RBG-30922, Provides Addl Info Re Use of Recirculation Sys Crack Growth Data for Feedwater Nozzle Weld Found in Feedwater Inlet Nozzle N4-A to Safe End Weld During Inservice Insp

Provides Addl Info Re Use of Recirculation Sys Crack Growth Data for Feedwater Nozzle Weld Found in Feedwater Inlet Nozzle N4-A to Safe End Weld During Inservice Insp

ML20247H404
Person / Time
Site:	River Bend
Issue date:	05/19/1989
From:	Booker J GULF STATES UTILITIES CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RBG-30922, NUDOCS 8905310230
Download: ML20247H404 (5)

Text

- . _ - . . - . - -

-7 p auze svares: urzzzrzas coarmary I hvEh DENO STATION POST OFFICE BOX 220 ' ST. FRANCISVILLE, LOUISIANA 70776 AREA CODE 604 636-6094 346 8651 i '

l May 19,1989 RBG- 30922 File Nos. G9.5 U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 i

Gentlemen:

' River Bend Station - Unit'l Docket No.'50-458 On May 17,. 1989, . a . conference call was held with NRC's Mr. Walt Paulson and Mr.-Bill Koo concerning Gulf States Utilities ' Company's submittal dated May.15,1989.(RBG-30883). This submittal documents the indication found in a feedwater inlet nozzle N4-A to safe end weld during an Inservice Inspection (ISI).

Additional information was requested during the conference call. This information includes justification for the use of recirculation system crack growth data for a feedwater nozzle weld and information concerning methods used to produce the weld (shielded metal arc weldment versus TIG weldment). A report which provides the requested information is attached.

If you need any additional information, please contact Mr. David N.

Lorfing at (504) 381-4157.

Sincerely, 8905310230 890519 "

gDR ADOCM 05000458

' ['

PW ' J. E. Booker Manager-River Bend Oversight River Bend Nuclear Group Attachment cc: U. S. Nuclear Regulatory Commission g

//N N

,f Region IV gd 8f 611 Ryan Plaza Drive, Suite 1000

/s 8[ g :/EJ ASI [ 8//#

Arlington, TX 76011 NRC Senior Resident Inspector P.O. Box 1051 St. Francisville, LA 70775

\

DRF# 137-001

- SASR# 89-37

. APPENDIX A This Appendix. addresses additional questions that were brought up during a review of the report:

1. Can the crack growth data for recirculation piping system be applied to evaluate crack growth in the feedwater nozzle to safe end weld?

The water inside the thermal sleeve and the feedwater sparger'is-somewhat lower in oxygen content (compared to that in the recirculation line) and is at lower temperature (420*F). From the viewpoint of IGSCC, the feedwater environment is less aggressive. The safe end. weld is exposed to the water in the annulus between the nozzle safe end and the thermal sleeve, which is a combination of the downcomer flow and the feedwater flow. The temperature of the water flowing in the annulus is the average of the feedwater temperature (420'F) and the downcomer flow (550'F) and the oxygen content is probably close to that of the recirculation flow.

Other dissolved impurities are also comparable. Thus, the water

. chemistry and temperature of the flow in the annulus region near the feedwater nozzle / safe end weld are comparable to that in the recirculation line. Thus, the CAVS crack growth data for recirculation 1

flow can be applied to predict crack growth for the feedwater nozzle / safe end weld.

2. Is the nozzle / safe end weld made of shielded metal arc weldment (SMAW) and was the indication evaluated using the SMAW evaluation tables?

The weld between the nozzle and the safe end is made of Alloy-82, which is a TIG weldment. However, the nozzle and safe end weld butters are made of shielded metal art weldment (SMAW) Alloy-182. In general, it is known that a SMAW stainless steel weldment has somewhat lower toughness than the TIG weldment or the basemetal. To allow for this,Section XI, ASME Code has special flaw acceptance tables (IWB-3641-5) for stainless flux welds. The allowable flaw sizes for the flux welds are somewhat smaller than those for the base material or TIG weldment. However, Alloy-182, even with the SMAW condition is expected to be tougher than SASR89.37 - _ _ _ _ - - _ _ _ - _ _ _ - _ - _ _ _ _ _ _ _ _ _ - _ _ _ _ _ .

~

l DRF# 137-001 SASR# 89-37 stainless steel flux weld material since it is completely austenitic and does not contain the ferritic phase, which tends to reduce the toughness.

Available data on Alloy-182 show uniform elongation of 39% (over 1-inch

_ gage length). This is high, almost comparable to'that of the basemetal, in view of this, it is reasonable to use the allowable flaw size tables corresponding to austenitic base material. As shown in the report, the flaw is acceptable after 12,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> operation.

