4,.|q''..o. -f!.o,

Og ~-t ** ,- {

'

'' ASME CODE STRESS INTENSIFICATION FACTORS FORCOMANCHE PEAK STEAM ELECTRIC STATION,

UNITS 1 AND 2 |

S. E. Mooreh

~

1. INTRODUCTIC-N

The official Code-of-Record for the p' ping stress analysis effort being/

performed by the Stone and Webster Engineering Corporation (S'a'EC) for Comanche

Peak, Units 1 and 2, is the ASME Code,I 1974 edition including the Summer 1974

Addenda.* That edition of the ASME Code contains a complete set of rules for

the design stress analysis of ASME Class 2 and 3 nuclear power plant piping in

Articles SC-3600 and ND-3600, respectively. Further, those rules include a set

of design criteria statements (equations) written in terms of nominal stresses,

stress intensification fag. tors (SIFs) and stress limits. The intent of the

criteria statements is that the c. .tservative combination of internal pressure C

i

stresses, cross-section moment stresses, and thermal stresses represented by'

the left-hand side of the equations will not be greater than the allowable *

stress limits on the right-hand side. ) j.t

Since 1974, the design criteria equatior.o. including the ASME Code re-t

quired SIFs, of Articles NC-3600 and ND-3600 have been the same for Class 2 \

and Class 3 piping. Howe er, ever the years' a number of changes in the design

rules and SIFs have been adopted by the ASME Code Committee and published in '

later editions and addenda to the Code. Some of the revisions have been more

restrictive and some have been less restrictive than the Comanche Peak 1974

Code-of-Record. Application of a specific change must, therefore, be justi-7

fied and acceptable to the enforcement authorities having jurisdiction at the,

a

*The terms ASME Code. ASME-III, or Code as used herein refer to SectionIII of the ASME Boiler and Pressure Vessel Code, Ref. 1. Specific editions of i

Lthe Code and the relevant Addenda are identified by date, enclosed in brackets.e.g., [1974-S74]. Sections, Articles. Subarticles. Paragraphs, and Subpara-graphs are identified according to the Code numbering system, e.g., ArticleNC-3000,

t

-=- - - -. -. -.

,- -- ----- -- ------- - - - - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ .

? \' t* '

. g* ',- 2 --.

;ya. /

'

nuclear plant site. The purpose of this study is to investigate the accepta-,

A bility of using SIFs from Subparagraphs NC/ND-3673.2(b) of the 1983 ASME Code

edition (1983-V84) in the Stone and Vebster, Comanche Peak, piping stressj

analysis effort _or to provide suitable alternatives for.the following items\

in conformance with the Cc,de-of-Record provision of Subarticle NA-Il40.

1. Branch Connections,

2. Girth Buttseld (mismatch formulation),

3. Circumferential Fillet Welded or Socket Welded Joints,

Subarticle NA-1140 (1974-S74] reads as follows:,

"NA-1140 Effective Dates of Code Editions, Addenda, and Cases. -

(a) Code Editions become mandatory on July 1 of the publicationyear printed on the cover. Addenda may be used on or after thedate of issue and become mandatory six months after the date ofissue.;

I *.

ff)CodeEditions,' Addenda,andCaseswhichhavenotbecomemanda-tory on the contrac.t date for a component may be used by mutualconsent of the Owner or his agent and Manufacturer or Installer c tor after the dates permitted by (a) through (d) above. It is per-,mitted to use specific provisions within an Edition or Addenda pro-vided that all related requirements are met.

(g) Caution is advised when using Addenda or Cases that are less~''t restrictive than former requirements without having assurance that

they are acceptable to the enforcement authorities having jurisdic-tion at the nuclear plant site.'

(h) ...".

Figures 1 to 3 show the specific SIFs under consideration with the appro-1| A priate notes and sketches as they were given in 1974 Figures 4 to 6 show

corresponding SIFs, notes, and sketches from (1983-V84). The current SIFs,

| notes, and sketches (1986-SS6] are identical to tnose in Figs. 4-6, where|

we have identified the pa',11caton dates of the latest rule change in the margin,'

i|

|I

\'

,. . . . . . . - -. -- . ._ _ ;. . ---,

.f'-"

>,.

'.. -.,- _3+

s

$ / 4..

.' u ~'. ..

- . - -,.%#

k

.!- ,

-4-,

.

the B31.1 industrial piping code. In fact, for the design stress analysis

requirements, the B31.7 code simply refers to B31.1.

In (1971-571] the ASME Code extended its coverage to include nuclear piping

by simply incorporating the B31.7 rules for Class 1 piping and the B31.1-1967

rules for Class 2 and 3 piping. In [1974-S74), however, a complete new set of

design criteria equations was introduced for the required design stress analy->

sis of Class 2 and Class 3 piping. This new stress analysis procedure was a

hybred between the B31.7 Class 1 analysis and the B31.1 Class 2 analysis of the

1971 Code. Subsequent changes in the design analysis rules for Class 2 and 3

piping have retained this dual nature. Although the Code makes some distinctions

between Class 2 and Class 3 piping, the design basis stress analysis require-

ments for the two Classes have been identical since [1971-571]. We.shall,

therefore, refer only to the Class 2 rules hereinafter.

One particularly important relation between the Class 1 and Class 2 design

stress analysis criteria is the following:

i = 1/2 C K2 2 > 1.0 , (1)

where i is the Class 2 SIFs, and C and K are the Class 1 "primary plus secon-2 2

|

j. dary" and "peak" stress indices for piping system moments, respectively.l

Although-this re..ationship was used by the writers of B31.7 (see Foreword to'

B31.7, Ref. 9) and has been used extensively in later ASME Code rule stress

analysis developments, it was not formally incorporated into the Code until

| [1977-577], h'C-3673.2(b) . The lower limit of i = 1.0 was added in [1983-S84].|

|It is important to realize, however, that Eq. (1) has been a valid relationship

(~ since before 1969 when the Class 1 simplified analysis method was introduced.

_

_

_ _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - - - - - _ _ _ _ _ _ _ _ - _________ _ - _ _ -_-_ _ -________--

.

*' i-5-

,

o

Rules for the design and construction of Class 2 nuclear piping are given

in Article NC-3600, in Subarticles NC-3640 and NC-3650. SIFs are used specif-

ically in the design criteria equatior.s that must be satisfied at every point

in the piping system by a suitable stress analysis. In 1974 those equations

were given in Paragraph NC-3652 as follows (using the Code nomenclature and

numbering):

NC-3652.1 Sustained Loads

PD 0.751 MA

S 1 1.0 S (0)= +gg 4t Z hn

NC-3652.2 Occasional Loads,

[ + 0.751(M, + M ) 51.2 SP D

BS (9)=OL 7 h

n

NC-3652.3 Thermal Expansion

iMA 1S (10)g g.

and

f i'(Sh+S)' (II)^+ 0.75i +1S =TE An

where (1) is a unique stress intensification factor, SIF for each of the dif-3

ferent types of piping products and welds that make up a piping system. SIFsi

for commonly used products and welds are specilled in Subparagraph NC-3673.2.|

| The SIFs under consideration in this report are given herein in Figs. I and 4

(See the Code for nomenclature definitions.)

The intent of Code Eqs. (8)-{11) is that the conservative combination of

pressure stresses (P terms) and cross-section moment stresses (M , M , and M3 B C

!;

. - _ . _

.

. .

-6-..

.

terms) represented by the left-hand side of the equations will not be greater

than the stress limits given on the right-hand side in terms of the allowable

stress S f r steady state and occasional loads and the allowable stress rangehS for cyclic loads. Equations (8) and (9) are for protection against plastic3limit-load collapse or rupture from primary loads. Equations (10) and (11) are

for protection against large deformations and fatigue failure from cyclic loads.

In [1974-W76), the Code added the concept of Service Level limits to the

occasional load cateogry, Eq. (9), in recognition of the fact that more liberal

allowable stresses could be tolerated without unacceptable damage - depending

on the load source and post incident inspection and repair. In essence, the

right-hand limit of Eq. (9) was multipled by a factor that depended on the

severity classification-of the postulated incident loading. The four Service

Levels and corresponding stress limits are shown below.

Service Level Stress Limit

Design /A (nromal) 1.0 Sh

B (upset) 1.2 Sh-

C (euergency) 1.8 Sh

D (faulted) 2. 0 S.n

It is our understanding that the [1974-W76] Service Level stress limits have

been specifically approved for use in the Comanche Peak piping stress analysis.

The Class 2 piping design bases remained unchanged until (1980-W81] when

the Code Committee made a major change in the stress evaluation criterion for

primary loads based on studies by Rodabaugh and Moore. 1,12 Equations (9) and

(9), written in terms of the fatigue data based SIFs, were replaced by new

equartons written in terms of the Class 1 "B" stress indices developed from

e

_ _ _ _ _ _ - _ _ - _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _

..*

t

-7-..

,

plastic-collapse limit-load considerations. The new equations are:*

NC-3652 Consideration of Design Conditions

PD MS =B +B 11.5S (Sa)gt 12t 2 hn

NC-3653.1 Occasional Loads

P D M +M3

SOL " bl 2 Z+B $ 1.8 S (9^)h'n ,

but not greater than 1.5 S ,y

where S is the Code specified minimum material yield strength. The B and By y 2stress indices are taken from Subarticle NB-3680 for Class 1 piping design.

