ML20045D672

Suppls 920116 & 930430 Responses to Unresolved Items in Edsfi Repts 50-373/91-19 & 50-374/91-19 Re Inadequate Contractor Terminal Voltages on Div 3 Motor Control Circuits.Unit 1 HPCS Valve Mod Installed During Fall Outage

ML20045D672
Person / Time
Site:	LaSalle
Issue date:	06/22/1993
From:	Depuydt M COMMONWEALTH EDISON CO.
To:	Murley T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
References
NUDOCS 9306290288
Download: ML20045D672 (5)

Text

_ _ _ - - _ _ _ - - _ _ _ _ - _ - _ _ - - _ - _ - - _ _ _ _

Crmm:nw:alth EdisIn

[ Zf } 1400 Opus Place .  !

i

~*

k Downers Grove, Illinois 60515

{

i June 22,1993 Dr. Thomas E. Murley Office of Nuclear Reactor Regulation :

U.S. Nuclear Regulatory Commission Washington, DC 20555 Attn: Document Control Desk

Subject:

Supplemental Response to EDSFI Unresolved

- Items #373/91019-06 and 374/91019-06 for 4160V Degraded Voltage LaSalle County Station Units 1 and 2 Docket Nos. 50-373 and 50-374

References:

1. : T. Martin (USNRC) to L. DelGeorge (CECO), dated March 12, 1993,-

Engineering / Technical Support Inspection Report Nos. 50-373/93002 and 50-374/93002 -

2. T. Kovach (CECO) to USNRC, dated April 30,1993, Supplemental Response on Unresolved Item for 4160 Volt Degraded Voltage

3. T. Kovach (CECO) to USNRC, dated January 16,1992, Respo.nse to

~

EDSFI Report

Dear Dr. Murley:

In the original response for the subject unresolved item (Reference 3),'

Commonwealth Edison Company (CECO) committed to perform specific actions 'to resolve the ESF Division 3 motor control circuits with inadequate contactor terminal voltages.

While CECO has not altered their intent or schsdule to modify. these circuits, the implemented modification varies slightly_from'that indicatedJn -

Reference 3. During the. week of January.11,-1993 anLon' site Engir.eering and Technical Support NRC inspection _ examined'one of the'ESF Divisi3n 3 motor s control circuit modifications and had no concerns. However, this chanr,e in; corrective actions was no.t explicitly mentioned in the resulting inspection report (Reference 1).

ThErefore, LaSalle is submitting a supplemental response to outline:

the corrective actions that will be implemented for the problem ESF Division'31

~

motor control. circuits? A description of the scope of the work for.'these modifications is provided in Attachment A.

1 .

/scl:mbdjune,wpf:3' ..

pO

'9306290288-930622" . <

1

\M-9 2PDR:;ADOCK.050003734 -

.Os PDR=

" ' T (J

.7 .

a* .

l-t Dr. Thomas E. Murley . June 22,1993  :

. Also included, as Attachment B, is'a status of the voltage calculations .l for the 120 VAC distribution circuits. >

l

'If there are any questions regarding this information, please. contact .

thisoflice.

. Respectfully,-.

Mary Beth Depuydt~ .

Nuclear Licensing Administrator b

Attachments: i cc: . J. Martion, Regional Administrator - RIII -

R."Stransky, Project. Manager -- NRR ..

.D. Hills, Senior Resident ~InspectorL- LSCS Office of Nuclear Safety - IDNS !

1 l .-i

! I l

(

l L

L .-

l I

7scl:mbdjune.wpf: 4 s

o

4

] l NITACHMENT A

. ESF DIVISION 3 MOTOR CONTROL CIRCUITS-1 In our response of January 16,1992, to the Electrical Distribution System ,

Functional Inspection (EDSFI) at LaSalle County Station,_it was indicated that the -

4 contactors for the following equipment had inadequate voltage to pickup at the original degraded voltage setpoint of 3814 +/ - 76 volts: '

i

1. HPCS Diesel Generator Cooling Water Pump,1 (2) E22-C002-

2. HPCS Pump Discharge Valve,1 (2) E22-F004 - <

3. HPCS Diesel Generator Room Vent Fan,1 (2) E22-F004

4. HPCS Switchgear Room Exhaust Fan,- 1 (2) VD07C l

5. HPCS Cubicle Cooler Fan,1 (2) VYO2C To help resolve the voltage concerns'with these circuits, it was stated that these d

contactors would be field inspected to determine if nuclear grade or commercial grade models ~are installed, and replace the commercial grade models with nuclear grade models. Commercial grade models have a vendor certified pick-up voltage of 85% of rating while nuclear grade models have a minimum certified pick-up :

voltage of 75% of rating.

