05000369/LER-2001-001
| Docket Number | |
| Event date: | |
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| Report date: | |
| 3692001001R00 - NRC Website | |
APPROVED BY OMB NO. 3150-0104 EXPIRES 04/30/98
ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY
INFORMATION COLLECTION REQUEST: 50.0 FIRS. REPORTED LESSONS
LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED
BACK TO INDUSTRY. FORWARD COMMENT'S REGARDING BURDEN
ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH
(T-6 F33), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.
FACILITY NAME (I) DOCKET NUMBER (2) 05000 � 369 LER NUMBER (6) PAGE (3)
BACKGROUND:
The Emergency Personnel Hatch (EPH), also known as the Submarine Hatch, is used as an emergency egress for personnel between the lower and upper containment compartments.
The EPH also functions as part of the Divider Barrier between lower and upper containment. The divider barrier consists of the operating deck and associated seals, personnel access doors, and equipment hatches. Divider barrier integrity is necessary to minimize bypassing of the ice condenser by the hot steam and air mixture released into the lower compartment during a Design Basis Accident (DBA). This ensures that most of the gases pass through the ice bed, which condenses the steam and limits pressure and temperature during the accident transient. Limiting the pressure and temperature reduces the release of fission product radioactivity from containment to the environment in the event of a DBA.
Divider barrier integrity ensures that the high-energy fluids released during a DBA would be directed through the ice condenser and that the ice condenser would function as designed to limit containment pressure and temperature. The limiting DBAs considered relative to Containment temperature and pressure are the loss of coolant accident (LOCA) and the steam line break (SLB).
Event Description:
On June 21, 2001, the Unit 1 EPH (containment upper/lower divider barrier) door was found not fully sealed. Maintenance personnel discovered that two (2) required tamper seals were missing from the submarine hatch door handle and the door did not appear to be fully closed as evidenced by handwheel closure alignment marks.
The Operations Shift Manager (OSM) was informed of the problem. The Unit 1 EPH and the Containment Divider Barrier were declared inoperable at 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> per Technical Specification 3.6.14, "Divider Barrier Integrity.
The Work Control Center (WCC) Senior Reactor Operator (SRO) was dispatched into Unit 1 containment. The hatch was fully closed/sealed at 1415 hours0.0164 days <br />0.393 hours <br />0.00234 weeks <br />5.384075e-4 months <br /> as evidenced by obtaining proper alignment of the handwheel with the closed alignment marks. By 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br />, Maintenance procedure MP/0/A/7150/106, "Emergency Personnel (Submarine) Hatch Status Determination, Gasket Inspection and Maintenance, was successfully completed. This procedure implements Technical LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 50.0 HRS. REPORTED LESSONS LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED (T-6 F33), U.S NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.
FACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER 6) PAGE (3) Specification surveillance requirements 3.6.14.2 and 3.6.14.3 which require verification, by visual inspection, that EPH seals and sealing surfaces are appropriately aligned, free of cracks or defects, seal material deterioration does not exist, and that the EPH is fully closed.
Appropriate NRC and Management notifications were completed in accordance with Work Process Manual 404 requirements.
CAUSE:
The root cause for the EPH seal integrity compromise could not be conclusively determined. The most likely cause is traffic in the vicinity of the closed hatch during performance of an Extra High Radiation Lamp (EHRL) inspection/replacement procedure. The inspections were performed between April 19, 2001 and May 9, 2001.
The procedure is performed in upper containment and does not require a transit entry through the EPH. No evidence existed which would indicate an entry occurred. The procedure (HP/0/B/1006/009) lacked instructions to verify the EPH had not been disturbed after EHRL inspection/replacement.
CORRECTIVE ACTIONS
Immediate:
The Operations Shift Manager (OSM) was informed of the problem. The Unit 1 EPH and the Containment Divider Barrier were declared inoperable at 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> per Technical Specification 3.6.14, "Divider Barrier Integrity.
The Work Control Center (WCC) Senior Reactor Operator (SRO) was dispatched into Unit 1 containment. The hatch was successfully closed/sealed at 1415 hours0.0164 days <br />0.393 hours <br />0.00234 weeks <br />5.384075e-4 months <br /> as evidenced by obtaining proper alignment of the handwheel with the closed alignment marks.
Maintenance performed surveillances per Technical Specification 3.6.14 on the divider barrier per MP/0/A/7150/106, "Emergency Personnel (Submarine) Hatch Status Determination, Gasket Inspection and Maintenance." The required surveillance were successfully completed per Technical Specification requirements at 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br />.
Appropriate NRC and management notifications were completed in accordance with Work Process Manual 404 requirements.
The Unit 2 EPH seal was verified in the closed position.
APPROVED BY OMB NO. 3150-0104 EXPIRES 04/30/98
ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY
INFORMATION COLLECTION REQUEST: 50.0 HRS. REPORTED LESSONS
LEARNED ARE INCORPORATED INTO THE LICENSING PROCESS AND FED
BACK TO INDUSTRY. FORWARD COMMENTS REGARDING BURDEN
ESTIMATE TO THE INFORMATION AND RECORDS MANAGEMENT BRANCH
(T-6 F33), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.
FACILITY NAME (1) DOCKET NUMBER (2) 05000 � 369 LER NUMBER (6) PAGE (3) Subsequent:
An analysis was performed to verify containment operability. The additional divider barrier bypass leakage associated with the as found condition of the subject hatch would not have resulted in unacceptable post LOCA containment peak pressures.
None Planned:
Radiation Protection procedure HP/0/B/1006/009 will be evaluated for potential enhancements.
SAFETY ANALYSIS
The primary safety concern with having the hatch open during plant operations is the additional open area presented for steam bypass flow. Should a high-energy line break (HELB) or loss of coolant accident (LOCA) occur, some volume of steam which would normally pass through the Ice Condenser would proceed through the hatch area and increase pressure in upper containment.
Although analyzed peak upper containment pressure would increase inside containment, calculations demonstrated that containment remained operable with the latch not fully secured.
If the Unit 1 EPH were fully open, calculations also demonstrate that the increase in peak containment pressure would remain well below the design pressure and the divider barrier could have performed its intended safety function. Divider Barrier bypass leakage has no effect on other design basis accidents.
There were no releases of radioactive materials, radiation exposures or personnel injuries. There was no impact on the health and safety of the public or plant personnel due to this event.