05000323/LER-2006-001
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | 03-31-2006 |
|---|---|
| Report date: | 05-01-2006 |
| Initial Reporting | |
| ENS 42459 | 10 CFR 21.21 |
| 3232006001R00 - NRC Website | |
I. Plant Conditions
Unit 2 did not operate in any plant modes with the described defect installed.
II. Description of Problem
A. Background
On June 2, 2005, Pacific Gas and Electric Company (PG&E) initiated purchase of an 8-inch tilting disk, stainless steel check valve [CKV], to be built for installation in the Unit 2 Residual Heat Removal (RHR)[BP] System. The check valves in these locations were initially installed in response to NRC Bulletin 88-04, "Potential Safety Related Pump Loss.
The valve was manufactured by Flowserve, Flow Control Division, of Raleigh, North Carolina, in accordance with Vendor Assembly Drawing W9023267, and ASME Section Ill, Subsection NC, 1989 Edition.
Purchase Order No. 125492 was identified as 10 CFR 21 applicable.
B. Event Description
On March 2, 2006, during post-receipt bench testing, PG&E identified incorrect disc dimensions that caused the disc to stick in the valve bonnet, i.e., in the open position. This defect could have prevented the valve from performing its intended safety function of closing to prevent pump-to-pump interaction when both RHR pumps are running.
On March 8, 2006, PG&E notified Flowserve of the defect via Supplier Audit Finding Report No. 060670010, and requested corrective actions be taken.
On March 13, 2006, Flowserve concluded that the defect was caused by disc design error and test procedure error.
On March 16, 2006, Flowserve initiated Quality Problem Corrective Action Plan No. 169, that concluded a 10 CFR 21 evaluation was not required.
On March 31, 2006, the PG&E Vice President - Diablo Canyon Operations and Station Director, concurred with a quality review determination that a significant defect potentially adverse to safety had been identified in a component received for use in a safety-related application for Unit 2.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) On March 31, 2006, at 1301 PST, PG&E notified the NRC in accordance with 10 CFR 21.21(d)(1) via Event Notification Number 42459.
C. Inoperable Structures, Systems, or Components that Contributed to the
Event
None.
D. Other Systems or Secondary Functions Affected None.
E. Method of Discovery This condition was identified during post-receipt bench testing.
F. Operator Actions None.
G. Safety System Responses None.
III.�Cause of the Problem A. Immediate Cause The defect identified involved incorrect valve disc dimensions that caused the disc to stick in the valve bonnet, in the open position.
B. Root Cause The vendor concluded that the cause of the incorrect valve disc dimensions was design error.
C. Contributory Cause The vendor's test procedure did not test the valve with the bonnet installed.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) Diablo Canyon Unit 2 0 5 0 0 0 3 2 3 2006 0 OF
IV. Assessment of Safety Consequences
The identified defect could have prevented the valve from performing its intended safety function of closing to prevent pump-to-pump interaction when both RHR pumps are running. Failure of this check valve, had it been installed, could have resulted in the loss of one RHR train on Unit 2, which could impact the ability to shut down the reactor and maintain it in a safe shutdown condition.
The defect was identified during bench testing prior to installation, thus, the defect was prevented from being placed in service. If the defect had not been previously identified, PG&E's Inservice Testing Program requires that the valve be full flow and reverse flow verified prior to declaring the system operable.
Therefore, this event was of very low risk significance, was not a Safety System Functional Failure, and did not adversely affect the health and safety of the public.
V.�Corrective Actions A.�Immediate Actions 1. Bench testing activities were stopped, a problem report was initiated, and the vendor notified.
2. Supplier Audit Finding Report No. 060670010 was issued to Flowserve.
B.�Corrective Actions PG&E repaired the valve in accordance with vendor instructions.
VI.�Additional Information A. Failed Component: 8-inch tilting disk stainless steel check valve.
Manufacturer:�Flowserve; PG&E Purchase Order No. 125492 Flow Control Division, Raleigh, North Carolina Reference: Vendor Assembly Drawing W9023267, Part Serial No. AY777 ASME Section III, Subsection NC, 1989 Edition
B. Previous Similar Events
None.