Part 21 Report - 1998-251

ACCESSION #: 9803040126 LICENSEE EVENT REPORT (LER) FACILITY NAME: Clinton Power Station PAGE: 1 OF 5 DOCKET NUMBER: 05000461 TITLE: Incorrect Calculation in Diesel Generator Control Circuitry Results in Insufficient Voltage and Inoperability of the Division I Diesel Generator EVENT DATE: 01/31/98 LER #: 98-006-00 REPORT DATE: 03/02/98 OTHER FACILITIES INVOLVED: None DOCKET NO: 05000 OPERATING MODE: 4 POWER LEVEL: 000 THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR SECTION: 50.73(a))(2)(ii) OTHER LICENSEE CONTACT FOR THIS LER: NAME: M. G. McMenamin, Design Engineer TELEPHONE: (217) 935-8881, Extension 3469 COMPONENT FAILURE DESCRIPTION: CAUSE: SYSTEM: COMPONENT: MANUFACTURER: REPORTABLE NPRDS: SUPPLEMENTAL REPORT EXPECTED: NO ABSTRACT: With the plant in Mode 4 (COLD SHUTDOWN) and the sixth refueling outage In progress, a discrepancy in a Direct current voltage calculation for the Division I Diesel Generator control circuitry was discovered. The calculation did not Include the existence of two cables that are run to the Remote Shutdown Panel and their effect on the voltage drop to the Diesel Generator control panel. Preliminary evaluation of the impact of this error indicated that there has not been sufficient voltage to the control panel for all of its connected equipment. The cause for this event was due to an erroneous calculation provided by Sargent and Lundy design engineers. The engineer failed to include the cable lengths from and to the Remote Shutdown Panel in the voltage drop calculation for the Diesel Generator control Panel. This error was overlooked in several subsequent revisions. The corrective actions for this event are to restore the Diesel Generator control panel voltage to an acceptable level, to review other voltage calculations to ensure no other circuits omitted cabling, to review the control circuits that pass through the Remote Shutdown Panel and to brief engineering personnel on reasons learned from this event. This issue is also reportable under 10CFR21. END OF ABSTRACT TEXT PAGE 2 OF 5 DESCRIPTION OF EVENT On January 31, 1998, the plant was in Mode 4 (COLD SHUTDOWN) for the sixth refueling outage (RF-6), and reactor (RCT] coolant temperature was being maintained within a band of 95 to 115 degrees Fahrenheit (F) and pressure was zero pounds per square inch. A review was being performed by Nuclear Station Engineering Department personnel of the Emergency Diesel Generator (EDG) [EK] control circuitry due to a supplier deficiency noted with the air start solenoids [SOL]. During this review, a discrepancy was identified with a calculation for the Direct Current (DC) feed to the Division I DG control panel (1PL12JA) (PL). The identified error was that certain cables [CBL3], which comprise part of the normal DC feed to the Division I DG control panel, had not been included in the voltage drop calculation to the panel. An informal calculation of the resistances and voltage drop, with the additional cable lengths included, indicated that the acceptance criteria of the original calculation had not been met. Condition Report (CR) 1-98-01-452 was written to address this issue. The control power feed to 1PL12JA has an alternate feed through the Remote Shutdown Panel (RSP). This alternate feed is routed through a transfer switch located on the RSP. On February 4, 1996, during the review of the voltage requirements for 1PL12JA, it was noted that the amperage specifications for the transfer switch an the RSP were not adequate for the revised calculation. CR 1-98-02-060 was written to address this inadequacy. The normal 125 volts (V) DC power is supplied to panel 1PL12JA through a feed cable (1DG01N) from the DC Motor Control Center (MCC). This cable is a three conductor, 1/0 gauge utilizing two of the conductors to carry the current to the panel. This cable choice appears to have treated the voltage drop issue as the limiting factor for this circuit and, at the time of installation, provided some margin in the design. In order to provide the capability to transfer to an alternate source of DC power, the normal feed circuit passes through the remote shutdown panel. This was accomplished by the addition of cables to and from the RSP, connecting through the transfer switch. This cabling (1DG01M and 1DG01P) consists of #6 American Wire Gauge (AWG) size conductors. This part of the design failed to adequately evaluate the loads that existed at the diesel panel versus the rating of the transfer switch contacts (20 Amps (A) continuous, 6.5A inductive interrupting). At the time of the initial design, the maximum continuous