The Service Level limits to be used on the right-hand side of Eqs. Ga) and (9a)

were also changed at the same time to the following:

. _ . _ _ .

Service Level Stress Lindt

Design 1.5 Sh

'B 1.8 S 5 1.5 S,hC 2.25 S 5 1.8 Sh yD 3.0 S 5 2.0 Sh 7

Except for the addition of an equation similar to Eq. (10) for checking single

nonrepeated anchor movements, the remaining design basis criteria have not been

changed since (1974-S74].

*We have numbered the (1980-W81) equations as (8a) and (9a) to distinguishthem from Eqs. (8) and (9) introduced earlier.

- ,. ~ . _ - - . _ - _ _ , -- _- - ,. . - . . - - - .-. . .

_ _ _ - _ _ _ _ _ - _ - _ - _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ . . _ _ - .

.

.. .-

-8-.

.

December 31, 1981, corresponding to the publication of (1980-W81] and

its mandatory application date of July 1, 1982, as required by Subparagraph

NA-1140(a), are important to this investigation because changes in the SIFs

made after those dates may not be appropriate for use with Eqs. (8) and (9)

[1974-S74] for the primary load caregory stress evaluations. Other parts

of the design basis criteria, however, are not effected provided that all

other related requirements are also met.

2.2 Functional Capability Criteria

In a somewhat related move, the Nuclear Regulatory Commission (NRC) .

imposed supplemental requirements for assuring the "functional capability"

of essential safety related nuclear piping.I ' ' The criteria to be satis-

fied are given in Ref. 13 (1978), subject to constraints imposed by the NRC14

staff that were based in part on Ref. 11 (July 1978). For Class 2 and 3

essential piping, those criteria made use of Eq. (9) and SIFs from NC-3672

(1977-S78].

According to Ref. 14. functional capability for Class 2 or 3 essential

piping with D,/t < 50, except branch' connections, is assured without further

proof if the following equation is sat:sfied:*

P D M

+ 0.751 -f- < 1. 5 S (9f)***0.5 y,

n

*We have numbered this equation as (9f) for functional capability todistinguish it from the other Eqs. (9) and (9a). It is the same as Eq. (9)

|

|with a different right-hand limit.

|

|

I

i

_ . _ _ _ _ . , . _ _ , _ - . . . _ _ _ _ _ .. _ _ _ . _ . _ . _ _, _ _ _ . . _ _ _ _ , , . _ _ . _ _ _ _ _ _ _ ._

..

./ .

-9..

where M equals the resultant moment due to weight, earthquake (considering1

only one-half the range and excluding anchor displacements), and other sus-

tained mechanical loads. Specified values for 0.751 are given in Ref. 14

Equation (9f) is the same as Eq. (9) (1974-W76] with Service Level B limit of

1.2 S replaced by the more liberal limit 1.5 S .h y

For Class 2 or 3 branch connections, Ref. 14 requires the Class 1 cri-

teria to be satisfied. Because those criteria do not make use of SIFs, func-

tional capability for branch connections is not addressed in the present study.

3. BRANCH CONNECTION SIFs

SIFs for branch connecticas with the approp'riate notes and sketches from

(1974-574] for both primary load and thermal expansion fatigue evaluations are

shown in Figs. 1 and 2. Since that time the following chances have been made

as noted in the margin of Figs. 4 and 5.

(1) (1977-579] when a new equation was added for calculating the SIF for

checking run-end moment loads. At the same time defining equations for calcu-

and the run-end section modulus Zlating the branch-end section modulus Z3 r,

were moved from Paragraph NC-3652.4 to Fig. NC-3673.2(b)-1 [ Fig. 4 herein}.1

(2) (1980-S80] when note 6(d) was revised by the Code Committee to

|exempt branch pipe sizes less than 4-in. NPS from the inside corner radius

l

! requirement,to remove a difficult and expensive fabrication step that was

judged to be almost unenforceable. The revision had no impact on the calcu-

lated SIF values because the variable r is not included in the SIF equations.y

~

(3) (1980-S80] when note 6(h) was added to exempt branch connections

from the outside corner radius requirements of note 6(e) provided that the SIFs

are multiplied by an additional factor of 2.0, with a minimum SIF = 2.1.

l

|

\l

- - _ _

- -. - . - - - _ . - _ . . - - . - .

. . .

-10-.

J

(4) [1980-S82) when General Note 2 was added to Fig. NC-3673.2(b)-2

(Fig. 5 herein) to redefine the midwall radius ry of the branch. ..

(5) (1980-S83] when a minor editoral correction of.no technical con-

sequence.was made to note 6(c).

Revisions (1) and (4) are less restrictive and according to NA-1140(g)

must be justified for use with the [1974-S74] design basis equations.

Revision (3) is more restrictive. It is our unders tanding, however, that -

note 6(h) is being used in the SWEC piping stres''sinalysis for Comanches

Peak. Revision (1) is discussed below in Sect. 3.1. Revisions (4) and

(3) are discussed in Sect. 3.3.

3.1 Run-End SIFs

From 19'/4 to 1979 the following equation [1074-S74] was specified for

calculating SIFs for both the branch-end and the run-end,

i=1.5(TR 2/3 c' 1/2 T{ r;

> 1.0 , (2)I rr a r p

subject to the restrictions identified in Fig. 1 under note 6. According to

Subparagraph NC-3652.4, the branch-end and the run-end were to be evaluated

( separately using Eqs. (8)-(11) with the appropriate moments and section modulusl

Z #2'b r

Equation (2) was developed by Rodabaugh in 1970 for branch connections

with moment loadings on the branch. His data base consisted of measured maxi-

mum stress data for 23 models, fatigue test data from 8 models, and Bijlaard's

; theory for correlation guidance. However, in the absence of sufficient data"

for branch connections with moment loadings through the run, Eq. (2) was also1

specified for calculating run-end SIFs on the considered judgment of the Code

Committee that it was adequately conservative. (It is conservative with respect

to the single data point that existed in 1970.)

_ . _ _- ,_ __ --_ _ _ _ - _ - - -- , _ . - _ . - _ _ _ _ _ _ - . - _-

-__ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - _ _. - _ - - _ _ _

.

., .

-11---.

In (1977-S79] a distinct SIF for checking the run ends was introducedI7

based on Class 1 stress index studies by Rodabaugh and Moore which in-

cluded additional stress analysis data not available for the earlier study.

The new run-end SIF equation was

/R 2/3 /r')

l R,j -> 1.5 .(3)*i = 0.4 1 E I

T\r \This is the same equation that appears in [1983-W84] and in the present Code

[1986-586].

Although Eq. (3) does not correspond exactly to the Class 1 stress indices

g (see Eq. (1)] proposed in Ref.17 'and adopted in (1980-S81], it isC and K2conservative with respect to the same data base. Equation (3) actually cor-

and K . Table 1responds with an earlier unpublished draft proposal for C2 2

shows comparisons between the SIFs from Eqs. (2) and (3), the corresponding

Class 1 stress index product C K and the Ref. 17 data base for coment load-22ings en the run. These data consist of fintte element results obtained by

18Bryson, Johnson, and 3 ass for a series of unreinforced nozzles (U Models),

uniform thickness reinforced nozzles (S1 Models), and compact tapered thick--

ness reinforced nozzles (P30 Models); and experimental data reported by

15 (Weldolet), Corum et al.I9 (ORNL-1), and Gwaltney et al.20,21Rodabaugh

(ORNL-3, ORNL-4). .

Table 1 shows that Eq. (2) gives a poor fit to the run moment data,

being excessively conservative for many of the models and unconservative

at the lower limit of i = 1.0 (21 = 2.0). Equation (3) provides a much

better fit to the da'ta, being conservative with respect to all the dataJ

except for the unreinforced U models and ORNL-4. None of these particular

models met the reinforcement requirements of note o(a), and the ORNL models

also failed to meet the outside corner radius requirement of note 6(e). If

._ _ _ _ _ . - _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _

.

, ,

-12-.

the data from models that failed to meet Code requirerents are neglected,Thethen Eq. (3) is conservative with respect to all the relevant data.

Class 1 stress indices, however, give the best fit t'o the data and are

actually less conservative than Eq. (3), the current run-end SIF.

Because Eq. (3) was introduced into the Code prior to [1980-W81] and

because it is conservative with respect to the available stress analysis data

base, it is clear that its use for checking run-end stresses with the [1974-574]

piping stress analysis criteria is justified even though it is less restrictive

than the previous SIF, Eq. (2).

.

3.2 Branch-End SIFs

In addition to developing the run-end Class 1 stress indices, Rodabaugh

and Moore also checked the Class 1 equivalent of Eq. (2) for branch-end mo-

ment loadings against the additional finite element stress anlaysis data ob-

tained by Bryson, Johnson, and Bass. O Table 2 shows the comparison between

21 > 2.0 from Eq. (2) with the finite element data from Table 10 of Ref. 17.,

|

Equation (2) is conservative with respect to all the finite element data

except for the unreinforced U modelsr' As noted earlier, those models did noti

meet the reinforcement requirements of note 6(a). The small amount of uncon-.

servatism for those models, however, is not of direct consequence in validat-

ing the SIFs for use in checking the branch-end moment stresses.