The proposed schedule for performing the inspections was the fourth refueling outage for Unit 2 (winter,1992) and the fifth refueling outage for Unit 1 (fall, 1992). The proposed schedule for installing the nuclear grade contactors was the subsequent refueling outage for each unit.

A field inspection of the Unit 2 and spare contactors did not identify any nuclear grade models. Since the ESF. Division 3 systems for each unit were purchased at the same time from General Electric (GE), the Unit 1 contactors were also assumed to be all commercial grade. Thus, an inspection of the Unit 2 contacts was determined not be required.

Based on the results of the Unit 2 contactor inspections, Engineering started to .  ;

prepare the modification design change packages for. the ESF Division 3 motor.

control circuits identified above in May,1992 for both units . Engineering issued the design package for the Unit 1 HPCS Pump Discharge Valve 1E22-F004 starter-circuit in' July 1992, and the remainder of the design changes by early November.

The Unit 1 HPCS valve modification was installed during the fall refueling outage,

and the modification for the Unit 1 HPCS Switchgear Room' Exhaust Fan  !

(1VD070) has been completed'since then. The remaining modifications for both -

units are scheduled to be installed prior to startup following the Unit 2 fifth . i refueling outage which is currently scheduled from early Septe'mber to late j November,1993.  ;

l 1

/sc1:mbdjune.wpf:5

ATTACHMENT A ESF DIVISION 3 MOTOR CONTROL CIRCUITS (condnued)

The approved design changes for all ten HPCS motor control circuits are similar.

For each circuit the modification consists of replacing the existing 120 VAC coil in the contactor with a coil rated at 460 VAC +/- 10% and disconnecting it from the 120 VAC control circuit. The new contactor coil is then wired to the 480 VAC bus at the motor control center and interlocked with a contact from a new relay connected to the control circuit. The new contactor coil was purchased as commercial grade and dedicated for use in this safety-related application.

The design changes that are being implemented for these circuits differ slightly from that originally indicated in Reference 3. At the time the' original response was submitted the intent was to replace the existing 120 VAC commercial grade contactors with nuclear grade contactors of the same voltage rating. However, calculations showed that this design change would require the replacement of cables in the circuit and would provide less margin than the final approved design.

In addition, the minimum delivery time for nuclear grade models was sixteen (16) weeks after receipt of order. Therefore, it was decided to upgrade the voltage rating of the contactor coils. This change eliminated the voltage drop across the control transformer and cables by allowing the contactor coil to be directly connected to the 480 VAC bus at the motor control center. Since this terminal voltages will exceed 85% of rating at the degraded voltage setpoint of 3814V, nuclear grade models are not required.

During the week of January 11,1993, the NRC reviewed the starter circuit modification for HPCS valve 1E22-F004 and had no concerns.

/ sc1 :nibdj une .wpf : 6

1

/. ..[? -

}

, .. o ATTACHMENT B ' ,

120 VAC Distribution Circuits. ';

During the NRC inspection from January 11 through.15,1993, it was indicated that additional voltage calculations were being performed to resolve potential; .

voltage concerns with the 120 VAC distribution circuits. While these calculations -

are not yet completed, the preliminary results indicate that only.nine (9) Unit 1 - , ,

and seven (7) Unit 2 safety-related circuits may have inadequate l voltages too

perform their safety function after an accident at the degraded voltage setpoint of. ,

3814V. The calculations also show that all distribution circuits have. adequate l voltages under the compensatory measures.taken by the station.

Within one month following the end of ths Unit 2 fifth refueling' outage, al

! supplemental response will be submitted to provide the final results of these calculations and to' identify the corrective actions that will be taken for the 120.  !

,' VAC distribution circuits with voltage concerns.  ;

[. +

I i

l:

j I

! 1 V

L i

' l I

i -I L

ll J 9/sclf:inbdjune.wpf j 7 b ' '

4 n, m .h _j,,_,