ML20042F332

Forwards Detailed Description of Facility Steam Generator Girth Weld Insp Results.Licensee Concludes After Review of Flaw Evaluation That Indications Acceptable

ML20042F332
Person / Time
Site:	Zion File:ZionSolutions icon.png
Issue date:	05/01/1990
From:	Chrzanowski R COMMONWEALTH EDISON CO.
To:	Murley T Office of Nuclear Reactor Regulation
References
NUDOCS 9005080182
Download: ML20042F332 (3)

Text

,.

s f

b.

LCommonwealth Edison

,~

t Zion Generating Station -.

Lr

~-

.C*

- Shiloh Blvd. & Lake Michiganm Zion. Illinois 60099 '

Telephone 708 / 746-2084 May 1,-1990 l

l Dr. Thomas E. Murley, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission-

-Hash _ington, DC 20555

Subject:

Zion Station Unit 2 Steam Generator _ Girth Held Indications NRC_Dccket No.i50-304-l 4

Dear'Dr. Murley:

j Commonwealth Edison has. performed. external examinations.oniall four;of.

the Unit 2 Steam Generator. Girth Helds' due to the Unit 11 Steam Generator girth-J weld cracks discovered during the Fall-1989' refueling outage.

Based on the 4

results ofs the Unit 2 examinations, all locations that' appeared to contain:.

/

surface or near surface-indications utilizing UT have been internally-examined a

by magnetic particle. Any surface: indications that were: discovered were:

i removed by grinding and blending.or were removed as!a boat sample.'

1 The attachment to this letter.contains a. detailed descripti_onof-the Unit-2 Steam Generator Girth Held inspection results.- The flaw evaluations-completed for Unit-2-were based on a stress analysis performed with'the"same care and consideration as that performed for Zion Unit 1.

'After a careful-review of the-flaw' evaluation,. Commonwealth Edison has concluded that-the; indications are all acceptable.

In'an effort to#obtain additional information that may helpiidentify the root cause of the indications, hardness tests were performed on the girth-weld: And the surrounding areas.

1he results of these' tests,-along with results'of the boat sample analyses, will be submitted with the-Zion Unit 2

[

report.

.Please direct any questions regarding this>mhtter to this office.

j

.Very truly yours,

}

gecfg 1

g t

R. A.

hrza nows',1 -

Nucle r Licensing s

. Administrator j

1 o

cc:

C. Patel - NRR

' /

M. Hum - NRR:

1 80f Zion Resident Inspector i

Office of Nuclear Reactor Safety - IDNS y

9005080182 900501 Oll3b PDR ADOCK 05000304 l

{!

Q PDC 1

1

ATTACHMENT l

Based upon the girth weld cracks discovered in the Zion Unit 1 steam generator during the Fall 1989 refueling outage, Commonwealth Edison decided.

to perform external ultrasonic examinations of 100% of all four Unit 2 steam generator girth welds.

Regarding Unit 1, Zion Station extended the recording beyond the.ASME code requirements.

The ASME code requires any indication that-is 1 50% of DAC to be recorded.

Zion Station recorded any indication.that was 1 20% of DAC.

i The following table describes the results of the ultrasonic examinations j

from Unit 2:

a f,tenerator

1. of Ind's (45*)

1. of Ind's (60*)

A 5

1 B

14 6

C 8

0

' i D

12 10-j All locations that appeared by UT to contain surface or near surface indications were internally examined by magnetic particle..Any surface indications were removed by grinding and blending or were removed as a boat

-l sample.

The following table describes the bounding subsurface indications in each generator (all dimensions in inches):

.i Generator Ind 2a Dim LDim S Dim Y.. Dim all alt 1*Q A

No subsurface indications 1 50% DAC B

17 0.52 1.50 0.29 1.00 0.17 7.0 C

No subsurface indications 1 50% DAC D

18 0.48 0.70 0.15 0.63.

0.34 6.4 One of the surface indications from the A steam generatr wts removed as a boat sample.

This sample was from the weld =itself. -An ar.ccmpt:was madeito remove one of the subsurface indications from the D steam ganerator as a boat sample. This effort was not entirely successful, however, the sample will be.

completely analyzed to obtain all information-possible.

Aftcr all identified surface indications were removed, another external UT examination was performed to obtain baseline thformation and to verify i

which of the remaining subsurface indications exceeded 50% of DAC and must be dispositioned by fractere mechanics to demonstrate their acceptance by the

.]i criteria of the ASME code, paragraph IHB-3600.

This work made use of-the guidelines of. Appendix A of ASME Section XI.

The analyses were specific to the Zion steam generator girth welds.

The detailed technical basis behind these analyses will be submitted separately, but the approach was the same as that used for Zion Unit 1, which was the same as that used for the flaw evaluation handbook : submitted earlier for the Byron and Braidwood steem generators and pressurizers. A complete description and details may be found in Westinghouse HCAP-11063, " Background and Technica' Basis, Handbook on Flaw

> Evaluation, Byron and Braidwood Units 1 and 2" by U.S. Lee and H.H. Bamford.

't i

0113b

CI The flaw evaluatiens' completed for-Zion Unit stress analysis performed.with the same care and'e2 have been based on a consideration as that performed for Zion unit

1.

The. conclusion react.ed was that:the indications

.are all acceptable by a wide margin..

\\

'l L

'.i'l t.

i N

.g

)

+

j i

e i

11 s

., f

'.I 1

1

+\\

.. l

.i f

-i 1

~

l 01.13b 1

,