05000346/LER-2003-001, Potential Inability of Air-Operated Valves to Function During Design Basis Conditions
| ML030990229 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/31/2003 |
| From: | Myers L FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NP-33-03-001-00 LER 03-001-00 | |
| Download: ML030990229 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3462003001R00 - NRC Website | |
text
FENOC 5501 North State Route 2 FirstEnergy Nuclear Operating Company Oak Harbor, Ohio 43449 Lew W My'ers 419-321-7599 Chief Operating Officer Fax 419321-7582 NP-33-03-001-00 Docket No. 50-346 License No. NPF-3 March 31, 2003 United States Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Ladies and Gentlemen:
LER 2003-001-00 Davis-Besse Nuclear Power Station, Unit No. I Date of Occurrence - January 30, 2003 Enclosed please find Licensee Event Report 2003-001, which is being submitted to provide written notification of potential inability of air-operated valves to function during design basis conditions. This issue was identified during development and implementation of an Air-Operated Valve Reliability Program as previously committed in Licensee Event Report 2002-004. Commitments associated with this LER are listed in the Attachment.
Very truly yours, GMW/s Enclosures cc:
Mr. J. E. Dyer, Regional Administrator, USNRC Region III Mr. C. S. Thomas, DB-1 NRC Senior Resident Inspector Utility Radiological Safety Board
Docket Number 50-346 License Number NPF-3 NP-33-03-001-00 Attachment Page 1 of 1 COMMITMENT LIST The following list identifies those actions committed to by the Davis-Besse Nuclear Power Station in this document. Any other actions discussed in the submittal represent intended or planned actions by Davis-Besse. They are described only as information and are not regulatory
commitments
Please notify the Manager - Regulatory Affairs (419-321-8450) at Davis-Besse of any questions regarding this document or associated regulatory commitments.
COMMITMENTS
DUE DATE
- 1. Install proper sized air accumulators for valves CC1467, CC1469, and CC1495.
- 2. Install a new valve actuator capable of closing the valve MU3 against the maximum differential pressure.
- 3. Submit results of safety significance evaluation in revision to Licensee Event Report.
- 1. Prior to startup
- 2. Prior to startup
- 3. Prior to startup
Abstract
On January 30, 2003, with the reactor defueled, it was determined that several air-operated valve (AOV) actuators had negative operating margins.
After further review, it was determined that four valves were not capable of performing their designated safety functions for all required conditions.
Valves CC1467 and CC1469, Decay Heat Removal Heat Exchanger Outlet Isolation Valves, may not fully open upon a loss of non-safety grade instrument air because their associated air accumulators are undersized.
Similarly, CC1495 may not fully close to isolate cooling water flow to non-essential equipment on a loss of instrument air because the air accumulator was also undersized.
Larger air accumulators are being installed on all three of these valves. Valve MU3 may not close against maximum Reactor Coolant System pressure to isolate letdown flow from inside containment, but would close against normal system pressure.
A new actuator is being installed to allow MU3 to close against maximum Reactor Coolant System pressure.
These conditions, apparently caused due to improper sizing of air-operated valve actuators and accessories during initial design, are being reported in accordance with 10CFR50.73(a)(2)(i)(B) as operation or condition prohibited by the Technical Specifications.
NRC FORM 366 (7-2001)
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies ofNRC Forn 366A) (17)
ANALYSIS OF OCCURRENCE:
At the time of discovery there were no Technical Specification operability requirements for the affected systems with the reactor defueled.
However, the plant operated in this condition when the Decay Heat/Low Pressure Injection System was required to be operable per DBNPS Technical Specification (TS) 3.5.2 and TS 3.5.3, the Component Cooling Water System was required to be operable per TS 3.7.3.1, and Containment Isolation Valves were required to be operable per TS 3.6.3.1.
Therefore, this issue represents a condition prohibited by the Technical Specifications, and so is reportable in accordance with 10CFR50.73(a)(2)(i)(B).
While the Reactor Coolant System Letdown Outlet Isolation Valve (MU3) may not have closed against a maximum Reactor Coolant System pressure of 2500 psig, the valve would have closed under normal operating conditions.
Calculations show the valve would have closed against a differential pressure of 2180 psig, and with normal operating pressure of the Reactor Coolant System at approximately 2155 psig, the expected differential pressure would have been approximately 2100 psig.
If a leak in the Reactor Coolant System caused pressure to decrease to the SFAS Level 2 actuation setpoint of 1600 psig, MU3 would have closed to perform its safety function of isolating containment and Reactor Coolant System Letdown flow.
Additionally, valve MU2A is located outside of containment in compliance with General Design Criteria 55 to isolate letdown flow upon receipt of the same SFAS Level 2 signal.
This motor-operated valve remained fully capable of isolating letdown flow at any postulated Reactor Coolant System pressure due to a low Reactor Coolant System pressure or high containment pressure.
The Decay Heat Removal Heat Exchanger Component Cooling Water Outlet Isolation Valves (CC1467 and CC1469) may not have fully opened when required in response to an SFAS Level 3 signal in conjunction with a loss of non-safety grade instrument air.
However, the valves would have partially opened with the amount of air available in the accumulators, allowing a portion of the required cooling water flow through the Decay Heat Removal Heat Exchangers.
The Component Cooling Water Auxiliary Building Non-Essential Isolation Valve CC1495 may not have fully closed in the event of a loss of non-safety grade instrument air in conjunction with either an SFAS Level 3 signal or a low Component Cooling Water Surge Tank level.
In the event of a low level in the Component Cooling Water Surge Tank, motor-operated valves CC5096 and CC5097 also receive a closure signal, and these two valves would then isolate the non-essential header to isolate the leak.
Evaluations into the safety significance of these deficiencies are ongoing, and the results of these evaluations will be reported in a revision to this Licensee Event Report.
(if more space is required, use additional copies of NRC Form 366A) (17)
CORRECTIVE ACTIONS
An AOV Reliability Program is being implemented, in part, to ensure that AOV actuator sizing and setpoints are reviewed to verify and document their adequacy.
As previously committed in DBNPS LER 2002-004, for all Category 1 and 2 AOVs and their associated components, the design basis requirements, including the correct installed orientation, will be established in accordance with the AOV Reliability Program Manual.
The requisite engineering documents will be developed to implement any required changes. Any modifications needed to restore these components to their design requirements will be completed prior to plant restart.
Post-modification testing will be performed to verify compliance with design bases.
For valves CC1467, CC1469, and CC1495, modifications are being developed to install the proper sized air accumulator.
For valve MU3, a modification is being implemented to install a new valve actuator capable of closing the valve against the maximum differential pressure. The modifications to all four valves will be implemented prior to plant startup.
FAILURE DATA:
DBNPS LER 2002-004 documents similar problems discovered with air-operated valves for which the actuators did not have the capability to properly position the associated valve for all postulated conditions.
It was during the performance of the corrective actions as stated in LER 2002-004 that the problems associated with the four valves described above were discovered.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
NP-33-03-001-00 CRs 03-00830, 03-01040, 03-01253