load of the panel would have been approximately 14A but the inductive load represented by two DG lube oil motors [MO] would have been approximately 12.6A. The cable selection was acceptable from an ampacity viewpoint but the voltage drop was not considered. The original design current of 14A results in a voltage drop that does not meet the criteria of Sargent and Lundy standards with respect to motor feeds. The resultant configuration should have been included as part of calculation 19-D-28, "Review of Division I DC System 1A," (Revision 0 dated June 6, 1985). This calculation recognized that the DC lube oil motors at the diesel would be running. In the "voltage drop in DC feeder circuits" portion of calculation 19-D-28, the feeder circuit breaker to 1PL12JA was evaluated, but only with the three conductor 1/0 cable (1DG01N) included and not the alternate feed through 1DG01M and 1DG01P. Based on the calculation layout, the preparer of calculation 19-D-28 was most likely working from the MCC key diagram and waxing TEXT PAGE 3 OF 5 diagram as well as the cable database. These documents show 1DG01N feeding 1PL12JA and terminating there. In order to identify the additional cables involved, it would be necessary to go to the wiring diagrams for the DG panel and the RSP, but there was nothing to specifically lead the preparer to look at those documents. After issuance of the initial calculation, it was unlikely that the error would be subsequently identified since changes would tend to be loads and this would only lead to revision of the numerical values and not re-verification of the base data. This proved to be the case when the diesel pre-lubrication modification (DG-08, Engineering Change Notice 6644, dated November 19, 1985) was issued. In revision three of the calculation (issued February 18, 1987), the battery loading was revised to reflect the two new DC motors at the diesel. However, the "voltage drop in DC feeder circuit" was not revised. When this modification was issued, the transfer switch at the RSP was not re-examined for the additional load of two DC motors which took the continuous load to 26A, which is greater than the switch rating of 20A. In revision eight to calculation 19-D-28 (issued June 15, 1991), the voltage drop portion was redone. This revision reformatted the calculation and examined not only the voltage drop to 1PL12JA, but also examined the addition of the two DC motors for pre-lubrication. However, the revision failed to identify the cabling through the RSP and so the acceptance values achieved were in fact not present at the motor terminal. as a result of this error, the Division I DG control panel would not have had sufficient voltage to operate all connected equipment in the event of an actual lose of Alternating Current(AC) power start. No automatic or manually initiated safety system responses were necessary to place the plant in a safe and stable condition. This event was not affected by other inoperable equipment or components. CAUSE OF EVENT There was an initial error in the preparation of calculation 19-D-28 provided by Sargent and Lundy, which was not detected in the initial review nor subsequent revisions to the calculation. Thin error was further aggravated by the improper selection of a transfer switch that was marginal for its purpose and not further evaluated during later design changes. CORRECTIVE ACTION The corrective actions for this event includes a resolution to the voltage level required at the DC control panel. DC calculations for the safety-related batteries will be reviewed to ensure no other circuits emitted cabling. The control circuitry that runs through the RSP will also be analyzed for other components to ensure proper voltage/amperage is adequate for their operation. Engineering personnel will be briefed on the lessons learned from this event. TEXT PAGE 4 OF 5 ANALYSIS OF EVENT This event is reportable under the provisions of 10CFR50.73(a)(2)(ii)(B) due to the plant being in a condition outside of its design basis in that there could have been insufficient voltage to the DG equipment fed by the control panel such that they would not have performed their design function. An assessment of the safety consequences and implications of this event concluded that this event was safety significant. In the event of a true Loss of Alternating Current (AC) Power situation, the lack of sufficient voltage could have had significant adverse affect to the operation of the Division I DG up to and including failure of the diesel to start within the required time period. This condition has existed since initial plant