ML18018B563

Forwards Addl Info Re SER Open Item 4 Concerning Min Wall Thickness of Class 1,2 & 3 Piping Sys.Response Clarifies Design Procedures Used to Control Min Wall Thickness & Responds to Specific NRC Concerns

ML18018B563
Person / Time
Site:	Harris
Issue date:	02/07/1984
From:	Mcduffie M CAROLINA POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8402130338
Download: ML18018B563 (14)

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ACCESSION NOR:8002130338 DOC,DATE: 64/02/07 NOTARIZED:

NO FAGIL:50 000 Shear on Harris Nuclear Power Planti Unit 1p Carolina AUTH'AME AUTHOR AF F ILIATION MCDUFFIEiM<A, Carol ina Power 8 Light Co, RECIP NAME RECIPIENl'FfILIATION DENTONiH ~ R.

Office of Nuclear Reactor Regulationr Director

SUBJECT:

For wards addi info re SER open Item 0 concerning min wal l thickness of Class 1<2 8

3 piping sys

~ Response clarifies design procedures used to control min wall thickness 8,

responds to specfic NRC concerns, DISTRIBUTION CODE:

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@ME, Carolina Power & Light Company FEB 07 1984 SERIAL:

NLS-84-044 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington DC" 20555 SHEARON HARRIS NUCLEAR POWER PLANT UNIT NO.

1 DOCKET NO 50-400 ADDITIONAL INFORMATION CONCERNING MINIMUM WALL THICKNESS OF CLASS 1, 2,

AND 3 PIPING

Dear Mr. Denton:

Carolina Power

& Light Company hereby submits additional information in response to the Shearon Harris Nuclear Power Plant (SHNPP) Safety Evaluation Report Open Item 4 concerning minimum wall thickness of Class 1, 2, and 3 piping systems.

The attached response provides additional clarification of the design procedures used to control minimum wall thickness and responds to specific staff concerns.

If you require additional information concerning this subject, please contact our staff.

Yours very truly, M. A. McDuffie Senior Vice President Nuclear Generation JHE/pgp (9402JHE)

Attachnent cct Mr. B..C. Buckley (NRC)

Mr. G. F. Maxwell (NRC-SHNPP)

Mr. J.

P. O'Reilly (NRC-RII)

Mr. Travis Payne (KUDZU)

Mr. Daniel F. Read (CHANGE/ELP)

Chapel Hill Public Library Wake County Public Library Mr. D. Terao (NRC)

Mr. E. Rodabaugh (Consultant)

Mr. Wells Eddleman Dr. Phyllis Lotchin Mr. John D. Runkle Dr. Richard D. Wilson Mr..

G.

O. Bright (ASLB)

Dr. J.

H. Carpenter (ASLB)

Mr. J. L. Kelley (ASLB) 8402130338 840207 PDR ADOCK 05000400 E

PDR 411 Fayetteville Street o P. O. Box 1551 o Raleigh, N. C. 27602

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Shearon Harris Nuclear Power Plant SER Open Item 4 Minimum Wall Thickness The staff has identified a concern regarding the control of minimum wall thicknesses in ASME Class 1,

2, and 3 piping systems.

In the Piping Specification (CAR-SH-M-30), a minimum wall thickness is specified (1) at weld end preparations, (2) after machining or grinding the pipe wall, (3) in trimming the pipe inside diameter, and (4) after counter-boring the pipe ends.

The applicant has stated that these minimum wall thicknesses are based on the equations per ASME Code,Section III, Subparagraphs NB/NC/ND-3641.1.

However, the use of the nominal wall thickness in the piping stress analyses (rather than the minimum wall) and the use of a stress intensification factor of 1.0 for girth butt welds is not acceptable because these factors can result in an underprediction of piping stresses at those girth butt welds where the piping wall thickness is less than the nominal wall thickness.

The staff considers this item to be open and will address its resolution in a supplement to the SERo

~Res onse Further clarification of "minimum wall thickness" as used in Ebasco Specification CAR-SH-M-30 is given below:

An example of a 14 inch outside diameter pipe with 0.145" calculated wall thickness has been described by the NRC consultant.

