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Safety Insp Rept 50-341/87-42 on 870921-30.No Violations or Deviations Noted.Major Areas Inspected:Licensee Action on Previous Insp Findings,Review of Design Changes to Resolve Swing Bus Design Deficiency & Training
	ML20235X138
Person / Time
Site:	Fermi
Issue date:	10/13/1987
From:	Falevits Z, Gardner R; NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:	;
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ML20235X123	List: ML20235X120; ML20235X138;
References
	50-341-87-42, NUDOCS 8710190227
	Download: ML20235X138 (6)
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U.S. NUCLEAR' REGULATORY COMMISSION

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REGION III

' Report No.' 50-341/87042(DRS)

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, : Docket'No. 50-341' License No.'NPF-43-

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. Licensee: -Detroit' Edison Company

2000 Second. Avenue

-Detroit, MIJ 48224'

Facility.Name: Enrico Fermi Nuclear Power Plant, Unit 2

Inspectior At: Enrico Fermi 2 Site, Newport, Michigan

-Inspection Conducted: . Sept 21-30, 1987

Y " d ymber

Inspector: Zelig Falevits /0//Y/7. I

... Date

Approved By:

FAN lhW

Ronald N. Gardner, Chief

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Plant Systems Section 'Date

Inspection Summary

Inspection on September 21-30, 1987 (Report No. 50-341/87042(DRS))

Areas Inspected: Special safety-inspection of licensee action on previous

inspection findings, review of design changes to resolve the Swing Bus design-

deficiency, and training. (92701, 37702, 41400) . _

Resultsi Of the three areas inspected, no violations or deviations were-

identified. I

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- s: DETAILS

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-1. Persons: Contacted

-Detroit Edison Company

+B.LR.-Sylvia, Group Vice. President

+F.? E. Agosti, Vice President, Nuclear Engineering >

.

S. P.- Zoma. .' Supervisor,_ Nuclear : Engineering.

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- ,+ L. Collins,iEngineer,' Nuclear Engineering-

+L. F. Wooden,ESupervisor, ElectricalLEngineering

.

+T. R. Randazzo, Director, Regulatory Affairs

+R. C. Anderson,-Engineer, Nuclear Engineering

+E.' R. Bosetti, Engineer

+R. Gondek, Engineer

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.

+T. McKelvey, Engineer

< '*S.-Cashell,_ Licensing Engineer

Excell Corp

+D.~ R. Hoffman, President

+S.-R.~ Frost, Licensing Supervisor. ,

+J. E. Price, Licensing Engineer

L. K.'Comstock'

S. Williams, Engineer, P & PE Electrical

USNRC-

+W. Rogers, Senior Resident Inspector

+J. J. Stefano, Fermi 2 Project Manager, NRR

+S. Rhow, Electrical Engineer, NRR/EST

+D. Tandi, Section-Chief, NRR/EST

+ Denotes those attending the Swing Bus meeting on September 23, 1987.

Denotes those participating in the telephone exit meeting on

September 30, 1987.

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2. Licensee Action on Previously Identified inspection Findings

a. (Closed) Unresolved Item (341/87014-02(DRP)): This item concerned k

licensee failure to perform adequate seismic and structural i

evaluation on installed termination box to motor adapters on

i ECCS' room cooler motors. These adapters developed cracks or failed

structurally causing a cooling unit motor to become separated from

its termination box and leaving the termination boxes inadequately

supported. To correct this problem, the licensee replaced the

rubber adapters with newly designed and fabricated aluminum adapters.

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-During the' previous inspection and'during review of the newly designed.

adapters additional concerns have been raised. The inspector noted-

that four of.the~12 motor termination boxes'using the new aluminum-

adapters were.not rigidly attached to the motors. In addition,;the

inspector noted that the:"SGTS North Room ESS Cooling Unit T4160B016"

contained a rubber like gasket adapter and the termination box was

observed not to be rigidly attached to the Westinghouse-motor.

