05000446/LER-1994-001, :on 940106,personnel Air Lock Outer Door Equalizing Valve Inadvertently Left in Open Position Due to Procedural Weakness.Outer Door Cycled Full Closed & Appropriate Procedures Will Be Revised
| ML20063E626 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/02/1994 |
| From: | William Cahill, Guldemond W, Walker R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| LER-94-001, LER-94-1, TXX-94036, NUDOCS 9402100142 | |
| Download: ML20063E626 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) |
| 4461994001R00 - NRC Website | |
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- TXX-94036 File # 10200 TUELECTRIC Ref.
- 50.73(a)(2)(i)
February 2, 1994 William J. Cahill, Jr.
Group Vice President U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) - UNIT 2 DOCKET NO. 50-446 OPERATION PROHIBITED BY TECHNICAL SPECIFICATION LICENSEE EVENT REPORT 94-001-00 Gentlemen:
Enclosed is the Licensee Event Report (LER) 94-001-00 for Comanche Peak Steam Electric Station Unit 2 " Procedure Weakness Caused the Personnel Air Lock Outer Door Equalizing Valve to be Lef t in Mid-Position."
Sincerely, William J. Cahill, Jr.
By:
9 Roger D. Walker Manager of Regulatory Affairs OB:tg cc: Mr. L. J. Callan, Region IV Mr. L. A. Yandell, Region IV Resident Inspectors, CPSES 350023 9402100142 940202
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SUMMARY OF Tile EVENT, INCLUDING DATES AND APPROXIMATE TIMES On December 30, 1993, at 11:04 a.m., Auxiliary Operator (utility, non-licensed) and Security Test Group personnel performed a door open alarm test on the outer door of the CPSES Unit 2 Personnel Air Lock (PAL)
(EIIS:(AL)(NH)).
The test was accomplished by electro / hydraulic partially opening the PAL locking ring approximately six (6) inches to disengage the magnetic switch and verifying that the appropriate alarm was received in the Cent *al Alarm Station (CAS). The locking ring was then cycled closed electrically.
l During normal operation the CPSES Unit 2 Containment PAL uses an installed electro / hydraulic system to rotate locking rings which secure the inner and outer doors (EIIS:(DR)), full rotation of the locking ring enables operation of the door. The system has interlocks to ensure that equalizing valves (EIIS:(V)) between the safeguards building and the PAL and the Containment Building and the PAL are opened and closed in proper
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Proper sequencing of the system components is based on a full cycle of the PAL. Partial cycling of the door operating system can result in misalignment of components and prevent subsequent door operation.
On January 6, 1994, at approximately 8:10 a.m., the Unit Supervisor (utility, licensed) and a member of the Security Test Group (contractor, non-licensed) were discussing the performance of the door open alarm test on the CPSES Unit 2 PAL. The Unit Supervisor (utility, licensed) requested that the test be rescheduled to coincide with a normal entry in order to minimize the number of door seal tests, which are required to be performed, if the Unit is in Mode 1 through Mode 4.
The Security Test Group informed the Unit Supervisor that the outer door did not have to be fully cycled to perform the test.
The test which was performed on December 30, 1993, had been performed by rotating the outer door locking ring approximately six (6) inches to produce the alarm, and the closing the locking ring. During this discussion.the Unit Supervisor stated that a partial cycle of the locking ring / door could result in the mispositioning of the equalizing valve. An Auxiliary Operator (AO)
(utility, non-licensed) was immediately dispatched to confirm / verify the position of the equalizing valve. The A0 reported the equalizing valve for the outer door was in mid-position.
E.
THE HETH00 0F DISCOVERY OF EACH COMPONENT OR SYSTEM FAILURE OR PROCEDURAL ERROR After discussion with the Security Test Group, the Unit Supervisor dispatched an A0 to verify the position of the outer door equalizing valve and confirmed that the valve was in mid-position.
II. COMPONENT OR SYSTEM FAILURES A.
FAILURE MODE, MECHANISM, AND EFFECT OF EACH FAILED COMPONENT Not applicable - there were no component failures associated with this event.
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CAUSE OF EACH COMPONENT OR SYSTEM FAILURE Not applicable - there were no component failures associated with this event.
D.
SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY FAILURE OF 1
COMPONENTS WITH MULTIPLE FUNCTIONS Not applicable - there were no component failures associated with this event.
III. ANALYSIS OF THE EVENT
A.
SAFETY SYSTEM RESPONSES THAT OCCURRED Not applicable - no safety system responses occurred as a result of this event.
B.
DURATION OF SAFETY SYSTEM TRAIN IN0PERABILITY Technical Specification 3.6.1.1 requires that Containment Integrity be maintained at all times when operating in modes 1,2,3 and 4.
This is i
demonstrated in part by verifying that each containment air lock is in compliance with the requirements of Technical Specification 3.6.1.3, which requires that both doors be closed except when the airlock is being used for normal exit or entry to containment. Closure of the associated pressure equalization valves is considered a requirement for satisfying the operability requirement for the containment airlocks.
With one containment air lock door inoperable the action requires the operable door to be maintained closed and locked closed within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
j The outer door equalizing valve was known to be in the closed position on December 22, 1993, when the PAL was fully cycled for a containment entry.
The inner door and equalizing valve were known to be in the closed position during the entire period of misalignment of the outer door equalizing valve, but not locked as required for an inoperable outer door.
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C.
SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT During this event the potential for a direct path from the Containment atmosphere to the Safeguards Building was greater than had previously been assumed. A passive failure of the PAL inner door system combined with the misalignment of the PAL outer door equalizing valve could provide a path from the containment atmosphere to the Safeguards Building. However, during the period when the outer door equalizing valve was left in mid-position, no direct path from the Containment to the Safeguards Building existed for the release of fission products and at no time during this period did an actual condition exist that i
threatened the health and safety of the public.
IV. CAUSE OF THE EVENT
The cause of the event was determined to be procedure weakness.
The Unit 2 PAL outer door was partially cycled allowing for a component misalignment.
- - i The security test procedure which required movement of the door locking ring did not adequately consider the impact of the locking riag on the associated door equalizing valve.
V.
CORRECTIVE ACTION _S A.
IM1EDIATE:
After the discovery the outer door was cycled full open and closed.
The equalizing valve was verified to stroke and close properly.
B.
ACTIONS TO PREVENT RECURRENCE The appropriate procedures will be revised to prohibit partial cycling of the PAL door for both Units. Additionally, test methods used by Security Test Group with respect to PAL will be revisad for both Units.
VI. PREVIOUS SIMILAR EVENTS
There have been no previous similar events reported pursuant to 10CFR50.73 which involved partial cycling of the outer door equalizing valve of the Personal Air Lock.
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