05000346/LER-2005-002
| Docket Number12 28 2003 2005D-002D-00 07 01 2005 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| Initial Reporting | |
| 3462005002R00 - NRC Website | |
PLANT CONDITIONS AT THE TIME OF THE EVENT:
Event Date: December 28, 2003 MODE: Mode 4 (Hot Shutdown)
DESCRIPTION OF OCCURRENCE:
On December 4, 2003, with the plant in Mode 5 during Refueling Outage 13, Technical Specification (TS) quarterly surveillance testing (procedure DB ME-03001 Revision 5, "Station Batteries Quarterly Surveillance") Acceptance Criteria was signed off as acceptable for Station Battery [EJ - BTRY] 2N.
Station Battery 2N Cell 60 float voltage reading was recorded as 2.114 vdc.
This was below the Technical Specification (TS) 4.8.2.3.2.b.1, Table 4.8-1 Category B operating limit of 2.13 vdc, but above the Table 4.8-1 Category B allowable value of 2.07 vdc.
During performance of surveillance test DB-ME-03001 on December 4 2003, the Station Battery 2N Cell 60 float voltage reading was not identified as not meeting the surveillance test's Acceptance Criteria of TS Table 4.8-1 Category B float voltage operating limit of 2.13 vdc. The surveillance test procedure was completed by electrical maintenance personnel, signed off, reviewed, approved and submitted to records without detection of the condition. Additionally, the system engineer designated reviewer did not identify that the Station Battery 2N Cell 60 voltage was less than the 2.13 vdc Acceptance Criteria.
Technical Specification Table 4.8-1 allows the battery to be considered operable up to 7 days if a Category B operating limit (i.e., 2.13 vdc) is not met as long as the applicable Category B allowable value is met, including float voltage allowable value of 2.07. vdc. This low reading went undetected and the Cell 60 voltage was not restored to 2.13 vdc within 7 days as required by TS Table 4.8-1. Station Batteries 1P, 2P and 1N were operable and passed the required surveillance testing during this time period.
The low reading on station Battery 2N Cell 60 should have started the TS Table 4.8-1 seven (7) day period to restore Station Battery 2N Cell 60 float voltage to 2.13 vdc. Based on this, Cell 60 float voltage should have been restored by December 11, 2003, or Station Battery 2N (Train B) would be inoperable. The Cell 60 voltage was not demonstrated to have been restored to above the 2.13 vdc operating limit within the seven (7) day period and Station Battery 2N (Train B) should have been declared inoperable.
In Mode 5 only one (1) Station Battery Train (e.g., Train A - 1N and 1P; Train B - 2N and 2P) is required to be operable. On December 28, 2003, the plant entered Mode 4 requiring two (2) Station Battery Trains to be operable.
DESCRIPTION OF OCCURRENCE (continued):
On December 28, 2003, (event date), the plant entered Mode 4. Technical Specifications 3.8.2.3 required both Station Batteries to be operable.
Based on a lack of demonstrated operability, the plant was in a condition prohibited by Technical Specifications because Station Battery 2N Cell 60 was below the TS 4.8.2.3.2.b.1, Table 4.8-1 Category B operating limit of 2.13 vdc for longer than 7 days. Therefore, Station Battery 2N (Train B) should have been declared inoperable on December 11, 2003. The plant should not have entered Mode 4. This is a condition prohibited by TS 3.0.4 and TS 3.8.2 Limiting Condition for Operation (LCO). This event is reportable via a 60-day Licensee Event Report in accordance with 10CFR50.73(a)(2)(i)(B).
BACKGROUND INFORMATION
During the 2005 NRC Safety System Design and Performance Capability (SSDPC) Inspection, a potential issue was discovered by one of the NRC inspectors.
Technical Specification (TS) 4.8.2.3.2.b.1, Table 4.8-1 Note (b) appeared to require temperature compensation of individual cell float voltage for average electrolyte temperature for the station batteries. Condition Report (CR) 05-02369 was initiated to track this issue.
During the review of CR 05-02369, past Station Battery quarterly surveillance tests were reviewed by Davis-Besse Nuclear Power Station (DBNPS) personnel. During this review, it was noted that the December, 2003 DB-ME-03001 quarterly surveillance Acceptance Criteria for Station Battery 2N Cell 60 was recorded as 2.114 vdc. On April 25, 2005, CR 05-02415 was initiated. Condition Report 05-02415 was initiated to determine if this reading was accurate, correct the voltage for temperature, if required, and determine if it caused Station Battery 2N to be inoperable. On May 4, 2005 (discovery date), the system engineer determined that the Station Battery 2N Cell 60 reading was accurate, and temperature compensation would not bring the Cell 60 voltage above the operating limit of 2.13 vdc. Therefore, it could not be concluded that Station Battery 2N (Train B) was operable on December 28, 2003, and this past condition was determined to be reportable.
Overall Sequence of Events On December 4, 2003, the DB-ME-03001 surveillance test Acceptance Criteria was signed off as acceptable. The results of this quarterly surveillance test for Station Battery 2N Cell 60 was less than the TS Table 4.8-1 Category B Float Voltage operating limit of 2.13 vdc. This low reading was not detected and the test Acceptance Criteria was signed off on December 4, 2003.