As correctly stated, carbon steel pipe is rarely used with nominal wall thickness less than standard weight which is 0.375" for 14" O.D. pipe.

However, under no circumstances could the girth butt weld detail for this 14" O.D. pipe look like Sketch A (enclosed) provided by the NRC consultant.

This is supported by the following:

For those instances where the weld end preparation consists of a counterbored

section, the "C" dimension (or machined inside diameter) is calculated in accordance with the equations given in Ebasco Design Guide M4-3 which is part of the Project General Power Piping Specification, CAR-SH-M-30 (a complete set of this specification containing the Design Guide M4-3 was previously furnished).

A copy of Design Guide M4-3 is enclosed for your quick reference.

Using the appropriate equation from the Design Guide M4-3 (equation A 1:C = A-1.75t-0.041) the "C" dimension is equal to 13.303" (i.e.

14.0 1.75 [.375]

.041

= 13.303).

This corresponds to t i

= 0.348" at the girth butt weld rather than t i

= 0.145" indicated 7n the Sketch A.

The equations in the Ebasco Design Guide M4-3 are in accordance with ANSI B16.25 which in turn is referenced by ASME III, NC-3130.

20 As stated in the previous response, the wall thickness/schedule shown in the Line List is a nominal wall thickness (except for a few heavy wall main steam and feedwater piping components supplied by Cameron).

We wish to reiterate that the "only" wall thickness available to Southwest Fabricating is the nominal wall thickness indicated in the Line List and (9402JHEpgp)

J

RESPONSE (Cont'd) the fabricator is obligated to furnish the piping with wall thickness per this list (including the area at the girth butt weld).

From another viewpoint, the wall thickness at any point along the pipe run is equal to t i l which might be decreased by a mill tolerance permitted by nominal the code (12 1/2% for seamless pipe or 0.010" for welded plate pipes, as appropriate).

In the extremely unlikely event that the machined inside diameter calculated per equation described in Item 1 above

("C" dimension at the counterbore) violates the specified nominal wall thickness tolerances, Southwest Fabricating would "butter" the pipe cross section with weld metal in order to comply with the requirements of the Line List.

We have secured a letter from Southwest Fabricating to confirm the

above, and are enclosing it in the attachment to this response (letter from J Harris dated December 5,

1983).

Considering the aforementioned, the Shearon Harris piping design with regard to wall thickness requirements at the girth butt weld is "conservative" and meets the intent of ASME-III.

With respect to NC-3672.6(b), while this Paragraph cautions against situations such as one detailed in NRC Sketch A, it does not provide the engineer with a specific design alternate to minimize the occurrence of such cases Furthermore, based on NC-3672.6(c), this reduction of cross section is a concern on materials of relatively low ductility.

Such materials are not utilized on the Shearon Harris Project.

Shearon Harris Project adherence to the two positions presented above reflects good engineering judgement which is in accordance with the code requirements.

In summary, Ebasco's verification on a case-by case basis would under no circumstances involve the case such as shown on NRC Sketch A.

Our'valuation would consider only "minor" deviations from the nominal wall thickness.

Based on all questions received from Southwest Fabricating on acceptance of wall thicknesses less than t i l (including the counterbored section) to date, nominal the "minor" deviations can be defined as no more than 10% of originally specified nominal wall thickness (provided that the minimum required wall thickness per code equations plus the erosion/corrosion tolerance is not violated).

Taking again the example of 14" O.D.

CS seamless pipe with specified nominal wall thickness 0.375",

the worst condition considered for acceptance would be a deviation of 0.038".

If accepted, this wall thickness is in excess of 0.145" used in the example and introduces no increase in i-factor.

(9402JHE/ccc)

RESPONSE (Cont'd)

We will indicate in the next general revision of the specification that the wall thicknesses/schedules indicated in the Line List are nominal unless specified otherwise.

The Southwest Fabricating definition of "minimum required wall thickness" meant the nominal wall thickness minus the code permitted mill tolerance and as such it meets the intent of ASME III'rom that point of view, revision of the specification is not warranted.