licensing. This cabling configuration only effects the Division I Diesel Generator. The DC feed to the Division II and III Diesel Generators do not have the extra cabling that runs through the RSP. ADDITIONAL INFORMATION NO equipment or components failed during this event. Illinois Power has not reported any events of insufficient DC voltage or underrated control switches in the past two years. For further information regarding this event, contact M. G. McMenamin, Nuclear station Engineering, at (217) 935-8891, extension 3469 10CFR, PART 21 REPORT 21-98-014 On January 31, 1998, a review of the DC power to the control circuitry of the DG control panel revealed that there was an error in the base calculation for the required voltage to DC equipment associated with the Division I DG. This error in preparing the calculation should be reported under the provisions of 10CFR21. The basis for the reportable conclusion is that the lack of sufficient voltage to the DG equipment could have adverse effects to its operation when required. (1) Walter G. MacFarland, IV, Chief Nuclear Officer of IP, Clinton Power Station, Highway 54, 6 miles East, Clinton, Illinois, 61727, is informing the Nuclear Regulatory Commission of a condition reportable under the provisions of 10CFR, Part 21. (ii) The activity involved in this condition is the calculation 19-D-28, "Review of Division I DC System 1A," (Revision 0 dated June 6, 1985). (iii) This calculation was prepared and supplied by Sargent & Lundy. (iv) The error in tho calculation was a failure to analyze the cabling run from the DG control panel to the Remote Shutdown Panel for its impact on the minimum required voltage required for operation of the DC loads off of the DG control Panel. Insufficient voltage to this equipment could result in failure for the equipment to perform its desired function when required by plant conditions. TEXT PAGE 5 OF 5 (V) The error in this calculation was discovered an January 31, 1998, and determine to be potentially reportable under the provisions of 10CFR21. The inadequacy of the transfer switch was identified on February 4, 1998, and was determined to be potentially reportable due to the error in the calculation 19-D-28. (vi) The scope of the generic applicability of this issue at CPS has not been determined. A review of DC calculations will be performed and an analysis of other circuit configurations that pass through the Remote Shutdown Panel will be performed. (Vii) Corrective actions being taken by Illinois Power are discussed in the corrective action section of the LER portion of this report. (Viii) IP has no advice for other purchasers or licensees regarding this issue. ATTACHMENT TO 9803040126 PAGE 1 OF 1 POWER REACTOR EVENT NUMBER: 33819 FACILITY: CLINTON REGION: 3 NOTIFICATION DATE: 03/02/98 UNIT: [1] [ ] [ ] STATE: IL NOTIFICATION TIME: 14:25 RX TYPE: [1] GE-6 EVENT DATE: 03/02/98 EVENT TIME: 14:25[CST] NRC NOTIFIED BY: BYRON SHERMAN LAST UPDATE DATE: 03/02/98 HQ OPS OFFICER: JOHN MacKINNON NOTIFICATIONS EMERGENCY CLASS: NOT APPLICABLE 10 CFR SECTION: CCCC 21.21 UNSPECIFIED PARAGRAPH VERN HODGE (PCEB) NRR UNIT SCRAM CODE RX CRIT INIT PWR INIT RX MODE 1 N N 0 COLD SHUTDOWN CURR PWR CURR RX MODE 0 COLD SHUTDOWN EVENT TEXT INCORRECT CALCULATION IN DIESEL GENERATOR CONTROL CIRCUITRY RESULTS IN INSUFFICIENT VOLTAGE AND INOPERABILITY OF THE DIVISION 1 DIESEL GENERATOR. A DISCREPANCY IN A DIRECT CURRENT VOLTAGE CALCULATION FOR THE DIVISION 1 DIESEL GENERATOR CONTROL CIRCUITRY WAS DISCOVERED. THE CALCULATION DID NOT INCLUDE THE EXISTENCE OF TWO CABLES THAT ARE RUN TO THE REMOTE SHUTDOWN PANEL AND THEIR EFFECT ON THE VOLTAGE DROP TO THE DIESEL GENERATOR CONTROL PANEL. PRELIMINARY EVALUATION OF THE IMPACT OF THIS ERROR INDICATED THAT THERE HAS NOT BEEN SUFFICIENT VOLTAGE TO THE CONTROL PANEL FOR ALL OF ITS CONNECTED EQUIPMENT. THE CAUSE FOR THIS EVENT WAS DUE TO AN ERRONEOUS CALCULATION PROVIDED BY SARGENT AND LUNDY DESIGN ENGINEERS. THE ENGINEER FAILED TO INCLUDE THE CABLE LENGTHS FROM AND TO THE REMOTE SHUTDOWN PANEL IN THE VOLTAGE DROP CALCULATION FOR THE DIESEL GENERATOR CONTROL PANEL. THIS ERROR WAS OVERLOOKED IN SEVERAL SUBSEQUENT REVISIONS. THE CORRECTIVE ACTIONS FOR THIS EVENT ARE TO RESTORE THE DIESEL GENERATOR CONTROL PANEL VOLTAGE TO AN ACCEPTABLE LEVEL, TO REVIEW OTHER VOLTAGE CALCULATIONS TO ENSURE NO OTHER CIRCUITS OMITTED CABLING, TO REVIEW THE CONTROL CIRCUITS THAT PASS THROUGH THE REMOTE SHUTDOWN PANEL AND TO BRIEF ENGINEERING PERSONNEL ON LESSONS LEARNED FROM THIS EVENT. LER WAS SUBMITTED BY THE LICENSEE. *** END OF DOCUMENT ***

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