05000293/LER-2001-002

LER-2001-002,

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(vii)(D), Common Cause Inoperability 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
2932001002R01 - NRC Website

FACILITY NAME (1) DOCKET NUMBER (21 LER NUMBER 0) PAGE (3) P ---

REASON FOR SUPPLEMENT

This supplemental report is submitted to include the Root Cause Analysis that had not been completed at the time the original LER was submitted.

BACKGROUND

The Pilgrim Station Control Room high efficiency air filtration system (CRHEAFS) is designed to provide filtered air to the Control Room during conditions when normal intake air may be contaminated.

CRHEAFS consists of two 1,000 cubic feet per minute (CFM) filter trains. Each train includes dampers, a prefilter, a heating coil, a high efficiency particulate air (HEPA) filter, charcoal absorber tray filters, and � .

a final HEPA filter. During emergency situations, CRHEAFS is manually initiated and has the capability to provide sufficient filtered air to maintain the Control Room at a positive pressure to prevent infiltration of contaminated air. This system is located in Fan Room 2 of the Radwaste Building. , CRHEAFS is safety-related and was designed to meet single failure and seismic Class I requirements.

CRHEAFS interfaces with the normal Control Room ventilation system, which was constructed to seismic Class II criteria. CRHEAFS auto initiates when Halon is released in the cable spreading room.

CRHEAFS is manually initiated in response to a fuel handling accident. Upon receipt of a Control Room radiation high alarm or a Control Room air inlet radiation high alarm, CRHEAFS is manually initiated and the normal Control Room ventilation is manually secured within 30 minutes. The normal Control Room ventilation is secured to limit the recirculation flow requirements and isolate CRHEAFS from the normal ventilation system.

was submitted in 1998 to report that the Control Room normal ventilation ductwork was not seismically qualified and may impact the seismic capability of CRHEAFS. Corrective actions included development of a permanent modification to fully restore seismic capability to CRHEAFS. This modification entailed design and installation of seismic isolation dampers in the locations where CRHEAFS ductwork interfaced with non-seismic ductwork. These modifications were being implemented under plant design change (PDC) 99-18.

Temporary Procedures (TP) were developed to support the activities associated with the damper installation. These procedures include TP00-007, "TEMPORARY PROCEDURE FOR POSTWORK TESTING OF ISOLATION DAMPERS INSTALLED VIA PDC 99-18," and TP00-008, "TEMPORARY

COMPUTER ROOM HEATING, VENTILATION, AND AIR CONDITIONING SYSTEM DURING THE

INSTALLATION OF PDC 99-18." These TPs were issued to ensure adequate controls existed at the ventilation interfaces to maintain CRHEAFS integrity.

EVENT DESCRIPTION

Structural modifications to the Control Room ventilation system were being made as part of the corrective actions from LER 98-016-00 to ensure an adequate seismic boundary for CRHEAFS. On January 30, 2001, Pilgrim Station entered a limiting condition for operation to perform TP00-008 to demonstrate its ability to maintain a positive pressure in the Control Room. The positive pressure is FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) - - - I REVISION PILGRIM NUCLEAR POWER STATION 05000-293 2001;"

• verified by smoke stick testing at Control Room doors 145, 147, 150 and door 159. It was observed that air flowed out of doors 145, 147, and 159 as expected. However, the smoke stick test indicated airflow into the Control Room through door 150. An attempt was made to pressurize the Control Room in the area of door 150 by running the alternate train of CRHEAFS. This effort was unsuccessful and the test of CRHEAFS was terminated.

When neither CRHEAFS train could establish positive flow through door 150 in the access control area outside the Control Room, CHREAFS was declared inoperable. The NRC Operations Center was

• notified in accordance with 10 CFR 50.72(b)(3)(v)(D), at 1940 hours0.0225 days <br />0.539 hours <br />0.00321 weeks <br />7.3817e-4 months <br /> on January 30, 2001 due to the discovery that CRHEAFS could not maintain the Control Room at a positive pressure.

