Part 21 Report - 1998-071

ACCESSION #: 9801220103 LICENSEE EVENT REPORT (LER) FACILITY NAME: Clinton Power Station PAGE: 1 OF 5 DOCKET NUMBER: 05000461 TITLE: Incorrect Cable Resistance and Brake Horsepower Data Used in the Design Divisions 1 and 2 Emergency Diesel Generator Vent Fans Results in Design of Fan Motors Being Outside the Design Basis of the Plant EVENT DATE: 09/29/96 LER #: 97-034-00 REPORT DATE: 01/16/98 OTHER FACILITIES INVOLVED: DOCKET NO: 05000 OPERATING MODE: 5 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: A.B. Haumann, Nuclear Engineering TELEPHONE: (217) 935-8881, Department Extension 4078 COMPONENT FAILURE DESCRIPTION: CAUSE: SYSTEM: COMPONENT: MANUFACTURER: REPORTABLE NPRDS: SUPPLEMENTAL REPORT EXPECTED: YES EXPECTED SUBMISSION DATE 03/19/98 ABSTRACT: Station engineers determined that during degraded voltage conditions, the Divisions 1 and 2 emergency diesel generator (EDG) room vent, fans could cause offsite power supply breakers to trip on undervoltage during transient electrical bus loading conditions associated with a Lose of Coolant Accident (LOCA) block start. Improper cable resistance values and brake horsepower ratings were used in the original design of the Divisions 1 and 2 EDG vent fans. The cable resistance values, provided by Sargent & Lundy, did not account for the fans' "tin-coated" copper conductor cables which have a higher resistance than uncoated conductor cables. Additionally, the brake horsepower of the fan motors was based on an operating temperature of 96 degrees Fahrenheit (F). The Divisions 1 and 2 EDG room vent fans are required to operate at temperatures below 96 degrees F and thus higher than originally calculated brake horsepower is required for proper operation. The cause and corrective actions for this event have not been determined at this time, The cable resistance issue in also reportable under 10CFR21. END OF ABSTRACT TEXT PAGE 2 OF 5 DESCRIPTION OF EVENT On October 23, 1997, 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 100 to 120 degrees Fahrenheit (F) and pressure was zero pounds per square inch (psi). Engineers were investigating degraded voltage margins and identified that at least five electrical voltage calculations for the Alternating Current (AC) [ED] and Direct Current (DC) [EJ] electrical distribution system design used improper cable [CBL] resistance data provided by Sargent & Lundy (S&L) in Table B of S&L Standard ESA-102, "Electrical Engineering Standard for Electrical and Physical Characteristics or Class B Electrical Cables." The standard established the Clinton Power Station (CPS) design basis cable resistance used for determining cable tray [TY) loading and voltage drop calculations. Per S&L Power and Control Cable Specification STD-EA-253, "General Specification for Power and Control Cable Insulated with Ethylene-Propylene Rubber," CPS cables with voltage ratings below 5 Kilovolts (KV) have "tin-coated" copper conductors, however, Table B of Standard ESA-102 provides resistance data for "uncoated" copper conductor cables. Coated cables have higher resistance values than uncoated cables and yield slightly lower equipment terminal voltages than established in at least five electrical calculations. Condition report 1-97-10-414 was written to Investigate and track the issue. The Operations Shift Supervisor (SS) entered additional restraints against restoring operability for Technical Specification (TS) Limiting Condition for Operation (LCO) 3.8.2, "AC Sources-Shutdown," and 3.8-10, "Distribution Systems-Shutdown," as operability per these TS LCOs was already restrained for other reasons. On December 19, 1997, engineering determined that the Divisions 1 and 2 emergency diesel generator room vent fans [FAN], 1VD01CA and 1VD01CB, could cause a loss of offsite power during a LOSS of Coolant Accident (LOCA) block start coincident with a degraded voltage condition. This determination was based on increased cable resistance due to tin coated conductors and higher than originally calculated fan brake horsepower. The brake horsepower for these fan motors is based an a fan operating temperature of 96 degrees F. Analysis has identified that the fans are required to operate at temperatures below 96 degrees F. As air temperature decreases more horsepower is required to drive the fans. The combination of increased brake horsepower and cable resistance could cause the Divisions 1 and 2 emergency diesel generator room vent fans to exceed a 13 second starting time under degraded voltage conditions. CPS degraded voltage analysis calculation 19-AQ-02, assumes that the 1VD01CA and 1VD01CB fans accelerate to operating speed in less than 13 seconds. Failure of the fans to start in 13 seconds could cause the offsite power supply breakers [BKR] to trip on undervoltage due to transient loading during a LOCA block start resulting in a lose of offsite power. Considering the increased cable resistance due to tin-coated copper conductors and increased brake horsepower due to colder air temperatures, the assumptions of calculation 19-AQ-02 may not be valid. Therefore, the design of the Divisions 1 and 2 emergency diesel generator room vent fans, 1VD01CA and 1VD01CB, in not in accordance with the design basis of the plant. The operability of Division 3 emergency diesel generator room vent fan is not affected by this condition. TEXT PAGE 3 OF 5 The tin coated copper conductors and increased brake horsepower conditions for the Divisions 1 and 2 emergency diesel generator room vent fans have existed since initial plant licensing on September 29, 1966. At that time the plant was in Mode 5 (REFUELING) for initial fuel loading, and reactor coolant temperature wag ambient and pressure was atmospheric. 