!

3.3 General Note 2. Fic. NC-3673.2(b)-2

|In [1980-582] General Notes (1) and (2) were added to Fig. NC-3673.2(b)-2

l

! as shown in Fig. 5. General Note (1) simply states that certain variables used

in the branch connection SIFs are defined in the figure. General Note (2) re-!

defines the midwall radius of the branch r' as the midwall radius of the

|

ii

. . . _ _ . _ - - _ _ - - _ , .

.. ,

-13-

.

reinforced portion of the nozzle if the reinforcement length Lg is greater than

0.5(r T ) , where r is the inside radius of the branch and T is the wallgb 1 bthickness of the reinforced nozzle. General Note (2) is technically in error

and cannot be justified for use in the SWEC Comanche Peak piping stress analy-

sis effort, either for primary load evaluations or for thermal expansion

fatigue evaluations - independent of when the revision was introduced into

the Code.

Note (2) was originally perceived as solving a definition problem to

distinguish between T andT{forbranchconnectionsthatlooklikesketch(d),bFig. 5, but are considerably thicker walled than needed to satisfy the internal

pressure reinforcement requirements of NC-3643 as required by note 6(a). As

originally proposed, note (2) was only to be used in calculating the SIFs for

the branch-end, Eq. (2), and the run-end, Eq. (3); but n_ot for calculating the

branch-end section modulus. As published, however, it is clearly evident that

General Note (2) may be used in calculating the branch-end section modulus as

well, i.e.,

Z = (r') T{ . (4)b ,'

The result is that the calculated moment stresses (0.751 M/Z) and (i M/Z) as

used in the stress criteria Eqs. (8)-(11) can be reduced as a function of

(r') simply by increasing the wall thickness of the branch.As pointed out in Ref. 17, however, the maximum stress in nozzle connec-

tions from moment loadings on the branch pipe is not a function of branch

pipe wal'. thickness., The maximum stress generally occurs in the shell side

and is inversely related to the outside diameter of the nozzle reinforcement.

The variable r is included in SIF Eq. (2) to account for that influence. Inp

,

,. - -- ._ - -_ , - _ _ . .. - -- , . . - _ - ..---.- - - .

.

.. .

-14-.

a recent study of branch connection SIFs conducted for the Pressure Vessel

22Research Committee, Rodabaugh compared various correlating equations from

the technical literature and the different codes. All the correlating equa-,

tions are indepen' dent of the branch wall thickness.

3.4 An Alternate to Using General Note (2)

In the event that not using General Note (2) would cause an undue hard-

ship in the SWEC effort, we can offer the following for consideration. Ref-

erence 22 contains a substantial amount of fatigue test data on specialty

product branch connection fittings (WFI products) that were not previously -

available. Those data show that the current branch connection SIFs, i.e.,

Eq. (2) and (3), are overly conservative for fatigue evaluations when the

multiplying factor of 2.0 from note 6(h) [1950-S80] is included. As a con-

sequence, Rodabaugh recommends that note 6(h) be deleted from the Code.

If the Ref. 22 recommendation is adopted by the ASME Code Committee, it

would apply for thermal expansion fatigue evaluations using Eqs. (10), (11)

[1974-S74] but not for primary load evaluations using Eqs. (8), (9). This is'

proper because note 6(h) [1980-S80] was originally introduced as a fatigue!

I reduction factor to account for the local stress concentration caused by an

undressed weld at the branch-run intersection. Thus removing note 6(h) on.

the basis of new fatigue test data should only effect the Code fatigue

evaluatin procedures. Moreover the present Code (1986-S86] requires the|

use of Eqs. (8a), (9a), which do not involve SIFs, for primary load evaluations.

A suitable alternative to using General Note (2), Fig. NC-3673.2(b)-2, is

to perform the Comanche Peak piping stress analysis as in the past using note

||

|

,_ -. . - . - - - ,_ .. --- .. . - , . - - _ - _ - . _ _

.

** *_15

.

6(h) but not using General. Note (2) for the primary load evaluations, Eqs. (8)-

and (9). Then reanalyze only those cases that fail to meet the required stress

limits using Eqs. (8a) and (9a) (1980-W81] and the moment combination procedure

for Class 1 branch connections as required by Subparagraph NC-3653.3(b)

[1980-V81], but not using either General Note (2) or note 6(h). The thermal

expansion fatigue evaluations may be performed as in the past but without using

either General Note (2) or note 6(h).

3.5 Related Requirements

A thorough review of Articles NC-2000 Materials, NC-4000 Fabrication

and Installation Requirements, NC-5000 Examination, NC-6000 Testing, NC-7000

Protection Against Overpressure, and NC-8000 Nameplates, Stamping, and Reports;

and comparisons of the contents of {1983-W84] with those of (1974-S74] was con-

ducted to determine whether any changes would impact the SIT calculations in

the piping stress analysis. None were found. It is thus concluded that all

related requirements for branch connections, other than those from Article

NC-3000 specifically discussed above, are met as required by Subparagraph

NA-1140(f) [1974-S74].-

4. GIRDi BITTT WELD SIFs

4.1 Mismatch -

Prior to [1974-S74] the SIF for a Class 2 butt welding joint between

sections of straight pipe, between straight pipe and reducers, and between

straight pfpe and welding neck flanges was simply i = 1.0. In [1974-S74] an

entirely new design analysis procedure for Class 2 piping was introduced. This

new procedure included the use of SIPS from the earlier Codes, but they took

.. ,

-16-,.

on new meaning in parallel with the Class I stress indices through the relation

i = 1/2 C K f Eq. (1). For girth butt welds, three different values for the22SIF were given depending on whether the nominal wall' thickness t was greater

n

than or less than 3/16 in. , and whether the mismatch 6 was greater than or less

than 0.1 tn, as shown in Fig. 1. Mismatch 6 was defined in note (1) and the

sketch as shown. These SIFs corresponded exactly with the (1971-573] Class I

stress indices as noted below.

Type of weld C K 1 2 1.02 2

a) flush 1.0 1.1 1.0

b) as-welded, 1.0 1.8 1.0t, 2 3/16 in and /t 5 0.1n

c) as-welded, 1.8 2.5 1.8t < 3/16 in, or /t > 0.1

n n

At the same time, [1971-S73], footnote (12) was added to the Class 1 piping

stress index table, Table NB-3683.2-1, defining 5 as follows. Figure NB-4233.1

from the 1971 Code is included herein as Fig. 7." is defined as the maximum permissible mismatch as shown inFig. NB-4233.1. A value of 6 less than 3/32 in. may be usedprovided the smaller mismatch is specified for fabrication."

The following sentence was added in the 1977 Code. '

"For flush welds, defined in footnote (2), 6 may be taken as zero."

In [1980-S81] the definition of 5 was moved from footnote (12), Table NB-36S3.2-1,

to Subparagraph NB-3683.1(a) and the last sentence was revised to read:

i "For flush welds, defined in NB-3683.1(c) and for t > 0.237 in.5 may be taken as zero."

|i

._

_ - - - _ _ _ _ _ _ _ . _ __. _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ - _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ - _ - _ _ ___ _ __

.

..

-17-

.

This last sentence and the final form of the definition was taken from recom-

mendations by Rodabaugh and Moore published in September 1978.

Although the above definition for 6 was not added to the Class 2 SIF

formulation until (1983-W84], as shown under note (1), Fig. 4, it is clear

that its intended application, for flush welds and for welds with 6/t 1 0.1nwas developed as early as 1971 when the Class 1 stress indices were introduced

into the ASME Code. The exact correlation between the (1971-S73] Class 1 stress

indices and the (1974-S74] Class 2 SIFs for girth butt welds confirms the con-

clusion. Thus, this particular Code revision is neither more nor less restric- --

tive than the Comanche Peak Code-of-Record.

No other changes in the Class 2 girth-butt weld SIF were made until (1953-

W84] when the mismatch restriction was dropped entirely for pipe with nominal

wall t > 0.237 in, based on the recommendation of Ref. 23. The SIF for -n

pipe with t < 0.237 was expressed in equation form, as shown in Fig. 4, i.e.,n

. .:

' ~~~

..#'

1.0 $ i = 0.9 (1 + 3 6/tn) 5 1.9 .~ (5)-

, , . . . . ___ _.E- ''

* -.

This SIF corresponds exactly with the (1980-S81] Class I stress indices for

as-welded girth butt welds joining items with nominal wall thickness t < * 'n| '. ,NB-3683.4(b ), i.e. , ..|l

-

, , , ,,

1 -

C., = 1. 7 + 3 ( 6/ t ) < 2.-1 , -, , .(6), "'j ,

K, = 1.8 , ;' ..~ . -

_ -r

as recommended by Rodabaugh and Moore in 1978.

Reference 23 includes an extensive study of girth butt veld stress indices

including the effects of weld reinforcement, mismatch, and abrupt thickness

. _- . . ,- - _ _ _ _ . _ . _ _ . _ _ . . _ . _ _ _ _ _ _ . . _ _ _ . . _ _ _ _ - - ,

. . .

