result in water hammer conditions when the HPCI system would need to restart and could possibly result in loss of integrity of the HPCI pump (EIIS: P) discharge piping.
At the time of discovery, a Logic System Functional Test of the HPCI system was being performed. The HPCI system was not in operation. The swap over logic that controls the HPCI system suction path being either from the CST or Suppression Pool was being tested. When the normally closed motor operated suction valves (MO-57 and MO-58) from the Suppression Pool were opened as part of the test, water from the CST flowed back through the open check valve located between the MO-57 and MO-58 valves to the Suppression Pool until the CST suction line isolation valve MO-17 closed. The CST suction line isolation valve MO-17 closes when the MO-57 and MO-58 valves are open. Operations personnel promptly halted the LSFT at approximately 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br />. The test performance was exited at approximately 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br />. Although HPCI was considered inoperable, HPCI was returned to a condition of being available for automatic injection using the CST as a suction source at approximately 1415 hours0.0164 days <br />0.393 hours <br />0.00234 weeks <br />5.384075e-4 months <br />.
Troubleshooting of the HPCI suction check valve 61 was completed by 12/11/03 at approximately 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> confirming that the check valve could not be fully closed.
This condition was promptly reported to the NRC on 12/10/03 at approximately 1150 hours0.0133 days <br />0.319 hours <br />0.0019 weeks <br />4.37575e-4 months <br /> pursuant to the requirements of 10CFR 50.72(b)(3)(v)(D) (Event Notification 40384).
In body repairs were made to the HPCI Suction Check Valve 61 and HPCI was declared operable by approximately 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> on 12/12/03.
(f more space Is required, use additional copies of (If more space Is required, use additional copies of NRC Form 366A) (17)
Cause of the Event
The cause of the HPCI suction check valve 61 not closing properly was attributed to the valve disc not seating properly on the valve seat. This was primarily caused by excessive clearance that existed between the disc post and the disc arm. This condition had no affect on the valve disc opening. However, when the valve disc would close, this condition could result in slight cocking of the disc relative to the seat, thereby resulting in improper disc seating. The underlying cause of the condition is attributed to less than adequate direction in the associated maintenance procedures concerning the specific criteria for the clearances and the verification of the as-left alignment of the valve disc to the seat. The valve was last worked in April of 2002 and had operated properly since that time. However, the excessive clearances combined with normal wear in the in-body components resulted in the inoperable condition of the valve discovered on 12/10/03.
The check valve is a 16-inch Free Flow Reverse Current Valve with Double Bearing Covers originally supplied by Atwood & Morrill Co.
Corrective Actions
Troubleshooting of the HPCI suction check valve 61 was completed by 12/11/03 at approximately 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> confirming that the check valve could not be fully closed.
In-body repairs were made to the HPCI Suction Check Valve 61 and HPCI was returned to a fully operable condition by approximately 1445 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.498225e-4 months <br /> on 12/12/03.
The valve manufacturer was consulted and appropriate valve in-body component clearances were determined.
Maintenance procedures will be upgraded to provide enhanced guidance on valve assembly including appropriate valve in-body component clearances and positioning of the valve disc. This will result in assurance of proper alignment of the valve disc to the valve seat.
Additional corrective actions are being evaluated in accordance with the corrective action program.
Maintenance records of the similar Unit 3 HPCI 61 check valve were reviewed resulting in confidence concerning the operability of the Unit 3 valve. An extent of condition review is being performed in accordance with the corrective action program for other similar check valves.
Previous Similar Occurrences A similar event was reported in LER 3-01-01 concerning leakage through the corresponding check valve for Unit 3. Also, in-body maintenance was performed on the Unit 2 HPCI check valve 61 in April of 2002. Actions involved with these previous occurrences were limited to repairing the check valves and did not include upgrading the maintenance procedures with enhanced guidance concerning in-body clearances.