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 The cause for this event is still under investigation and will be provided in a revision to title report. IP expects to issue a revision to this report identifying the cause, corrective actions, agreement of the safety consequences and implications, and previous similar events by March 19, 1998. CORRECTIVE ACTIONS This corrective actions for this event have not been determined but will be provided in a revision to this report. ANALYSIS OF EVENT This event is reportable under the provision of 10CFR50.73 (a) (2) (ii) (B) due to the design of the 1VD01CA and 1VD01CB fan motors being outside the design basis of the plant. An assessment of the safety consequences and implications of this event will be provided in a revision to this report. ADDITIONAL INFORMATION No equipment or components failed as a result of this event. Previous similar event information regarding this event will be provided in a revision to this report. For further information regarding this event, contact A. B. Haumann, Engineering Projects, at (217) 935-8881, extension 4078. TEXT PAGE 4 OF 5 10CFR21 REPORT 21-97-051 On October 23, 1997, Engineers were investigating degraded voltage margins and identified that at least five electrical voltage calculations for the Alternating Current (AC), and Direct current (DC) electrical distribution system design used improper cable resistance data provided by Sargent & Lundy (S&L) In Table 2 of S&L Standard ESA-102, "Electrical Engineering Standard for Electrical and Physical characteristics of Class B Electrical Cables." The standard established the Clinton Power Station design basis cable resistance used for determining cable tray loading and voltage drop calculations. Per S&L Power and Control Cable Specification STD-EA-253, "General Specification for Power and Control Cable Insulated with Ethylene-Propylene Rubber," CPS cables with voltage ratings below 5 Kilovolt (KV) have "tin-coated" copper conductors; however, Table B of standard ESA-102 provides resistance data for "uncoated" copper conductor cables. Coated cables have higher resistance values than uncoated cables and yield slightly lower equipment terminal voltages than established in at least five electrical calculations. Condition report (CR) 1-97-10-414 was written to investigate and track this issue. IP determined that this condition was potentially reportable under 10CFR, Part 21 on October 25, 1997. IP has completed an revaluation of this issue and concludes that it in reportable under the provisions of 10CFR, Part 21. IP is providing the following information in accordance with 10CFR21.21(d)(4). Initial notification of this matter will be provided by facsimile of thin letter to the NRC Operations Center in accordance with 10CFR21.21(d)(3) within 2 days of the data the responsible officer approves this report. (i) Walter G. MacFarland IV, Chief Nuclear Officer of Illinois Power Company, Clinton Power Station, highway 54, 6 miles East, Clinton, Illinois, 61727, is informing the NRC of a condition reportable under the provisions of reportable under the provisions of 10CFR21 by means of this report. (ii) The basic component involved in this report is the use of an incorrect design standard, S&L standard ESA-102, in the design of the cables installed at Clinton Power Station. (iii) The cable design using S&L standard ESA-102 was supplied to CPS by Sargent & Lundy. (iv) As discussed in the DESCRIPTION OF EVENT portion of this report, the nature of the defect is inaccurate cable resistance values supplied in S&L standard ESA-102 report for design of cables rated below 5 KV. This information was used in electrical voltage calculations for the AC and DC electrical distribution systems. As discussed in the DESCRIPTION OF EVENT portion of this report, under degraded voltage conditions, the impact of increased cable resistance in conjunction with air temperatures below 96 degrees F an the Divisions 1 and 2 emergency diesel generator room vent fans could cause offsite power supply breakers to trip on low voltage during a LOCA block start. A loss of offsite power reduces Clinton Power Station's defense in depth during a LOCA. TEXT PAGE 5 OF 5 (v) On October 23, 1997, Illinois Power identified that improper cable resistance values from data provided by Sargent & Lundy In Table B of S&L Standard ESA-102 wave used in at least five electrical voltage calculations for the AC and DC electrical distribution systems IP determined that this issue was potentially reportable under 10CFR, Part 21 on October 25, 1997. (vi) The Improper cable resistance values were used to determine cable tray loading and voltage drop of cables rated for less than 5 KV at CPS. Those applications have been evaluated and IP has concluded that this issue adversely affects the Divisions 1 and 2 emergency diesel generator room vent fans, 1VD01CA and 1VD01CB, IP is not aware of other facilities that stay be affected by this issue. The supplier of the improper cable assistance values (Sargent & Lundy) is aware of this issue. (vii) The corrective actions that IP will take for this event have not been determined but will be provided in a revision to this report. (viii) IP has no additional information to offer. *** END OF DOCUMENT ***

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