ML20133G590
| ML20133G590 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 01/31/1997 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML19310E989 | List: |
| References | |
| WCAP-13089, WCAP-13089-R04, WCAP-13089-R4, NUDOCS 9701160093 | |
| Download: ML20133G590 (136) | |
Text
{{#Wiki_filter:_ _ _ _ _ _ _ _ _ _ _- - - - - - - - - - Westinghouse Non-Proprietary Class 3 WCAP-13089
.$'.$'$ $ $ $ $ $ Revision 4 Westinghouse Series 44 i and 51 Steam. Generator-Generic Sleeving Report,. .
Laser Welded Sleeves - 1 Westinghouse Energy Systems Wasm ht $ -
"> ? 48 o ,a
l.k.. .;... . .'.-. - "
.f.s*f f, f. .g;vf;'ehc.
. - - - , .s . .. .s , , . . u, ,
5 5:. lY!.l.; lU.! , h'h. , ,,e .. . . < , h.h ,?. g , M. .%. . W z . t% , 1: ;".'ry.9 M WON Z g_ Y hf.
';.ff,.,
-l?s k, d 4 $ M
.'k,f 'f k @; a ,p .. hf Nf :
i.y.#v.n .W. . WM. . M@WW@: .B $ jb;l$e.j.hR r@ %.,
. !m l{ Wl::? :!: . @. *Il, . ;.!)h. oO.: l%.h..
;77..O :. :O '
4 4MI.MMdMif ts .
.,e.1s; 8 Y, .;. W &p$g%.'Q:%,W.
n.N. y. 4. - -
@s@a# A ..v, '.. W*..g f -
i ;l ' ga - V.1.b .. j d'I'.;h .
. .g' f.tQ
- p
- ? [/ :.. ;.t:.:; .-:.,i
. .t. F5.. .: . : +.f.. ,;~::\ WfW '( l'j:t? dl{,;.~l7, 9. ' ':
j) k. . ,.&'.,,*,&&;$,i'N.W W
- l? g.Q. ',*f E.fk":;)%_t%;:%.l:.&
- t. . l D. N ,
.r;;;? .t :wltip;p,, :n :.. w;?.t yml.'. .: .dr.x ,:, ,, ., hll;:'Y:q: .
- , c:n . y;m:. p . .t ...?
- , .', - : Y , : .
~
. t . ;
...:. .L.2 ; k. h, : ht:..-:N.fw .n.),Il,s 5 h:5il. k f..h..Y'E.h.. l h :lb,.l, N f':!.
. . ' { , , .. ' j p *$y, ks . , ,
.s T . ;., ';.7, . s . %; r..
s .L c ,' . ,ct ~ \!... ;y; .: . : l,.l.py.g . l%. ; ;;;h,: .;:
,y : e
- 7'l .. +q . i ll. . .&:? .', .2fn:$!:,l", ,: N ?.r ,'. *;: Y.
, . g*' [* ll: ':.. 'i. - )l:C, . ' :
f.;.,, .,', .,. ,:vs';!l' .; ;' 5
; i
{f} . '$ al ,n,. ..-
-:g t;);l.Q . . :..:t%. ., ':
. n. '~&,5...o '. - l}. .:l: . _ , : . 'l k;t . l, l) f.[$: ~5'b..,'.,s T' } {' 1 ( l.}:,k.;p:.., ',,- ..l. hk;,? n.,Q;'d
'::'- ,'- ..1
- b. l?, .*'s. , N..[ f:' ' .i,'.[ .*., e.'..i;' , .l') 'r..i.
f.A '[ **.**.b lI '. , '. '.'?;,?.f.+*f, . . . '. ss .,% , . R:
' ^ ' .
- s f.ll.;&; h' _*.. % ' '
..- . *s. . . . ..2. e~yrr;.'..) '.'.;t..,s..
t
.l*
i s r
.. 2 ."i&',
; .-:.:'. ,..e4 _fl * ,;'.;.[ ;T. , Q,',
4 >%..~.,%.. ..e..m *
.: vl4 '.'y)d: . y ; :: .. ..,*.z", ...s ....':.
c,y,
. ll ..* .u: i/
- r :.' :
), . ;l,' D. . ,,. c.l.,- ls, y:: .'
j ~- "' . , .y .. 3 . .
, ,. '* . r.G. *.',t..i.:', s j ";, ? . '
,'}, . f . 4,: u Q .,':.. ., .~f.Q;#:?
t .( , .4,l'f* ?') .P yil;5< : < f. .;
,, " wi ;l g .:, -
l R['-
. .-. . . , ~ .
. ,,, ., . ; . .,. & 'f , . p,' , ,. , ,;. . ' _ s".' L.s. f, f<<fllll:.r;'lu
.,.q,3;'.;llT,c,' ..y . .
.4 6;,f,. ' ._ .. ." . ." ' . . . , *^
, ' .,Tlc .{ un lG [( . g . .; , :y;. ',,l.
,Eg " y -
a<... d. ;.:t?.L ' '.*e ' .i:1.l - d..'.',-G:' *-l'..'.- * :
.i.,.3,.__._ a. '.;,. ': ,.,'s.".., .. " :-l %, . . ; :. *
. ;). .
..,...,,7 ..'. '.
v.-. ....;.'......,e..._L,e.,
. . .s , ,; ...,.l+,
f . ;,,m ;. ,t , y: g-%. ., . . . ..,. ,. E.*', ,. . ' *; "..J 3.' ' .:l. ^ ,-
.v,..: ,..
o., ,e ..,.;
; .:; q,.. , ; .
; g ;,,j . . . . . .. g y . . _ . , . . . . . ..> .' , ' . .
j :;; ! ,. .,'.-l ^. ,D. :tcs.. , ' . . ' v ,l;;.f' , ::: :...
.a a s s, - . . .
.. . _ , , ,,.,., .. ;.<v~
,'l 7, ' n.'. y v."*
p& ;
.,..s,..-
, p. .. .- , .
..,.t.
h ';:Q Q . ., . g. ..; . . c 4 . t . .::y,Y ; ; &~;. '.'.}: '.t,' ?, ):l-l ~.y . . *. t.J';%'o',;.
; ;;; :. , .: . : :'.e. ..e: .;-. ,.,. :,,, ,,p.:,,.,., , ); dr , f... .,,w
....<.,?2..*,....q.
,.a. . . . 3: n .'.g . . s. tr . [.
.f.. :;,s .- ws, y -
,s.~* _^;l .:y lsl;;. . .; :'c t,
.._: .e . * , . . . . . ' . : ?, r;;g ..: . .y ;, n. ..xg = , . A s,..r . ~; (, . .
, , ~
,..se; 4 - : ;y ..".... ;' -l ,,9n.q.: .9 .. '.:
p.. Q. . ..t.'. y.l . :.l:':.
,. r:: :. ., ,, n
*:.W'll.
.::.r*, .< ..' r .;. '..p g.- .:Qt n.e'1. p. . . . -... .. . t. ' ,.; ~: x.f tT.
s
. g : n r*> ;: ;q
= ;.:i" -;.. - ' . . . . .+
- s. , .y ,l.s . .a .
gy.1. . , .- .....y_..R., .,y ;.,') }, v; 1.y::, : , .. n.,:;,
.;l. ,., '. i, ..
.T 3 ' . . ,
..,;..'.,v.,".-- <
, , .%.:. ; r f. : ' ; ~ I-: r .i,: : - .:- . .s ',: . ',.
s '. . G. ; a . .:.,...r.,.,s q:'i s .. ,: . '
<.., .s..,y, ... :' ..c:,. ;.,:h::e ) .y, -.' ._.
"t, .. 1 ,.
~.',',:;,.,yt ,
.: ',t: *. . ; . . ,; . *$' ::I *9.,.% q*
.,; i n 1, . *. ? , .,, e ,. , ,s . :. - .., ;, t,
.v. *= _ . s . _ ; *: -, 4 ,,: ; .t ,
- o. : ;, :
- - ; {, [./.% *,
- s, : y '-
- s. . ,.;. .. g
. , .' :.~ _ .g. ;. p y S.-l\ g y,. .',3. ,
- l . ;,p's;'
t ,s . . ;
',y*:",.'..'b
- - .. ...:. ;. , s ,*'...r.,p.<.'. .'Je / = f,Y '. 5..
L; :,..
;l - in j . :*
,. r :-l ';. . , . . . . . (:....'.
K
, y.
- ?,
, ,g;, g .
J :%,:b (9 - ; _v,,;,.
.: 6
'..i,~*.'.',.'y
, . ' i'.,"p.,.*.."*,
r,,*s
~,a
. g' :,. ':.i;f' . . ' ,) ; . '.* . .% : . ; a :-
Y ...K..
.A
'."L ..: :i '.;.< . ..g.., R::
; -v;:. ;,'.:L :. . .' .;.i L ,
.' ' ,t-.,g: . * ,., .V.' *;;'i,* i:..,".'.'.%.c.'.e. ' ? ' '.l v.s .I f , . ': ,'
..l:. ': : ' ,;, 's,' , ~. . . 'c. :;. . ) . ?,. >: ip:.: :;<.~;
.r , v. -),'. ,*. i : % . :,
.c. - ;. .
-' .,'.i.. ;i, . '; '. ' ,. . _ . , .;, ' :.
*. .. . p2. :.. , . . 9.; . , . . .p
.'.M '.; : - l v: ;. . ~:: ' : *:';3, ;.^. '. 'Q ,. ' %; p .p .v, ..;. "-) .a;.-6...' {':;tM; 4 :^'.l. .;..... :.y
" . . .$);; :.;;}. . .%-}-
*l
.. . ;% . . .: . . ;' ; . V . . :n .
c s:,' 'h* .- n,'. 4^ .: .:.y. l _ .'l* %. _ \ , ' .% : - - : :9 . - e: W '. . ,. .
. :p.'. '.;G l:
* ;'- G ;e*,-' F> ~ . ' _ .
' : ,, , - '
- Ln ' ;, .;; ' *l. .t..'.Q r
... ;.'..l,, ,
_ .y.;.
+ . - -
;[;*'
a"- ': ::, L.. 'k l :.'.: s .I;l[_,' - , N;:, Ml ..' h: ^? lh,l , '
.* :: . . :. l% . h . . :.K; .': .
- ).T. ., lg*;;.:* r. :
,'Y:f: .,,, .: ; . ;: . . , :. .:* f. .:,' . .(; : .' . '
~ .y. . , ; ; . ., ;j, , , ,.., .:,.,'5,e y *':. .-',..,(: ] ':;
\* *
..e<
3's. . :- ._.,_;o-
. r-
.'._.;. . . , ' .nL...'
.s
- a. .a,: '.
;. ' i -
9.
, ..* '. ', .f. "c,, z.*w.
- F
!!: . N.Y .l.#.
.~,s_.,n. sLv, ., s,'t
; 3 _ .. . T..,l.;;; ._ - ,
;.1 . .; , > , . ., ,_
.c .[ >
n.-
,,3n. :> . ;. a;. : .::
. .' r
'.}l.hY: .$ [ h.,., . .n. :::o~:;,;. . .., '.a.lf. lh. *.I; h*'s f. ; . yf. .h ;. .,~;p :', . v .Y .& ... -. ;c,; I.a..:h. ~. , ' f. .Y.~. . :;,: .
.... ~ . .*. i .. < ..,3
. '. ' . h ;
. (. '.- ...~- %
.lV
- e. ",. ' yt. ., .U,~ , . .*.,,...,4,.s....i<..:n.* a*
-v , . . g . : g : s.,wa, 9 *+ .
- f. l ' .'.p. L * * ' i' . ..*
}* ' .: .. :^- . . ... **.. ..
- '.p 'e S...,,,,...e
.3.
.<.. y;Q. . ~..:',.,l .Y.
'?.
..u l '. .
.. . ;i i: ,' . l.*
.. . '. a;p. . .~ .., ,.*';.
f ) . . ,. . .
; .; . 5, * *.... .. .. .. >1;l :
; }; :' '1
.'.,_g..., ,
, , J. , ,...) . :*t ,.,o._ - ,
na .- p
. s, z. ....v .: ,.., .*y .:.,,.,..,, .- . .;., ,,,3, ;, .., :, .
- .. y ;; . m ..
,h: * " 'e n . :.
.,. ,,;t. . . ; . : ; s,
,.,......- .~: ..:
...'.,.'m,.,,.,.,e'.$,'
- ,.~
;",.*,'.'.,.j..,...',.
- ...-' . . c :. .....~.2,.
. '. * .*(..,':~*....
. . '.'d. . .; .;, .[y). . .;s.t':.'d,'f'.4.: . ,' ':e e_ .s. .,
.,t.,.,..
..a .
,p .
v.. > .;. ' ' .-.. .' .- .
. s
..:' ,3 j.- ' ,4: h p;....
g
?.'; .._.n.,
,,.. : :j : ' j,2. ..gsj* i ' r' ,' ' . . . , ., j.
s . '..l
- :r.' :, .T. ' . s. i , ,
....'.p.-.'&.-
u.
-e',., g. ;;. f' ..:a .'
*.,..,.l,.,.:~'.
"l$..
l, *r ,.: .v .U. F:.,~
- g : ; ... t . ..,
' . ~::.<i a,- '.y.
.. s. ? ,,
- , , .c., ~' , -l .s. . l 'l ,'. .. 's, .2.$ ;. e' -; *. .v&: ~
a
.84
; .s ;.. :.,
~-c.'*.. . - -*,':... %
. : n
/.~.
- a
- 1:
o'.".5....'l....:
.. .. 3..,
i ' g *3.f. .:' ': l*J:- : '.: -
'f.;p,f. ^ . l.k' ; * ; f lJ'i .,,7:i,W:.^;,:. *: .. .' :.,.g:, ..., * < ; V'; l
. ~
- u .,.. . - *w. pa ."
- .3. %,... .$,. ,/*.e <..
- /a ?" .,,.j>.- .%
.'.6- ) . . <.~, .h'. , .~. ,'.y .N: #$. .; -
t" #.
...*..'.:I' *[ ~. .i'.(;. . ;. . .,,.< .. .'
- c. .
' . l '. a... '
% L.- .',gA s* ? .*
- . '..'.^: l~ . , :a*., ','. ;
. 'l' ; . 'l*';:'..:,*? l
? .l '.',',' '
' '1:#
l: k ll . . i ' ,'
$ .Y.$;,$;QD l:Y.^ ? "* .b .l ' ,% .t. ,:.
0 $._ . .. :N, 5 ,..!5 4.:.*
. {,Y_. . ?f;:;s,Q; ', '.Y. . .(.
;.?: .&. . *.'..,\ '..r. '.,,. :.,._m ) .h.'h:.: .* ,, .. ._ .;;p..,.,
,s..s;; , '..- ;r .~l. .1..'. ,; '. y. .-.'y.
.r.. ..*.s
*. . . . ,. c -
.. * . . g ..:g.,s ,.;.q
.n... y ?'.y.,4 ..l': . . ;vz :: :.,;,- p. , ,; .~..a. -: , . , '$ ;. :.: . k. . . L ':*.f ' .
..' ' [..;Q. .4'[ ?" . .
p...I, j : '.,,. i ;; a. . : . t.
- .;. f. .i.."1c <. a. e
*l.f : -{r %.,fg'. \ i, . ' ::._' 'l: ;lgl: . f;, ., :< :
, ,po :y fyy,<.l. ?:l.
3;{ic,(. : D,, . af .,;; z;;;.,,,,y.es. QS,. .N }^n.. ['.;,'.;,.. -:... . l. . . .#j.' .. ,v. l. .l';. -+; . . f,.-
. Q :, . :j ,, e- - y. J.;?,.'J 9. ..' G. . , lj. .j .~,..:.
., + .,., - .
....u.
- .- . ;, c: ,i,%, . ny' u:Q .~2:c:p?v#; ::: 1' <..;v
.. c. . .
