05000000/LER-1950-237, Updated LER 50-237/01L:on 760406,unacceptable Ultrasonic Indication Found on Isolation Condenser safe-end.Caused by Cracks in safe-ends.Cracked safe-end Removed & Sent to Bmcl for Metallographic Analysis

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Updated LER 50-237/01L:on 760406,unacceptable Ultrasonic Indication Found on Isolation Condenser safe-end.Caused by Cracks in safe-ends.Cracked safe-end Removed & Sent to Bmcl for Metallographic Analysis
ML20086S457
Person / Time
Site: Dresden, Surry, 05000000
Issue date: 07/13/1976
From: Stephenson B
COMMONWEALTH EDISON CO.
To: James Keppler
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20086S443 List:
References
BBS-#76-531, LER-50-237-01L, LER-50-237-1L, NUDOCS 8403020366
Download: ML20086S457 (3)
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LER-2050-237, Updated LER 50-237/01L:on 760406,unacceptable Ultrasonic Indication Found on Isolation Condenser safe-end.Caused by Cracks in safe-ends.Cracked safe-end Removed & Sent to Bmcl for Metallographic Analysis
Event date:
Report date:
0002050237R00 - NRC Website
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text

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, FYEfiT DESCRIllIOv- Continued) ,

s of cracking in furnace-sensitized stainless steci forgingshave occurred on'

, both Unit-2 core spr.;y loops as well as on the !!PCI steam line.-

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  • The safe-end (which was SA-182 F316 stainicss steel) was replaced with one forged from SA-182 F316L stainless ste'e1. -(50-237/1976-21) ,, ,

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l CAUSE DESCRIPTION (Continued) ,

and four axially-oriented cracks at the 1:00, 4:00, 4:45, and 5:00 positions. The depth of the circumferential crack was found to be 0.261 inches, while the axial cracks ranged in depth from 0.255 to 0.500 inches. The circumferential crack was located approximately 3/8 inch from the safe-end-to-pipe weld and was 0.60 inches long at the I.D. surface. The axial cracks ranged from 0.23 to 0.43 inches in length and extended to within 1/16 inch of the safe-end-to-pipe weld.

The metallographic exanination revealed similar. features in both the axial and circumferential cracks: initiation at the I. D. surface, and .

intergranular propagation in a heavily-sensitized microstructure. Microprobe analyses of fracture surfaces and cross sections of the cracks indicated no chlorides, fluorides, sulfides, or other possible corrosives. Moderate residual l stresses from welding and possibly from inner surface grinding (up to 5 mils of cold working were observed) may also have been contributing factors. The mechanism I

of cracking is the'same as that experienced in'the HPCI safe-end, the 10-inch core spray piping, and the 4-inch recirculation bypass piping.

The cracked safe-end was manufactured from'SA-182 F316 stain 1 css steel and was unclad. It was approximately 5 inches long, with a 14-inch 0.D. at the piping end (0.56-inch wall thickness) end a 16-inch 0.D. at the nozzle end (1.08-inch wall thickness). The safe-end was furnace-sensitized during the post-weld stress relief treatment of the pressure vessel. .

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BBS Ltr. #76-531 ' July 14, 1976 h (, g

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(- A 10 l Mr. James.C. Keppler, Regional Director 9,l s ' -

j Directorate of Regulatory Operations - Region III  %

U. S. Nuc1 cur Kegulatory Commission g, ,

799 Roosevcit Road s p /

, Glen Ellyn, Illinois 60137

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Enclosed pleaset find an update report to Reportable Occurrence report

, number 50-237/1976-21. This report is being submitted to your office in accordance with the Srcsden Nuc1 car Power Station Technical Specifications, Section 6.6.B.

.. f. .w

. 'S t ep)ienson Station Superintendent Dresden Nuclear Power Station BBS:jo Enclosure .-

cc: Director of Inspection & Enforcement -

Director of Management Information & Program Control i

File /NRC s

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COPY SENT REGION

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~T mnE-st-76-io  !