A priority 1 maintenance request was initiated to troubleshoot and restore CRHEAFS to an operable condition. CHREAFS was flow tested and determined to be performing correctly. It was discovered that there was increased pressure in the access control area outside Control Room door 150.. Pilgrim Station procedures affecting CRHEAFS operation were revised to require securing the ventilation in the Control Room access control areas when CRHEAFS is required to operate. The Control Room access control area supply and recirculation fans were secured in accordance with the revised procedures and CRHEAFS provided positive air flow out through each Control Room door, including door 150. The access control area ventilation system is not required to operate under accident conditions. Operability evaluation OP 01-008 concluded that CRHEAFS was operable after the procedure revisions securing the access control area ventilation system. CHREAFS was restored to operable status by 0100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> on January 31, 2001. I This condition occurred at 100 percent reactor power with the reactor mode selector switch in the RUN position. The reactor vessel pressure was about 1035 psig with the water temperature at the saturation temperature for that pressure.

CAUSE

The root cause determined that the original plant designers did not recognize that a non-safety related HVAC system could cause a safety related HVAC system to fail to meet it's design function. This condition was determined to be a legacy of Pilgrim's circa 1970's design basis, which did not establish comprehensive design criteria to preclude potential adverse interactions between Class II/Class I systems, structures and components.

CORRECTIVE ACTION

Corrective actions taken include the following:

PNPS procedures 2.2.46 (Rev. 30), 8.7.2.7 (Rev. 22) and TP00-008 (Rev. 3) reflect revisions to secure the ventilation in the access control area outside the Control Room when CRHEAFS is required to operate. Testing of CRHEAFS was performed after the access control area ventilation was secured.

Positive airflow was observed from all Control Room access doors.

• An engineering evaluation EE# 01-008 was performed in support of Operability Evaluation OP 01-008 and concluded that CRHEAFS was operable after procedures TP00-008, 2.2.46, and 8.7.2.7 were revised to secure Control Room access control area ventilation FACILITY NAME (1) DOCKET NUMBER (21_ LER NUMBER (6) PAGE (3) , � . YEAR I � RE VISION

ACTION TO PREVENT RECURRENCE

A review of all other safety related HVAC systems was conducted to determine if safety related functions could be adversely affected by non-safety related HVAC system/component interfaces. It was determined that no other systems could be adversely affected by non-safety related HVAC system components.

Training on this condition was conducted for plant operators and engineering personnel.

SAFETY CONSEQUENCES

The condition posed no threat to public health and safety.

Previous CRHEAFS surveillance tests demonstrated its ability to pressurize the Control Room. � The test .conducted on January 30, 2001 provided positive air flow through three of the four Control Room doors. � The fourth door, which is located away from the operator area, had some air infiltration as indicated by the smoke stick test. � LER 98-024-00 reported that even with up to 100 CFM infiltration (which is greater than the observed inleakage) operators would not experience exposure above 10 CFR 50 Appendix A GDC 19 dose limits. � Procedures, equipment and training are provided to Control Room personnel for airborne radiation.

Should CRHEAFS have been required to operate when the higher pressure existed in the access control area to the Control Room, a continued radiation alarm would have alerted the operators to a degraded condition. � After the procedure revisions, CRHEAFS pressurized the Control Room.

Operator action is required to manually initiate CRHEAFS and to secure normal ventilation within 30 minutes of receipt of a Control Room radiation high alarm or a Control Room air inlet radiation high alarm. The interim corrective action taken has minimum impact on the operator since the controls for both normal Control Room ventilation and the access control area ventilation are on adjacent panels.

These interim corrective actions prevent adverse impact on the Control Room environment.

REPORTABILITY

This report is submitted in accordance with 10 CFR 50.73(a)(2)(v)(D) and 10 CFR 50.73(a)(2)(vii)(D).

SIMILARITY TO PREVIOUS EVENTS

A review was conducted of Pilgrim Station Licensee Event Reports (LERs) issued since 1995. The review identified the following reports involving CRHEAFS: LER 98-008-00, "A Section Of CRHEAFS Seismic Class I Ductwork Was Found To Be Supported By Class II Ductwork," LER 98-016-00, "Control Room Ventilation Exhaust Damper And Ductwork Not Seismically Qualified," and LER 98-024- 00, "Control Room High Efficiency Air Filtration System Outside Design Basis.

• FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

PILGRIM NUCLEAR POWER STATION

. 1 J TEXT (If more space is required, use additional copies of NRC Form 366A) (17) � 1 ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) CODES The EIIS codes for this report are as follows:

COMPONENTS � CODES Door � DR 1 Fan � FAN

SYSTEMS

Control Complex Environmental Control System � VI Control Room High Efficiency Air Filtration � . � AHU 1 System (CRHEAFS)