,*.:.~. .;:4 ..:.:8;p. s:: . w: . .! : .:i. : .;. +. . .,. c . . ..:. . . . .... , .N:. ':. 3- p::-
- '. . W.n.. : .::r. ..'; ..,.. ~
} ' f.. ;.*u: . ? ~ :m.'
.,.c.,( ; ; 1, ' :, *,:y M ..:.q;*'<h::;4. .L .:..;
. ; \Q* ' '.i.?.. Y :: '
. u.. ,
j ., . . - y,, .
, , ].*'l ;a l. .{.-
,'. n,.Ty c .g. ;. ...)
'. ./ .,.';;
f.r< .'.* N,.:,.'.t.
?. . *;1:3
,.4 r t..Q. f~e:
.L
;. ,, .v:ir
?.. ..9,',,.
- s. ..y ~s ... . . ,. . .f, l :s .
;Y 4t. a .7: . , p.:.a. s.. . s3. . p. ,L, .' i ;. .\ . .e. .'I~. .l. ..::.w , ". '. ., . ':%ll; '. .E'
.. ,1 u s
, . .,pn, :s . ..c 3. *- .w n .% r . .: ,
A. :.l ;:.;, . e. .. , , ., ,,.ms ,. . ',.. . 9 ;;- Q: b '.O , ' .+. fn. . ,a.$. . . ..:m.t.,y .j~l'..%.,*g 4 g ;= f;sju ** *'Q' *! f s,'...; ;,.._v f. o, & .... .,-u' .r" .v.. 4.:.'..:, g.3...v y.h.
;'.p./" ~;'& g,p# ;f,%Yf.Q:.y;^.Q.
..u... .
3 %. 3': , ..f. 9 n-e.r. %,. /;f.: .x,4': .w
. g. p p. .':y ,Y' ,g.:.: e c..,;e. fy}9... V:::.r.,.*'..;.. :
4;,, ';
. . s. v .m . .,4.n
- . - ' g v . .y;O yu, ..s?lA.;l
- Q ,n %
*9 p.,M:, '.: .:;Q. . .n. s
?:Q[py.,..p' ...,6., . l*,Q..-,4ll lb ,n',
s,
,: ;:H,.itys .. , :y.:.. %':; + c 4 ;'g.,
, 3 .a. .
p s:y; ,h .:k...< m > :. . ' ac,y
. ng?:qs_%Qv.N;y;j
- qd , :\q i
+v-,gu.~ .. . m@%.&y ,, ;u ..g ." ..-
w... m. p!. ,.::s'. .
... a n . n.
-:,>4. c : :.wyn - .e .w h..%.,.;e;Q:~!:y.. -
)r,5l,l@> V..ihv.p&.
W,c $...
.: ..$s...n,q, &,. N .b;;;.,:;,y;,.
. s:.
&p?Q c.
& 4 "y;wy:SWJh&m..a?..v;s..y , :,v. . . m. .,. , .
w%), Q&:(.
.~
- s ;
v.d, ;,6.,. .. ,
., . s.
. um . 4. o 4.<g . .g.>. ,*[%p N
,.g.'.y.p . o 3,; _ s,.n N.l.7:;U;h,
... t. 4m
- 4 1l,':$.f.;.?). . , . .
9* "1:, p.~c . .. i G.Q f
%.Mf$ &u T.M N,(@fy;W.&' W :
~
i:
- O.V.R bh g?> i - -
W, Q. *
%:hmgf!:% 1SQ .!
Rnk.%.&Q#@y%blhh@?k9 %%;..MQ:yfn;)$:; ;paq t 4. A Q:.&;.: MSW 2;yu:T% %.% n, yf? mQ G .
.;;7: Q y& ~p.g:l ; pQW h; p pg k.. .%
y
- 9h&
&g:%:% % ::c h k: !;k I: k ;(
$h,.k. .k
.hkf. .:?.htb.hh.
fh$?$ ~ .
.h%
~
9701160093 970110 .. PDR ADOCK 05000348 gc ga :: 4 /J ' d W '~ v' p PDR ,g Mg $ 4, Wg% W WM j . ir-l.l 9 C %' 4 - Q . 4., z
. g NN '
# * ~
WESTINGHOUSE NON-PROPRIETARY CLASS 3 g WCAP-13089 Revision 4 4
~
WESTINGHOUSE SERIES 44 AND 51 STEAM GENERATOR GENERIC SLEEVING REPORT LASER WELDED SLEEVES JANUARY 1997 C 1997 Westinghouse Electric Corporation
, All Rights Reserved WESTINGHOUSE ELECTRIC CORPORATION l NUCLEAR SERVICES DIVISION P.O. BOX 355 PITTSBURGH, PA 15230
ABSTRACT f Under Plant Technical Specification requirements, steam generator tubes are periodically inspected for degradation using non-destructive examination techniques. If established inspection 1 criteria are exceeded, the tube must be removed from service by plugging, or the tube must be
- brought back into compliance with the Technical Specification Criteria. Tube sleeving is one i
technique used to return the tube to an operable condition. This report summarizes a generic structural analysis of two distinct types of sleeves for Series 44 and 51 steam generators, a l tubesheet sleeve and a support plate sleeve. (A type of tubesheet sleeve in which the sleeve is elevated in the tubesheet, or " elevated tubesheet sleeve", is added in this revision.) l The analysis includes a primary stress intensity evaluation, a primary plus secondary stress range
- - evaluation, and a fatigue evaluation for mechanical and thermal conditions. Calculations are also
- performed to establish minimum wall requirements for the sleeve and a corresponding plugging I limit for tubes where sleeves have been installed.
4 i Based on the results of this analysis, the design of the laser welded tubesheet sleeve and the tube
- support plate sleeve are concluded to meet the requirements of the ASME Code. The lower l
bound, applicable plugging limit for the sleeve is 25% of the initial wall thickness. Mechanical tests were used to provide information related to sleeve joint performance. This testing was concerned with joint leak resistance and strength. Prototypical sleeve-to-tube joints were subjected to cyclic thermal and mechanical loads, simt.ating plant transients. Other joint
- test specimens were subjected to loads to the point of failure, beyond the bc
- nding loads which 1 result from normal operation and accident conditions.
a The resistance of the laser welded sleeve joint to in-service corrosion was evaluated by an accelerated primary water stress corrosion cracking (PWSCC) test. Free-span post weld heat treated joints were tested, in comparison with an Alloy 600 tube roll transition, a structure which is potentially susceptible to PWSCC. No PWSCC or other corrosion was noted on the Alloy 690 portion of the joint. The post weld heat treated joint exhibited an improvement of over 10 times, compared to the as-welded joint. The entire sleeve process, from sleeve manufacturing through installation and nondestructive I
~
examination (NDE), was detailed. The installation NDE involves eddy current test (ECT) and ultrasonic test (UT). The baseline NDE involves ECT and the inservice NDE will require alternate techniques if the inservice ECT exhibits changes from the baseline inspection. 9
TABLE OF CONTENTS Section Title Page
1.0 INTRODUCTION
1-1 1.1 Report Applicability 1-2 1.2 Sleeving Boundary 1-3 l 2.0 SLEEVE DESCRIPTION AND DESIGN 2-1 2.1 Sleeve Design Description 2-1 2.1.1 Tubesheet Sleeve 2-1 2.1.2 Tube Support Plate Sleeve 2-4 2.1.3 Sleeving of Previously Plugged Tubes 2-4
~
2.2 Sleeve Design Documentation 2-4 l 2.2.1 Weld Qualification Program 2-5 2.2.2 Weld Qualification Acceptance Criteria { 2-5 1 3.0 ANALYTICAL VERIFICATION 3-1 3.1 Structural Analysis 3-1 3.1.1 Component Description 3-1 3.1.2 Summary of Material Properties 3-2 l 3.1.3 Applicable Criteria 3-2 3.1.4 Loading Conditions Considered 3-2 3.1.5 Analysis Methodology 3-3 3.1.6 Heat Transfer Analysis 3-5 3.1.7 Tubesheet/Channelhead/Shell Evaluation 3-5 1 3.1.8 Stress Analysis 3-6 3.1.9 ASME Code Evaluation 3-7 3.1.10 Minimum Required Sleeve Wall Thickness 3-8 3.1.11 Determination of Plugging Limits 3-9 3.1.12 Application of Plugging Limits 3-10 3.1.13 Structural Analysis Conclusions 3-11 3.1.14 Effect of Tubesheet Rotations on ETS Contact Pressures 3-11 3.2 Thermal Hydraulic Analysis 3-13 3.2.1 Safety Analysis and Design Transients 3-13 , 3.2.2 Equivalent Plugging Level 3-14 3.2.3 Fluid Velocity 3-17 ' i l l ii
TABLE OF CONTENTS (continued) j ; 4 Section Title Page
- 4.0 MECHANICAL TESTS 4-1 4.1 Mechanical Test Conditions i 4-1
.4.1.1 Generic FLTS Sleeve-to-Tube Mechanical Joints and Laser Welded Joint 4-1 !
] 4.1.2 ETS Generic Lower Joints 4-2 3 4.2 Acceptance Criteria 4-2
- 4.3 Sleeve Lower Joint 4-2 l- 4.3.1 Results of Testing 4-3 j 4.3.2 Description of Additional Test Programs - HEJ Lower Joint with 4-3
- . Exceptional Conditions l l 4.4 Free Span Joint Mechanical Testing 4-4 ;
j 4.4.1 Stress Relief of Specimens 4-4
- 4.4.2 Free Span Joint Test Results 4-4
- 5.0 STRESS CORROSION TESTING OF LASER WELDED SLEEVE JOINTS 5-1 l 5.1 LWS Process and SG Design Variables '
I 5-2 5.2 Residual Stresses vs. Stress Relief Temperature in LWS Sleeve Repairs 5-2 5.3 Corrosion Test Description 5-3 s 5.4 Corrosion Resistance of Free-Span Laser Weld-Repaired Tubes - 5-4 l- As-Welded Condition j 5.5 Corrosion Resistance of Free-Span Laser Weld-Repaired Tubes - 5-5 i with Post Weld Heat Treatment ! 5.6 Corrosion Resistance of Free-Span Laser Weld-Repaired Tubes - 5-5 with Post Weld Stress Relief and Conditicm of Axial Load During Test j 5.7 Estimated . Sleeve Performance at Plant A 5-7 1 5.8 Outer Diameter Surface Condition 5-9 i i 6.0 PROCESS DESCRIPTION 6-1 l 6.1 Tube Preparation 6-1 j 6.1.1 Tube End Rolling (Contingency) 6-1 ! 6.1.2 Tube Cleaning (Optional) 6-2 3 6.2 Sleeve Insertion and Expansion 6-2 l- 6.3 Lower Joint Hard Roll (Tubesheet Sleeves) 6-3
- 6.3.1 Full Length Tubesheet Sleeves 6-3 i-6.3.2 Elevated Tubesheet Sleeves 6-4 l 6.4 General Description of Laser Weld Operation 6-4
} 6.5 Rewelding 6-4 6.6 Post-Weld Heat Treatment and Tooling 6-5
- 6.7 Lower Joint (Elevated Tubesheet Sleeves) 6-5 l 6.8 Inspection Plan 6-5 i m' "
i
TABLE OF CONTENTS (continued) Section Title Page I l 7.0 NDE INSPECTABILITY 7-1 7.1 Inspection Plan Logic 7-1 ; 7.2 General Process Overview of Ultrasonic Inspection 7-2 7.2.1 Principle of Operation and Data Processing of Ultrasonic Examination 7-2 7.2.2 Laser Weld Test Sample Results 7-3 7.2.3 Ultrasonic Inspection Equipment and Tooling 7-4 , 7.3 Eddy Current Inspection 7-4 7.3.1 Cecco-5/ Bobbin Principles of Operation 7-4 7.4 Alternate Post Installation Acceptance Methods 7-5 7.4.1 Bounding Inspections 7-6 7.4.2 Workmanship Samples 7-6 ! 7.4.3 Other Advanced Examination Techniques 7-6 7.5 Inservice Inspection Plan for Sleeved Tubes 7-6 ' 1 i l l e l l iV l
. -.- . - - , . . . . - . - - - . - _ . ~ - - - - - - - . . - - . - .
i j @- , 4 l LIST OF TABLES * } Table Title Page 2-1 ASME Code arid Regulatory Requirements 2-6 i j 3-1 Summary of Material Properties - Tube Material - Mill Annealed Alloy 600 3-18 l 1 ! 3-2 Summary of Material Properties - Sleeve Material - 3-19 l
- Thermally Treated Alloy 690 l
j 3-3 Summary of Material Properties - Tubesheet Material - SA-508 Class 2 3-20 4 i-3-4 Summary of Material Properties - Channelhead Material - 3-21 ) SA-216 Grade WCC i j 3-5 Summary of Material Properties - Cylinder Shell Material - 3-21 SA-533 Grade A Class 1 " i 4 i 3-6 Summary of Material Properties Air 3-22 4 3-7 Summary of Material Properties Water 3-22 1 3-8 Criteria for Primary Stress Intensity Evaluation (Sleeve) - Alloy 690 3-23 , 1 3-9 Criteria for Primary Stress Intensity Evaluation (Tube) - Alloy 600 3-23
- i. 3-10 Criteria for Primary Plus Secondary Stress Intensity Evaluation 3-24 Sleeve Alloy 690 1
l 3-11 Criteria for Primary Plus Secondary Stress Intensity Evaluation 3-24 { Tube - Alloy 600 Sleeve 1 3-12 Sununary of Transient Events 3-25 j 3-13 Umbrella Pressure Loads for Design, Faulted, and Test Conditions 3-26 }, 3-14 Summary of Maximum Primary Stress Intensity Full Length Tubesheet 3-27 Laser Welded Sleeve - Sleeve / rube Weld Width of [ ]** e j~ 3-15 Summary of Maximum Primary Stress Intensity Full Length Tubesheet 3-28
- Laser Welded Sleeve - Sleeve / Tube Weld Width of [ ]**
1 i 3-16 Maximum Range of Stress Intensity and Fatigue Full Length Tubesheet 3-29 j Laser Welded Sleeve - Sleeve / Tube Weld Width of [ ] - j Tube Severed and Dented 1 l V 4
.- . - . ...- - .-.- - . . - - . - . - . - . . - . - - . - ~ . . - l LIST OF TABLES (continued) - Table Tith Page 3-17 Generic Tube Sleeving Calculations - Flow Reduction and 3-30 Hydraulic Equivalency for Series 44 SGs 3-18 Generic Tube Sleeving Calculations - Flow Reduction and 3-31 Hydraulic Equivalency for Series 51 SGs 4-1 Mechanical Test Program Summary 4-5 4-2 Typical Bounding Maximum Allowable Leak Rates for Series 44 and 51 4-6 Steam Generators . 4-3 Verification of Test Results for As-Rolled Lower Joints 4-7 4-4 Test Results for Lower Joints with Exceptional Conditions for 4-10 Tube and Sleeve 4-5 Additional Tests Results for Lower hints with Exceptional 4-11 Conditions for Tube and Sleeve 4-6 Free Span Joint Maximum Stress Relief Temperature 4-12 4-7 Free Span Joint Leak Rate and Loading Data 4-13 5-1 Summary ofImpact of Laser Welded Sleeve Operations on Stresses 5-10. ; 5-2 Far-field Stress as a Function of Stress Relief Temperature 5-11 5-3 Results of 750*F Doped Steam Tests for Nd:YAG Laser 5-12 Weld-Repaired Mockups l 5-4 Doped Steam Corrosion Test Results for 3/4 inch Tube-Sleeve 5-13 Mockups - Tested Without Axial Load 5-5 Summary of Temperatures, Stresses and Corrosion Test Results for 5-14 7/8 inch Sleeve Mockups - Tested with Applied Axial Load - 6-1 Sleeve Process Sequence Summary 6-6 _ vi
(
.. - - . .- - -..- - . . . - . - . - -- - . - - . - . . . ~ . . . - . - . . . . ~ . .
