ML18024A056

Letter Supplementing PP&L Letters Dated April 17, 1978 and July 14, 1978 and Attaching a Final Report of a Deficiency in Seismic Qualification of Medium Voltage, Metal Clad, Safeguards Switchgear

ML18024A056
Person / Time
Site:	Susquehanna
Issue date:	09/15/1978
From:	Curtis N Pennsylvania Power & Light Co
To:	Grier B NRC Region 1
References
Download: ML18024A056 (12)

Text

REGULATORY INFORMATION DISTRIBUTION SYSTEM (BIDS >

DISTRIBUTION FOR INCOMING MATERIAL 50-387 REC: GRIER 8 H ORG: CURTIS N W DOCDATE: 09/15/78 NRC PA PNR 5 LIGI-lT DATE RCVD: 09/22/78 DOCTYPE: LETTER NOTARIZED: NO COPIES RECEIVED

SUBJECT:

LTR 1 ENCL FURNISHING SUPPLEMENT TO APPLICANT"S LTRS OF 04/17/73 AND 07/14/78 CONTAINING FINAL CONSTRUCTION DEFICIENCY REPT CONCERNING DEFICIENCY IN EISMIC QUALIFICATION OF MEDIUM VOLTAGE M.TAL CLAD SAFEGUARDS WITCHGEAR.

PLANT NAME: SUSQUEHANNA " <<UNIT 1 REVIEWER INITIAL: X JM DISTRIBUT0B INITIAL~

u v%%%%%%%%%%%%%%% DISTRIBUTION OF THIS MATERIAL IG AS FOLLOWS  %%<%%%%%%%%%%%%%%%

NOTES:

SEND IS(E 3CYS FSAR 8( ALL AMDTG CONSTRUCTION DEFICIENCY REPORT <10CFR50. 55E)

(DISTRIBUTION CODE 8019>

FOR ACTION: ASST DIR VASSALL0%%W/ENCL BR CI.IIEF LWR03 BC%%W/ENCL PR MINER%%W/ENCL LIC ASST LWR83 LA<<W/ENCL INTERNAL: .6 FILE%% /ENCL NRC PDR%%W/ENCL 0 OELDu~W/ENCL ENCL, GOScSICK Rc STAFF%%W/ENCL MIPC%%W/ENCL DIRECTOR DPM%%W/ENCL DEPUTY DIR DPM%%W/ENCL QAB%%W/ENCL DIRECTOR DSS%%W/ENCL AD FOR ENG%kW/ENCL AD FOR REAC SFTY%%W/ENCL AD FOR PLANT SYSTEMS%%W/ENCL AD FOR SYS 8( PROJ%%W/ENCL STANDARDS DEV. %%W/ENCL K SEYFR IT/IE%%W/ENCL FERD DREHER/IE%%W/ENCL EXTERNAL: LPDR S NILKES BARREi PA%%M/ENCL TERA<<%W/ENCL NS I C%%W/ENCL ACRS CAT B%%W/16 ENCL CONTROL NBR: 780860147 At ~

THE END

~ '

I

"~

~ g ~

~;-

TWO NORTH NINTH STREET, ALLENTOWN, PA.

s 18101/g es

),$)I) ~~.(gP

$ITJNE: (215) 821-5151 g~XKD NORMAN W, CURTIS Vice President Engineering 8 Construction 821-5381 CJ Pl o>

I SeptEmber 15, 1978 r r

c's '

<o na P1

~CD nv>

+ m C

Mr. Boyce H. Grier n rn C)

Director, Region I Cll U. S. Nuclear Regulatory Cczanission 631 Park Avenue King of Prussia, Pennsylvania 17406 SUSQUEEQKA STEAM ELECTRIC STATION F3'EPORT OF A DEFICIENT',CY IN SEISMIC QUAIZFICATION OF I%DEN VOLTAGE, M'TAL CLAD, SM."%GUARDS SWITCHGFAR DOCKET NO.: 50-387 LICENSE NO: CPPR-101 ER 100450 FILE 840-4

' I PLA 289 ~ = I ~ 4 \

Dear Mr. Grier:

This supplements PPSZ letters PLA-246, dated April 17, 1978 and PLA-271, dated July 14, 1978, and provides a final report of the subject deficiency as recpuzed by 10CFR50.55 (e) .

