ML19210A245

Abnormal Occurrence 75-33 Re Failure of de-ice Makeup Valve NR-V-4A to Close Using Control Room Remote Pushbutton.Caused by High Resistance Contact in Closing Control Circuit. Contact Cleaned,Tested & Returned to Svc

ML19210A245
Person / Time
Site:	Three Mile Island
Issue date:	09/19/1975
From:	Colitz J METROPOLITAN EDISON CO.
To:
Shared Package
ML19210A242	List: ML19210A241 ML19210A245
References
NUDOCS 7910240956
Download: ML19210A245 (1)

Text

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R0 Temp.:

579 F PRZR Level: 220 inches 0

PRZR Temp.: 655 F (6)

Descripticn of Occurrence:

At 2230 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.48515e-4 months <br /> on September 17, 1975, after terminating =ake-up flev to the Nuclear Services Cooling-River Water Circulating Water System, NR-V hA (De-Ice Make-Up Valve) failed in the open position. Since the valve could not be closed using the re=ote pushbutten, it was cicsed locally using its handwheel. The engineered safety (ES) pcsitien fer this valve is closed.

The redundant valve (NR-V hB) had just previcusly been closed to secure make up flow to the system thus verifying its operability.

The NR-V hA centrol circuit was investigated to determine the cause of the failure and a high resistance contact in the closing control circuit was discovered. The contact was cleaned and checked for proper operation.

The valve was then tested satisfactorily and returned to service.

(7)

Designation of Apparent Cause of Occurrence:

The apparent cause of this occurrence was caterial in that investigation revealed that NR-V hA failed to close as the result of a high resistance contact in the closing control circuit. This contact serves as part of an electrical interlock to prevent the valve fran receiving an open and close cc= mand at the same time. When the valve is stopped at any position this centact is nor= ally closed.

The contact developed a high resistance and when a close signal was applied to the circuit, enough voltage was dropped across the centact to prevent the closing contacter coil frc= fully energizing, thereby preventing the valve fran closing. The high resistance contact was an auxiliary centact on the opening contactor.

(8)

Analysis of Occurrence:

The failure of NR-V hA did not represent a threat to the health and safety of the public in that:

a.

One Isolatien valve is sufficient to isolate the Nuclear River Water System from the Circulating Water System.

b.

The redundant isolation valve, NR-V h3 had been closed (ES positicn) to isolate make up flow to the Circulating Water Systen just prior to the failure of 3R-V hA, verifying its operability and providing the necessary isolation.

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. (9)

Corrective Action:

In addition to the h=nediate corrective acticns previously =enticned lcng ters corrective actions are as follevs:

a.

All the contacts in the :iE-V hA control circuit vill te checked for proper continuity and operation.

b.

The running current, torquing currents, and travel time of the valve vill be measured. Repairs or adjustments vill be made as required.

The Plant Operations Review Cc==ittee and the Station Superintendent have revieved and approved the above listed corrective actions and have taken steps to ensure ce=pletien of the yet to be ecmpleted long ter= corrective actions.

(10)

Failure Data:

ITE Auxiliary Contact Block No. F10 NOCR Similar Occurrences: None Sincerely, I

'Lll lC. Arnold r.

Vice President RCA:C'4S :tas File:

20.1.1 / 7.7.3.5 1 cc: Cffice of Inspection and Enforcement, Region 1

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l4tetma rowr* no nocor's METROPOLITAN EDISON COMPANY POST OFFICE BOX 542 READING PENNSYLVANIA 19603 TELEPHONE 215 - 929-3601 September 29, 1975 GQL 1553 Director

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Docket No. 50-289

%j ev Operating License No. DPR-50 Three Mile Island Nuclear Station Unit 1 (TMI-1)

Pursuant to our letter of July ll,1975, please be informed that as a result of analyses perfomed on the rip rap of the dikes at TMI, the folleving deficiencies have been identified:

1.

In several areas the rip rap is smaller or thinner than originally specified. To correct this situation, additional rip rap of the prcper sice vill be placed in these areas.

2.

In one 225-fcct-long area just scuth of the Unit 2 intake structure the existence of a toe can not be verified due to the presence of a thick covering of spoil =aterial. To provide such verificaticn, a trench vill be dug thrcugh the spoil. If this excavation reveals the presence of a toe, all spoil =aterial covering the tce vill be removed; if it does not, a toe vill be placed.

3 In the area between the two intake structures and in another 250 foot-1cng aren just north of the Unit 1 intake structure a tee probably does not exist. To ccrrect this situation, additional, coarse rip rap material vill be placed at the base cf the rip rap facing in these two areas to serve as a tee.

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In the area between the two intake structures and just north of the Unit 1 intake structure there is essentially no filter blanket present. This is not considered to represent a sericus situation in that any additicnal rip rap which is placed en the facing to restore lost filter volume vill increase the thickness of the facing and thereby decrease the neec for a filter; therefore, no attempt vill be made to replace the filter blanket in these areas except by the applicatien of additional rip rap to the dike facing.

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-2 All of the repairs mentioned in items 1 thrcugh h above are expected to be cenpleted by the end of 1975, river eenditions and other facto 1:

permitting.

In the meantime, a region-by-region analysis performed by cur censultants indicates that the existing rip rap facing of the dike vill be adequate to withstand design flev velocities and wave heights.

We trust this submittal is adequate; hcVever, should you have any questions regarding this catter, please do not hesitate to centact =e.

Sincerely,

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C R. C. Arnold Vice President RCA:JFV:tas File:

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POGT O-:F;OE COX 430 M!DOLETOWN. PENNSYLVANIA 17CS7 TEl 2PHO?JE 717 W,4-4C :-

Septec.hcr 19, 1975 fir. J. P. O'Reilly Dirceterate of."'cguietary ' Operations l?cgicn 1 (FF_",, ~,hn 1'a

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Subject:

Ahncmil Occurrence L:o. 75-33 tear 'qr. OT.eilly:

This toicpr.: is to c:nfim the telecen totwcon A. L Fasano (rcgicn I 7"'CS ard J. J. Coiite (T i! Unit 1 Superincendent) at 1630 tours, S:.ptseber 13, 1975.

The -To11 ming re::crt is suMitted in acccreacco with ;:aracra,ch G.7.2 a.4 (page 6-11) of the Technical Specifications.

On Sectenber 17, 1975 felic: ting cc olot'on c? addin, make-t:

Circulatin : ator Sycter thraut h :'?. *.A & <3

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0 vant tn the ti e re ete cushhutten in the Ccr. trol Roem.

,:C-V-?A fail 7d to clese " W by use of tha har.dnhes1.

fir-V-4A was then closed icesi?y The redundant valve. N?.-?43, was initially used to isolate mho-uo fW to t e Circulatin !!atcr S Istc : before tw 0 */ 'A fatture a s discrerrs_

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nit 'ai i ';estigation re fccie:: a 5:ich

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es testc'i by c cninq c.M closing tha valve wich :.:e re'r.cce control rec:a pushtottens and ret.urned to servica.

Very truly yours,

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'J. U. Coi i O Unit i Surerintendent Three !!ile Is!cr.ri ::ecle.r Statica k%%e,cn 4

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. v ee The Servei11ce.cc Precedures used to leak etteck both t! e Reactor Buildi a gr30nn0I cn'j Raceter T._iidir.1 Cquinant dcar : cls will 'ce revic<2d abd rcquired r0 Viced to prevent future cc:urrcace.

Very truly yours,

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