< Subsequently, the licensee conducted a field inspection of all

applicableLsafety-related motors to determine.the rigidity of

the motor junction boxes. 'The licensee determined.that because

of the thin wall on the motor frame,'the torque placed on the bolts

which hold the adapters to.the motor frames was " restricted or lower

than.normally desirable." Therefore, .the licensee initiated EDP 7588

to add external supports for the 12 ECCS Room Cooler motor termination

boxes. The licensee planned to implement this change by the LCRT

outage. In the interim, Loctite thread compound was used to maintain

the bolt loading. The licensee's AE reviewed this design and found-

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it adequate for this application. The licensee verified that except

for the 12 motors noted no other motors contained such a thin wall

thickness for bolt engagement on their motor frame. In addition,.

the-licensee issued ABN-7554-1, Rev. B, to establish torque values !

for bolts holding termination boxes onto motor frames. This ABM-

covered all QA I motors and the torque values were based upon

calculations done by the-licensee's AE and the motor manufacturers.

The licensee has verified via field walkdowns that all safety-related

boxes are secure in place. Furthermore, the torque of all QA-I motors

would be verified against the values in ABN-7554-1 as part of the

preventative maintenance program. j

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Implementation of licensee corrective actions should provide long

term assurance that this problem will not recur. The inspector

will followup this issue during future inspections. 2

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b. (0 pen) Unresolved Item (341/87025-01(DRS)): This item concerned

failures of mounting bolts on termination boxes for the RHR pumps. '

The licensee noted that the mounting bolts for RHR "B" pump were

sheared (specifically, all four mounting bolts and two of the four

alignment bolts); that three of the four motor junction box mounting

bolts for RHR "A" pump motor were broken, and that the four bolts

holding the junction box to the RHR Pump C motor were finger tight.

DER-87-184, dated May 26, 1987, describes the root cause of the

"B" pump bolts failure as vibration induced fatigue of the bolts

and welds, and over torquing due to improper assembly. Subsequently,

y EDP-7440, Revision A and Design Calculation DC 367, Revision B, were

I issued to address the RHR pump mounting bolt issue. Corrective action

taken by the licensee to resolve the mounting bolt problem involved '

the specification of new torque values for RHR Pumps A, C, and D and

the installation of larger bolts (1") at 200 ft-lbs for RHR Pump B.

In addition, the licensee adopted an action plan to generically

resolve this issue.

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On June 18, 1987, the licensee conducted a field walkdown of all !

accessible large vertical motors and all small motors to verify the I

rigidity of the termination box mounting. The walkdown identified

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that altogether 17 motor termination boxes required immediate l

corrective action. This was completed by. July 7, 1987. j

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During this inspection, the inspector reviewed the licensee's i

corrective action and conducted a field inspection of the RHR

and LPCS pump boxes. The review indicated that vibration induced

by the RHR "B" pump caused a mechanical fatigue failure (crack) in

the tread root of the EECW pipe nipple to the RHR Pump B seal water

cooler. DER 87-300 dated August 13, 1987, was issued to document

this finding and WR No. 007A081387 was generated to replace the

nipple. In addition, the alignment straps and the 3/8" bolts

connecting these to the RHR "B" pump frame failed. The licensee

removed the four alignment bolts (ECR-7440-2) since they were not

considered in the calculations. As part of the corrective action,

the licensee installed acce'lerometers on RHR Pumps B and D. Data

collected from these instruments is presently being reviewed by

DECO Engineering Research Department and will be used to verify

the adequacy of the existing installations against the design

calculations.

On September 11, 1987, the licensee noted that the mounting brackets

for the seal water cooler on RHR Pump "D" were cracked (DER 87-358).

The brackets were replaced by WR No. 010A 091187. This item remains

unresolved pending licensee resolution and NRC review.

3. Review of Licensee Design Change to Resolve the Swing Bus Design Deficiency

During a recent operations activity, a design deficiency was uncovered

when an operator, in error, removed the fuses from D.C. Distribution

Cabinet 2PA2-14 Position 2. All D.C. control power was removed from

Bus 72C and its associated breakers. This caused the "29" contactor

in the Bus 72C feed to MCC 72CF to drop out and deenergize MCC 72CF.