-18-.

change resulting from joining two pipes with different wall thickness. The

recommended C and K stress indices are "... deemed to be adequate to take2 2care of both Code permitted weld reinforcements and mismatch." It is thus

clear that the [1983-W84] SIF formulation for girth butt velds, including

mismatch 6, is also appropriate for use in the SWEC piping stress analysis

effort for Comanche Peak.

-

.

l

-,

|

|

||

. . . -. . . - -, .-

.. ,

-19-.

4.2 Radial b' eld Shrinkane

Radial weld shrinkage at girth butt welds is no.t generally included in

the design stress analysis of nuclear piping, even though it appears obvious

that excessive drawdown would effect the stresses in the immediate region of

the weld. That concern could be relieved to a certain degree by imposing

fabrication tolerances on the amount of radial weld shrinkage permitted dur-

ing construction. That approach was apparently taken for the Comanche Peak24

Class 2 and 3 piping fabrication where the radial weld shrinkage a was

limited to

a$t I# * < 0.375 in., orn n

A $ 0.1815 for e > 0.375 in.nThe question, "Should that amount of radial weld shrinkage be considered

explicitly in the piping stress analysis?", naturally arises. The answer to~

this question is developed below.

Reference 23 includes an extensive study on the effects of radial weld

shrinkage on the stresses at girth butt welds. Based on an analytical param-

eter study, using a conservative mode) for the weld joint and thin-shell

theory, the report shows rather high stresses at the joint, particularly-for

for moment loading. Figure 16 from Ref. 23, included herein as Fig. 8 shows

the maximum normalized axial stresses from a bending moment, corresponding to

the effect on the C stress index, as a function of the veld shrinkage ratio2

/3 t. The bounding equation from that figure, i.e.,

c/S = 1.0 + 2.9 a/t (7),

could be used to characterize the influence on C . Equation (7), along with2

K and Eq. (1) could then be used to characterize the SIF. Using 4/t = 0.57 n

1.8 would then give i = 2.2 (for piping with t > 0.237 in. so thatand K =3 n

,

- e ,,- -,- -,y _# ,,- - , - ..-,,,,,v_ _ - . , _ , _ , , _ _ _ . _ _ ..

_ _ _ _ _ _ _ - _ _ _ - - ._ _ - _- - _ _ -______ __-- - _ _ _-- -____-___ _ _ _ _ _ - _ _ _ _ _ - - _ _ _ _ - - _ _ _ _ _ _ _. - . - _ _ _ _ -

.,

-20-.

mismatch could be ignored). If D/t for specific pipe sizes were included in

the calculation, Fig. 8 indicates that the"SIF would be so~ewhat less than 2.0.

Reference 23 goes on, however, to point out the conservative and uncertain

aspects of the study, and finally concludes that veld shrinkage a should be

ignored in the stress analysis of Class I piping, provided that 4/e < 0.25.nThat recommendation was incorporated into the Class 1 rules in [1980-581} by

addition of the following in NB-3683.4(b):

"... Girth welds may also exhibit a reduction in diameter due toshrinkage of the veld material during cooling. The indices arenot applicable if /t is greater than 0.25 where a is the radialshrinkage measured from the outside surface. " +

The question for Comanche Peak Class 2 and 3 piping thus beco=es "Should

radial weld shrinkage be considered in the stress analysis if 0.25 < a/t < 0. FnConsider the following, however. A restriction on radial weld shrinkage for

the stress analysis of Class 2 and 3 piping has never been included in the

Code; and was not added in (1980-S81] when consideration of mismatch was added

for Class 2 piping and restrictions on weld shrinkage were added for Class 1

piping, in spite of the fact that both revisions were based on the same

reference study (i.e., Ref. 23). This indicates that the Code Committee in-

tended that radial weld shrinkage not be considercd in the' design stress. .' i .

~ ' -,-,;,.... , J,'

,,

. FM 33-' : "' " ' ''analysis of Class 2 or 3 piping. 3, 1, ; H

25 g Vs. , .' 1 . A at ,--a --.;' s u ~ ,, , , . . -r'I ,z . .. .,In a reore recent study, Rodabaugh evaluated the fatigue design margin ; ~,

~~

for both Class 1 and Class 2 nuclear piping against moment loading fatigue

test data on girth butt welded pipe (see Ref. 5). Figure 3 from Ref. 25,

included here as Fig. 9, shows !! ark 1's f atigue-to-failure ' correlation line and

the Class 2 design stress-range limit lines as a function of fatigue cycles

for SA 106 Grade B carbon steel piping. The figure also shows a "design

allowable stress-range" line based on a safety factor of 2.0 on stress-range.

-- .. . - - . .

.

. . .

-21-.

Below 7,000 cycles the real design margin for Class 2 piping is considerably

greater than 2.0, even for a sustained load S = 0; the S = 0 line mights 3represent the thermal expansion stresses in an empty pipe. Above 7,000

cycles the design margin is about equal to 2.0.

The Ref. 25 study also considered th'e fatigue behavior of austenitic

stainless steel and showed that the Class 2 design rules are more conserva-

tive than for carbon steel. We, therefore, conclude that the design margin

in the Class 2 piping stress analysis rules is more than adequate to accom-

modate weld shrinkage up to a/t = 0.5 for fewer than 7,000 cycles of fullyn

reversed loading. For more than 7,000 cycles, however, it would be prudent

to increase the SIF by the factor represented by Eq. (7).

4.3 Functional Capability

As noted in Sect. 2.2 complete instructions for assuring the functional

capability of essential safety related nuclear piping were provided by the NRC''in 1978. The requirements on mismatch in Ref. 13 are the same as in

(1974-S74) and to our knowledge have not been altered. However, the argu-

ments presented in Sect. 4.1 are as valid for functional capability evaluation

as for structural evaluations. The'r'efore, these same arguments could be pre-

sented to NRC in a request for permission to use the (1983-W84] mismatch for-

mulation in the functional capability evaluations.,

Consideration of radial weld shrinkage is not included in Ref. 13. As:

we have shown in Sect. 4.2 radial weld shrinkage a 1 e /2 need not be con-n

sidered in the structural evaluations for piping with less than 7,000 loading

cycles. However, plastic-collapse, and thus functional capability, is not

influenced by cyclic loading within the limits permitted by the Code rules.

Thus, we conclude that veld shrinkage 4 5 t /2 need not be considered inn

functional capability evaluations even for girth butt welds with more than

7,000 loading cycles.

.- . . , _ _ _.. _ . . . _ . . _ _ _ . _ _ _ _ .

- - . _ . . . - .

s

. . .

-22-

.

4.4 Related Requirements s

We have examined all relevant Articles of the Code and have compared the

contents of (1933-V84] with those of [1974-S74] to determine whether any

chances. other than those discussed above, would impact the SIF calculations

or the piping access analysis procedures for girth butt welds. None were

found. In particular the permissible mismatch given in Fig. 7 from (1974-574]

has not changed, i.e., the requirements are the same in [1983-W84]. It is

thus concluded that all related requirements are satisfied as required by

NA-1140(f) [1974-S74].

5. CIRCDIFERENTIAL FILLET WELD SIFs

5.1 Structural Criteria

Prior to (1974-574] the SIF for fillet welded joints, socket welded flanges,

and single welded slip-on flanges were i = 1.3 based on the earlier work of

Markl ,5 and Markl and George.6 In (1974-S74) when the new piping stress4

analysis criteria were introduced into the Code, the SIF was increased to-

i = 2.1 for fillet welded socket joints and the appropriate notes and sketches

shown in Figs. 1 and 3 were added, the SIF for a "full fillet veld" was left at

i = 1.3. Since that time the following changes have been made as noted in

the margin of Figs. 4 and 6.

(1) [1980-S83] when the two fillet weld categories were combined under a,

single category identified as "circumferential fillet welded or socket welded

joints" and Brazed joints" were identified under a separate category with an

SIF of i = 2.1 from the previous Code. The SIF for circumferential fillet

welded ... joints was expressed by the following equation

- . -. ... . - - - _ . - . - . - - . - _ _ _ - - . . .

i~

.

..

* -23-.

i = 2.1/(C,/tn) 2 1.3 , (12)

as noted in Fig. 4, where C, is the length of the fillet weld leg and t is thennominal pipe wall thickness.

(2) [1980-583} when Note (11), which had been added in [1980-S82] to

permit a lower SIF of 1.3 provided that both weld legs were greater than 1.6 tn'

was revised to define C, for fillet welds with uneqnl leg lengths as the length

of the shorter leg.

(3) [1980-583] when Fig. NC-3673.2(b)-3 was deleted and the reference

SIF sketch was changed to Fig. NC-4427-1. Reference to Fig. ND-3673.2(b)-3

was changed to Fig. NC-3673.2(b)-3 in [1977] to identify the intended Subarticle.