j 1 l LIST OF FIGURES i i Figure Title Page 2-1 Full Length Tubesheet Sleeve - Laser Welded - Installed Configuration 2-7 2-2 Elevated Tubesheet Sleeve - Laser Welded - Installed Configuration 2-8 2-3 Tube Support Plate Sleeve - Laser Welded - Installed Configuration 2-9 3-1 Schematic of Full Length Tubesheet Sleeve ConfiEuration 3-32 i 3-2 Channelhead / Tubesheet / Shell Model 3-33 . 1
~
3-3 Thermal / Hydraulic Boundary Conditions - Tubesheet Sleeve Analysis 3-34 3-4 Channelhead/Tubesheet/Shell Model - Primary Pressure 3-35 Boundary Conditions 3-5 Channelhead / Tubesheet / Shell Model - 3-36 Distorted Geometry Primary Pressure Loading 3-6 Channelhead / Tubesheet / Shell Model - 3-37 Channelhead Thermal Boundary Conditions 3-7 Channelhead / Tubesheet / Shell Model - 3-38 Distorted Geometry Channelhead Thermal Loading 3-8 Boundary Condition for Unit Primary Pressure - Intact Tube: P ru > Psse 3-39 3-9 Boundary Condition for Unit Primary Pressure - Intact Tube: Ppu < Psse 3-40 3-10 Boundary Condition for Unit Primary Pressure - Severed Tube: Peu > Psse 3-41 3-11 Boundary Condition for Unit Primary Pressure - Severed Tube: Ppu < P ste 3-42 3-12 Boundary Condition for Unit Secondary Pressure - Intact Tube: P,u > Pste 3-43 3-13 Boundary Condition for Unit Secondary Pressure - Intact Tabe: Peu < Pste 3-44 3-14 Boundary Condition for Unit Secondary Pressure - Severed Tube: P,u > Psge 3-45 3-15 Boundary Condition for Unit Secondary Pressure - Severed Tube: Peu < Ps3e 3-46 3-16 ASN Location - LWJ 3-47 vii
LIST OF FIGURES (continued) Figure- Title ' l Page i 3-17 Finite Element Model of Channelhead/Tubesheet/ Stub Barrel of 3-48 ) Series 51 S/G 3-18 Contact Pressures for Normal Conditions With an Intact Tube 3-49 3-19 Contact Pressures for Normal Conditions With a Separated Tube 3-50 i 3-20 Contact Pressures for Faulted Condition With an Intact or Separated Tube 3-51 l 3-21 Hydraulic Equivalency Number for Series 44 Steam Generators 3-52 3-22 . Hydraulic Equivalency Number for Series 51 Steam Generators 3-53 l 4-1 Full Length Tubesheet Sleeve Lower Joint Test Specimen 4-14 1 4-2 Free-Span Laser Welded Joint Test Specimen 4-15 5-1 Corrosion Test Specimen for Doped Steam Testing of a LWS Joint 5-15 5-2 Test Stand used to Fabricate 7/8 inch OD Tube /LWS Mockups 5-16 Under Locked Tube Conditions 5-3 Schematic of Test Assembly used for Doped Steam Testing of 5-17 Tube /LWS Mockups under Conditions of Applied Axial Loading 5-4 'IGSCC in Alloy 600 Tube of YAG Laser Welded Sleeve Joint After 5-18 109 Hours in 750*F Accelerated Steam Corrosion Test 6-1 Full Length Tubesheet Sleeve With Reweld 6-7 7-1 Ultrasonic Inspection of Welded Sleeve Joint 7-8 7-2 Typical Digitized UT Waveform 7-9 7-3 A, B, C and Combined C-Scan Display for Weld in UT Calibration Standard 7-10 7-4 UT Calibration Standard 7-11 7-5 Cecco-5 Sleeve Calibration Standard 7-12 7-6 Strip Chart Display for Cecco/ Bobbin Data 7-13 viii
4 ). LIST OF FIGURES (continued) Figure Title < Page 3 7-7 Response of Cecco-5 Probe to 60% OD Axial Notch in 7-14
- j. Parent Tube Located at Expansion Transition 7-8 Response of Cecco-5 Probe to 60% OD Circurnferential Notch in
" 7-15 Parent Tube Located at Expansion Transition i. 5 l l 2 I l 4 f e 4 f l l-b i' 5 1 2 4 iX l
- l 1
_. __ . - ~ _ . _- _ _ ._ -- __- . . _ . - _ . _ . - .-- .. _- .. - . ._ _ l NOMENCLATURE i ACRONYM TITLE AILL Accident-Induced Leakage Limit ARC Alternative Repair Criteria CP Contact Pressure dpm Drops per Minute l ETS Elevated Tubesheet Sleeve l FLB Feed Line Break FLTS Full Length Tubesheet Sleeve ' FNP Farley Nuclear Plant L' (A variation of ARC)
- MIF Mechanical Interference Fit No.P. Normal Operation OSL Onset of Significant Leakage RT Room Temperature i
SG Steam Generator ' SLB Steam Line Break TSS Tube Support plate Sleeve l l l I X l
i
1.0 INTRODUCTION
Under Plant Technical Specification requirements, steam generator tubes are periodically inspected for degradation using non-destructive examination techniques. If establishedinspection criteria are exceeded, the tube must be removed from service by plugging or the tube must be brought back into compliance with the Technical Specification Criteria. Tube sleeving is one technique used to return the tube to an operable condition. Tube sleeving is a process in which a smaller diameter tube or sleeve is positioned to span the area of degradation. It is subsequently secured to the tube, forming a new pressure boundary and structural element in the portion between the attachment points. This report presents the technical bases developed to support licensing of the laser welded sleeve installation process for use in steam generators with 7/8 inch diameter tubes. Sleeves for two different regions of the tubes are addressed, namely tubesheet sleeves and tube support plate sleeves. Each of these sleeve types has several installation options which can be applied. There are two types of tubesheet sleeves. The first one extends the full length of the tube within the tubesheet, is joined to the tube in the vicinity of the tubesheet bottom and is referred to as the full length tubesheet sleeve (FLTS). The other type extends over approximately j one-third of the tube length within the tubesheet, is joined to the tube approximately 15 inches above the tubesheet bottom and is referred to as the elevated tubesheet sleeve (ETS). The latter type of sleeve allows much greater radial coverage of the bundle, i.e., installation closer to the bundle periphery, than the FLTS. The FLTS is appropriate for all plants which have degradation at the top of the tubesheet, and/or within the tubesheet above the lower joint because the lower joint is formed at the bottom of the tubesheet. Depending on the length of the FLTS and l elevation of the lowest baffle / support plate in the bundle, this sleeve may also address degradation above the tubesheet. The ETS is appropriate for all plants with SG tubes which have degradation at the top of the tubesheet, and/or within a distance of several inches below the top of the tubesheet. Depending on the length of the ETS and elevation of the lowest baffle / support plate ir. the bundle, this sleeve may also address degradation above the tubesheet. The tube support plate sleeve (TSS) may be installed to bridge degradation located at tube support plate locations or in the free span section of the tube. Installation and inspection options will be selected in advarice of performing the field campaign. This determination will be made based on degradation history, current degradation rates, utility steam generator maintenance strategy, schedule, and cost. Thus, the application can be optimized , to utility needs by applying the proper combination of' modular' sleeve-tube joint options. This technical basis for laser welded sleeves is applicable to plants with Series 44 and 51 steam generators. However, changes in plant operating parameters can occur as a result of system or operating modifications. Therefore, prior to installation of laser welded sleeves at any plant with Series 44 or 51 steam generators, a supplementary plant specific review of the applicable 1-1 . 1 l l
operating parameters at the time of sleeve installation, relative to the design basis parameters, will be performed. This review will be documented in a separate report, and the two reports will form the plant specific design basis for the laser welded sleeves. 1.1 Report Applicability This report is applicable to Westinghouse Series 44 and 51 steam generators. These steam generators are U-tube heat exchangers with mill annealed Alloy 600 heat transfer tubes which have a 0.875 inch nominal outside diameter (OD) and 0.050 inch nominal wall thickness. Data are presented to support the application of the two sleeve designs: tubesheet and tube I support plate. Moreover, with each design, several utility-selectable application options are - provided. The sleeve sizes and options are: Tube support olate sleeve
- 12 inches long welding with post weld heat treatment Tubesheet sleeves Full Length:
- 27 to 36 inches long [ ]6 straight or bowed (enhanced for peripheral coverage) weld joint with post weld heat treatment Elevated:
- 12 to 36 inches long
- weld joint with post weld heat treatment The sleeves described herein have been designed, analyzed, and/or tested to meet the service requirements of the Series 44 and 51 steam generators through the use of conservative and enveloping thermal boundary conditions and structural loadings. The structural analysis and mechanical performance of the sleeves are based on installation in the hot leg of the steam generator. [
]* All of the FLTS, TSS and ETS upperjoints and the FLTS mechanical interference fit (MIF) lowerjoints have been qualified -
previously and are in use. The ETS generic MIF lower joint is very similar to the FLTS lower joint; a minor confirmatory qualification will be performed to verify this application at an . appropriate point in the sleeving program. If a site specific MIF lower joint already exists for the ETS, that qualification will be included in the site specific WCAP and no additional work is required. 1-2
l l @ l 1.2 Sleeving Boundary Tubes to be sleeved will be selected by radial location, tooling access (due to channelhead geometric constraints), sleeve length, and eddy current analysis of the extent and location of the , degradation.
- The boundary is determined by the amount of clearance below a given tube, as well as tooling and robot delivery system constraints. At the time of application, the exact sleeving boundary will be developed. Owing to the constant development of tooling, designs and processes, essentially 100 percent coverage of the tubesheet map, for tubesheet and tube support plate j sleeves, is expected.
l. 1 l I l l I l i l l 9 1 ) 4 5 I l-3
2.0 SLEEVE DESCRIPTION AND DESIGN 2.1 Sleeve Design Description Tube sleeves can effectively restore a degraded tube to a condition consistent with the design requirements of the tube. The design of the sleeve and sleeving process is predicated on the l design rules of Section III, Subsection NB of the ASME B&PV Code. Also, the sleeve design l addresses dimensional constraints imposed by the tube inside diameter and installation tooling. These constraints include variations in tube wall thickness, tube ovality, tube inside diameter, tu've to tube sheet joint variations and runout / concentricity variations. The sleeve material, thermally treated Alloy 690, was selected to provide additional resistance to stress corrosion l cracking. 2.1.1 Tubesheet Sleeve i 2.1.1.1 Full Length Tubesheet Sleeve The reference design of the tubesheet sleeve, as installed, is illustrated on Figure 2-1. At the upper end, the sleeve configuration consists of a section which is hydraulically expanded. The hydraulic expansion of the upper joint brings the sleeve into contact with the parent tube to achieve the proper fitup geometry for welding. Following the hydraulic expansion, an autogenous weld is made between the sleeve and the tube using the laser welding process. This joint configuration is known as a laser welded joint (LWJ) and it occurs in the free spvi, i.e., above the tubesheet. The full length tubesheet sleeve (FLTS) extends from the tubesheet primary face to the free span, i.e., above the top of the tubesheet (TfS). The tube degradation may be anywhere between the inboard extent of the "soparation distances" of the respective upper and lower joints. (The separation distance is an axiallength of tube which separates the main structural part of a sleeve joint, such as the " inboard-most" weld for the upper joint of an FLTS, from the extreme extent of the degradation which caused the tube to be repaired by sleeving.) For the FLTS and all other types of laser weld sleeves, assessment of the extreme extent of the degradation will be performed with the NDE process, essentially ECT, appropriate to the type of degradation expected and/or known to exist based on previous inspections. The ECT process will be consistent with meeting an appropriate uncertainty in elevation of the degradation extreme extent.
, If the uncertainty in elevation for a particular ECT process exceeds this value, appropriate changes will be made in the separation distances during the preparation phase of the outage. In ~
order to optimize the sleeve length and allow for axial tolerance in locating degradation by eddy current inspection, the inboard-most weld, i.e., either the initial weld or the reweld at the specified lower elevation, must be separated from the extreme extent of the degradation by a [ yu 2-1
{ j
.y >
The upperjoint is designed to provide [ <
.l y.e..
At the lower end, the sleeve configuration consists of a section which is [ l p.<,. l The separation distance for degradation in the vicinity of, and above, the roll expansion portion of the FLTS MIF lower joint is determined similarly' to that of the upper joint. In this case, the uppermost extent of the effective axial length (EAL) of the roll expansion, based on a study of' the sleeve and tube component and installation axial dimensions and roll expansion installation tolerances, must be a minimum of the uncertainty in elevation per ECT (ECTU) " outboard" of. .j the degradation lowermost extent of the tube degradation. Within the tubesheet, as in the free
- span, the separation distance between degradation and the EAL of the roll expansion portion of the MIF joint is based on avoiding locating the roll expansion portion of the joint in a portion ;
of degraded tube. [ l
]* No attenuation length is necessary within the tubesheet. [
y.e , 2.1.1.2 Elevated Tubesheet Sleeve The sleeve elevated in the tubesheet, or " elevated tubesheet sleeve" (ETS) is illustrated in Figure 2-2. It is applicable to steam generators in which the tubes were installed in the tubesheet by a - full-depth expansion. The ETS upper joint is identical to other free span joints, i.e., the upper joint of the FLTS and the TSS The ETS lowerjoint is fabricated by the same types fo processes which are used to fabricate the FLTS lower joints, i.e., hydraulic expansion and roll expansion. The preferred approach to design of the lower joint is direct fabrication on the tube with no preparatory roll expansion. Based on the qualification of MIFjoints in explosive expanded tubes and hydraulic expanded tubes for other tube sizes and for multiple-roll-pass joints for a 7/8 inch tube design, it is expected that a single-roll-pass MIF joint will be readily qualified for the 2-2 .1
__.. .. _....__._...__.____.______.._..____.._.m.____.. ____. ~ generic Series 44/51 steam generator application by direct fabrication on the tube. The ETS is similar to the FLTS in that it is designed to address tube degradation in the tube free span and in the vicinity of the tubesheet top. However, unlike the FLTS,it is limited to these applications and is not designed to address degradation in the remainder of the tube within the tubesheet. 1 [ { i j ; a-i !- I f )..c.. As in the case of the FLTS free span joint, the ETS inboard-most weld, i.e., either the weld at j the initial elevatien or the reweld at the specified lower elevation, must be separated from the j extreme extent of the degradation by a [ i
)a.c.e ' j The separation distance for degradation in the vicinity of, and above. the ETS MIF lower joint '
4 roll is determined the same way as it is determined for the FLTS MIF lowerjoint. As discussed j for the FLTS, the ECT process used to determine the extreme extent of degradation will be - -,
- appropriate for the type of degradation expected and it will meet the required uncertainty in l elevation of the degradation. [
t i. ] )c 2 i The separation distance for degradation in the vicinity of, and below. the ETS MIF lower joint
.is determined similarly to that for the FLTS MIF lower joint. The lowermost extent of the EAL of the roll expansion portion of ETS MIF lowerjoints, based on the appropriate sleeve, tube and tubesheet component dimensions and sleeve and tube installation tolerances, must also be separated from the uppermost extent of degradation below the joint by the ECTU. [ .h j ..
2-3
p 2.1.2 Tube Support Plate Sleeve The tube support plate sleeve (TSS) is shown in Figure 2-3. Each end of the sleeve has a hydraulic expansion region within which the weld is placed. The weld configuration is the same for both upper and lower joints and is the same as the upper weld in the tubesheet sleeves.' Tube support plate sleeves are qualified for the second-from-highest support plate elevation through the lowest elevation for both series of steam generators. (Qualification of the sleeve at the top support plate would require a structural evaluation and modifications to the tooling. The primary side hydraulic equivalency and flow reduction calculations have already been made for support
- " plate sleeves at all elevations for both series of steam generators and are reported in Section 3.)