Please advise should you recure additional information.

Very truly yours, N. W. Curtis Vice President-Engineering 6 Construction Attachment ARS:mcb cc: Mr. J. G. Davis (15)

Acting Director-Office of Inspection 6 Enforcement U. S. Nuclear ReyQatory Ccmiission--

Washington, D.C. 20555 Mr. G. MDonald, Director (1)

Office of Managanent,,Information 6

'U. S. Nuclear Regulatory Ccmtission

~am Contxol Washington, D.C. 20555 t78p86p147 PENNSYLVANIA POWER 8, LIGHT COMPANY 9'e~t

Mr. B. H. Grier Sept.anber 15, 1978 cc: Mr. Robert M. Gallo U. S. Nuclear Regulatory Gmxnission P.O. Box 52 Shickshinny, Pennsylvania 18655

OF A DEFICIENCY IN SEISMIC QUALIFICATION OF MEDIUM VOLTAGE, MEAL CLAD, SAFEGUABDS SWHCHG1RR FOR THE SUSQUEHANNA STEAM 1KZCTRIC STATICN D. P. Parsons SSES Electrical Group Supvr.

Approved By: .. ~~~

A. M. e 9 r~ pg.

Supervising Engineer-Design-Suscpehanna Reviewed:

A. R. Scil Manager-Nuclear Quality Assurance PENNSYLVANIA HMK 6 LIGHT CCMPANY AL'EZKTQWN, PENNSYLVANIA S1M.'EMBER 15, 1978

TABLE OF CONTENTS Introduction Pg. l Description of Deficiency Pgs, lg 2g 3 Analysis of Safety Implications Pg. 3 Corrective Action Pgs. 4, 5 Conclusion Pg. 5

INTRODUCZION This report is prepared in accordance with the requirements described in Title 10, Code of Federal Regulations, Part 50, Section 50.55(e) .

PPK was advised, through its A/E (Bechtel) organization, t1wt Westinghouse supplied, medium voltage, metal clad switchgear was not capable of withstanding the postulated seismic event for Susquehanna Plant. Bechtel was requested to review the situation and advise PPsZ of its findings. On Parch 31, 1978 the NRC was informed that a deficiency, potentially reportable under 10CFR50.55(e),

was being evaluated, and on April 17, 1978, following an engineering review, PAL issued its Interim Report of the deficiency.

The deficiency was determined to be reportable under 10CFR50.55(e) for the following reasons:

1. The deficiency, were it to remain uncorrected, could have resulted in a safety hazard to the operation of the plant.

2. The deficiency represented a deficiency in final design as approved and released for fabrication and installation.

3. Eight safety-related switchgear units had, been shipped and accepted for installation before the deficiency was discovered.

DJHCRIPTION OF DEFICIENCY The Susquehanna Plant was supplied eight deficient safety related medium voltage switchgear units by Westinghouse. Four of these switchgear units supply power directly to 4kv safety related equipnent, pump rmtors and load centers, >Rich are used to mitigate the effects of an accident in Unit l.

Likewise, four switchgear units are used as the supply for 4kv safety related loads on Unit 2.

Each switchgear unit, contains three potential transformer circuits, one of the circuits consists of ~ potential transformers connected in an open delta. The other two circuits each contain one potential transformer used to sense single phase potential. The potential transformers are used to obtain 120 volt, potential irr3ication for use with relays on the switchgear units'he IIedium Voltage Ywtal Clad Switchgear (Safeguards) Specif ication (8856-E-109) requires the equipment to meet seismic recpdxements of Project Specification 8856-6-10, IEEE Standard M. 344, and to reaein functional, koth, during and after an OBE or DBE.

Westinghouse advised Bechtel on January 24, 1978 that the potential transformer secondary disconnecting contact assanblies on equignent similar to that supplied for Susquehanna had failed to withstand recent seismic tests.