(4) [1980-580] when Fig. NC-4427-1 was revised to its present form as

shown in Fig. 6. Changes relevant to the fillet weld SIF are the following:

(a) the definition for the size of an unequal leg fillet weld was changed

from

"... the size of the weld is the leg lengths of the largest righttriangle which can be inscribed within the fillet weld crosssection."

to ,

"The size of an unequal leg fillet veld is the shorter leg lengthof the largest right triangle which can be inscribed within thefillet weld cross section."

(b) The minimum value for C, was changed from ..."1.09 t 2 1/8 in." '

E = n minal phe van tMchess?to "1.09 tn' " '#8 n

Except for applicaton to "Full fillet welds" revisions (1), (2), and (4)

cay be less restrict,ive than [1970-574] and therefore must be justified for

use with the (1974-S74) desiFn basis. Revision (3) may be considered as

editorial and of no technical consequence. Revisions (2), (4a), and (4b).

are technically the same because the restrictions on C, identified in note (11)

_ - . _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ __ - - . _ _ _ - _ _ _ _ _ . _ _ _ . _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

. . . .

-24-e

and in Fig. NC-4427-1 are necessary definitions for evaluation of the SIF Eq.

(12) in revision (1). The restrictions on C,, however, are actually more

restrictive than [1974-S74] because the earlier definition for fillet welds

with unequal legs was incomplete. Thus only Eq. (12) is less restrictive

than [1974-574].

Equation (12) was presented to the ASME Code Committee, Working Group on

Piping Desing (WGFD) in September 19-82, in response to a request from the

Main Committee to relieve the unrealistic abrupt change in the SIF from 1.3

for a full fillet weld to 2.1 for a fillet welded joint. Equation (12) was

justified on the basis of studies of Class 1 stress indices for fillet welded

joints described in NURFG/CR-0371,23 1978, and Markl's earlier fatigue test

4-6data. In Ref. 23 (p. 28) it was concluded that the Code values of C2 = 2.1

and X = 2.0 [1977 ed.] were "amply conservative." Using Eq. (1) then gives2

the upper SIF value of i - 2.1. The lower SIF value of i = 1.3 is consistent

with the earlier value for fillet welds with suf ficiently large leg lengths, i.e. ,

C = 1.6 tn, fr m the earlier note (11) [1980-582}, and Markl's data. Equationx(12) simply provides a linear relation between the upper and lower bounds.

Reference 23 (p. 56, 57) also examined Class 1 B stress indices for

fillet welds. It concluded that,

"If the fitting material and the weld material are as strong as thepipe material, the (fillet welded, ed.] joint is deemed to be as, -...'strong as the pipe."

\

|Thus we conclude that the [1983-W84] fillet weld SIFs including the related

footnotes and reference sketch restrictions on the variable C , are adequatex

and appropriate for.use with the [1974-574] structural design basis,

t

1

. _ . _ _ _ _ _ _ _ _ _ _ - - _ _ - _ _ _ _ _ _ _ _ - _ _ _ _ _ - - _ - _ - _ _ - _ _ _ _ _ _ - _ - _ _ _ _ _ _ _ - _ _ _ _ _ _ - - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

.

.. .

-25-.

5.2 Functional Capability

As noted previously complete instructions for assuring the functional

capability of essential safety related nuclear piping were provided by the NRC

in 1978. The more recent Code revisions for fillet welds discussed in this

Section do not alter those instructions. Nevertheless, if the subject were

of sufficient interest, a case could be made to the NRC to permit use of the

(1983-W84] SIFs for fillet welded joints in functional capability evaluations.

It is of interest to note that currently efforts are under way in the ASME Code

Committee (WGFD item No.192) to modify the Class 1 B and C stress indices to

conform with the equation format of the Class 2 fillet weld SIF, and to incorpo-

rate Code Case N-316, into the Code.

5.3 Related Requirements

We have examined all relevant Articles of the Code and have compareo the

contents of [1984-W84] with those of (1974-574] to determine whether any

changes, other than those discussed above, would impact the SIF calculations

or the piping stress anlaysis procedures for circumferential fillet welds.-

None were found. In particular, although revisions have been made to Par.agraph

NC-4427 "Shape and Size of Fillet Welds", the material relevant to the piping

stress analysis is fully incorporated into Fig. NC-4427-1 and note (11) of

Fig. NC-3673.2-(b)-1. That material was discussed. We therefore conclude

: that all related requirements are satisfied as required by NA-1140(f) [1974-574].l

l

!

|

|

t

|

- - -

_ . . _ _ _

. .. _ _ _ _ . _-

.

~

e

-26-.

.

6. REC 0FDIENDATIONS

,

This Section is a summary of the recommendations developed in this re-

port relative to the use of the (1983-W84] SIFs in the Stone and Vehster

piping stress analysis effort for Comanche Peak Steam Electric Station,

Units 1 and 2, as requested in Refs. 2 and 24. Recommendatidhs for each of

the three types of components that we examined are summarized below.

6.1 Branch Connections

The [1983-W84] Code involves 5 revisions potentially significant to the.

calculation of branch connection SIFs for use with the I1974-S74] piping

stress analysis basis. These are (see Figs. 4 and 5):

(1) [1977-579] when Eq. (2) was added for checking run-end moment loads.

(2) [1980-S60] when note 6(d), Fig. NC-3673.2(b)-1, Fig. 4 herein, was

revised to exempt branch pipe sizes less than 4-in. NPS from the inside cor-

ner radius requirements.

(3) (1980-5S0] when note 6(d), Fig NC-3673.2(b)-1, was added to exempt

branch connections from the outside corner radius requirement provided that

the SIFs are multiplied by an additional factor of 2.0, with a minimum value of

i = 2.1.

(4) [1980-S82] when General Note 2 was added to Fig. NC-3673.2(b)-2,

Fig. 5 herein, to redefine the midwall radius r' of the branch, subject to

'estrictions on the nozzle-wall reinforcement length, andr

(5) [1980-582] when a minor editorial correlation of no technical con-

sequence was made to note 6(c), Fig. NC-3673.2(b)-1.

All these revisions, except No. 4, have been shown to be either not

less restrive or technically justified for use with the [1974-574] design

. - .. - - . . ._. -- .

'

.. .

-27-

4

basis. As an alternate to using revision (4), which is technically in error,

we recommend that the piping branch connections be analyzed according to

[1974-574' vith revisions (1), (2), (3), and (5). Reanalyze only those

branch connections that do not meet the (1974-S74] acceptance criteria

using the later [1980-W81] criteria, i.e., the B stress index formulation

for primary loads, but without using either revision (4) or the revision (3)

penalty factor of 2.0. This procedure is justified by fatigue test data not

previously available.

6.2 Girth Butt Velds

The [1933-W84] Code involves 4 revisions potentially significant to the

calculation of girth butt weld SIFs for use with the (1974-574] piping,

stress analysis basis. These are:

(1) [1983-W84] when the restriction on mismatch 5 was dropped for piping

with nominal wall thickness t > 0.237 in, so that the SIF for girth buttn

welded joints for such pipe is i = 1.0.

(2) [1983-W84] when Eq. (5) was added for. calculating the SIF for,. girth

butt welded. Joints..in pipiog with.t is.0.237.n

(3) [1983-W84) when note (1), Fig. NC-3673.2(b)-1 was revised to permit

the use of mismatch 6 < 1/32 in for the SIF calculation if the smaller mis -~'

match is specified for construction.l

(4) [1980-S81] when a restriction on radial weld shrinkage a was added

to NB-3683.4(b) that prohibited use of the Class 1 stress indices as given

in the Code when r">jD.75 t *n

t

I

li

i

I

|E . ,. . _ _ . . . _ . . _ , _ . _ . _ __, - . _ _ _ . . _ _ _ . _ _ _ - _ _ _ _ _ . _ , . . . ___ _. _ .- . _ _._

,

.. s

-28--..

Revisions (1), (2), and (3) have been shown to be either not less

restrictive or technically justified for use with the [1974-S74 } design

basis. Revision (4), concerning radial weld shrinkage 4, was examined

because of concern that the less restrictive weld shrinkage criterion of

4/t 5 0.5 specified for construction of the Comanche Peak Class 2 and 3n

piping might adversely ef fect the stress analysis acceptance criteria. It

was determined that the Code revision applies only to Class 1 piping. It

was also determined that for Class 2 and 3 piping, radial weld shrinkage

A/t 1 0.5 need not be considered either in the functional capabilityn

evaluations or in the structural evaluations provided that the number of loading

cycles is less than 7,000. For more than 7,000 cycles, it is recommended that

the structural evaluations but not the functional capability evaluations

include consideration of radial weld shrinkage 0.25 1 a/t 10.5 oy applica-n,

tion of Eq. (7),

6.3 Circumferential Fillet Welds

The [1983-W84) Code involves 4 revisions potentially significant to the

calculationofcircumferentialfilleIweldSIFsforusewiththd[1974-S74]piping stress analysis basis. Those are:

(1) [1980-S83] when Eq. (12) written in terrrs of the fillet weld leg length

was added for calculating the SIF for circumferential fillet velded joints and

for socket welded joints.

(2) [1980-S83} when note (11), Fig. NC-3673.2(b)-1, was revised to define

C as the shorter leg length for fillet welds with unequal legs.X

(3) [1980-S83) when the reference SIF sketch was changed to Fig. NC-4427-1.

