05000333/LER-2009-002
| Docket Numbermont Sequential Revday Year Year Month Day Yearh Number No 05000 | |
| Event date: | 01-28-2009 |
|---|---|
| Report date: | 04-09-2009 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3332009002R00 - NRC Website | |
BACKGROUND
System Operation The Battery Room Ventilation System (see attached figure) is started manually and maintains ventilation and reasonably constant temperature in the battery rooms. The equipment, ductwork and controls are completely independent from other plant ventilation systems. The system independence ensures uninterrupted operation during normal shutdown and design basis accident modes.
Each battery room is served by a full capacity system including one air handling unit, two exhaust fans and one recirculation exhaust fan. The systems are each connected to a separate source of emergency electrical power to prevent shutdown in the event of a loss of offsite power.
Air may be recirculated from the two battery charger rooms through modulating dampers or exhausted to the atmosphere according to the room temperature. Total air is exhausted to the atmosphere from the two battery rooms at all times. Temperature is maintained by modulating the recirculation damper and the heating coil, in sequence, in response to the room thermostat.
During normal operation the two AHUs draw in outside air from the protected air inlet through a common air header and modulating inlet dampers. Each AHU exhausts - 6000 CFM of air into the Battery Charger Room in which it is located. A portion (-1000CFM) of the air flows into the Battery Room corridor thru the open fire damper in the Battery Charger Room wall. Air flow through each battery room is a result of the operating battery room exhaust fan drawing -1000 CFM of air out of the associated battery room. The removal of the air causes an equal amount of air to be drawn into the room from the battery room corridor through the open fire damper in the battery room wall. The recirculation/exhaust fan in each Battery Charger room draws -5000 CFM of air from its battery charger room into the recirculation duct work. Based on the temperature in the Battery Charger Room the recirculation modulating damper is balanced with AHU inlet modulating damper and recirculation air exhaust modulating damper so that the AHU has a relatively constant air supply of -6000 CFM. Air not recirculated to the AHU is exhausted to the common air exhaust plenum where it is joined by the -1000 CFM of air that is moved through each battery room.
As shown on the attached figure the battery room corridor forms a common air plenum for the two battery charger and battery rooms.
TRM Development The original Stone and Webster design for the Battery Room Ventilation System called for two redundant 100 % capacity 12,000 CFM AHUs. During the construction of JAF it was identified that interferences prohibited installation of 12,000 CFM AHUs. The design was changed and two 6,000 CFM AHUs were installed, one to serve each Battery/Battery Charger room.
In August of 1988, while operating under Custom Technical Specifications (CTS), Technical Specification Interpretation (TSI) 06 was developed, to provide guidance to the Operations department on the "operability" of the Battery Room Ventilation System. This guidance was developed using the Stone and Webster conceptual design notes dated November 23, 1970 (TSI-06 Reference 8). The conceptual design notes described the ventilation system as having two 100% capacity redundant AHUs, they had not been updated to reflect the change in size during installation. Based on the understanding that the AHUs were 100% capacity redundant units, it was believed that battery room corridor would act as a common plenum and the recirculation fan in the battery charger room that did not have an operating AHU would draw 5000 CFM of air into the battery charger room through the open fire damper in the wall of the room, thereby ensuring adequate cooling. The TSI concluded that the Battery Room Ventilation System remained Operable for an indefinite period with a single AHU in service.
In March of 1999 the TSI was revised, to replace a battery electrolyte temperature requirement with a room temperature. However, the description of the required AHUs and fans for "operability" remained unchanged.
In July of 2001, during the conversion from CTS to Improved Technical Specifications (ITS), Technical Requirements manual (TRM) Section 3.7.A "125VDC Battery Room Ventilation System" and its associated Bases was developed based on CTS TSI-06. Consistent with TSI-06, TRM 3.7.A allowed for just one AHU to be available to constitute an operable/functional Battery Room ventilation system. Therefore, if a single AHU was non-functional, then the Battery Room Ventilation system would still be considered operable/ functional and the TS LCO Action(s) for the supported equipment would not be applied.
EVENT DESCRIPTION
During power operations, on January 28, 2009, a Condition Report (CR) reported the following:
TRM Bases section B.3.7.A "125VDC Battery Room Ventilation System" was developed assuming that each air handling unit (72AHU-30A and B) was 100% redundant to each other when in fact they were each designed to only serve their respective battery and charger room (see TSI 29, Rev 0 from CTS).
Background: The original Stone and Webster design of the Battery Room ventilation was to install two 12000CFM air handling units (one of which was to be-an installed spare). Due to interferences, two 6000CFM units were installed (one each to serve their respective Battery rooms). TRM B.3.7.A allowed for one air handling unit (72AHU-30A or 72AHU-30B) to be available to constitute an operable/functional Battery Room ventilation system.
This condition was identified while preparing engineering input for a scheduled maintenance activity. As described above the condition was the result of a design change made during the construction of the James A.