Westinghouse further stated that, under seismic conditions, it is possible that the slip-fit secondary contacts could be dislodged fran their normal positions resulting in open or. short circuiting of the secondary circuits.

Westinghouse requested that Bechtel evaluate the condition to detaanine if it auld constitute a safety hazard.

.Westinghouse confirmed that there were no failures of potential transformer circuits during the original seismic qualification tests. However, these circuits were subsequent1y redesigned and the new design was analytically qualified. Situal seismic tests on switchgear units incorporating the new design resulted in the potential transformer circuit failures >M.ch are the subject of this report.

Westinghouse also confirmed that the seianic qualification of all other canponents in these assemblies remain valid.

MALYSIS OF SMOKY IMPLICATIONS The engineering evaluation determined that the open or short circuiting of any of the seco~ contacts could result. in incorrect operation of a switchgear unit. It was concluded that the worst condition results fran the loss of all three potential transformer circuits on each switchgear bus.

Under this condition, the tm inccming bus feeders frcm the safeguard transformers (one from each offsite source) would be automatically disconnected frcm each switchgear bus and the diesel generator power source connected restoring power to the bus.

A LOCA occuring during or after the postulated, seismic event would initiate a closing signal to the motor feeder breakers of the shutdown loads, i.e.

RHR and Core Spray Hotors. These feeder breakers would close and ismMiately trip due to the false undervoltage indication as sensed by the undervoltage relay. The circuit breakers would be unable to close again because of the permanent undervoltage trip signal imposed on them. The above analysis assumes'hat, the failures concurrently occur on all redundant m~tchgear huses.

Based upon the evaluation of Bechtel Engineering~it is concluded that this condition of not being able to supply power to the shutdown loads under a DXK condition constitutes a safety hazard to the operation of the plant and represents a deficiency in final design.

,I P,

t,, ~

CORRECTIVE 'ACTION Action Taken to Contxol 'Deficient.'Items The actions taken by Bechtel prior to the suhnittal of the interim report of the deficiency by PP&L are domunented in PZA-246 dated April 17, 1978.

In addition to the measures previously identified, and in the interest of obtaining documented evidence of Bechtel Pxoject Engineering's evaluation of the condition's cause, corrective action required, and reportability under 10CFR50.55(e), Bechtel QA generated Ihnagerrent Corrective Action Request No.

1-22 dated March 28, 1978.

Corrective Action to 'Control 'Resolution 'of 'the Def iciencies Westinghouse has supplied modification kits which provide for eliminating the stationaxy, secondary disconnecting contact assemblies from the potential transformer circuits. Twenty-four (24) (three kits for each of the eight safety-related switchgear units) potential transfoxmer secondary fieM rmdification kits (Westinghouse Style No. 628F14G01) have been provided.

These rrodification kits have been installed by Bechtel field electricians per the instructions on Westinghouse drawing 628F146. These changes were made under the supervision of the Westinghouse Engineering Service Personnel.

The modification consists of hard wiring the secondary arable contact to a texminal block via a wiring harness. The PT secondary circuits are then connected to the field side of the terminal block. The secondary stationary contacts are removed entirely, thus eliminating the source of the seismic failure.

I

( ~

~

~

Westinghouse has seianically qualified the potential transformers with the

@edified secondary contact arrangement. Donznented evidence of this qualification has been provided to Bechtel through a revision to the original qualification report.

COVZIJSXONS l4xlifications have been made to aU. the Westinghouse safety-related, median voltage switchgear units containing potential transformers and purchased under P.O. 8856-E-109AC for Susquehanna Steam Electric Station. The Bechtel generated hMnconfoxmance Report (NCR hM. 2514) will not be closed out until Bechtel Quality Contxol has performed the attendant inspections and has verified that the mxlification kits rare installed according to design requirements-The andified switchgear units are qualified to meet the postulated seismic event. for Susquehanna and documentation of this seismic qualification has been received and will be reviewed by Bechtel Engineering. Bechtel's acceptance of this documentation will result in an acceptably documented revision to the Westinghouse Seianic Qualification Report.

The switchgear units~as presently modified, are compatible with purchase order, PSAR and FSAR requiranents.