(4) [1980-S83] when Fig. NC-4427-1 was revised to include a corrected

definition for C,.

,,. . . - ,_ . - . - . - -. -. ...

. , .s,s. ..

-29-.'..

.

N

All four of these revisions have been shown to be either not less Jtrestrictive or technically justified for use with the [1974-S74] Jesign '

,

basis. It is also noted that the revisions could be justified for use -

in functional capability. evaluations. Approval by the NRC, however,s

would be needed. '-s

6.4 Related Requirements -s

We have also examined all relevant Articles of the Code and havei

determined by comparison of [1983-W84[ with (1974-S74] that no revisions,\

other than those discussed herein, would adversely impact the.use of the

subject S1Fs in the Stone and Webster, Comanche Peak, piping stress analysisNefforts. We therefore conclude that all related requirements are satisfied

3,

asrequiredbyNA-1140(f)[1\74-574].

l,' ,.

. .

s

6

O

l

'

s\'s .,

I

\

- , - _ , _ _ , , _ - _ . . . . . . . _ _ ._ _ _ _. _ _ _ - - . - - _ - _ _ , , . - _ _ _ _ _ . . _ - _ _

i w 3a.1 . Ww!

\s

yf. .

.

-30- 'q..

REFERENCES

1. ASME Boiler and Pressure Vessel Code, Section III, Div. 1, Nuclear PowerPlant Components, ASME, New York.

2. Letter, A. W. Chan, Stone and Webster Engineering Corp, to S. E. Moore,Engineering Consultant, 1983 SIFs for CSPES, Comanche Peak Steam Electric.Station, Units 1 and 2, Texas Utilities Generating r.;., J.0, Nos.15454.05 and 15616.05, CH1-CPO-389, dated August 23, 1956.

3. USAS B31.1.0-1967, "USA Standard Code for Pressure n ping, Power Piping,"ASME, New York, 1967.

4 A. R. C. Mark 1, "Fatigue Testing of Welding Elbows and Comparable Double-Mitre Bends, " Trans. ASME, Vol. 68, No. 8, 1947.,

5. A. R. C. Mark 1, "Fatigue Tests of Piping Components," Trans. ASME, Vol. 74,No. 3, 1951.

6. A. R. C. Markl. "Piping-Flexibility Analysis," Trans. ASME, February 1955.

' 7. A. R. C. Marki and H. H. Garge, "Fatigue Tests on Flanged Assemblies,"! Trans. ASME, January 1950. ,

3. E. C. Rodabaugh and H. H. George, "Effect of Internal Pressure on Flexi-) bility and Stress Intensification Factors of Carved Pipe or Velding Elbows,"' Trans. ASME, May 1957.

9. USAS B31.7-1969, "USA Standard Code for Pressure Piping, Nuclear PowerPiping," ASME, New York, 1969.

10. Private communication with W. Evans, Stone and Webster Engineering Corp.,Sept. 17, 1986.

11. E. C. Rodabaugh and S. E. Moore, "Evaluation of the Plastic Characteris-tics of Piping Pr'oducts in Relation to ASME Code Criteria," NUREG/CR-0261,

s ?3L/Sub-2913/8, Oak Ridge National Laboratory, July 1978.O.

i 12. S. E. Moore and E. C. Rodabaugh, "Background for Changes in the 1981Edition of the ASME Nuclear Power Plant Components Code for ControllingPricary Loads in Piping Systems," J. Press. 7essel Tech. , ASME Trans.104: 351-61 (November 1982).

13. "Functional Capability Criteria for Essential Hirk II Piping," NED0-21985,7SNED174, General Electric C< . , September 1978.

~

.

,

|

N' *

-

; y e, a n --m + - ~ . - - . - - - - - -

, . , - 2.n p'

.- 1X '

y

,. e' (i 1

,

,,

@ - / ,h31- 3''

,

!%, ( ,q lr ,f, j 14 USNRC Memorandum, J. P. Knight, Assistant Director for Components and'

'

| Structures Engineering, Division of Engineering to R. L.sTedesco,./ Assistant Director for Licensing, Division of Licensing,'"Evaluation of' ,-

3 Topical Report 4 Piping Functional Capability Criteria," dated July 17,/,

- ,/ >? ' 1980, s"

', ,. c

i

15. E. C. Rodabaugh, "Stress Indices for Small-Branch Connections with External /'

Loadings," ORNL/TM-3014. oar Ridge National Laboratory, August 1970., ,,

''.

,16. P. P. Bijlaard, "Stresses from Lot'al Loadings in Cylindrical Pressure .

"' Vessels," Trans. ASME, Auguat 1955.,

I

17. E. C. . Rodabaugt and S. E. Moore, "Strera Indices and Flexibtlity Factors'I for Nozzles in Pressure Mes'dels and Piping,",NUREG/CR-0778, ORNL/Sub-

2913/10, Oak Ridge National Laboratory, June 1979.,,

|\<18. . J. W. Bryson, W. G. Johnson, and B. R. Bas.N "Stresses in Reinforced c.]J Nozzle / Cylinder Attachments Under External Loadings Analyzed by the

/?initeElementMethod-AParameterStudy,'NUREG/CR-0506QRNL/NUREG-5}.Oak Ridge National Laboratory. August 1979

19. ,'J. M. Corum et al. , "Theoretical and Experimental-Stress Akalhsis of,; ' OENL Thin Shell Cylinder-to-Cylinder Model No.1," ORNL-4553, Oak Ridgei

National Laboratory, October 1972.,

20. R. C. Gwahney fet al,, "Theoretical and Experimintal Ctress Analysis cfORNL Thin-Shell Cylinder-to-Cylinder Model 3," ORN -5020, Oak RidgeNati:nal Laboratory,< June 1975.r

,

21. R. C. Gwaltney et al. f"Iheoretical and Experimental Strass d.alvsir of| ORNL Thin Shell Cylinder-to'-Cylinder Model 4," ORNL-5019, Oak'Rfdge; National Laboratory, Jury 1975. q

' '- ,

22. E. C. Rodabaugh "Accuracy of Stfess Intensification Factors for BranchConnections," Draft WRC qulletin, May W M

^

!

| ),-

I 23 .' E. C. Rodabaugh and S. E. Moore, "Stress Indices for Girth Welded Joints,Including Radial Weld Shrinkage, Mismatch, and Tapered-Wall Transitions,"NUREG/CR-0371, ORNL/Sub-3913/9, Oak Ridge Natonal Laboratory, September,

'1978.s," ;f .; ,

24 Pri.vate communication with A. J. Cokonis, Stone and Webster Engineering'

|~ .f Orp.:c.oncerning Brown and Root Pipe Fabrication and Equipment Instal-; lation Instruction No. QI-QAP-11.1-26, Rev. 19, on Nov. 18, 1996.| t, , ,,

I 25. / E. C. Rodabaugn. "Compari. son of ASME Code Fatigut Evaluation Methods'! for Nuclear Class 1 Piping with Class 2 or 3 Piping," NUREG/CR-3243,1 ORNL/Sub/82-22252/1, Oak Ridge Nation'*1 Laboratory, June 1983.'

t

'

)| -

.. .

'

-32-,

26. Minutes of Sept. 13, 1982. Working Group on Piping Design (SGD) (SCIII).ASME Boiler and Pressure Vessel Committee.

'

27. Case N-316 Alternate Rules for Fillet Veld Dimensions for SocketWelded Fittings Sect. III, Div. 1, Class 1, 2, and 3. Cases of theASME Boiler and Pressure Vessel Code, Dec. 11, 1981.

.

Y

wb

_ _ . _ _ _ _ .

>.

s*

Table 1. Comparison of run-end SIFs with stress analysis,data from Ref. 17'

,

D21 2i b

Model a ER,/T ry/R, y/T #$# max Eq. (2) Eq.(3) 22r r p

UA 50.5 0.50 0.50 0.990 4.62 l'4.35 5.46 5.33UB 40.5 0.50 0.50 0.988 4.54 12.36 4.72 5.05UC 20.5 0.50 0.50 0.976 4.09 7.75 3.00* 4.26UD 10.5 0.50 0.50 0.955 3.60 4.86 3.00* 3.60UE 5.5 0.50 0.50 0.917 3.17 3.03 3.00* 3.06*UF 5.5 0.08 0.08 0.917 3.11 2.00* 3.00* 3.06*

SIA 50.5 0.50 0.50 0.861 2.98 12.48 5.46 3.11SIB 40.5 0.50 0.50 0.843 2.87 10.54 4.72 3.00SIC 20.5 0.50 0.50 0.780 2.43 6.20 3.00 2.69SID 10.5 0.50 0.50 0.705 2.11 3.59 3.00 2.65SIE 5.5 0.50 0.50 0.623 2.07 2.06 3.00 2.65

| Sif 20.5 0.32 0.32 0.732 2.36 2.98 3.00 2.65S1G 10.5 0.32 0.32 0.649 2.23 2.00* 3.00 2.65S1H 5.5 0.32 0.32 0.563 2.08 2.00* 3.00 2.65

SII 20.5 0.16 0.16 0.646 2.49 2.00* 3.00 2.65S1J 10.5 0.16 0.16 0.555 2.38 2.00* 3.00 2,65S1K 5.5 0.16 0.16 0.468 2.33 2.00* 3.00 2.65

S1L 20.5 0.00 0.08 0.551 2.52 2.00* 3.00 2.65SIM 10.5 0.08 0.08 0.459 2.61 2.00* 3.00 2.65SIN 5.5 0.0S 0.08 0.391 2.63 2.00* 3.00 2.65

P30A 50.5 0.32 0.32 0.808 2.30 5.99 3.50 3.00P30B 20.5 0.32 0.32 0.743 2.39 3.02 3.00 2.65P30C 10.5 0.32 0.32 0.695 2.27 2.00* 3.00 2.65P30D 5.5 0.32 0.32 0.659 2.05 2.00* 3.00 2.65P30E 5.5 0.08 0.08 0 J56 2.68 2.00* 3.00- 2.65

3.00 2.65Veldolet 12.25 0.35 2.15- - -OKNL-1 49.5 0.50 0.50 0.990 5.00 14.16 5.39 5.30ORNL-3 24.5 0.115 0.84 0.870 3.20 6.25 9.06 2.70ORNL-4 24.5 0.125 0.32 0.950 4.00 2.72* 3.45* 3.57*

* is the maximum stress intensity normalized to M/Z.bValues marked with an asterisk (*) in this column are less than the

corresponding value of IT,,,.| .Z: ..