() LICENSEE EVENT REPOPN V

..w CONTROL BLOCK l l l l l l l (PLEASE PflNT Att RECulRED INFCRMATl!N) 1 6

t Cf N51 tVlN1 L CE *.M t TYPE fvPE NtWI tiCENGE NUV0t R

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O IDuring the preparations to test the startinn of #1 cmernency diesel neverator (EDC). BO 7 oo diesel nenerator was fr=ediatej

@ l water was detected in #7 cylinder. The backup ernernency 60 7 H9 h { ly tested satisf actorily_and the repfi rs cormence) on #1 EDG. The _ engine was re.pnited 80 l 7 o9 l

@ [by replacing the cylinder head _ and 13 3 d gasket. This is a reportable cecurrenceJ n CO 7 tl 9 l

@ laccordance with Technical Specification _{t.6.2h (2). (lfSRE S1-76-lo) 80 p.,vr 7 u9 ccwn Nt councNtsr s,su v C .ta s. min Mar.ur Ac Tu.* n votAYON CDOf CCDF COVPON' NT CODE h l E l [E_j IE IM i Cl I! NI El17 d43 44 iElIl4l7l 47

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@ [EMD-G51 Turbo Vee _20, 3810 Bhn diesci onnine surtained a 60 7 H9 inc ke t;. Thets w.3terfroml iextendedbetweentwoexhaustvalveseatsandthrounhthewater 60 l HH }

it.he Sylindet head unter Jacket u n porriittted to drip int _o the cylinder. (Continued) c-VI1HDD Of f AOut y DiSCG.f4v O'SCOvE nY Ot ECD'PflON

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SO 7 0 11 ADDITIONAL i ACIOHS 3 IThe hackup enernency diesel rencrator was demonstrated _to be operable. eO Therefor 7 89 l

1- Isafety systems would have functioned if they had been requ_ ired. (Continued) eo 7 U9 T. I,. Ilaticota PHONE: (804) 357-3184 NAME. G9 0 801 961

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CAUSE DESCRIPTION (CONTINUED)

Inspection of the engine prior to starting permitted detection of the water and prevented further damage to the engine.

This is the sixth cylinder head on this engine to be found with a crack, in a tima frame of juct over three months. USRE S1-76-07 listed the other incidents and Indicated the probabic cause as either a cylinder heat imbalance or a heat stresF as a result of an engine overheat condition at some previous time.

The location of /S head on the engine does not conform to the previous pattern and tends to eliminate a cylinder heat imbalance as the probable cause. It appears that a previous engine overheat condition has heat stressed the cylinder heads to such a point that premature metal f atigue f rom vibration is causing the cracks to appear between the exhaust valve seats. This is an area of high heat and vibration stress.

To ensure the reliability of this engine, the weekly testing of thic engine as outlined in USRE S1-76-07 will continue. New cylinder heads have been ordered and total replacement should preclude any additional failure. This course of action has been thoroughly discussed with the manufacturer's representative who concurs with this procedure.

ADDITIONAL FACTORS (CO:TTINUED)

Accordingly, no hazard to the safety or health of the generai public existed.

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VIMOINI A ELI:CTHIC AND l'OWHH COMI*ANh p Hica:Moxn.V HO M A nUM61 1

August 4, 1976 11 . 5 , + s

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'll s3 Mr. Normn C. !!oscley, Director Scrial No.173 Office of Inspection and Enforcement P0&M/ALil:jlf U. S. Nuclear Regulatory Comission Region II - Suite 818 Docket No. 50-280 230 Peacht.rce Street, Northwest License No. DPR-32 Atlanta, Georgia 30303

Dear Mr. Moscicy:

i Pursuant to Surry Power Station Technical Specification '6.6.2, the Virginia Electric and Power Company hereby submits a copy of Licensco Event Report No. USRE-S1-76-10.

1 The substance of this report has been reviewed by the Station Nuclear Safety and Operating Comittee and will be placed on the agenda' for the next meeting of the Syctem Nuclear Rafety and operating Comittee.

Very truly yours, 26.D7.ssaa:;,y l C. M. Stallings Vice President-Power Supply and Production Operations Enclosure -

I cc: tir. Robert W. Reid, Chief (40 copics)

Operating Reactors Branch 4 i

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