Although the Alloy-182 could be treated as basemetal, still the flaw was conservatively evaluated as SMAW weldment using IWB-3641-5 tables. Since this includes the thermal expansion stress, it is necessary to include thermal expansion moments. The thermal restrained free expansion (RFE) moments and shear specified in the design specification was used. Since these values'are generally specified before the piping design is complete, the magnitude of the RFE shear and moment tend to be over estimates. Thus, use of the design specification value for the analysis is conservative and lower values can be justified using the piping stress report. Nevertheless, the design specification values were conservatively used in this analysis.

Total RFE moment including additional moment at the weld from the shear force

= 1455 in-kips + 13.3 in x 58.2 kips

= 2229 in-kips The associated thermal expansion stress Pe = Me/Z Where Z = Section modulus = n ( 14 -11,750 ) / (64 x 7) = 135.72 in 3

The thermal expansion stress = 2229/135.72 = 16.4 ksi Stress ratio = (P ,+ Pb + P e/2.77) / Sm

= (3 + 11 + 16.4 / 2.77) / 23.3

= 0.855 SASR89.37 - - _ - - _ - _ _ _ - _ _ _ _ _ - _ - _ _ - _ _ - _ _ _ _ - _ _ - _ _ _ . _ _ _ _ _ _ -

DRF# 137-001 SASR# 89-37 The M factor in IWB-3641-5 for SMAW' piping less.,than 25 in diameter is 1.0.

Using the calculated stress ratio, th'e allowable flaw depth ratio for 16%

circumference flaw is 0.55 (see attached table). This can be compared with the nondimensional flaw depth at the mid-cycle inspection. Assuming the upperbound crack growth rate and the peak initial depth (0.2 in.) the predicted flaw depth at the mid-cycle inspection (i.e., after 7,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of operation is:

-5 A, = 0.2 + 7000 x 5 x 10

= 0.55 in.

This is equivalent to a flaw depth ratio of 0.55/1.125 = 0.489. This is less than the allowable flaw depth ratio of 0.55. Thus, the flaw is acceptable even assuming conservatively that the flux weldment allowables are applicable.

l SASR89.37 l l

Hf

$ TaWe IWB-3641:5 . SECTION XI- DIVISION 1 1986 Edition -

t

. .e .

TABLE IWB-3641-5 ALLOWABLE END-0F-EVALUATION PERIOD FLAW' DEPTH 2 TO THICKNESS RATIO '!

FOR CIRCUMFERENTIAL FLAWS IN SHIELDED METAL ARC AND SUBMERGED ARC WELDS -

NORMAL OPERATING UNCLUDING UPSET AND TEST) CONDITIONS Ratio of Flaw Length, t,, to Pipe Circumference INote (3)]

Stress Ratio 0.5 (Note (2)] 0.0 0.1 - oj6 ' O.2 0.3 0.4 or Greater 1.05 (4) (4) (4) (4) (4) '(4) 1.00 0.60 0.25 0.16 0.13 (4) (4) 0.95 - 0.60 0.47 0.25 0.18 0.13 ' ' O.12 0.90 0.60 0.60 0.27 0.22 0.19

, 0.85 0.60 - 0.M9,gg;0.39 0.51 0.36 ' O.29 0.25 0.80 0.60 - 0.60 0.60 0.45 - 0.36 0.30 O.75 . 0.60

. 0.60 0.60 0.52 0.43 0.35 0.70 0.60  :

0.60 0.60 0.60 0.51 0.41-0.65 - ' 0.60 0.60 0.60 0.60 0.55 0.45

s 0.60 O.60 0.00 "0.60 0.60 0.60 ' O.49

. NOTES:

L'*

(1) Flaw depth - a,for a surface flaw .

. 24,for a subsurface flaw i = nominal thickness Linear interpolation is permissible.

A87 (2) Stress ratio = M(P,+ P,+ P,/2.77)/S, where S, = allowable design stress intensity (in accordance with Section IID P, = primary longitudinal rnembrane stress (P, s 0.55.)

i P. = primary bending stress P, = expansion stresses resulting from restraint of free end displacement M = 1.0 for shielded metal arc welds where 0.0 s 24 in.

=

1.0 + 0.01(0.D. - 24) for shielded metal arc welds where 0.D. > 24 in.

= 1.08 for submerged arc welds where 0.D. g 24 in.

- 1.08 + 0.009(0.D.- 24) for submerged arc welds where 0.D. > 24 in.

(3) Circumference based on nominal pipe diameter.

(4) IWB-3514.3 shall be used.

(

r

(-

i e e' ap ., e ah ., e n.,3,, g,,. .k.ek g 7 e e, 4 J , $' i #, p 4. M d'.E .18 - %M %g - N agr bh. *%.*

• 122

. LU

..,..e

. .