!

|

|

!

I

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ - _ _ _ - _ _ _ _ _ _ _ _ _ _ _

O. ..

'

o Table 2. Comparison of branch-end SIFs withstress analysis data from Ref. 17a

bModel R,/T r'/R, Tf/T #'/I'

21r p max

UA 50.5 0.50 0.50 0.990 16.60 14.35'UB 40.5 0.50 0.50 0.988 15.05 12.36*UC 20.5 0.50 0.50 0.976 10.85 7.75*UD 10.5 0.50 0.50 0.955 5.77 4.86*UE 5.5 0.50 0.50 0.917 3.50 3.03*UF 5.5 0.08 0.08 0.917 1.36 (2.00)

SIA 50.5 0.50 0.50 0.861 11.07 12.48S1B 40.5 0.50 0.50 0.843 9.84 10.54SIC 20.5 0.50 0.50 0.780 5.64 6.20SID 10.5 0.50 0.50 0.705 2.81 3.59SIE 5.5 0.50 0.50 0.623 1.56 2.06

S1F 20.5 0.32 0.32 0.732 2.56 2.98SIG 10.5 0.32 0.32 0.649 1.43 (2.00)S1H 5.5 0.32 0.32 0.563 1.39 (2.00)

S1I 20.5 0.16 0.16 0.646 1.22 (2.00)S1J 10.5 0.16 0.16 0.555 1.26 (2.00)S1K 5.5 0.16 0.16 0.468 1.33 (2.00)

SIL 20.5 0.08 0.08 0.551 1.22 (2.00)SIM 10.5 0.08 0.08 0.459 1.21 (2.00)SIN 5.5 0.08 0.08 0.391 1.21 (2.00)

P30A 50.5 0.32 0.32 0.808 3.73 5.99P30B 20.5 0.32 0.32 0.743 1.84 3.02P30C 10.5 0.32 0.32 0.695 1.39 (2.00)P30D 5.5 0.32 0.32 0.659 1.35 (2.00)P30E 5.5 0.08 0.08 0.556 1.20 (2.00)

aSee Table 10 of Ref. 17.b21 > 2.C from Eq. (2). An asterisk (*) indi-

cates that the calculated SIF is less than the 3'datum. Forentheses () around the number indicate!*that the calculated SIF is less than the permittedminimum.

-

-

t .

ARTICLU NC.3000 . )EstGN Fig. NC 367).2(bl.(

*e

F lo s eu.lify Secess anienget. cat.on

Dem ui.on F ac tee. k F c ioe. . s6eich

15(64,,, '/. r'm*/,h',,g , m)f gfr*

- F eg. N o.36 73.2(ul-2o eeach 3/ t 6 a nd [, 4 0.1

| \ / . ~s~ ^a, i|t n |wButt weld (11 f1.0 for fivia we'd r

4 f 1.8 for as weidedit. A 3/16 orto > 0.1

*

F eliet welded joint, socket Fig. NO.3673.2(bl 3wedded flange, or singie 1 2.1 sk.'tches (a),(bl. (c),weeded sho on fienge (el * so (Il

%. NOW3.2(bb3.Fo e f.siea wed i 1.3s ske tch (d)

NOTES:(1) The following nomenctatwee apol.es.

r o mean radeus of pepe, inches Imatch ng pioe ior sees and coowsl.t, e nomenal weil th. cham of o.oe. inches (maicheng p oe for tees and ebows. see note (91).R * bend eadews of e60ow or pipe or so. enches.# * one half angle between ediacent rmter ases,s a meter soacing at cenier I ne, enenes.

f, e te nf orced th ck ness, enches.4 * mesmatch. .r.ches.

O, e outs.de diameter, enches.

(6) The edtion aophes only of the ionoeg cond.tions are met:

(a) The re nlorcernent een reoverements of NO.3643 are met.(b) The amis of the branch pipe is normal to the martace of run poo wl.

|(c) For branch connections in a poe, the arc distence measured between the centers of ediacent branches along the surf ace of the

run pipe is not less than three times the surn of the.c inside rad i in the longitudinal direct.on or es not less than two times the7

|sum of their radie *long the circumf erence of the run pipe.

(d) The ens de cornet red us r, (F sG.NO 3673.2(bl.2)is berwan 10% and 50% of r,.(e) The outer rad.us.c ,is not less than the targer of r /2.1Te * yl/2 (FIG.NO 3673.2(bl.2 sketch (cIl or T,/2.e(f) The outer redeus . . es not less tasa the larger of

-

(tl 0.002# do(2) 2 (sen fi' teen t%e offset for the configurations shown en Figs. NO.3673.2(bl.2 sketches Ni and (bl.

(g) Mm/Tr4 50 end r% :stm 40.5.t

|t .

FIG. NC 36tl.2(b).1 FLEX (BILITY AND STRESS INTENSIFICATION FACTORSI

\ .

( Figure 1.1

l, - .| e: |||

||

|

|t

.

o e

ARTICLE NC 3000 1)ESIGN Fig. .NC 3673 21b12e

I-> b (-- T 'b ''BRANCH PIPE-* (-- * 4--Ib,

NE# hd -r ro 3 d - r3/ en 4 45' (,,*

Ns c' -,'

( -en:90'3 r

~

Yo %- OFFSET y ? - OFFSET

) %

.

.. .

Fig. NC 3673 2(b) 3 SECTION lli. DIVISION I - SUBSECTION NC.

*

SURFACE OF --[ VERTICAL MEMBERSSURFACE OF 9

'

d4 / HORIZONTAL MEMBERS \ &_\ l J 7THEORETICAL THROAT #

(Al CONVEX EQUAL LEO FlLLET WELO 18) CONCAVE EQUAL LEO FILLET WELO

NOTE: The "sire" of an equalleg finet weed es the length of me largest inscribed right nosceies triente.Theoretcal throat 0.7 x sae.

SURFACE OFVERTICAL MEMBERS

4,,

y$o SURFACE OFdb [ HORIZONTAL MEMBERS \ c- -THEORETICAL THROAT -

(CI CONVEX UNEQUAL LEG FILLET WELD (D) CONCAVE UNEQUAL LEC FILLET WELO

Note: For uneovat leg f dlet welds, the "sae** of the we4C es the leg lengths of the largest right trengtewhich can be specribed within the idlet weed cross section.

Q -+ (--X7, , -/ rX g

_s f CnA AXXAx w

i i]* Pl/16" APPROX.BEFORE WELDING

(E) SOCKET WELDING FLANGE |

r a nommal o.oe wail thicknessna m.n. * 1.4 faor th.ckness of the hwD. whichever es smaller but not less ''ian 1/8"

-t NOMINAL PIPEnW/4LL THICKNESS

X-

E

- t/16" A PPROXIM ATE'.Y -T ] J8EFORE WEL0 LNG

7\ '7

(F) SOCKET WELOING FITTING~

s men = 1.09 ta but notseis tnan Ita*

FIG. NC 3673-2(bi 3 FILLET AND SOCKET WELD DIMENSIONS (not permitted forconnections over 2 inch nominal pipe size)

,

136Figure 3.

&$l*.

-_.- ,

..

.

19tL3 Edition W84 NC4000 - DESIGN Fig. NC M73.24b).1c. .

.

F ie s .b.s.ry Suess inteasif.caic'Desce.ptu Factor a F actor , Sketch

,o, .. mne~

z..w.).Te.

'5( F T @ (t)m .,m ac - -,.ent~o,ei.n t ,o.e-s ,rwne~, ,m.un m

z - . i A. ) T.

r "(F(2)tnet not less than 1.5

Girth twet wow (Note (II) i 1.ot, t 0.2 3 7 sn.