FitzPatrick Nuclear Power Plant (JAF) and a misinterpretation of the design in the development of a TSI while the plant was operating under CTS. The error made in the TSI was carried forward into ITS during the conversion process.
In response to the CR it was determined that if one AHU is not functional there may not be adequate cooling to maintain the operability of the associated Battery Charger Room without realigning the system. Inadequate cooling in the Battery Charger Room could eventually result in the associated 125 VDC distribution subsystem being inoperable. Thus, without adequate cooling to the Battery Charger Room, either the Battery Charger or the associated 125 VDC distribution subsystem should be declared inoperable. TS 3.8.4, DC Sources — Operating, requires that an inoperable 125 VDC electric power subsystem be restored to OPERABLE within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, and if not restored, be in MODE 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and MODE 4 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
As part of the plant CR investigative process, the functionality of the Battery Room Ventilation System was reviewed for the period starting January 1, 2006 through February 5, 2009. This review found two periods when a Battery Room Ventilation System AHU was tagged out for greater than the TS 3.8.4 125 VDC electric power subsystem allowable out-of-service time. The first occurrence was when 72AHU-30A was tagged out for 34 hours3.935185e-4 days <br />0.00944 hours <br />5.621693e-5 weeks <br />1.2937e-5 months <br /> and 3 minutes during April 2006 (04/05/2006 at 0309 to 04/06/2006 at 1312). The second occurrence was when 72AHU-30B was tagged out for 76 hours8.796296e-4 days <br />0.0211 hours <br />1.256614e-4 weeks <br />2.8918e-5 months <br /> and 49 minutes during September 2008 (09/17/2008 at 0309 to 09/20/2008 at 1504). Each of these occurrences constitute a past "operation or condition which was prohibited by the plant's Technical Specifications," and thus, they require a Licensee Event Report (LER) per 10 CFR 50(a)(2)(i)(B).
EVENT ANALYSIS
Each time an AHU was taken out-of-service without realigning the ventilation system, the system may not have been capable of supplying adequate cooling, under all design conditions, to the Battery Charger Room in which there was no operating AHU. Therefore, the condition should have resulted in either the associated Battery Charger or 125 VDC electric power subsystem being declared inoperable and the associated TS LCO being entered. In each of the cases reviewed, the ventilation system was taken out-of-service for planned maintenance.
The period of maintenance was short, and Battery and Battery Room temperatures remained within the acceptable temperature range.
CAUSE OF EVENT
The direct cause of the events was an inaccurate TRM 3.7.A condition. The underlying cause was an error in preparing a TSI in 1988 that was carried forward. The TSI was based on "Conceptual Design Notes" rather than the actual installed design which was documented on a Stone and Webster Field Change. The error was then carried forward when the TSI was converted into TRM 3.7.A.
EXTENT OF CONDITION
The Quality Assurance Department performs annual audits of the Technical Specifications Program, which have included the Technical Requirements Manual since the conversion to ITS was approved. These audits have demonstrated the overall quality of the Technical Specifications and Technical Requirements Manual. This occurrence is considered to be an isolated case.
FAILED COMPONENT IDENTIFICATION
There were no component failures as a result of this event.
CORRECTIVE ACTIONS
Immediate Corrective Actions:
1) Evaluated current functionality of the Battery Room Ventilation System.
2) Established administrative controls on the system, by entering a tracking LCO, pending engineering analysis.
3) Reviewed past functionality of the Battery Room Ventilation System, and its potential impact on the operability of the supported systems.
Completed Corrective Actions:
1) Performed engineering analysis to define the capability of the ventilation system.
2) Revised the TRM to require a functionality review of the Battery Room Ventilation System if a system component becomes non-functional.
3) Added Required Actions to ensure the appropriate Technical Specification LCO is entered if it is determined that the Battery Room Ventilation System can not perform its support function.
4) Revised operating procedures to be consistent with the engineering analysis and provide instruction for system realignment to ensure adequate cooling to both Battery Charger Rooms when one AHU is out of service.
ASSESSMENT OF SAFETY CONSEQUENCES
While the TRM error identified in this report did result in exceeding the Technical Specifications for the supported systems, the event is considered to be of low safety significance. During the periods of non compliance, the TRM criteria, in place at the time, required monitoring the temperature in the rooms and there was no adverse change in temperature. The plant also had in place specific procedures for supplying temporary cooling to the battery and battery charger rooms and the operations department personnel are trained to execute those procedures. So, if there had been a rise in room temperature, there were means available to supplement the available cooling.
SIMILAR EVENTS
No similar events have occurred at JAF during the past ten (10) years.
REFERENCES
JAF Condition Report CR-JAF-2009-00358.
UFSAR Section 9.9.3.6 Battery Room Ventilation Technical Specification Interpretation TSI-06 Rev. 0, Dated August 8, 1988 Technical Specification Interpretation TSI-06 Rev. 1, Dated March 30, 1999 Design Basis Document 72, Figure 1.1-4, Battery Room HVAC