05000272/LER-2001-001

LER-2001-001,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
2722001001R00 - NRC Website

FACILITY NAME (1) DOCKET (2)

PLANT AND SYSTEM IDENTIFICATION

Westinghouse — Pressurized Water Reactor Auxiliary Building Ventilation System {VF} (ABV) * Energy Industry Identification System {EllS} codes and component function identifier codes appear as (SS/CCC)

CONDITIONS PRIOR TO OCCURRENCE

Salem Unit 1 was in Mode 1 at 100% power.

No structures, systems, or components were inoperable at the time of the occurrence that contributed to the event.

DESCRIPTION OF OCCURRENCE

On January 6, 2001, at 1410 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.36505e-4 months <br />, the number 12 auxiliary building exhaust fan {FAN} was removed from service to perform preventive and corrective maintenance. Upon completion of the work on January 6, during the operability retest of the exhaust fan, utility non-licensed operators noted that the emergency flow rate (air flow being discharged through the HEPA-Charcoal adsorber {FLT}) was less than the 21,400 SCFM ± 10% required by Technical Specifications. The observed flow rate was 13,718 SCFM.

At this point the licensed control room operators entered Technical Specification (TS) 3.7.7.1 for Salem Unit 1. Specifically, TS 3.7.7.1 requires that at least one Auxiliary Building exhaust air HEPA filter train associated with the charcoal adsorber bank shall be OPERABLE. TS 3.7.7.1 Actions a and b state:

a) With the above required HEPA filter train inoperable, restore the HEPA filter train to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

b) With the charcoal adsorber bank inoperable, restore the charcoal adsorber bank to OPERABLE status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

Operability of the filter train is determined by measuring a flow rate of 21,400 SCFM ± 10%.

FACILITY NAME (I) DOCKET (2)

ANALYSIS OF OCCURRENCE

On January 6, 2001, at 1410 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.36505e-4 months <br />, the number 12 auxiliary building exhaust fan was removed from service to perform preventive and corrective maintenance. Upon completion of the work on January 6, during the operability retest of the exhaust fan, utility non-licensed operators noted that the emergency flow rate (air flow being discharged through the HEPA-Charcoal adsorber {FLT}) was less than the 21,400 SCFM ± 10% required by Technical Specifications. The observed flow rate was 13,718 SCFM. Investigation into this flow shortage revealed that the 1ABS-8 damper {DMP} was closed. This damper (ABS-8) is an excess flow damper in the exhaust ductwork from the Salem Unit 1 mechanical penetration area to the ABV exhaust plenum. The damper is designed to close on high flow during a high-energy line break (HELB) in the penetration area.

1ABS-8 damper closure during a HELB would prevent steam intake into the ABV exhaust plenum and steam transfer to other adjacent areas via exhaust ductwork.

The damper was manually opened, however it would not remain fully open when released. Utility maintenance personnel replaced one of the damper's springs. The damper was reopened, and flow through HEPA-Charcoal was measured to be approximately 18,000 SCFM, however the damper would not remain open. The 18,000SCFM flow is still below the required minimum TS flow of 21,400 SCFM ± 10%.

Further investigation into the flow shortage and why the 1ABS-8 damper would not remain open revealed that fire damper 1ABF-13 was also closed. Closure of this damper had caused the flow through the 1ABS-8 damper to increase to its closure set point thereby closing the 1ABS-8 damper, as designed.

The closure of the 1ABF-13 and 1ABS-8 dampers isolated the pipe chase, mechanical penetration and residual heat removal area effluents.

The 1ABF-13 damper was reopened and flow through HEPA-Charcoal was measured to be within the TS acceptable flow range of 21,400 SCFM ± 10%. However, a four hour report was submitted in accordance with 10CFR50.72(b)(2)(iii) on January 7, 2001, because with these two dampers closed air flow through the HEPA-Charcoal adsorber filter train from some of the emergency core cooling system areas could not be demonstrated to be within the assumptions made in the Salem dose analysis calculation.

This report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR50.73(a)(2)(v).

CAUSE OF OCCURRENCE

The apparent cause for the 1ABF-13 damper being closed is attributed to the locking wing nut being loose. The manual arm lever attached to the shaft, which holds the damper in the desired position, was found with the locking wing nut loose.

This fire damper uses a McCabe Link to perform its fire protection function. This link connects to the shaft and the spring load louver assembly using a pin attached to a bi-metallic strip. When heated, the bimetallic strip will bend causing the pin to release the spring-loaded louver assembly.

