United States Nuclear Regulatory Commission - Protecting People and the Environment


ACCESSION #:  9804130273

                       LICENSEE EVENT REPORT (LER)



FACILITY NAME:  Clinton Power Station                     PAGE: 1 OF 6



DOCKET NUMBER:  05000461



TITLE:  Incorrect Cable Resistance and Brake Horsepower Data Used

        in the Design of 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:  09/29/86   LER #:  97-034-01   REPORT DATE:  04/03/98



OTHER FACILITIES INVOLVED:  None                    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

             Department                     TELEPHONE:  (217) 935-8881,

                                                        Extension 4078



COMPONENT FAILURE DESCRIPTION:

CAUSE:      SYSTEM:       COMPONENT:       MANUFACTURER:

REPORTABLE NPRDS:



SUPPLEMENTAL REPORT EXPECTED:  NO



ABSTRACT:



Station engineers determined that during degraded voltage conditions, the

Divisions 1 and 2 emergency diesel generator (EDG) room vent fans,

1VD01CA and 1VD01CB, could cause off-site power supply breakers to trip

on undervoltage during transient electrical bus loading conditions

associated with a block start Loss of Coolant Accident (LOCA).  Improper

cable resistance values and brake horsepower ratings were used in the

original design of the 1VD01CA and 1VD01CB vent fans.  This condition is

outside the design basis of the plant.  The cause of this event was

determined to be insufficient detail provided in a S&L standard and

design engineer's oversight when determining the brake horsepower ratings

of 1VD01CA and 1VD01CB.  Corrective actions include revising

calculations, developing a new cable impedance standard, providing

required reading for appropriate individuals on the new cable impedance

standard, verifying other S&L standards, and performing a plant

modification to correct this condition.  The cable resistance issue is

also reportable under 10CFR21.



END OF ABSTRACT



TEXT                                                          PAGE 2 OF 6



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 of 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 at or

below 1 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 this 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 the auxiliary power system to separate from the off-site

power source and transfer to the emergency on-site power system during a

Loss of Coolant Accident (LOCA) block start coincident with a degraded

offsite 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 on 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 within 13 seconds could cause the off-site power supply

breakers [BKR) to trip on undervoltage due to initial transient loading

during a LOCA block start, resulting in the transfer to the emergency

on-site power source.  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, is 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 6



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, 1986.

At that time the plant was in Mode 5 (REFUELING) for initial fuel

loading, and reactor coolant temperature was 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 of this event was determined to be insufficient detail provided

in S&L standard ESA-102, Table B.  ESA-102, Table B did not identify and

quantify cable construction and installation elements which affect

resistance and reactance values.  Additionally, the 1VD01CA and 1VD01CB

brake horsepower ratings were based on a less conservative temperature of

96 degrees F rather than the minimum design temperature due to the design

engineer's oversight.



CORRECTIVE ACTIONS



CPS has developed a cable impedance standard, EE 02.00, "Cable Resistance

and Reactance Data," that contains the correct cable impedance values for

CPS.  S&L standard ESA 102 has been clearly marked to indicate that it is

not applicable for use in determining cable impedance at CPS and that

Standard EE-02.00 should be used.



A briefing was held with the individuals who are qualified to prepare

electrical calculations to make them aware that a new cable impedance

standard has been issued that reflects the correct impedance values for

CPS.



Electrical calculations will be revised to reflect the correct cable

impedance for tin coated copper conductors.



Appropriate power loading and voltage calculations will be revised to

account for safety related Heating Ventilation and Air Conditioning

(HVAC) fan motor horsepower ratings at their minimum design operating

temperature.



The Updated Safety Analysis Report (USAR) will be revised to reflect the

horsepower ratings of safety related HVAC equipment at their minimum

design operating temperature.



A sample of S&L standards will be reviewed to verify accuracy, degree of

precision, and proper application of the standard at CPS.  Any anomalies

found during the review will be evaluated for impact on the plant, and

corrected if required.  Based on the results of this review, the need for

additional action will be evaluated.



TEXT                                                          PAGE 4 OF 6



CPS has installed a temporary modification to delay the start of the

1VD01CB supply fan during a LOCA block start accident.  Delaying the

start of the supply fan will allow the auxiliary power system voltage to

recover from the initial power demand caused by the simultaneous starting

of safety related equipment.  This temporary modification will prevent an

undesired separation of the off-site power source from the auxiliary

power system.  A similar temporary modification is being prepared for the

1VD01CA supply fan.  The final determination as to whether a permanent

design change is necessary will be determined after the completion of a

modification that affects degraded voltage values.



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

has determined that this event has potential safety significance.  During

a LOCA block start accident concurrent with low outside ambient air

temperatures and degraded off-site grid voltage, the auxiliary power

system may separate from the off-site source because of low bus voltage.

In this case the safety loads would be picked up by the corresponding

divisional DG and the safety loads would restart on the emergency on-Bite

power system, however; this condition reduces the plant's overall defense

in depth.



ADDITIONAL INFORMATION



No equipment or components failed as a result of this event.



IP has reported other events where off-site degraded voltage conditions

reduced the safety margin of the plant in Licensee Event Reports 94-005

and 97-008.  As a generic corrective action, IP is pursuing alternate

methods in maintaining the off-site voltage being supplied to the

Auxiliary Power System during degraded voltage grid conditions.



For further information regarding this event, contact A.  B.  Haumann,

Engineering Projects, at (217) 935-8881, extension 4078.



TEXT                                                          PAGE 5 OF 6



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 B 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 at or

below I 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 (CR) 1-97-10414 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 completed its evaluation of this issue

on January 16, 1998 and concluded that it was 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 was made by

facsimile of IP letter U-602908 to the NRC Operations Center in

accordance with 10CFR21.21(d)(3) on January 16, 1998.



(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 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 drop 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 on the Divisions 1 and 2 emergency diesel

          generator room vent fans could cause off-site power supply

          breakers to trip on low voltage during a LOCA block start.  A

          loss of off-site power reduces Clinton Power Station's defense

          in depth during a LOCA.



TEXT                                                          PAGE 6 OF 6



(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 were 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.  These 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

          may be affected by this issue.  The supplier of the improper

          cable resistance values (Sargent & Lundy) is aware of this

          issue.



(vii)     The Corrective Actions that IP is taking for this condition are

          contained in the CORRECTIVE ACTION section of the LER.



(viii)    IP has no additional information to offer.



*** END OF DOCUMENT ***





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