ML20086B280

AO 50-267/74-17B:on 741021,teeth Roots of Curvic Coupling & Splitter Root on Six Pelton Turbine Buckets Discovered Cracked.Cause & Corrective Action Transmitted in Rept.W/O Encl

ML20086B280
Person / Time
Site:	Fort Saint Vrain
Issue date:	12/15/1974
From:	Brey H, Hillyard H, Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20086B283	List: ML20086B280 ML20086B325 ML20086B331 ML20086B335 ML20086B339
References
50-267-74-17B, AO-50-267-74-17, P-75025, NUDOCS 8311170134
Download: ML20086B280 (4)

Text

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48 pubne service company ** CoHonnHo P. O. Box 361 Platteville, Colorado 80651

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, , . December 15, 1975 1 MQgPm Fort St. Vrain Unit No. 1 s P-75025 Mr. E. Morris Howard, Director WPY Nuclear Regulatory Commission Region IV Office of Inspection and Enforcement Suite 1000 Arlington, Texas 76012 REF: Facility Operating License No. DPR-34 Docket No. 50-267

Dear Mr. Howard:

Enclosed please find a copy of Abnormal Occurrence Report No. 50-267/

74/17B, Addendum to Final, submitted per the requirements of the Tech-nical Specifications.

Very truly yours, }

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Frederic E. Swart Superintendent, Nuclear Production Fort St. Vrain Nuclear Generating Station FES/alk cc: Mr. Roger S. Boyd 8311170134 721215 PDR ADOCK 05000267 S

PDR 14344  ;

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O REPORT DATE: December 15, 1975 ABNORMAL OCCURRENCE 74/17B Page 1 of 3 4

OCCURRENCE DATE: jdetober 21. 1974 ) "

! (L i FORT ST. VRAIN NUCLEAR CENERATING STATION

! PUBLIC SERVICE COMPANY OF COLORADO l

P. O. BOX 361 PLATTEVILLE, COLORADO 80651 i

j REPORT No. 50-267/74/17B

{ Addendum to Final i

I IDENTIFICATION OF OCCURRENCE:

Physical examination of "A" helium circulator pelton wheel, Serial No. 4, indi-j cated cracking at the roots of the teeth of the curvic coupling and at the root

of the splitter on six (6) of the twenty (20) pelton turbine buckets. This was a

considered an abnormal occurrence per Item 2.1(f) of the Technical Specifications.

1 CONDITIONS PRIOR

, TO OCCURRENCE: Steady State Power Routine Shutdown Hot Shutdown .

Routine Load Change Cold Shutdown X Other (specify)

Refueling Shutdown Helium circulator had been re-moved to inspect failed static Routine Startup seal bellows.

The major plant parameters at the time of the event were as follows:

Power RTR

• wth -

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ELECT

• We ,

Secondary Coolant Pressure

• psig -

Temperature * *y Flow

• f/ hour Primary Coolant Pressure

• psig Temperature * 'F Core Inlet-

)

• *F Core Outlet Flow

• f/ hour

• Had no bearing on occurrence .

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O ABNORMAL OCCURRENCE 74/17B Page 2 of 3 ..

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CONDITIONS PRIOR TO OCCURRENCE (continued):

i "A" helium circulator had been removed from its normal position in its PCRV bottom head penetration and had been replaced by the spare due to problems with the static seal bellows (see Abrormal Occurrence Report #50-267/74/13 dated July 11, 1974, and #50-267/74/13A, dated October 3, 1974). Helium cir-culator components were being examined in manufacturer's shops in San Diego, California.

DESCRIPTION OF OCCURRENCE:

Removal of "A" helium circulator from the PCRV due to static seal actuating bellows problems afforded the opportunity to examine components of the helium circulator in detail.

.. A fluorescent penetrant (Zyglo ZL-22) examination of the " nuclear" pelton wheel coupling area' indicated uniform cracking at the root of all the coupling teeth and re.vealed six (6) of twenty (20) pelton turbine buckets with cracks at the root of the splitter. None of these cracks were visible to the naked eye.

APPARENT CAUSE 0F OCCURRENCE: X Design Unusual Service Cond.

Including Environ.

Manufacture Component Failure

. Installation /Const. X Other (specify)

Operator Incipent Failure Procedure

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ANALYSIS OF OCCURRENCE:

See additional information, which is presented in the attached report, "Inves-tigation into the Cause and Consequence of the Fort St. Vrain Pelton Wheel Incipient Fractures", GA-A13175, Supplement 1, published November 14, 1975.

CORRECTIVE -

I ACTION:

'See additional information, which is presented in the attached report, "Inves-tigation into the Cause and Consequence of the Fort St. Vrain Pelton Wheel l

Incipient Fractures", GA-A13175, Supplement 1, published November 14, 1975.

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O O ABNORMAI, OCCURRENCE 74/17B Page 3 of 3 EAILURE DATA /SIMILAR REPORTED OCCURRENCES:

See reports: October, 1973 To: Dr. Donald Knuth Directorate of Regulatory Operations Deficiency Report, Fort St. Vrain Helium Circulators August, 1972 To: Mr. F. E. Kruesi Directorate of Regulatory Operations Deficiency Report Fort St. Vrain Helium Circulators October 16, 1974 CA-A13175

" Investigation into the Cause and Consequence of the Fort St. Vrain Pelton Wheel Incipient Fractures" PROGRAMMATIC IMPACT: '

No additional impact.

CODE IMPACT:

None -

Submitted by:

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rveFyi W. j(111 yard ,/3r.

Technical Services Supervisor i

Reviewed by: MW

• H. Larry Brc y Superintendent, Operations (

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Frfderic E. Swart -

Superintendent, Nuclear Production l

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