[ -
]*
l As in the case of the FLTS and ETS free span joint, the TSS inboard-most weld, i.e., either the weld at the initial elevation or the reweld at the specified different elevation, must be separated from the extreme extent of the degradation by a [
] The upper and lower joints of the TSS are identical.
- 2.1.3 Sleeving of Previously Plugged Tubes Previously plugged tubes must meet the same requirements as sleeving candidates as never-plugged, active tubes. An example of this requirement is that the separation distance between the extreme extent of degradation and the bounding elevation of sleeve welds, [ ],is the same in both cases. Another example is that the tube deplugging process performed by Westinghouse as part of the sleeving process is designed to leave the tube in a condition to be returned to service unsleeved, excluding the degradation which caused the tube to be plugged in the first place. The deplugging process is dwigned to leave the tube-to-tubesheet weld and tube portion adjacent to the weld in a condition to perform the pressure boundary function without any added integrity from, for example, the sleeve-to-tube lower joint of an FLTS.
2.2 Sleeve Design Documentation The sleeves are designed and analyzed according to the 1986 edition of Section III of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, as well as applicable United States Nuclear Regulatory Commission (USNRC) Regulatory Guides. The associated materials and processes also meet the rules of the ASME Boiler and Pressure Vessel Code, Specific documents applicable to this program are listed in Table 2-1.
- 2-4
i 2.2.1 Weld Qualification Program The laser welding process used to install [ ]" nominal OD sleeves into 0.875 inch nominal OD tubes was qualified per the guidelines of the ASME Code which specify the ! generation of a procedure qualification record and welding procedure specification. ) , Specific welding processes were generated for: Sleeve weld joints made outside of the tubesheet Sleeve weld joints made outside of the tubesheet with thermal treatment Repair or rewelding of sleeve joints
- i. These processes address the weld joints necessary for installation of the tubesheet and support
; plate types of sleeves discussed earlier. . Representative field processes are used to assemble the specimens to provide similitude between the specimens and the actual installed welds. The laser welded joints are representative in length and diametral expansion of the hydraulic expansion zone of the free span joints. The sleeve and tube materials are consistent with the materials and dimensional conditions representative of the l field application. Essential welding variables, defined in ASME Code Section IX, Code Case N-l 395 and Section XI, IWB-4300, are used to develop the weld process. [
3 .u The documentation specified by ASME Section XI (sleeving codes '89 Addenda) may be l provided at any reasonable time before the actual sleeving job. This weld qualification . documentation is typically submitted to the customer no later than the date of submission of the j field procedures. 1 2.2.2 Weld Qualification Acceptance Criteria ! , For the qualification of the process, the acceptance criteria specify that the welds shall be free j of cracks and lack of fusion and meet design requirements for weld throat and minimum leakage path. The welds shall meet the liquid penetrant test requirements of NB-3530. . J 4 j 4 4 2-5
~ _ . _ . _ . . . __ _ _ . . _ . _ . _ _ - . _ . _ . - . . - _ . ._ _ ._ _ _ _._. _ ._ _ _ . . _ . _ . _ . _ _ . _ _
l Table 2-1 J i ASME CODE AND REGULATORY REQUIREMENTS Ilgm Aeolicable Criteria Reauirement ! Sleeve design i Section III NB-3000, Design Operating Requirements Analysis Conditions Reg. Guide 1.83 SG Tubing Inspectability - Reg. Guide 1.121 Plugging Margin , Sleeve Material Section II M.aterial Composition Section III NB-2000, Identification, Tests and Examinations j Code Case N-20 Mechanical Properties l Sleeve MIF Joints 10CFR100 Predicted Steam Line Break Leak Rate { Technical Specifications Operating Primary-to-and administrative rules Secondary Leak Rate t L l Sleeve Weld Joints Section IX Weld Qualification i l l Code Case N-395 Laser Welding Essential Variables, . i Section IX Procedure Qualification Record, [ Section XI Sleeving Procedure Specification, Certified Design Report, etc. e 2-6
i l W* I w a,c.e iJ i l l . 1 i l l l l l 1 i 9 L -s Figure 2-1 Full Length Tubesbeet Sleeve - Laser Welded - Installed Configuration i i 2-7 i
i
- a.C,e I
r 4 i t i a 1 j l l 1 1 Figure 2 2 Elevated Tubesbeet Sleeve (ETS) - Laser Welded Installed Configuration 2-8
l l l l , a,c.e l 1 . 4 1 i E N r 4 t r j i l
<'m.
..=.m...
Figure 2-3 Tube Support Plate Sleeve (TSS) Laser Welded Sleeve Installed Configuration 2-9
- 3.0 ANALYTICAL VERIFICATION
- This section of the report provides the analytical justification for the laser welded sleeves.
j Section 3.1 deals with the structural justification and Section 3.2 provides the thermal / hydraulic justification. 1 1 3.1 Structural Analysis Section 3.1 summarizes the structural analysis of the laser welded full length tubesheet sleeve, 4 elevated tubesheet sleeve, and tube support plate sleeve for plants with Series 44 and 51 steam generators. The loading conditions considered in the analysis represent an umbrella set of conditions based on the applicable design specifications, and are defined in Reference 8.1. The ' analysis includes finite element model development, a heat transfer and thermal stress evaluation, a primary stress intensity evaluation, a primary plus secondary stress range evaluation, and a fatigue evaluation for mechanical and thermal conditions. Calculations are also performed to i ' establish minimum wall requirements for the sleeve and to estimate the change in l sleeve / tube /tubesheet contact pressures at the lower joint of the elevated tubesheet sleeve. 3.1.1 Component Descriptions l 1 3.1.1.1 Full Length Tubesheet Sleeve l i t The design of the full length tubesheet sleeve (FLTS), as installed, is illustrated in Figure 2-1. [ ).e
- i i
At the lower tube / sleeve interface, the sleeve configuration consists of a section [
)
i At the upper end of the sleeve, the sleeve consists of a section that [ I
) .. A schematic of the tube / sleeve interfaces and the various [ ] is provided i in Figure 3-1. l 3.1.1.2 Elevated Tubesheet Sleeve i The instalied elevated tubesheet sleeve (ETS) is illustrated in Figure 2-2, and extends from a nominal [
l i 3-1
. _ _ _ . _ _ . _ . . _ _ _ _ _ = _ _ _ _ = _ - _ _ . . _ . _ _ - _ _ _ . . . _
d-
- 3.1.1.3 Tube Support Plate Sleeve 4 ,
j The installed configuration of the tube support plate sleeve (TSS) is shown in Figure 2-3. The sleeve is 12 inches long, and is ( l' 4 Ja.c 3.1.2 Summary of Material Properties , The material of construction for the tubing in Westinghouse Series 44 and 51 steam generators -! j is a nickel base alloy, Alloy 600 in a mill annealed (MA) condition. The sleeve material is also }. a nickel base alloy, thermally treated (TT) Alloy 690, which meets the strength requirements of - l- Reference 8.2. Summaries of the applicable mechanical, thermal, and strength properties for the j tube and sleeve materials used in this evaluation are provided in Tables 3-1 and 3-2, for Alloy i 600 and 690, respectively. The weld is evaluated at the lower strength properties of Alloy 600 in Table 3-1. The fatigue curves used in the evaluation of the sleeve, tube, and laser weld are the ASME Code fatigue design curves for and nickel-chromium-iron (Alloys 600 and 690) given in Figures I-9.2.1 and I-9.2.2 of Appendix I of Reference 8.2. The sleeve evaluation also includes the influence of the tubesheet, channelhead, and cylinder shell, which are constructed of SA-508 Class 2, SA-216 Grade WCC, and SA-533 Grade A Class 1 steels, respectively. A summary of the applicable mechanical and thermal properties for these materials is provided in Tables 3-3 to 3-5. Thermal properties for air and water, used in
' performing the heat transfer analysis, are provided in Tables 3-6 and 3-7, respectively.
3.1.3 Applicable Criteria. The applicable criteria for evaluating the sleeves is defined in the ASME Code, Section III, Subsection NB,1986 Edition (Reference 8.2). The welded sections, between the Alloy 690 sleeve and the Alloy 600 tube, are included in the analysis and are conservatively evaluated to the ASME Code criteria assuming the lower strength properties of Alloy 600. In establishing l minimum sleeve wall requirements for. plugging limits, Regulatory Guide 1.121 for tubes, Reference 8.3, is used. A summary of the applicable ASME Code stress and fatigue limits for j the sleeve and tube are summarized in Tables 3-8 through 3-11. i 3.1.4 Loading Conditions Considered The loadings considered in the structural analysis are defined in Reference 8.1 and represent an '
-i umbrella or bounding set of conditions for the evaluation of laser welded sleeves for plants equipped with Series 44 and 51 steam generators. The applicable temperatures and pressures are based on recent design specifications for modified steam generators. The analysis considers a full duty cycle of events that includes design, normal, upset, faulted, and test conditions. No conditions are listed as " emergency conditions" in Reference 8.1. A summary of the applicable l 3-2
l 1 transient conditions is provided in Table 3-12. This duty cycle considers all specified relevant
- transients for a 40 year fatigue design life. Umbrella pressure loads for design, faulted, and test
- conditions are summarized in Table 3-13.
- 3.1.5 Analysis Methodology i
i The analysis of the laser welded sleeve designs utilizes both conventional and finite element ) analysis techniques. Several finite element models are used for the analysis. For the full length 1 tubesheet sleeve analysis, [ i l j- 1 1
]" Typically, the tubesheet sleeve model incorporates a [
}" in the tubesheet.
For Series 44 and 51 steam generators, the type and extent [ i 1 a.c is considered in this analysis. The tolerances used in developing the sleeve models are such that [ ju The results for the upper joint for the full length tubesheet sleeve are concluded to apply conservatively to the elevated tubesheet sleeve and the tube support plate sleeve. This is based on the temperature and pressure loads for the full length tubesheet sleeve for all transient conditions being greater than or equal to those for the elevated tubesheet and tube support plate sleeves and the tube-sleeve attenuation lengths. The upper joints of all three laser welded sleeves (FLTS, ETS, TSS) are essentially the same as described above for the FLTS in Section 3.1.1.1. The attenuation lengths (given by the well known parameter 4.9(rt)"*, where r = mean radius and t = nominal wall thickness, Reference 8.5) for the sleeve and tube are relatively small, on the
)
order of 0.6 and 0.7 inch, respectively. Structural effects from the laser weld are fully attenuated over these distances, isolating the welded joints in all three sleeve designs. Therefore, only the FLTS, which is typical and limiting of all of the sleeves, needs to be modeled and evaluated. Figure 3-1 shows a schematic of the FLTS sleeve configuration that was simulated in the finite element model of the sleeve, tube, and tubesheet ligament. Note that the FLTS finite element
, model was developed and executed for [ ]" hydraulically expanded upper joint region, compared to the [ ]" long hydraulically expanded region in the current " sleeves. Again, based on the telatively small attenuation lengths, there would be essentially no difference in the structural response, since the upper welds are isolated. Therefore, the structural I evaluation of the FLTS, based on stress models with [ ]" hydraulically expanded regions, also applies to the three current sleeves with [ ]" hydraulically expanded regions.
3-3
l l The lower joint for the tubesheet sleeve is [ i s.C The analysis considers both [
]" The analysis also considers [
]"
The nominal width (interfacial axial extent) of the laser weld joining the tube and sleeve for all joints is [ ]" However, qualification tests for the weld process have shown that the welds may be as small as [ ]" Thus,in performing this analysis, weld widths of both [ ]" and [ ]" were considered. The stress and fatigue results reported later in the report are for the limiting weld geometry, or the [ ]" width. -l In addition to the sleeve models, a separate model of the tubesheet, channelhead, and lower shell , was developed and used to calculate tubesheet rotations under combined pressure and temperature ! loadings. Resulting loads imposed on the sleeve as a result of the tubesheet rc,tations are applied ; to the sleeve model in the form of radial pressures on the model outer boundary. i For both the sleeve model and the tubesheet, channelhead, and shell model, separate models were - developed for the Series 44 and 51 geometries. Separate calculations were then run for the two sets of models. A plot of the tubesheet, channelhead, and shell model for the Series 51 steam ' generators is shown in Figure 3-2. Results from these and previous sleeve analyses have identified regions in the tube / sleeve assembly that are most critical and have also quantified the effects of various potential f considerations (such as tubesheet rotation, tube separation etc.) that could influence the stresses in various regions. It has been determined that the [
]'
- As discussed elsewhere in this .l document, the mechanical interference fit (MIF) lower joint has been qualified and has been in l
service for many years. Qualification of the lower MIF joint of the ETS is fully expected based .j on previous experience with MIF joints and the analyses of the FLTS joint, discussed in Section 3.1.8 and the contact pressure analysis of the ETS joint discussed in Section 3.1,14. I 3-4 ?
3.1.6 Heat Transfer Analysis ' The first step in calculating the stresses induced in the sleeves as a result of the thermal transients,is to perform a heat transfer analysis to establish the temperature distribution for the sleeve, tube, and tubesheet. Based on a review of the transient descriptions, [ ] transients were selected for evaluation. They include the following events: [ i
]
In performing the heat transfer analysis, [ l l
] A sketch of the model boundary conditions for the heat transfer analysis is shown in Figure 3-3.
In order to determine the appropriate boundary conditions for the heat transfer analysis, [
]
3.1.7 Tubesheet/Channelhead/Shell Evaluation As discussed above, loads are imposed on the sleeve as a result of tubesheet rotations under pressure and temperature conditions. For this evaluation, tubesheet rotations are established for five reference loading conditions, and subsequently scaled to actual transient conditions. The five reference loading conditions consist of ( ] The [ ] loadings. The boundary conditions and subsequent deformed geometry for the primary side pressure load for Series 51 steam generators are shown in Figures 3-4 and 3-5, respectively. The [
]
A typical set of boundary conditions, and the resulting deformed geometry, for the case of [ ] for the Series 51 steam generators is shown in Figures 3-6 and 3-7. : 3-5
l Once the stress solutions for the reference load cases are obtained, [ t ja.c s ] The results from the tubesheet/channelhead/shell model of Figure 3-2 show that the maximum tubesheet rotations [ e 1 ja.c j j (Note that Section 3.1.14 discusses the tubesheet rotation effect on the contact pressures between
-{
the sleeve / tube, which is a different and distinct evaluation from the tubesheet rotational effect l on stresses in the critical locations of the sleeve and tube, discussed in this section.) 3.1.8 Stress Analysis l i In performing the stress evaluation for the sleeve models, [ l ]'* Sketches of the model boundary conditions { for the primaiy side pressure cases are shown in Figures 3-8 through 3-11. Sketches of the j model boundary conditions for the secondary side pressure cases are shown in Figures'3-12 ! through 3-15. It should be noted for both sets ofloads that the end cap load on the tube is not j included, but is considered in a separate load case. l
- As discussed above in Section 3.1.5, the structural analysis considers [ _
I l 4 l'* 4 3
- effect of thermal conditions in the tube and wrapper /shell regions
]
- effect of pressure drop across the tubesheet -
{ effect of pressure drop across the tube support plates
- - '* effect of interaction among the tubesheet, tube support plates, - 1 i
shell/ wrapper, stayrods, and spacer pipes 1 i j The effect of [ J Ja.c i ! 3-6 a
1
- [ ;
l
]'* Finally, [
]'* The total stress distribution in the sleeve-to-tube assembly is determined by combining the calculated stresses as follows:
P P Cant " 3 ( % pvmary M + 3 (% ammanyM + (%,rmat m ,ans) P P 1h Waert==yramnp aimme,s mono. & + 3W a w an ,.emy y m ,n y m nono= & AT A
+
(% Joodp -w mermat eposmo . ped + [T ( % saad p a wr mermat v - l~ AT
+
l (% sonep cw m,mai apa.m.. g.e) 3.1.9 ASME Code Evaluation 1 The AShE Code evaluation is performed using a Westinghouse proprietary computer code. The evaluation is performed for specific " analysis sections" (ASN's) through the finite element model. The ASN's evaluated to determine the acceptability of the sleeve design are shown in Figure 3-16 4 for the LWJ. The umbrella loads for the primary stress intensity evaluation have been given previously in Table 3-13. The largest magnitudes of the ratio " Calculated Stress Intensity / Allowable Stress , Intensity" for both the Series 44 and 51 steam generators are [ ]'* for design conditions, ! [ ]'* for faulted (feedline break) conditions, and [ ]'* for test (primary side hydrostatic) l conditions. The analysis results show the primary stress intensities for the laser welded sleeved tube assembly to satisfy the allowable ASME Code limits. A summary of the limiting stress conditions are provided in Table 3-14 with the [ j ]'* The results for maximum range of stress intensity and fatigue are summarized in Table 3-16 for the tube being [ 4 i ?- I
]'* The analysis results show J
the ASME Code limits to be satisfied. In evaluating seismic stresses, [
) .....