On December 11, 2003, Station Battery 2N Cell 60 (Train B) should have been restored to 2.13 vdc. � The Cell 60 voltage was not demonstrated to have been restored to above the 2.13 vdc operating limit within the seven (7) day period and Station Battery 2N (Train B) should have been declared inoperable.
DESCRIPTION OF OCCURRENCE (continued):
On December 28, 2003, the plant entered Mode 4 requiring Station Battery 2N (Train B) to be operable. The plant was in a mode requiring both trains (Train A and Train B, including Station Battery 2N) of Station Batteries to be operable. Because Station Battery 2N Cell 60 voltage was not demonstrated to have been restored to above the 2.13 vdc operating limit, Station Battery 2N (Train B) was inoperable. Therefore, the plant should not have entered Mode 4 and was in a condition prohibited by TS 3.0.4.
Additionally, the plant was in a condition prohibited by TS Limiting Condition for Operation (LCO) 3.8.2.3.
The start date of this event is December 4, 2003 (Cell 60 reading of 2.114 vdc). The event date of this condition is December 28, 2003 (entry into Mode 4, all Station Batteries required to be operable). The discovery date is May 4, 2005, when the surveillance test Acceptance Criteria for Station Battery 2N Cell 60 voltage reading of 2.114 vdc was determined to be accurate and it was concluded that Station Battery 2N should have been declared inoperable. This is a past inoperability issue.
DC System Configuration The Direct Current (DC) system (EJ] is described in the Updated Safety Analysis Report (USAR) Section 8.3.2, "DC Power System." The DC equipment consists of two 250/125 vdc motor control centers, four batteries (1N, 1P, 2N and 2P), six battery chargers, four essential distribution panels, four 480 vac /125 vdc rectifiers and four nonessential distribution panels.
The four station lead-acid batteries (EJ-BTRY] are 125 vdc, approximately 1500 ampere-hour, on an eight-hour discharge basis, and arranged to form two independent 250/125 vdc systems. The batteries have one minute, 1-hour and 8-hour capacities of 1400, 750, and 187 amperes, respectively. Each battery is maintained in a fully charged condition and is normally float charged at approximately 132 volts from its associated battery charger. Battery discharge will occur either when the DC requirements temporarily exceed the charger capacity or during a loss of a battery charger supply. Each battery is connected to one 125 vdc bus of one of the two DC motor control centers.
DBNPS has a total of four (4) Station Batteries in two (2) trains: 1) Train "A" consists of batteries 1N and 1P; and 2) Train "B" consists of batteries 2N and 2P.
The batteries are sized to supply the anticipated DC and instrument AC supply for a period of one hour after the loss of the battery charger supply. This includes approximately 20% over capacity to compensate for the loss due to aging of the batteries over a 20-year period.
DESCRIPTION OF OCCURRENCE (continued):
Technical Specification Requirement Technical Specification 3.0.4 states entry into an operational mode shall not be made unless the conditions of the Limiting Condition for Operation are met without reliance on provisions contained in the action statements unless otherwise excepted.
Station Battery Technical Specification Surveillance Requirement 4.8.2.3.2.b.1, requires quarterly test verification of Table 4.8-1 Category B individual cell float voltage to be greater than or equal to (>1=) 2.13 vdc. DBNPS TS Table 4.8-1 Category B footnote 2 states "for any Category B parameter(s) outside the limit(s) shown, the battery may be considered operable provided that they are within their allowable values (>1= 2.07 vdc) and provided the parameter(s) are restored to within limits within 7 days.
Technical Specification 3.8.2.3 LCO Action b requires with only one 125 vdc battery train of one motor control center (MCC) operable, restore the inoperable battery train to operable status within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or be in at least Hot Standby (Mode 3) 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 (Mode 5) within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Technical Specification Applicability For This Event Technical Specification 3.8.2.3 is applicable in Modes 1, 2, 3, and 4. This TS requires both Station Battery trains (Train A - 1N and 1P; Train B - 2N and 2P) to be operable. During the December 4, 2003, performance of DB-ME 03001 the plant was in Mode 5; however, on December 28, 2003, the plant entered Mode 4 in which TS 3.8.2.3 was applicable requiring four Station Batteries (2 trains).
In this specific event, on December 28, 2003, the plant entered Mode 4 however, Station Battery 2N Cell 60 was not demonstrated to have been restored to the operating limit of 2.13 vdc within seven (7) days.
Therefore, Station Battery 2N should have been declared inoperable causing Station Battery Train B to be inoperable. Technical Specification 3.0.4 prohibited entry into Mode 4 without both Station Batteries operable(Train B, Station Battery 2N Cell 60 had not been demonstrated to be operable).
Additionally, with the plant in Mode 4, the plant was in TS 3.8.2.3 LCO Action b. requiring entry into Mode 5 within 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The TS LCO action was not taken since it was not recognized that Station Battery 2N Cell 60 had not been demonstrated to meet the operating limit of 2.13 vdc.