The automatic transfer from Bus 72F feed could not occur as the Bus 72C

Position 3C breaker did not open to close the necessary 52b/3C

interlock in the Bus 72F Position SC feed breaker close circuit

(Ref. DWGS 61721-2573-11 and 25). This event placed the plant beyond

the analyzed condition for the design base of Fermi 2, whereby, a single {

failure which causes the loss of one division of D.C. power coincident

with a Loss of Offsite Power (LOSP) and a Loss of Coolant Accident

would have resulted in a loss of MCC 72CF (Swing Bus). This would have

caused the loss of LPCI (Div. I and II) valves fed from the moter control

center resulting in the loss of capability for all four LPCI pumps to

inject. Loss of the D.C. system in one division associated with the loss

of MCC 72CF, af ter reactor depressurization through a pipe break, would

have resulted in only two core spray pumps in the remaining division to

inject into the vessel.

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The 72CF. MCC is the only. ESF transferable bus used at Fermi 12' to-support

ECCS equipment fed by either..or both divisional ESF power sources.

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To correct this design deficiency, the licensee' developed a design

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change which will cause MCC 72CF and its; associated breakers to respond i

correctly, as stated in the FSAR,.to loss of all or part of the D;C.-

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system and thus place the plant within the previously analyzed events.

, On September 23,'1987, a design review meeting was held'at the Fermi site

Lbetween the licensee's engineering staff and NRC Regional and NRR staff.

The licensee's proposed design change.has been evaluated and analyzed

.by.the NRC and. licensee's engineers. The.new design will add a magnetic

m contactor in-series with.the breaker and the present magnetic contactor

of..each power feed to' MCC 72CF. This new magnetic contactor and its

auxiliary contacts will. replace the interlock contact functions of the

-480 volt breaker.used in the opposite' feed breaker control and assure.the

double break sep'aration required between' divisions.' Loss of D.C.. power

to the normal feed will cause both contactors on that feed to drop out

allowing the transfer to'the standby feed to re-energize lthe-72CF MCC.

l Previously, the normal 480 volt breaker would have remained closed and-

would'have prevented transfer to the standby feed. The licensee also

L- added a D.C. power monitor relay on the normal. feed breaker and a redundant

, undervoltage trip string. relay to trip the main breaker on loss of voltage

and thus force transfer of the 72CF MCC in the event of LOCA with LOSP and

a single failure of the loss of 0.C. to the load shed strings .only.

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LThe inspector examined the new design shown on the following design

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documents:

Schematic diagram 61721-2573-11, Revision "L"

Schematic diagram 6I721-2573-25, Revision "M"

Schematic diagram 61721-2573-43, Revision "I"

Schematic diagram 61721-2578-20, Revision "J"

EDP-7906, Revision 0.

The review indicated that the licensee made a concerted effort to

improve the faulty design of the circuit and that except for several

minor typographical errors noted, the design appeared to be adequate ,

to resolve the identified concern. The licensee indicated that the ]

change will be completed and tested prior to plant restart. The

inspectors will followup on this issue during future inspections.

4. Training ,

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The effectiveness of the licensee's training. program was reviewed by )

the inspector during the interviews and discussions with licensee's

engineering staff.- Personnel appeared to be knowledgeable of the

engineering task being performed.

.No violations or deviations were identified.

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5. Unresolved Items

An unresolved item is'a matter about which more information is required-

in order to ascertain whether it is an. acceptable item, an open item, a

deviation, or a violation.

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6. Exit Interview

The Region III inspector met with the' licensee representatives (denoted:

under Paragraph 1) at the conclusion of the inspection on September E3,

1986. The inspector summarized the purpose and findings of the inspection

during a. telephone exit interview held on September 30, 1987. The licensee

acknowledged this information. The inspector also discussed the likely

. informational content of tne inspection report with regard to documents

or processes reviewed by the inspector during the inspection. The licensee

did not identify any such documents / processes as proprietary.

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ML20235X138

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