3-7 4
- - . - - . - ~ _ _ - . . . - . - - . - - - - - - . - . - - . . - - . .-
l [ l i i ~ i j ja.c.e ! 3.1.10 Minimum Required Sleeve Wall Thickness, t. l In establishing the safe limiting condition of a sleeve in terms of its remaining wall thickness, the effects of loadings during both the normal operation and the postulated accident conditions - must be evaluated. The applicable stress criteria are in terms of allowables for the primary j membrane and membrane-plus-bending stress intensities. Hence, only the primary loads (loads .. necessary for equilibrium) need be considered. 4 ] For computing t,w, the pressure stress equation NB-3324.1 of the Code is used, that is: i 4 ' AP, x R' ! t** = P, - 0.5 (P, + P,) 5 l where: Pi = Primary side pressure P, = Secondary side pressure
- . APi = Primary-to-secondary pressure differential i R, - =
Sleeve inside radius [ ]"
=
3 P. Allowable stress. i. Normal / Unset Operation Loads f. ,! The limiting stresses during normal and upset operating conditions are the primary membrane l l stresses due to the primary-to-secondary pressure differential AP, across the tube wall. During i ! normal operation, the primary side pressure, P, i is [ i ! y.c
- The limits on primary stress, P., for a primary-to-secondary pressure differential AP,i are as follows
- -l Normal: P, < S/3 Upset: P, < Sy 4
i 3-8 M
Using the pressure stress equation, the resulting values for t , are [
)...
Accident Condition Loadines LOCA + SSE: The dominant loading for LOCA and SSE loads occurs [
).
FLB/SLB + SSE: The maximum primary-to-secondary pressure differential occurs during a postulated feedline break (FLB) accident. Again, [ ] the SSE bending stresses are small. Thus, the governing stresses for the minimum wall thickness requirement are the pressure membrane stresses. For the FLB + SSE transient, the applicable pressure loads are [
]*' The applicable criteria for faulted loads is:
P < lesser of 0.7 S, or 2.4 S. Using the pressure stress equation, the resulting value foro t ,is [ 1*' In summary, considering all of the applied loadings, the minimum required sleeve wall thickness is calculated to be [ ] remaining wall and occurs for normal operating conditions. 3.1.11 Determination of Plugging Limits The minimum acceptable wall thickness and other recommended practices in Regulatory Guide 1.121, Reference 8.3, are used to determine a plugging limit for the sleeve. This Regulatory Guide was written to provide guidance for the determination of a plugging limit for steam generator tubes undergoing localized tube wall loss and can be conservatively applied to sleeves. Tubes with sleeves which are determined to have indications of degradation of the sleeve in excess of the plugging limit, would have to be repaired or removed from service. As recommended in' paragraph C.2.b. of the Regulatory Guide, an additional thickness degradation allowance must be added to the minimum acceptable tube wall thickness to establish the operational tube thickness acceptable for continued service. Paragraph C.3.f. of the Regulatory Guide specifies that the basis used in setting the operational degradation allowance include the method and data used in predicting the continuing degradation and consideration of 3-9
i I eddy current measurement errors and other significant eddy current testing parameters. An eddy current measurement uncertainty value of [ ]** of the tube wall thickness is applied for use j in the determination of the operational tube thickness acceptable for continued service and thus, , determination of the plugging limit. Paragraph C.3.f of the Regulatory Guide specified that the basis used in setting the operational ' ' degradation analysis include the method and data used in predicting the continuing degradation. To develop a value for continuing degradation, sleeve experience must be reviewed. To date, no degradation has been detected on Westinghouse designed mechanicaljoint sleeves and no sleeved tube has been removed from service due to degradation of any portion of the sleeve. This result can be attributed to the changes in the sleeve material relative to the tube and the lower heat flux . due to the double wall in the sleeved region. Sleeves installed with the laser weld joint are expected to experience the same performance. As a conservative measure, the conventional practice of applying a value of [
]** of the sleeve wall is applied as an allowance for L continued degradation in this evaluation.
1 ! In summary, the operational sleeve thickness acceptable for continued service includes the l minimum acceptable sleeve wall thickness [ ]** and the combined i ) allowance for eddy current uncertainty and operational degradation [ ]**. These terms total ) to [ ]**, resulting in a plugging limit as determmed by Regulatory Guide 1.121 recommendations of 25% of the sleeve wall thickness. t 3.1.12 Application of Plugging Limits l Sleeves which have eddy current indications of degradation in excess of the plugging limits must ( be repaired or plugged. Those portions of the sleeve for which indications of wall degradation I must be evaluated are summarized as follows: l l [ S ' 1 3 - 10
. -- _. . ~ . - - . - - ---- -.-.- - _ - . - . - - - - - - - . - -
a 1 I 1 j 8,C ! 3.1.13 Structural Analysis Conclusior.s Based on the results of this analysis, the design of the full length laser welded tubesheet sleeve 1 (FLTS), the elevated tubesheet sleeve (ETS) and the tube support plate sleeve (TSS) meets the requirements of the ASME Code. The applicable plugging limit for the sleeve is 25% of the nominal initial wall thickness. !- 3.1.14 Effect of Tubesheet Rotations on ETS Contact Pressures The elevated tubesheet sleeves are to be installed in the upper half of the tubesheet, where tubesheet bow during operation tends to increase the diameter of the holes drilled in the tubesheet. This diameter increase will result in a decrease in the contact pressures between the sleeve / tube and tube /tubesheet produced by system pressures and differential thermal expansions among the sleeve, tube, and tubesheet. This section determines the effect of tubesheet rotations ' on the sleeve / tube contact pressures. Loads are imposed on the sleeve as a result of tubesheet rotations under pressure and temperature ! conditions. A 2-D axisymmetric finite element analysis of a Series 51 tubesheet, channelhead, { and lower shell has been performed. The model is shown in Figure 3-17. This provided ! displacements throughout the tubesheet for two pressure and three thermal unit loads. The three I temperature loadings consist of applying a uniform thermal expansion to each of the three . component members, one at a time, while the other two remain at ambient conditions. l [ 1'c . The radial deflection at any point within the tubesheet is found by scaling and combining the unit
, load radial deflections at that location according to:
Un = (0.76)(Ug)%(Primary Pressure /1000)
+ (0.76)(Ug)sec(Secondary Pressure /1000)
+ (Ug)rm[(Tubesheet Temperature - 70)/500]
+ (Ug)sheli[(Shell Temperature - 70)/500]
+ (Ug)chmi mu[(Channelhead Temperature - 70)/500]
3-11
This expression is used to determine the radial deflections along a line of nodes at a constant axial elevation (e.g. top of the tubesheet) within the perforated area of the tubesheet. , The expansion of a hole of diameter D in the tubesheet at a radius R is given by: 1. j Radial: AD = D { dun (R)/dR} Circumferential: AD = D {Un(R)/R} 4 Uais available directly from the finite element results. dug /dR may be obtained by numerical differentiation. 4 The maximum expansion of a hole in the tubesheet is in either the radial or circumferential direction. Typically, these two values are within 5% of each other. Since the analysis for .; calculating contact pressures is based on the assumption of axisymmetric deformations with-respect to the centerline of the hole, a representative value for the hole expansion must be used that is consistent with the assumption of axisymmetric behavior. A study was performed to determine the effect of hole out-of-roundness on the contact pressures between the sleeve and , tube, and between the tube and tubesheet. The equation used for the hole AD is: ' a AD = (SF)(AD,,) + (1 - SF)(AD,i,) r where SF is a scale factor between zero and one. For the eccentricities typically encountered-4 during tubesheet rotations, SF is usually between [ ]" ' This hole expansion includes the effects of tubesheet rotations and deformations caused by the ! system pressures and temperatures. It does not include local effects produced by interactions between the sleeve, tube, and tubesheet hole. Thick shell equations, from References 8.5 or 8.7 ;
- in combination with the hole expansions from above, are used to calculate the contact pressures between the sleeve and tube, and between the tube and tubesheet.
4 For a given set of primary and secondary side pressures and temperatures, the above equations ! are solved for selected elevations in the tubesheet to obtain the contact pressures as a function of radius between the sleeve and tube and the tube and tubesheet. The elevations selected were i the neutral axis of the tubesheet and three elevations spanning the section from the bottom of the ETS to two inches from the top surface of the tubesheet. i Normal Ooeratiom _ From Reference 8.1, the temperatures and pressures for normal operating conditions are:
- Primary Pressure = 2235 psig ~
; Secondary Pressure = 705 psig Primary Fluid Temperature (TJ = 616.8 *F l Secondary Fluid Temperature = 506.3 *F 1
1 3 - 12 n 4 ,-~+ -- w y, , ,
Fer this set of primary and secondary side pressures and temperatures, the contact pressures between the sleeve and tube and the tube and tubesheet are obtained as functions of radius for selected elevations in the tubesheet for both intact tubes and tubes separated above the tubesheet. Faulted Condition -i l From Reference 8.1, tha temperatures and pressures for the limiting faulted condition are: Primary Pressure = 2500 psig Secondary Pressure = 0 psig l Primary Fluid Temperature (Ty = 212 F l' Secondary Fluid Temperature = 212 F l ,, For this set of primary and secondary side pressures and temperatures, the contact pressures between the sleeve and tube and the tube and tubesheet are obtained as functions of radius for selected elevations in the tubesheet for both intact tubes and tubes separated above the tubesheet. Summary of Results i The contact pressures between the sleeve and tube, and between the tube and tubesheet are plotted versus radius in Figures 3-18 through 3-20. Results from these figures are summarized i in the table below: l a,c.e i l l These contact pressures are for the elevation four inches below the top of the tubesheet, which corresponds to the intended top of the hard roll of the ETS. They are conservative for any lower elevation in the tubesheet. Note that these contact pressure are in addition to the interference pressures between the sleeve and tube and tube and tubesheet produced during installation of the sleeves. Note also that, in all cases, the net effect of the tubesheet rotations, thermal expansions, and pressures is an increase in the contact pressure between the sleeve and tube, thereby - o enhancing the joint leakage resistance and structural integrity. i 3.2. Thermal Hydraulic Analysis 3.2.1 Safety Analyses and Design Transients From the standpoint of system effects, safety analyses and system transients, steam generator nbe sleeving has the same effect as tube plugging. Sleeves, like plugs, increase both the flow l
. . resistance and the thermal resistance of the steam generator. -
3 - 13
Each NSSS is analyzed to demonstrate acceptable operation to a level of plugging denoted as the plugging limit. When the steam generators include both plugs and sleeves, the total effect must be shown to be within the plugging limit. To do this, an equivalency relationship between plugged and sleeved tubes needs to be established. The following section derives a hydraulic equivalency number. This number represents the number of sleeved tubes which are hydraulically equivJem to a single plugged tube. It is a function of various parameters including
- 1) the number and location of sleeves in a tube, 2) the steam generator model, and 3) the operating conditions. Conservative bounding values are determined so that a single number applies to a given steam generator model and tube sleeve configuration.
Once the hydraulic equivalency number is established, the equivalent plugging level of a steam ~ generator and NSSS can be determined. The equivalent plugging level must remain within the plugging limit established for the plant. - 3.2.2 Equivalent Plugging Level The insertion of a sleeve into a steam generator tube results in an increase in flow resistance and a reduction in primary coolant flow in the sleeved tube. Furthermore, the insertion of multiple sleeves (tubesheet and/or tube support plate sleeves) will lead to a larger flow reduction in the sleeved tube compared to a nominal unsleeved tube. The flow reduction through a tube due to the installation of one or more sleeves can be considered equivalent to a portion of the flow loss due to a plugged tube. A parameter termed the " hydraulic equivalency number" (Nsy4) has been developed which indicates the number of sleeved tubes required to result in the same flow loss as that due to a single plugged tube. The calculation of the flow reduction and equivalency number for a sleeved tube is dependent upon several parameters: 1) the tube geometry, 2) the sleeve geometry, and 3) the steam generator primary flow rate and temperature. These parameters are used to compute the relative flow resistance of sleeved and unsleeved tubes operating in parallel. This difArence in resistance is then used to compute the difference in flow between sleeved (W.) - =msleeved (W ) tubes. The hydraulic equivalency number is then simply: The hydraulic equivalency number can be computed for both normal operating conditions and off-normal conditions such as a LOCA. For LOCA conditions, the equivalency number is established using flow rates consistent with the reflood phase of a post-LOCA accident when peak clad temperatures exist. The equivalency number for normal operation is independent of the fuel in the reactor. In all cases, the hydraulic equivalency number for normal operation is more limiting than for postulated LOCA conditions. As a result of the flow reduction in a sleeved tube and the insulating effect of the double wall at the sleeve location, the heat transfer capability of a sleeved tube is less than that of an unsleeved tube. An evaluation of the loss of heat transfer at normal operating conditions 3 - 14
1 indicated that the percentage loss of heat transfer capability due to sleeving is less than the percentage loss associated with the reduction in fluid flow. In other words, the heat transfer equivalency number is larger than the hydraulic equivalency number. Thus, the hydraulic equivalency number is limiting. The specific LOCA conditions used to evaluate the effect of sleeving on the ECCS analysis occur during a portion of the postulated accident when the analysis predicts that the fluid in the secondary side of the steam generator is warmer than the primary side fluid. For this situation, the reduction in heat transfer capability of sleeved tubes would have a beneficial reduction on the heat transferred from secondary to primary fluids. The goal of the hydraulic equivalency number calculations described below is to generate
. conservative results which envelope the results for all plants which have either Series 44 or 51 steam generators. As such,it was necessary to consider the effect of a wide variation in primary flow conditions for normal operation. Flow rates for these parametric calculations ranged from
[
]'** It was determined that the most limiting results (largest flow reduction and smallest hydraulic equivalency number for a sleeved tube) occur with
[ ) In addition to the effect of variations in the primary coolant conditions, the effect of differences in nominal tube geometries was evaluated. For the 51 Series steam generators there are some differences in the tube geometry in the tubesheet region, specifically, in the length of the expanded or rolled region. For some plants, this zone is short (2-3 inches), while for others with a full-depth roll it extends throughout the full thickness of the tubesheet (21-22 inches). Parametric calculations were completed to determine the specific tube configuration which produces the most conservative result; this geometry was then used in developing the final reported results. No differences exist in the nominal length of the expanded region for the plants with Series 44 steam generators. Therefore, it was necessary to consider only one tube configuration for the Series 44 plants. Many combinations of tubesheet (both hot and cold legs) and tube support plate sleeves have been considered in calculating the flow reduction and hydraulic equivalency. However, to insure that the results are enveloping, only the longest sleeves were used in the calculations. These included a 36 inch long tubesheet sleeve and a 12 inch long tube support plate sleeve. The 36 inch long tubesheet sleeve is expected to be long enough to span the degraded areas in the tubesheet and places the upper joint above the sludge pile in either the hot or cold legs. The flow effects of this sleeve length bound a range of possible tubesheet sleeve lengths which could be specified for any future sleeving program (27 to 36 inches). The parametric calculations considered four configurations with regard to the location of sleeves:
- 1) No tubesheet sleeves with various combinations of support plate sleeves in both hot and cold legs,
- 2) No tube sucoort olate sleeves - only hot and/or cold leg tubesheet sleeves, 3 - 15
l l
- 3) One tubesheet sleeve (cold leg) with various combinations of cold leg support plate sleeves, and
- 4) Both hot and cold lea tubesheet sleeves with various combinations of support plate sleeves.