APPARENT CAUSE OF OCCURRENCE:
The causes of this event have been determined to be: 1) less than adequate procedure DB-ME-03001 structure; and 2) less than adequate human performance (work practice errors) during performance of the surveillance test.
APPARENT CAUSE OF OCCURRENCE (continued) :
The primary cause was determined to be a less than adequate procedure (DB ME-03001) in that the method of presentation/structure of the procedure is complex/cumbersome creating a human performance error-likely situation.
Procedure DB-ME-03001 involves collection of over 900 pieces of data. The user is required to repetitively refer to several pages/steps during performance of the procedure because different data is recorded on different pages.
Following completion of the test, the Test Leader is required to review the data from the different pages against the applicable Acceptance Criteria.
The majority of the data is verified to be acceptable by signing one signature block. Since four individuals missed the low voltage reading, the procedure structure was reviewed for human performance error-likely situations. This review concluded that the structure of DB-ME-03001 was the primary cause of this event.
A contributing cause was determined to be less than adequate human performance (work practice) for the four (4) individuals involved in completing and reviewing the DB-ME-03001 surveillance test results. These individuals did not adequately self-check/verify to ensure the intended results were correct during their recording and reviewing the December, 2003 Station Battery 2N Cell 60 float voltage Acceptance Criteria, and did not detect that the results were below the surveillance test Acceptance Criteria of 2.13 vdc.
ANALYSIS OF OCCURRENCE:
Battery 2N Cell 60 did meet the allowable value of 2.07 vdc during the December, 2003 surveillance test therefore, the Station Battery 2N was capable of performing its design function in accordance with the DBNPS TS Bases 3.8, "Electrical Power Bases.
During the previous test on November 30, 2003, voltage of Station Battery 2N Cell 60 was acceptable at 2.175 vdc as recorded in test procedure DB-ME 03002, "Station Battery and Performance Discharge Test.
On December 3, 2003, Station Battery 2N was subjected to a discharge (Service Test). Station Battery 2N re-charge was completed at approximately 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> on December 3, 2003. The quarterly surveillance test Acceptance Criteria was signed off as acceptable (post-discharge test) on December 4, 2003. The completed data sheet recorded 2.114 vdc for Station Battery 2N Cell 60, but it was not recognized as not meeting the minimum of 2.13 vdc.
It is believed that Station Battery 2N Cell 60 may not have re-charged as quickly as the other cells.
During the next quarterly surveillance test completed on March 4, 2004, Station Battery 2N Cell 60 float voltage met its TS quarterly surveillance test Acceptance Criteria with a value of 2.17 vdc.
ANALYSIS OF OCCURRENCE (continued) :
It is not possible to determine at what time between December, 2003 and March, 2004 that the voltage for Cell 60 was restored to above the 2.13 vdc TS Table 4.8-1 operating limit. The Station Batteries are on a float charge following testing and it is not unusual for individual cell voltage to increase or decrease by a slight amount while in this state.
CORRECTIVE ACTIONS:
Corrective Actions Taken Since this event, procedure DB-ME-03001 has undergone several changes.
Improvements have been made that increase the likelihood that a cell voltage value that does not satisfy the Acceptance Criteria is identified in a timely manner. In addition, the acceptance criterion for float voltage has its own signature block, and the Test Leader no longer signs one space for four (4) different variables for all 60 Station Battery cells.
Additionally, the current Pre-Job Briefing program stresses identification of error-likely situations, critical steps, operating experience, and use of human performance tools.
Corrective Actions Planned DB-ME-03001 will be further revised to improve its use and to make it more conducive for users and reviewers to identify data that does not meet the Acceptance Criteria. This change to DB-ME-03001 will be in effect until the new electronic data recording mechanism described below is completely in place. This corrective action will be completed by October 20, 2005.
The DBNPS will implement an in-field electronic data recording mechanism for DB-ME-03001. The technology should be capable of flagging data that does not meet acceptance criteria. Implementation is currently scheduled for use during performance of DB-ME-03001 by October 20, 2005.
FAILURE DATA:
There have been no Licensee Event Reports at the DBNPS involving human performance-related causal factors for mode changes without equipment operable or involving the Station Batteries in the previous three years. Condition Reports (CR) and Potential Conditions Adverse to Quality Reports (PCAQR) were reviewed for similar events.
It should be noted that on December 4, 2003(same day as this event), Battery 2P Cell 52 voltage was low and CR 03-10486 was appropriately initiated and the voltage corrected within the time allowed by the TS.
FAILURE DATE (continued) :
There was one other occurrence identified in which Station Battery out of specification cell voltage data was recorded and not identified during the Maintenance review process. Condition Report (CR) 02-02758 involved a situation identical to the one described in this event. The electric shop/supervision did not identify the condition and the procedure was signed off as acceptable. The designated reviewer identified the condition.
Condition Report (CR) 02-02758 did not look at how the data was recorded and how the procedure was structured. The batteries were determined to have successfully passed their surveillance test and the equipment was operable when required by the Technical Specifications.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
NP-33-05-002-00� CR 2005-02415