(9402JHEpgp)

NRC SKETCH A Detail of Girth Butt Meld that Appears to be Permissible by Ebasco Specification CAR'-SH-M-30

= 0.375 n

t

= 0.145 m

t

= nominal wall thickness nt

= code-required minimum wall thickness m

Pipe Outside Diameter

CONTINUED FROM DESIGN GUIDE

-2 e

r MELD END PREPARATION "C" DIMENSION CONTROL SHEET C

A Am Bttm Mach ined Inside Diameter Nominal Outside Diameter Minimum Outside Diameter Specified Inside Diameter Nominal Thickness Minimum Thickness 61I to 22ll Over 22" to 30" Over 30" to 42"

+1/8II 0ll

+5/32" - 0"

+3/16" - 0" Cameron Extruded Pi e Mfr ID Tol h - The following applies to seamless pipe and velded pipe made by automatic

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velding with no addition of filler metal (+i,e. ASTM-A312):

1 - For pipe ordered to nominal OD and schedule and/or nominal vali.

C R

A-1.75t - 0.041 2 - For pipe ordered to nominal OD and minimal wall.

C R

A - 2.0t

- 0.041 m

3 - For pipe ordered to specified machined ID and minimum vali.

a -

C R

B (Note: Not applicable to tapered backing rings) b -

C R

B +.076 (For tapered backing rings only) 4 - For extruded pipe ordered to specified ID and minimum vali.

a -

C R

B + Mfr ID Tol +,066 (For tapered backing ring) b -

C R

B + Mfr ID Tol -.010 (For flat backing ring)

B - The following applies to rolled and welded plate pipe, electric fusion velded vith filler metal (i.e.

ASTM A155, A358): vali thickness greater than 1/2 inch.

C R

A - 2t

- 0.0625 0.010 C - The following applies for cases A and B above:

Tolerance and Dimensional Control 1 - The tolerance on "C" in all cases is +0.010 - 0.000.

2 - The tolerance on the OD of machined backing rings (not split), vhere used is - 0.010 + 0.000.

For flat rings, the ring OD equals "C"; for tapered rings, the ring OD equals "C" + 0.010.

3 - In cases of )oining pipe ordered to different criteria, the selected "C" dimension shall be the same.

4 - All ends shall be sized vithin 1/16 in, of the mean nominal diameter.

The use of welded ASTM-A312 pipe is prohibited vithout prior approval of EBASCO.

REY: 4 04TE7 / ~

APPROVED OES ERG'R MELD END'REPARATION "C",

DIMENSION CONTROL SHEET CONTINUED ON DESIGN GUIDE M4-4 M4-3 P. h

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EBASCO SERVICES INCORPORATED Bi4 DESIGN GUIDE

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- SOUTHWEST FABRICATING 8E WELDING CO., INC.

December 5, 1983 S-EB-759 Ebasco

Services, Inc.

Two World Trade Center, 81st Floor New York, NY 10048 Attention:

Mr. Pete Fiala

Reference:

Shearon Harris Nuclear Power Plant Your P.O.

NY-435035 Our S.O.

3301-3304 6 4121-4124

Subject:

SF&W Letter S-EB-748 Gentlemen:

This letter will confirm our telephone discussion today regarding mainte-nance of minimum wall thickness where pipe or fitting ends are counter bored.

The line list establishes the thickness requirement for each line.

Where a nominal thickness is specified, the minimum required thickness is not provided.

Southwest uses 87-1/2/ of nominal thickness as the minimum thickness when Ebasco's line list specifies a nominal thick-ness.

The counter bore diameter is determined from Ebasco's Design Guide M4-3.

When machining to that diameter for nominal wall material reduces wall thickness in the counter bored area to less than 87-1/2X of the speci-fied nominal thickness, Southwest will build up the area with weld metal so that the thickness is not less than 87-1'/2X of nominal thickness.

When a minimum thickness is specified, that minimum will be maintained in the counter bored area.

Where the counter bore results in 'a thick-ness below the minimum specified, the condition will be corrected using weld metal.

ry truly yours, hn E. Harris roject Manager JEH:cp 7525 Sherman Street

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P.O. Box 9449

~ Houston, Texas 77261-9449

~ (713) 928-3451

~ TWX: 910 881-1600

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