Note that the third configuration includes only cold leg tube support plate sleeves and no hot leg sleeves. The reason for this selection is that, because of the effect of the variation in primary fluid temperature in the two legs of the tube bundle, support plate and tubesheet sleeves located { in the cold leg produce slightly more conservative results (greater flow reduction) compared to I an identical number and placement of hot leg sleeves. Similarly, slightly more conservative results are obtained when support plate sleeves are located at the higher plate locations. For - these reasons, the results presented herein are generally limited to only those particular sleeve locations which yield the more conservative results. Support plate sleeves are qualified for the -; second-from-highest support plate elevation through the lowest elevation for both series of steam generators. (Qualification of the sleeve at the top support plate would require a structural evaluation and modifications to the tooling.) Nonetheless, the hydraulic equivalency and flow l reduction calculations were made for support plate sleeves at all elevations for both series of steam generators. 1 Table 3-17 presents a summary of the hydraulic equivalency numbers for the limiting ; combinations of tubesheet and support plate sleeves in 44 Series steam generators. Similar I results for 51 Series steam generators are provided in Table 3-18. From Table 3-17, the hydraulic l equivalency number for a configuration with no tubesheet sleeve and four support plate sleeves is[ ] and occurs when the sleeves are positioned at the top four support plates in ; the cold leg (#3, #4, #5, and #6). This means that about [ ] sleeved tubes of the type specified would have the same net ilow reduction as a single plugged tube. Similarly, if sleeves were also installed in both hot and cold leg tubesheets, the equivalency number would decrease to [ ] for a configuration with four support plate sleeves (Set #21 for support plate locations
- 5 and #6 in both legs).
The tubesheet sleeves specified in Tables 3-17 and 3-18 refer to full length tubesheet sleeves (FLTSs). However, the N 3y, and percent flow reduction results conservatively apply to 36 inch-long elevated tubesheet sleeves (ETSs). Similarly, the N3y , and percent flow reduction results for [ j.e.. . The information pesented in Tables 3-17 and 3-18 has also been used to construct Figures 3-21 and 3-22. These figures graphically illustrate the enveloping hydraulic equivalency numbers for 44 and 51 Series steam generators based on normal operating conditions. 3 - 16
The total equivalent number of plugged tubes is the sum of the number of plugs associated with
' sleeving (number of sleeves divided by the hydraulic equivalency number) and the actual number ! of plugged tubes. In the event that the total plugging equivalency derived from this information is near the tube plugging hmit for a particular plant application, then less conservative, l plant-specific equivalency calculations may be completed to justify increased sleeving. Rather than using the preceding conservative, enveloping conditions, these calculations could make use
[ of 1) actual plant primary side operating conditions,2) actual tube and sleeve geometries, and
- 3) actual locations of the tubesheet and support plate sleeves.
- The method and values of hydraulic equivalency and flow loss per sleeved tube outlined above l.
can be used to represent the equivalent number of sleeves by the following formula: j, P, = [P, + S/N ,a,i 3 + S,.i M 3,4,33 + . P,] j where: l P, = Equivalent number of plugged tubes J
- P, = Number of tubes actually plugged
- Si = Number of active tubes with a sleeve combination j N 3ya,i =
Hydraulic equivalency number for a sleeve configuration j P, = Equivalent number of plugged tubes due to other sleeve designs
. 3.2.3 Fluid Velocity 1
As a result of tube plugging and sleeving, primary side fluid velocities in the steam generator i tubes will increase. The effect of this velocity increase on the sleeve and tube has been evaluated ! assuming a limiting condition in which 20% of the tubes in either a 44 or 51 Series steam 3 generator are plugged. l I j Using the conservatively high primary flow rate defined previously [ ]'**, for a 0% j plugging condition, the velocity through an unplugged tube is approximately [ ]'^*. With 3 20% of the tubes plugged, the fluid velocity through an unplugged and unsleeved tube is about ] [ ]"', and for a tube with a single tube support plate sleeve, the local velocity in the
, sleeve region is computed to be [ ] However, these velocities are unduly conservative as a result of the assumed enveloping primary flow rate and temperatures.
If these calculations are repeated using more typical primary fluid conditions [
] These more typical velocities are smaller than , the inception velocities for fluid impacting, cavitation, or erosion-corrosion for Inconel tubing.
As a result, the potential for tube degradation due to these mechanisms is low. 3 - 17
. - .- .. - -- . . . - - - _ =. . . _ . - - _ - -
l TABLE 3-1
SUMMARY
OF MATERIAL PROPERTIES l TUBE MATERIAL { MILL ANNEALED ALLOY 600 ' l l l TEMPERATURE (*F) - PHYSICAL PROPERTIES 70 200 300 400 500 600 700 Young's Modulus 31.00 30.20 29.90 29.50 29.00 28.70 28.20 (psi x 1.0E06) . Coefficient of Thermal 6.90 7.20 7.40 7.57 7.70 7.82 7.94 , Expansion
]
(in/in/"F x 1.0E-06) ' Density 7.94 7.92 7.90 7.89 7.87 7.85 7.83 i (Ib sec'/in* x 1.0E-04) J Thermal Conductivity 2.01 2.11 2.22 2.34 2.45 2.57 2.68 (Btu /sec-in *F x 1.0E-04) Specific Heat 41.2 42.6 43.9 44.9 45.6 47.0 47.9 (Btu in/lb-sec' 'F) STRENGTH PROPERTIES (ksi) Sm 23.30 23.30 23.30 23.30 23.30 23.30 23.30 Sy 35.00 32.70 31.00 29.80 28.80 27.90 27.00 Su 80.00 80.00 80.00 80.00 80.00 80.00 80.00 1
*i a
l 3 - 18
l
@ i i
TABLE 3-2
- l S'UMMARY OF MATERIAL PROPERTIES SLEEVE MATERIAL ,
THERMALLY TREATED ALLOY 690 j 1 i TEMPERATURE (*F) PHYSICAL
, PROPERTIES 70 200 300 400 500 600 700 Young's Modulus 30.30 29.70 29.20 28.80 28.30 27.80 27.30 i (psi x 1.0E06)
Coefficient of Thermal 7.76 7.85 7.93 8.02 8.09 8.16 8.25 ! Expansion (in/in/*F x 1.0E-06) Density 7.62 7.59 7.56 7.56 7.54 7.51 7.51 (Ib-sec'/in' x 1.0E-04) Thermal Conductivity 1.62 1.76 1.9 2.04 2.18 2.31 2.45 (Btu /see in *F x 1.0E-04) Specific Heat 41.7 43.2 44.8 45.9 47.1 47.9 49.0 (Btu.in/lb secF) STRENGTH PROPERTIES (ksi) Sm 26.60 26.60 26.60 26.60 26.60 26.60 26.60 Sy 40.00 36.80 34.60 33.00 31.80 31.10 30.60 Su 80.00 80.00 80.00 80.00 80.00 80.00 80.00 4 i 3 - 19
TABLE 3-3
SUMMARY
OF MATERIAL PROPERTIES TUBESHEET MATERIAL SA-508 CLASS 2 1 i TEMPERATURE (*F) l PHYSICAL PROPERTIES 70 200 300 400 500 600 700
.]
Young's Modulus 29.20 28.50 28.00 27.40 27.00 26.40 25.30 (psi x 1.0E06) :
-Coefficient of Thennal 6.50 6.67 6.87 7.07 7.25 7.42 7.59 Expansion l (in/in/'F x 1.0E-06)
Density 7.32 7.3 7.29 7.27 7.26 7.24 7.22 ! 8 (Ib.sec /in' x 1.0E-04) i Thermal Conductivity 5.49 5.56 5.53 5.46 5.35 5.19 5.02 l (Btu /see-in 'F x 1.0E-04) i SpeciSc Heat 41.9 44.5 46.8 48.8 50.8 52.8 55.1 (Btu in/lb-sec' 'F) STRENGTH PROPERTIES (ksi) 1 26.70 Seu 26.70 '26.70 26.70 26.70 26.70 26.70 Sy 50.00 47.50 46.10 45.10 44.50 43.80 43.10 Su 80.00 80.00 80.00 80.00 80.00 80.00 80.00 l I 4 3 - 20
. . . - ~ . . - . . . - . - - _ .
i } Table 3-4 Summary of Material Properties Channelhead Material SA-216 Grade WCC i ) TEMPERATURE (*F) ! PHYSICAL I- PROPERTIES 70 200 300 400 500 600 700 i j Young's Modulus 29.50 28.80 28.30 27.70 27.30 26.70 25.50 j (psi x 1.0E06) i- Coefficient of Thermal 5.53 5.89 6.26 6.61 6.91 7.17 7.41 i Expansion
- ,, (in/in/*F x 1.0E-06) i j Density 7.32 7.3 7.29 7.27 7.26 7.24 7.22 Ob-sec'/in' x 1.0E-04) 3 f
i a < l l Table 3-5 i Summary of Material Properties q Cylinder Shell Material : SA-533 Grade A Class 1 l t 1 TEMPERATURE (*F) PHYSICAL i PROPERTIES 70 200 300 400 500 600 700 1 i Young's Modulus 29.20 28.50 28.00 27.40 27.00 26.40 25.30 { (psi x 1.0E06) 4 j Coefficient of Thermal 7.06 7.25 7.43 7.58 7.70 7.83 7.94
- Expansion (in/in/*F x 1.0E-06)
! Density 7.32 7.3 7.29 7.27 7.26 7.24 7.22 i M Ob sec'/in' x 1.0E-04) 1 j - 4 4 4 s { 3 - 21
TABLE 3-6
SUMMARY
OF MATERIAL PROPERTIES l AIR I TEMPERATURE (*F) PHYSICAL PROPERTIES 70 200 300 400 500 600 700 Density 10.63 8.99 7.79 6.89 6 17 5.59 5.11 4 (Ib-sec'/in x 1.0E-08) Thermal Conductivity 3.56 4.03 4.47 4.91 5.35 5.78 6.20 - (Btu /see in 'F x 1.0E 07) Specific Heat 9.27 9.31 9.38 9.46 9.55 9.66 9.78 - (Btu.in/lb sec' 'F x 1.0E+01) I l TABLE 3-7 l l
SUMMARY
OF MATERIAL PROPERTIES WATER TEMPERATURE ('F) PHYSICAL PROPERTIES 70 200 300 400 500 600 700 l Density 9.28 9.01 8.58 8.04 7.34 6.35 4.65 8 lb-sec /in' x 1.0E 05 Thermal Conductivity 8.46 9.07 9.14 8.89 8.24 6.9 4.42 Btu /sec-in *F x 1.0E-06 Specific Heat 3.82 3.88 3.96 4.12 4 '- 5.26 8.51 8 Btu in/lb sec *F x 1.0E+02 I mm - e b 3 - 22
g TABLE 3-8 CRITERIA FOR PRIMARY STRESS INTENSITY EVALUATION SLEEVE - ALLOY 690 4 CONDITION CRITERIA LIMIT (KSI) DESIGN Pm 5 S, Pm5 26.60 4 Pi + P3 51.5 S. Pi + P35 39.90 FAULTED P s .7 S, Pm5 56.00 Pi + P, s 1.05 S o Pi + P35 84.00 TEST P ,s 0.9 S, P, s 36.00 P + P3 5 L35 Sy i Pi + P35 54.00 ALL P i +P, + Pa 5 4.0 S, Pi +P, +P3 5106.4 CONDITIONS Note: Pi (i=1,2,3) = Principal stresses -4 1 l i TABLE 3-9 CRITERIA FOR PRIMARY STRESS INTENSITY EVALUATION ! TUBE - ALLOY 600 CONDITION CRITERIA LIMIT (KSI) l DESIGN Pm 5 S, Pm5 23.30 Pi + P3 51.5 S. P + P 35 34.95 3 FAULTED P, s 2.4 S m Pm5 55.92 l Pi + P3 5 3.6 S. Pi + P35 83.88 TEST P, s 0.9 S, Pm5 31.50 Pi + P3 51.35 S, Pi + P3547.25 ALL Pi +P3 + P35 4.0 S. Pi +P, +P3 5 93.20 CONDITIONS Note: Pi (i=1,2,3) = Principal stresses e 3 - 23
@ l TABLE 3-10 CRITERIA FOR PRIMARY PLUS SECONDARY STRESS INTENSITY EVALUATION SLEEVE - ALLOY 690 CONDITION CRITERIA LIMIT (KSI)
NORMAL, UPSET, Pi + P3 + Q 5 3 S,* and TEST P + P 3+ Q s 79.8 3 NORMAL, UPSET, Cumulative Fatigue 1.0 and TEST Usage
- Range of Primary + Secondary Stress Intensity TABLE 3-11 CRITERIA FOR PRIMARY PLUS SECONDARY STRESS INTENSITY EVALUATION TUBE - ALLOY 600 CONDITION CRITERIA LIMIT (KSI)
NORMAL, UPSET, Pi + P3 + Q s 3 S,* P + P 3+ Q 5 69.9 3 and TEST
- NORMAL, UPSET, Cumulative Fatigue 1.0 and TEST Usage Range of Primary + Secondary Stress Intensity 3 - 24
4 Table 3-12 Summary of Transient Events
.- - .a l Classification Conditions Occurrences i
- a,c.e Normal i.
1 1 l Upset i i l 4 4 .l
- Faulted i
1 i' 5 I Test m 3 - 25
@ l Table 3-13 l
Umbrella Pressure Loads for Design, Faulted, and Test Conditions l i Pressure Load, psig Classification Conditions Primary Secondary '
. . a,c.e '
Design Design Primary q Design Secondary
.i Faulted Reactor Coolant Pipe Break Feedline Break Steamline Break Loss of Secondary Pressure
= !
Test Primary Side Hydrostatic Pressure Test ' Secondary Side Hydrostatic Pressure Test Tube Leak Test Primary Side Leak Test Secondary Side Leak Test Subsequent Primary Side Pressure Test Subsequent Secondary Side Pressure Test Primary to Secondary Leak Test , i
.I 3 - 26
TABLE 3-14
SUMMARY
OF MAXIMUM PRIMARY STRESS INTENSITY FULL LENGTH TUBESHEET LASER WELDED SLEEVE Sleeve / Tube Weld Width of [ ]" [ ]* a,c,e e l 9 m ene c i 4 3 - 27 l
l TABLE 3-15 l
SUMMARY
OF MAXIMUM PRIMARY STRESS INTENSITY I FULL LENGTH TUBESHEET LASER WELDED SLEEVE l Sleeve / Tube Weld Width of [ ]" ,
- [ ju a,c,e 1 I
l l 1
-l i
e m 6 3 - 28
TABLE 3-16 MAXIMUM RANGE OF STRESS INTENSITY AND FATIGUE FULL LENGTH TUBESHEET LASER WELDED SLEEVE Sleeve / Tube Weld Width of [ ]" Tube Separated and Dented Calculated Allowable S.I. Calculated Component S.I. (KSI) (KSI) Allowable . Straight - a,c,e Sections Sleeve LWJ: Sleeve Tube Weld = f f Cumulative Fatigue Usage Factor [ ]" s 1.0 e 3 - 29
Table 3-17 Generic Tube Sleeving Calculations , Flow Reduction and Hydraulic F,quivalency for Series 44 SGs a,c e i k t I r l t I i I L " m !