Upon going closed the damper would make-up to a micro switch causing an alarm in the unit 1 control room area. Although this micro switch had not been working properly, it would not have been expected to annunciate the partial (not fully) closed damper position. The micro switch is designed to annunciate upon the damper being slammed closed by the McCabe linkage.

The closure of the 1ABS-8 damper is attributed to the closure of the 1ABF-13 damper, which caused the flow set point of the 1ABS-8 damper to be exceeded, thereby closing the damper as designed.

PRIOR SIMILAR OCCURRENCES

A review of 1998 and 1999 LERs for both Salem and Hope Creek identified no similar occurrences.

SAFETY CONSEQUENCES AND IMPLICATIONS

There were no safety consequences associated with this event.

The Salem ABV system is a once through ventilation and exhaust filtration system that maintains a slight negative pressure within the building, delivering outside air in sufficient volume to maintain auxiliary building temperatures within design limits.

The supply system consists of two fans, each of 100% capacity, powered from vital buses that deliver outside air via ductwork distribution throughout the building. Supply fan start circuits are administratively controlled to prevent more than one supply fan from operating at any time, avoiding pressurization of the Auxiliary Building.

DOCKET (2) SAFETY CONSEQUENCES AND IMPLICATIONS(continued) The exhaust system consists of three fans, each of 50% capacity, taking exhaust from a common plenum, three High Efficiency Particulate Air (HEPA) filters, and one High Efficiency Carbon Adsorber. The HEPA filters receive air from the exhaust system ductwork, and discharge it to the common plenum. The carbon adsorber can be aligned interchangeably between either of two of the three HEPA filters and the common plenum.

The third HEPA filter cannot be aligned to the carbon adsorber. The carbon adsorber is placed in the exhaust stream only during post LOCA conditions to remove radioactive iodine, which may be introduced to the auxiliary building through ECCS equipment. The exhaust fans are powered from vital buses and are designed for continuous operation. The exhaust fans maintain Auxiliary Building pressure slightly negative with respect to ambient atmospheric pressure. The system is normally operated with two exhaust fans and one supply, and in cases were the outside temperature is low enough, only exhaust fan(s) may be in operations.

During accident conditions the equipment room coolers mainly provide cooling of the ECCS equipment environment with the ABV system being mostly a back-up/support system. The room coolers were unaffected by this event.

During normal conditions the charcoal adsorber is not in service and filtration of the effluent is provided by the HEPA filter. Monitoring of the effluent is done by the installed radiation instrumentation {IL} in the plant vent {VL}. Although, the 1ABF-13 damper was found closed, enough leakage past the damper existed to contribute to the measured flows and to help maintain a negative pressure in the auxiliary building. The proper combination of supply and exhaust fans were maintained through this event (including the period when the 1ABF-13 and 1ABS-8 dampers were unsuspectingly closed). Therefore, maintaining a slight negative pressure between the auxiliary building and the outside atmosphere assures that all effluents will be discharged through the plant vent {VL}, filtered by the HEPA filter train, and monitored by the installed instrumentation {IL}.

Although these dampers were found closed, flow through the 1ABF-13 damper existed thereby providing some limited filtration through the HEPA-Charcoal adsorber of the effluents from the pipe chase, mechanical penetration and residual heat removal area during accidents conditions.

Because the flow and its impact on the dose analysis and cooling capability could not be quantified, PSEG Nuclear reported this event under 10CFR50.72(b)(2)(iii). However based on the above, PSEG Nuclear believes that this condition did not present a risk to the health and safety of the public or plant personnel.

DOCKET (2)

CORRECTIVE ACTIONS

1. Fire Protection personnel walked down all accessible dampers to ensure that the wing nuts were tight.

2. 1ABF-13 was opened and the wing nut was re-tightened. The Technical Specification required flow test was completed satisfactorily, thus assuring proper position of the ABV system's dampers.

3. The PSEG Fire Department is presently checking all accessible dampers, similar to the ABF-13, once per week. The position of the dampers is being verified locally and the wing nuts tightened, as necessary. This weekly verification will continue until completion of the evaluation stated in number 4 below.

4. This condition has been entered into the corrective action program and a level one root cause analysis is being performed. Additional corrective actions may be taken, as necessary, at the completion of the investigation.

COMMITMENTS

The corrective actions cited in this LER are voluntary enhancements and do not constitute commitments.