1.9 enan. orwg4 Cirth bwit we6d (Note (1)] g o 9(1 + 34/t.)

t c 0.23 7 in. but not less than 1.0

c. f { Circurnferential helet weideo F4 NC44271 $$02. I tic 11. )" * 'd'd N"'' g ga, ice,, gg.il. (c.2)'bwt not less than 1.3 and (c.31stued point i 2.1 Fig. NC4511 1 *

.

NOTES TO FIG. NC.3673.2(bh1:W84 (1) The following nomenclature applies.

t = mean radius of pipe,in. (matching pipe for tees and elbows)t, = nominal wall thickness of pipe, en. (matching pipe for tees and elbows, see Note (9))R = tend radius of elbow or pipe bend,in.

S4. # = ondalf angle between adjacent mater axes, deg.s = miter spacing at center line,in.t, = reinforced thickness,in.

8 = everage permissible mismatch at girth butt welds as shown in Fig. NC-4 2331. A value of 8 less than '/ in. maybe used provided the smetter mismatch is specified for fabncation. For "flush" welds. as defined in Fig.NB.3683.1(cF1. 4 may be taken as rero. i = 1.0, and flush welds need not be ground.

O, = outside diameter. in.

(6) The equation applies onhr if the follownng conditions are met:(a) The reinforcement eres r.quirements of NC.3643 are met.

.

(b) The axis of the branch pipe is normal to the surf ace of run pipe wett.$43 (c) For branch connections in a pipe, the arc distance measured between the centers of ediacent branches along the surf ace

of the run pipe as not less than three times the sum of their inside rodii in the longrtudinal direction or not less thantwo times the sum of their inside radii along the circumference of the run pipe,

go (d) The ineide corner radius r, (Fig. NC.3673.2(b).2) for nominel branch pipe site greater than 4 in, shall be between10% and 50% T,. The radiue r, is not required for nominal branch pipe site smaller than 4 its.

(e) The outer redeus e is no less then the larger of T 12. (T. + vll2 (Fig. NC.3673 2(b).2 sketch (c)) or T,I2.r(f) The outer radius r,is not less than the 'erger of

(1) 0.002# cr.,

(2) 2 (sin #)* times the offset for the configurations shown in Figs NC.3673.2(bh2 sketches (a) and (b).(g) A.lT, s 50 and r'.lA. s 0.5.

N yo th) The outer radius te is not required provided en additional multipher of 2.0 is included in the equations for branch andand run end stress intensificat.on factors, in this case, the calculated value ofi for the brenets or run snail not be lesethan 2.1.

$43 (11) C,is the fillet weld length. F'or unequel leg lengths, use the smaller tog length for C,..

, Figure 4.hc ?I

'

e, a s

" 190 f.dition NC 3000 - DESIGN Fig. NC.367J.2(hi 2,

T, .+ -o, T,o,

etenen p.pee. Yf +. +T-o. c

i i r3 r3d, ~ -| , 0 , < 45 oeg. (

ag

f 'I".5(2

'g

( [ g'\N h 0,,.Soe,,.

; ' '',

T. ; .. ,. . .

7 - offui -#'' 'c ,- of f sei q

, , - - :. , ,,' ITo = t = ,,9 pp,

* ._t r'2 t rr_es 7'. &\T ( Mad| a{ a{

R, T,R Tm o

(si 2 tel 2

Branen pipe

+4 + Tf -o,. e. Tf = TeStanch pepe

o 3 xu #

rf,, To * I'b + 0.667 y 8

6,, < 4 5''

T* '| r yg pW, / '?- 8,enen2 w 6,,

N' 3'

*

\ T,yy , ,m -. ,y_

[ 'I T,p y ,f h

', ( kSs@\h " r- 'Id'h i'^

u,

Wy& h f n .2-*= G - nmIci .

2 2(4)

v. e owes 4e o.emeter os beenen poe. a CENERAL NOTES:r. * mean red ws of beench ppe en. (Il I. 8. F.. fe. to. t, e# 3 y are genned in th.s 6gwtel'. e nomenal thechness of beencM peces. A (.'l if 1, ogwass or esceeds 0 5 % r, f. then t'. can t>e toten $32A. = mean red.ws of twa poe, a as the rad.ws to the cmtet of I..f, e nom.cel tm.ctness of twa p.pe en.

FIG. NC 3673.2(b) 2 BRANCH OIMENSIONS

Fig _ure 5. 169,,7 h

'

I

e

e. - .

.

O

1983 Edition NC 4000 - FABRICATION AND INSTALLATION Hg. ACw27 3

4 , Theoret, cal inroat , Theo,ei c # ihreatSurface of venecad memtwr s ,f ace of vert.ca4 memtwe/' _*' - \ Conves fillet wetd '

S.se of wed Cortave fdiet weedsy Surf ace ofs g{_ horizontal member

{|

'-- Site of weed--.

NOTEThe sete of en eoualleg fillet meid is the leg length of the largest inscribed right isosceles triangie.Theoretical throet = 0.7 a size of wedd.

(al Eeued Leg Feltet Wold

[p g Theoretical throat

Surface of vertical member s ace of un.cW mer/r

/'s Conven f.iiei weid (g Concave fdlet weldN % 's

'. N Surface ofhorizontal member

NOTE: The s.se of an unecas leg idiet need is tne shorter leg length of the largest right triangle wnich can be inscribed S$dwithen the f llet wed cross section.

(b) Unequal Log Fillet Weld

--. - a min.* ~*T4 e a men.

7-_, a m,n,

a m.n. - , .n. a m.6.

, dhN Y :' /)hk | k\kkkM' '

1'"

<

Y\YS\\YN MhM\\\M\M fr, or % in, whichever ht or 4 in.ewharf> gr I f ! f- ois erwier is smeder - 1/16 in. aooros.-Front and Back Weed - Fase and Back Weed

(e.1) Slip-en Fiange(c.2) Socket Wetding Flange

'- '$ --C 'n nom nal p.pe#

I I west th cknese NOTE 3: a men.= 1.4i or th'ckness of the hub, dichevernis smaller but not less than 1/8 in.e

,

C 'I'*I"'***'** C, men. = 1.09r, where t, = roninas pepe wall th.eknew 5T#before vuesdeng

;

It) Menemwm Wesdeng D monseons for Slepen 48uf/

Seckee We4deng F1anges and Seeket We6deng Fsttangs

(e 3) Sectet Weedeng Fittengs

|'

(FIG. NC44271 FILLET AND SOCKET WELO DETAILS AND DIMENSIONS

Figure 6er;e 6 23I

. _ -

o

y ~o

Fig. N B.4 23 31 SECTION lit. DIVislON I - SUBSECTION NB,

w

11/2 ' - 450 M A XIMU M' ; p WAX 2AM

SLOPE /

f

/

- -= .,

1/32 in. M AXIMUM UNIF ORM Mi!M ATCH BQRE DI AMETER 11/32 in.AROUNO JOINT PIPE ( , , _,

+-t OR 1/4 in. (LESSER)+' " /// S.

I ALTERNATE F COUNTEft90REo' ' ($ NOT USED

HiCKNEss. o'-

IN.

I

j (c),j CONCENTRIC CENTERLlHES

I

1 /

|

.3/32 6n.M AXIMUM AT ANY ONE

POINT AROUND THE COMPONENT (JOINT -

!J.

(b)OFFSET CENTERLINE 5

NOTETHE COMBINED INTERN AL AND EXTERNAL TR ANSITION OF THtCKNESS SHALL NOT EXCEED AN INCLUDED ANGLE

OF 30* AT ANY POINT WITHIN 1% i OF THE LAND.

FIG. NB423$1 BUTTWELD ALIGNMENT TOLERANCES AND ACCEPTABLESLOPES FOP. UNEQUAL 1.D. AND O.D.WHEN INSIDE SURF ACE IS

,

I INACCESSIBLE FOR WELDING OR FAIRING,

Figure 7.166

7.' ej

-

- - - - - - - - - -- - - ,. ._ ,, _ _ _

__

'I,

!{.,.

79'. i. .

,

e '

- /,

.

6 -

/t = 20

40 -5 -

80

Q-

4 -

*00

S +b

0 .3 -

|t

./2

l

.

I

I_

l

!

I~i i f i

oo o.5 i.o 1. 5 2.o

6/t

FIGURE 8. OUTSIDE SURFACE AX1AL STRESSES, GIRTH BUTT WELDWITH RADIAL WELD SilRINKAGE, MOMENT LOADING.

'.#.). f

__ ___ . - __ _ - - . . . _ - . .__- . . __

. . -

s

..D..o

.

O

CANL-owG 83-4597 ETO

3 | | | 1 | g i3

EO (9). CYCLES-TO-F ALLUREE0 (9),WITH F ACTOR-OF-7 SAFETY OF 2.0 0N STRESS -, 100 -

adg 50 Sg=0- -

/ Ss = Sn %

10 -[EO. (6), CODE 2 STRESS R ANGE LIMITSG

- ~.

{ 'e FOR A106 GRADE 8 UP TO 6500F

_

E Se Sn 15 kss PER B31.15 - ,

I | I | t | t | tg

10 102 103 toe tot 106 |CYCLES

Fig. 9. Comperison of Eq. (9) with Code 2 allowable stresses forSA106 Grade B material.

-

,

'

l

l

Fq, f --