+
3 -30
g Table 3-18 Generic Tube Sleeving Calculations Flow Reduction and Hydraulic Equivalency for Series 51 SGs a,c,e i k r I t r I 3-31 l i
l a.c I I i 1 l l Figure 3-1 ' Schematic of Full Length Tubesheet Sleeve Configuration 3 - 32
i 1 J a,c a i a i i 2-1 1 4 4 1 i h ], d r i 1 i E f 3. e 4 4 1 4
]
l s
- i
- 1 i. 4 Figure 3-2 i i Channelbend/Tubesbeet/Shell Model i ; 3-33 I
a a,c 4' i i h i k I 1 i Figure 3-3 Thermal / Hydraulic Boundary Conditions Tubesheet Sleeve Analysis 3-34
5 _ a,c.e
- I J
1 t i I i i i i i i-i , 4
- i. ,
i ' ) i i l 1 1 l l 1 i 4 d i Figure 3-4 Channelhead/Tubesheet/Shell Model Primary Pressure Boundary Conditions i 3 - 35 l
l
@ l l
_ . a,c,e I
-l
*l l
l l l l l l _ 1 _ 4 Figure 3-5 Channelheadfrubesheet/Shell Model Distorted Geometry Primary Pressure Loading 3 - 36
~ . . . . _ _ - . . _ . .-_ _ _ _ _ _ . . _ . _ . _ . _ _ - . - _ _ . _ _ . . . _ _ _ .. _ .. ._ _ .... . ____
l i a,c,e l l 4 I ! l T b .i l 1 1 e
- i. 1 i l e
l* I $ l I i 1 a I t k i 4 1 4 1 t 1 i } 1 l 1 i-1
; Figure 34 4
- Channelheadfrubesheet/Shell Model j .
Channelhead Thermal Boundary Conditions a 3 - 37
_ a,c,e l l l I 1 l l 1 l-Figure 3-7 Channelheadtrubesheet/Shell Model Distorted Geometry Channelhead Thermal Loading l 1 3 - 38
1 l _ a,c.e ; i 1 I i i 1 l l 4 4 l l . l 6 I 1 i i l 1 l l l l l l l s 1 Figure 3-8 Boundary Condition for Unit Primary Pressure Intact Tube: P,,, > Psec 3 - 39
i'
- a _,c.e d
b
- I i 1 s.
1 4 4 ! l i . i A Figure 3-9 Boundary Condition for Unit Primary Pressure Intact Tube: P,,, < Psse 3 - 40
. - . _ _ . _ . . _ . . . . ~ . - _ _ _ . . . . . . _ _ _ _ . . _ _ _ . . _ . . _ _ _ _ . . _ _ . . . . _
4 4 a,c.e a 4 I t t 5 i- t 1- , h
- i a, i I
e ' I l l l Figure 3-10 Boundary Condition for Unit Primary Pressure Severed Tube: Prai > P sec 3 - 41
i i i 1 a,c,e 3 1 J 5~ i A i i 1 4 4 i l 2 i a 1 i l i !i 4 h d i j J i d 1 I. 1 i i l' 4 1-1 1 i 1 Figure 3-11 -l i
. Boundary Condition for Unit Primary Pressure j Severed Tube: Prai < P,ge I l I 3 - 42 u - --
l l l - 3,C,e l l t l l l l Figure 3-12 Boundary Condition for Unit Secondary Pressure Intact Tube: Prai > Psec 3 - 43
a,c.e
~,
l i i l I Figure 3-13 Boundary Condition for Unit Secondary Pressure Intact Tube: Prai< Psec 3 - 44
^
\
a,c,e i 1 l 1
. Figure 3-14 I Boundary Condition for Unit Secondary P tessure Severed Tube: Prai> Psec 4
3 - 45 ! i i
i i [- @ . l a,c,e l
.I l
I i t 4 . Figure 8-15 l Boundary Condition for Unit Secondary Pressure Severed Tube: P,mi < Psee 3 - 46
a,c,e -e 1 l 1 i i i I l l l Figure 3-16 ASN Location - LWJ 3 - 47
3,C,C i
\
Figure 3-17 Finite Element Model of Channelhead/Tubesheet/ Stub Barrel of Series 51 S/G 3 - 48
b 1 a 4 d i 1 4 J1 i 1 i 4 &' Ci L 1 1 1 i l I l i l 2 4 i e 1 i 1 1 l 1 i l 4 i a 4, 4 4 j J-1 i. 1 4 Figure 3 18 Contact Pressures for Normal Conditions with an Intact Tube 3 - 49
4 a 1 i i J i 4 d h j J i 4 1 i I
.1
[k - 1 i 4 l 3 1 i I 1 1 _.J Figure 3-19 Contact Pressures for Normal Conditions with a Separated Tube 3 - 50
- . - - . . . .~ . .- . . . . . . . - - ...... . . - . . . . - . - . . . . . - .
i n a 1
- - Rto
_=i
. I 4
i 4 i 1 l i l 4 4 1 i
- I 3
1 l l
- i Figure 3-20 Contact Pressures for Faulted Condition with an Intact or Separated Tube 3 - 51
.- - . . . . . ..~. . - - ._. .. ... .. . - - _.. -. - - - . . . . . . - - . . . . - . - . a,b,e l
'l Figure 3-21 Hydraulic Equivalency Number for Series 44 Steam Generator i
I 4 3 - 52
! a,b,e ! 4 6 4
- l I
4 i , f I i ) u I 1 l l
- s. .
p 1 t < l i 1-F i
?
i i f i
=
Figure 3-22 Hydraulic Equivalency Number for Series 51 Steam Generators l i 3 - 53
,u,m.....m, .,..; ,,.w_...mm.#..--m. mm.,#m um..~u.-=- -- -
-- - - - - -- - - - - - _.=._m.,-*-,-2-..--~.--~ ~ ~w.4-. , - .-- -. .. . -
1 J l l 1 l e 1 I 1 i t l I l l l i I l 1 i l l F l i r i
?
i j J l I I r. 4 i
.. . . . _ _ _ __ _ . _ - . _ _ . . ~ . _ _ _ , . . . _ . _ . _ . . . . _ _ . _ . ._ .. . _. ._ _ . _ __.. .-._
4.0 MECHANICAL TESTS ' d Mechanical tests are used to provide [ ; 1 J a.c.e Mechanical testing was initially applied to sleeves with mechanical interference fit joints because it was not possible to describe analytically the interaction between the sleeve and tube. Because ( welded joints can be modelled, mechanical tests have been applied to verify the analytical 1 mojels used. 4-f 4.A Mechanical Test Conditions (l . t j 4.1J Generic FLTS Sleeve-to-Tube Mechanical Joints and Laser Welded Joint 1 Mechanical testing has been applied to both the mechanical interference fit, i.e., lower, joints j of the FLTS and to the laser weld to confirm analyses that evaluated the interaction between the i sleeve and tube. Mechanical testing is primarily concerned with leak resistance and joint strength, ! l including fatigue resistance. A consistent characteristic observed in the testing of the FLTS MIF ! joints is that leakage, when observed, is generally higher at room temperature (RT) and normal i
- operation, steamline break (SLB) and greater-than-SLB pressure differential conditions than at !
i elevated temperature and other applied-load conditions. This result $bviates essentially all of the l ) combined or separate elevated temperature leak resistance and applied-load types of tests and { permits qualification of additional MIFjoints such as the ETS lowerjoint on the basis of RT leak l resistance tests and the previous testing. (For redundancy, sleeve pullout resistance testing and l testing to determine the sleeve-to-tube contact pressure are performed for new MIF joints.) 1 During testing, specimens are subjected to cyclic thermal and mechanical loads, simulating plant transients. [ l
- ]'" Other specimens were subjected to tensile and compressive loads to the point of mechanical failure. These tests demonstrate that the required i
joint strength exceeded the loading the sleeve joint would receive during normal plant operations
, and accident conditions.
1 j, These conditions are summarized in Table 4-1, though specific test conditions (displayed in data , tables) may vary due to evolution of the testing process. Test parameters have also been modified slightly over time as more refined analysis of plant loading conditions are applied. l 4-1 l l
- , . , -r - , - , , - . - n - - . - e ,-- --
l 4.1.2 ETS Generic Lower Joints Previous ETS MIF lower joints have been developed for all applicable tube sizes for ' Westinghouse steam generators, including a site specific joint for a 7/8 inch tube SG and for several models of a competitor steam generator. Therefore, it is expected that a single-pass roll, ETS MIF joint will be readily qualified for the generic Series 44/51 SGs, based on confirmatory testing during the appropriate point in the preparations for a given sleeving outage. 4.2 Acceptance Criteria
~
Generic analyses have been performed to determine the allowable leakage during normal ; operation for sleeve application. The primary-to-secondary side leak rate criteria that have been established are based on typical plant administrative leakage limits, Technical Specifications and -! Regulatory requirements. The criteria are based on the assumption that each tube containing a sleeve with a within-tubesheet mechanical joint is degraded throughwall in the tube portion spanned by the sleeve; this is a conservative assumption. In actuality, based on tens of thousands of similar within-tubesheet, Westinghouse, mechanical joints, leakage has been negligible or I essentially zero. The laser weld joint free span joint is hermetic and exhibits no leakage. Table 4-2 shows the generic leak rate criteria for the Series 44 and 51 stemi generators. [ l
]* indicate acceptable joint performance. (Later criteria for pullout resistance have been increased slightly, above the 2500 lb. level, to the endcap load on the tube caused by three times the primary-to-secondary side normal operation pressure differential (3AP%). This more stringent criterion is typically approximately 2800 to 3000 lbs.
4.3 Sleen Lower Joint The tubesheet sleeve MIF lowerjoint consists of a hydraulic expansion and a roll expansion. As
- discussed earlier, the test joints are formed in unit cell collars. End caps are then installed on the collar and sleeve (Figure 4-1) to permit the samples to be pressurized. The end caps are -
threaded to permit tensile and compressive loading. 4-2
4.3.1 Results of Testing The test results for the Series 44 and 51 MIF lower joint specimens are presented in Table 4-3. The specimens [
]'" All of the three )
i as-rolled specimens were leak-tight during the Extended Operating Period (EOP) test. I 1 For the tests the following joint performance was noted: i Specimen MS-2: Initial leak rates at all pressures and at normal operating pressure following J- thermal cycling were [ a Ja.b.c.e l Specimen MS-3: [ t Ja.b.c.e Specimen MS-7: [ 1 J a.b.c.s 4.3.2 Description of Additional Test Programs - HEJ Lower Joint With Exceptional Conditions Additional test programs were performed to verify acceptable performance of the sleeve lower mechanical joint to accommodate exceptional conditions which may exist in the steam generator tubes and anticipated conditions which may be encountered during installation of sleeves. These exceptional conditions in steam generator tube characteristics and sleeving operation
. process parameters included:
a shorter lengths of roller expanded lower tube joints shorter lengths of roller expanded lower sleeve joints The specific exceptional tube conditions and changes to the sleeving process parameters tested in the first program, are shown in Table 4-4. 4-3
l Each process operation and sequence of operations employed in fabricating each test sample was l consistent with those specified for sleeves to be installed by field procedures. In addition, the I exceptional tube conditions and changes to the sleeving process parameters described in Table 4-5 were included in the assembly of tube and collar subassemblies. 4.4 Free Span Joint Mechanical Testing !' l Free span joints are representative of the tubesheet sleeve upper joint and both joints of the tube ; support plate sleeves. This joint configuration, where there is no tubesheet backing the tube, is simulated using a test specimen as shown in Figure 4-2. Eleven free span weld specimens were fabricated using representative field parameters. All specimens were then stress relieved to account for the mechanical property effects resulting from
- l thermal treatment.
4.4.1 Stress Relief of Specimens All test specimens were given a stress relief heat treatment in the range of[ l ] The temperature source was a radiant heater installed inside the sleeve which was centered on the weld. The maximum temperature attained by the tube was measured by thermocouple attached to the tube outer surface and summarized in Table 4-6. The temperature ! was ramped up [
]'**
Following stress relief the thermocouple attachments were filed off. l 4.4.2 Free Span Joint Test Results The welds were subjected to leak testing [
]"' No leakage was exhibited (Table 4-7). Some specimens were subjected to tensile and compressive loading to failure; acceptable results were obtained.
l Two welds were metallurgically examined following fatigue testing (L-552 and L-555). Based i on this examination [
)e Several compressive specimens were examined following testing (L-540, L-543) and [
]'^' under design loading conditions. -
l 4-4 i
. . . - - . . - ._ . - . ~. .. _ - - . . - _ - . - . - . - . _ . . . . . . . . . ...
4 Table 4-1 4 1 Mechanical Test Program Summary Full Length Tubesheet Sleeve - Mechanical Interference Fit Joint (Generic - Single Pass Roll) a,C,e l } I 4 a e a 5, e 9 i j i 4 I i I~ 4 4 4 l 4-5
I 1 I Table 4-2 Typical Bounding Maximum Allowable Leak Rates for Series 44 and 51 Steam Generators Allowable _ Condition Plant Most Limitine SG Leak Rate oer Sleeve ** ._
~
d,e 1 l d,e l 1 1
)
Typical administrative leak limit for steam generators containing sleeves. ,
** Based on installation of 667 tubesheet sleeves with non-welded lower joints - for a steam generator in a three loop plan'(2,000 sleeves in the plant).
)
w - 4-6
Table 4-3(a) Verification of Test Results for As-Rolled Lower Joints - 7/8 Inch Full Length Tubesheet Sleeves Alloy 690 Total Wall INITIAL LEAK RATE (DROPS / MIN.) Specimen Roll Thinning (%) Number Torque At Room Temperature At 600*F (in-lb.) 0.5" in 2.0" in 1485 psi 2485 psi 3110 psi 1485 psi 2485 psi 3110 psi from end from end a,c.e 6 - 6 M 6 m 6 m 6 h
- m I a 1 A a a a 3
- aum-, 4 4-7 l
_ m. _ . _ _ _ . . . _ - . _. . . . _ _ . . _ . _ . . . - _ __ _ . _ . _ _ _ Table 4-3(b) Verification of Test Results for As-Rolled Lower Joints - 7/8 Inch Full Length Tubesheet Sleeves Alloy 690 LEAK RATE LEAK RATE LEAK RATE AFTER THERMAL CYCLES No. of AFTER THERMAL No. of AFTER THERMAL No. of (DROPS / MIN.) Specimen Thermal CYCLES Thermal CYCLES Thermal Number Cycles Cycles Cycles Room Temp. 600*F (DROPS / MIN. RT) (DROPS / MIN. RT) Applied Applied Applied 1485 2485 3110 1485 2485 3110 1485 2485 3110 1485 2485 3110 psi psi psi psi psi psi psi psi psi psi psi psi a,c,e m - I 1 e - i 4-8 !
Table 4-3(c) Verification of Test Results for As-Rolled Lower Joints - 7/8 Inch Full Length Tubesheet Sleeves Alloy 690 i LEAK RATE AFTER FATIGUE PUSil-OUT TEST PULL-OUT TEST No. of (DROPS / MIN.) Specimen Fatigue Rem Temp. 600'F Test Slip Max. Test Slip Max. Force Number Cycles Temp. Force Force or Temp. Force or Force Applied 1485 2485 3110 1485 2485 3110 ('F) (Ib.) Force for (*F) (Ib.) for l* 1" Defl. Deft. a,c,e psi psi psi psi psi psi
--f 6
m usuEmum 6 6 I I I I I I 1 a a e f
= -
L L 4-9 r
H-An-sb-e * ,a6 +w-M6, 4--- W--4..= -3 m--A m.nms < aaMb &wAA kke-t
- t
. tii A
1 s aC 6 1 I v.! i IE { o at s:3 *
.a i l
8 5 2 & c 0
.s 5
k i
; l an .I 5
li s~ [!t I I i la .:
))
El, 1
}::
11 era 2.
Table 4-5 Additional Test Results for Lower Joints with Exceptional Conditions for Tube and Sleeve
. .c i
i i 4-11
Table 4-6 Free Span Joint Maximum Stress Relief Temperature Soecimen Number Maximum Temocrature ( F) _ _. a,c.e L-536 L-540 L-543 L-544 L-546 L-548 - L-550 L-551 L-552 L-555 l 1 "i 4-12
Table 4-7 Frec. ;, pan Joint Leak Rate and Loading Data _ a,c,e Specimen Number L-536 i L-540 L-543 L-544 L-546 L-548 L-550 L-551 L-552 L-55 m Leak rate is in drops per minute. l l i i 1 4-13
m 1 1 1 Figu're 4-1 i Full Length Tubesheet Sleeve Lower Joint Test Specimen l 4-14
4 1 a l t e a.b e 4 i i i i i i
- e
] l ? F Figure 4-2 Free Span Laser Weld Joint Test Specimen 4-15
i , 5.0 STRESS CORROSION TESTING OF LASER WELDED SLEEVE JOINTS i i I The Alloy 690 TT (thermally treated) sleeve material exhibits exceptional resistance to stress j corrosion cracking in steam generator environments (Reference 8.8). Based on all available l corrosion test results, Alloy 690 TT appears immune to stress corrosion cracking in primary water (PWSCC), and offers substantial advantage over other candidate SG tube alloys in faulted j secondary side environments. For this reason it has been the preferred alloy for heat transfer j tubing in new and replacement SGs since approximately 1988;its use for sleeving extends back 3 as far as 1984. 1 i ]' The resistance, therefore, of the laser weld-repaired sleeve joint is dictated by the resistance of j the Alloy 600 tubing at the repair elevation. Hence, the major threat to the operational integrity l- oflaser welded sleeve repairs is the magmtude of the stresses residual to the sleeve installation ! process. These stresses are the combined results of: (a) the hydraulic expansion of the sleeve and tube, (b) the stresses associated with the weldmg process, and (c) the far-field stresses that develop during post-weld thermal stress relief. The purpose of the thermal stress relief operation is to reduce the peak residual stresses in the fusion weld and, for certain installation geometries, the peak stresses in the uppermost (free-span) hydraulic expansion transitions. However, under conditions where the tubes are axially restrained by locking and/or denting at the tube support plates, the thermal stress relief can elevate substantially the far-field stresses that develop in the tubing. These stresses would be additive to any remaining unrelaxed stress at the laser weld / hydraulic expansion locations. As discussed in subsequent paragraphs of this section, the role of these stresses on the corrosion resistance of tube-sleeve assemblies has been recognized and an attempt made to evaluate their effects. In view of the role played by the stress level in determining the service performance of weld-repaired SG tubing, a discussion is presented in the next subsection of the influence of the LWS process parameters and SG design variables on stress. A subsequent section reviews briefly the ! effects of thermal stress relief on stress levels and is followed by a summary of the results of corrosion tests performed to evaluate the resistance to PWSCC oflaser welded sleeve-repaired tube mockups. Included in this summary are the results of tests on as-welded mockups (i.e., without post-weld stress relief), stress-relieved mockups tested under conditions without applied axial loads, and stress relieved mockups tested under conditions believed to reflect the conditions which might exist under conditions of axial restraint. The laser welding processes used to prepare the test specimens are representative of the field processes using the neodymium-YAG (Nd:YAG) pulsed laser currently in use by Westinghouse for sleeve welding. Not all data in this section are for Series 44 or Series 51 SGs, i.e.,7/8 inch OD tubing. Where the intent is merely to illustrate the effect(s) of certain variables or parameters on far-field stress or corrosion resistance, data from test programs or mockup fabrications of other size tube-sleeve
)
assemblies are also used. 5-1
5.1 LWS Process and SG Design Variables The influence of the sleeve process parameters and steam generator design features or tube conditions on stress levels is summarized in Table 5-1. As installed, i.e., prior to thermal stress relief or final hard rolling, the far-field stresses are generally low, on the order of a few ksi. The peak residual stresses at the laser weld, however, are quite high; they have been estimated as approaching 80 - 85% of the tensile yield strength of the sleeve-tube assembly. When corrosion tested in this condition, the failures occur in the parent Alloy 600 tube near the weld-tube interface at times [ jw, The residual stresses at the upper hydraulic expansion are somewhat lower - [
]*; however, this region may also be subject to relatively early corrosion failures if these stresses are not reduced. '
I The most practical means to relax these peak residual stresses is by thermal stress relief. For ! conditions in which the tube is free to expand axially, i.e., no fixity or restraint at the support plate locations, stress relief is an efficient process, and has a negligible impact on far-field stresses. However, recent experience with operating steam generators suggests this condition ' may not always exist, and it is useful to assume for conservatism that the tubes may in fact be , locked at the tube support plate (s); most recent corrosion tests have thus been performed under the more conservative assumption, i.e., under conditions of applied axial stress. i The consequence of a locked tube condition is that thermal stress relief, while lowering peak residual stresses at the laser weld and at the hydraulic expansion, may increase the far-field axial stresses in the tube and may lead to bulging distortion of the tube at and above the elevation of
}
the weld. Since this response is a consequence of the thermal expansion of the tube, the higher l the stress relief temperature or the greater the axial extent of the region being stress relieved, the ; greater the axial far-field stresses. i Hence, the thermal stress relief process must be carefully tailored to achieve a trade-off between reduction of the peak stresses at the weld and hydraulic expansion transition while at the same time minimizing the far-field stresses. In view of the influence of the tube-tube support plate span length on the magnitude of the far-field stresses, optimization of the sleeve installation and stress relief process must be defined on a plant (or SG design)-specific basis. ~ 5.2 Residual Stresses vs. Stress Relief Temperature in LWS Sleeve Repairs Table 5-2 summarizes the expected range of far-field stresses that result as a function of the stress relief process. These are conservative stress values from strain gage measurements above i 1 5-2
and below the laser weld location and are for temperatures measured at the weld and upper hydraulic expansions of sleeve mockups. The data shown were measured during preparation of pre-heat model SG sleeve mockups and are directly applicable to Model D or E SGs [ j u.. , These data show the substantial reduction of far-field stress that can be realized in LWS-repaired SG tubing by controlling the stress relief temperature to be in the lower portion of the allowable range. They also show the general trend that separate stress relief of the upper hydraulic '~ expansion (UHE) region tends to increase the far-field stress, and final hard rolling for the roll-last sequence contributes to a small reduction in far-field stress.- 5.3 Corrosion Test Description Since approximately 1988, Westinghouse has used the doped steam corrosion test to evaluate the resistance of test mockups or repair assemblies to primary water stress corrosion cracking (PWSCC). This test is conducted in dense steam in an autoclave operating at 750*F (400 C). [
.)w ,
This test provides an extreme acceleration of the corrosion process relative to that which occurs in an operating steam generator. In some respects, the doped steam test can be viewed as a stress-indexing test; failure times in the doped steam test can generally be analyzed in terms of the stresses (residual and pressure) present in the test articles. In view of the dominant role stress plays in PWSCC of Alloy 600, this is a particularly valuable feature of the test. The acceleration of the corrosion process provides the opportunity to evaluate the corrosion resistance of configurations appropriate to the repair process ofinterest, and avoids the need to rely on such stress-indexing tests as the stainless steel-MgCl 2 or Alloy 600-sodium tetrathionate tests which require surrogate materials or nonrepresentative microstructures. As mentioned above, corrosion tests have been performed on tube-sleeve mockups in the as-welded condition, and for conditions representing weld stress relief with and without the addition of axial loading. Generally, two types of specimens have been tested. The first of these, illustrated in Figure 5-1, has been used to test laser weld joints in the as-welded condition, or in the condition following thermal stress relief of the joint, but without additional axial load. The second configuration is somewhat more complex. In this mockup test, the specimen is fabricated using a test stand as shown in Figure 5-2. The purpose of the test stand is to permit 5-3
l the sleeve installation, hydraulic expansion, welding, and post weld thermal stress relief under
- locked tube conditions. The nominal span length between supporting plates is varied to simulate ,
the appropriate values for the SG model/ design of interest. The stresses that result from the { several stages of fabrication are measured by placing strain gages above the weld location. ' i Temperatures are recorded throughout the stress relief process. i Following all specimen fabrication steps, the specimens are unloaded and prepared for corrosion testing. The configuration of the test assembly used for these tests is shown in Figure 5-3. By means of the threaded end fitting at the top of the assembly and the compression cylinder /Belleville washer assembly at the bottom, the axial load is established and maintained . on the sleeve joint throughout the corrosion test. , To facilitate interpretation of the corrosion test results and to provide verification of the ; aggressiveness of the test envi onment, roll expansion transition mockups, prepared of Alloy 600 tubing with known low resistance to cracking, are included in the test autoclaves. 5.4 Cerrosion Resistance of Free-Span Laser Weld-Repaired Tubes
- As-Welded Condition l
Corrosion tests have been performed on laser weld-repaired tube assemblies prepared using both { the CO2 and the Nd:YAG laser processes. The former process is no longer of interest and will l , likely not be used for field operations; hence, data are presented here only for the Nd:YAG process. The corrosion tests on as-welded mockups have been performed on specimens of the l configuration shown in Figure 5-1; i.e., without added axial load. The doped steam test results for these tests are summarized in Table 5-3. (Table 5-3 also includes some data for stress-relieved Nd:YAG welds.) While the data exhibit typical scatter in the results from different test sets, the results generally show that the as-welded joints [
]'", while the specimens stress relieved at 1400'F exhibit much greater resistance to cracking.
A limited number of as-welded 3/4 inch tube-sleeve mockups have also been tested (ca.1994) i to support a field sleeving campaign. For these tests, failures [
]'", encompassing the range observed previously.
Figure 5-4 is a micrograph showing the typical failure location in these test specimens. The l failures invariably occurred in the Alloy 600 base metal adjacent to the weld. The cracking is "! intergranular, typical of PWSCC, and is circumferential in orientation. This failure mode has been observed in essentially all laser weld-repair mockups tested, irrespective of whether or not the specimen was stress relieved, or subjected to additional axial load during the test. 5-4
5.5 Corrosion Resistance of Free-Span Laser Weld-Repaired Tubes
- with Post Weld Stress Relief 4
In addition to the results presented in Table 5-3 referred to in the previous subsection, doped steam corrosion tests were performed on 3/4 inch tube-sleeve mockups to support the 1994 field sleeving campaign. These specimens were tested without the imposition of axial loading. One of the objectives of this test program was to evaluate the effectiveness of the post weld thermal stress relief over th:: !emperature range [ l
]* The results of these doped steam tests are presented in Table 5-4.
1 1 These tests were, for the most part, terminated at [ ]*, a time period agreed upon ! with the utility as sufficient to demonstrate adequate resistance to in-service degradation through
)
the remaining service performance of the steam generators. All specimens were post-test I destructively examined by splitting and flattening. Only specimens that were intentionally stress relieved well above the field process maximum temperature [ jw 5.6 Corrosion Resistance of Free-Span Laser Weld-Repaired Tubes
- with Post Weld Stress Relief and Conditions of Axial Load During Test i
Experience related to a field sleeved-tube inspection campaign indicated that restraint to axial expansion due to locking of the tube at the tube support plate (TSP) elevations could lead to
" bulging" of the tube above the sleeve, and the introduction of large axial "far-field" stresses. l This provided the incentive to include conditions of restraint both during fabrication of mockups for testing and during corrosion testing.
The degree of axial restraint varies (see discussion in Subsections 5.2 and 5.3) with span length (e.g., the distance from tubesheet to TSP) and installation / fabrication parameters - in particular, with the thermal stress relief. Hence, most recent tests have used conditions which recognize these factors for the specific plant or sleeve application of interest. Nine 7/8 inch sleeved-tube mockups were prepared for doped steam corrosion testing using parameters appropriate to tubesheet sleeves in Series 51 SGs. These mockups were prepared in sets of three to represent the following variations in sleeve installation: ! o Mockups APR-1 thru -3 The post-weld stress relief was performed only at the laser weld elevation. [ jw This set of mockups represent the conditions used to install most laser welded tubesheet sleeves in operating Series 51 SGs. 5-5
_- . . - . - . - . . -... -. -_ _ - . - - . . - - _ . . . - - . . - . . ~ . . . - -. 4 o Mockuos APR-4 thru -6 1 Post-weld stress relief was performed at the laser weld elevation, the tube was permitted to cool to near room temperature, and the UHE transiti.on was subsequently stress relieved. The distance from the LW to the UHE transition was [ ]"' ! i i } This set of mockups was prepared to examine the efficacy of performing stress relief of l the UHE transitions in the future - i.e., after some period of operation of the initial LW l sleeve installations. I J o Mockuos APR-7. -8. -11 ~i This set of mockups was fabricated using modified tooling which establishes the distance from the laser weld to the UHE transition at [ ]" *. This modification was performed to permit a sir.gle post weld stress relief, performed just above the laser weld elevation, to effect at least partial stress relief of the UHE transition as well. j A summary of the stress relief temperatures realized during mockup fabrication, the stresses used for corrosion testing and the results of testing are provided in Table 5-5. In order to test under the most conservative conditions, i.e., under conditions of maximum far-field stress, the test stress values reported in Table 5-5 include: the residual stress (from strain gages) measured during mockup fabrication, plus two standard deviations; an "end cap" stress term due to internal pressurization; and an additional 10% allowance for stress relaxation during testing at 750'F. These latter additional stress terms add significantly to the total stresses used during testing. For example, the following table summarizes the various stress components for each set of mockups.
~~ a,c,e e
a.m. 5-6
The experience accrued in the fabrication and testing of tube-sleeve mockups has been used to optimize the field sleeving process so as to minimize field installation time while at the same time arriving at a configuration in which the local weld stresses and far-field tube stresses are l controlled so as to maximize fielc' :;ervice performance of the sleeve repairs. This optimization l involves modifying the equipment such that the distance between the laser weld and the UHE is l kept to a practical minimum. Inereby permitting effective stress relief of both regions at the same ' time. The other importart parameter that contributes to process optimization is the use of a nominal stress relief temperature in the mid-range of the [specified 1250 to 1600 F range; Westinghouse currently recommends a target of 1350 to 1400 F]'" Both of these factors were 4 . recognized in the test matrix described in Table 5-5. l Use of the conservatively high applied stresses should ensure that the corrosion data are l appropriate to the earliest field failures, i.e., those sleeved-tube assemblies with maximum residual-plus-applied stresses. Note re. Current Field-Installed Laser Welded Sleeves The performance of laser welded sleeve repairs in operating steam generators has been excellent. Tubesheet and TSP sleeves have been in service in a domestic nuclear power plant for over four years with no indications of degradation. These sleeves are in tubes known to have some degree of lock-up at the TSPs; far-field stresses are estimated [ ]'" Stress relief was limited to the weld region and was performed at [ ]'" In a non-domestic plant, approximately 5 years of operation had been attained with LWS-repaired tubes at the time the repaired SGs were replaced, again with no incidents of degradation. In another non-domestic plant, over 11,000 elevated tubesheet sleeves were in service for approximately 24 months at the time the SGs were replaced. After approximately 10 months of l operation, NDE of all sleeved tubes and destructive examination of ten pulled tube-sleeve assemblies revealed no in-service corrosion degradation of the laser welds, the hydraulic l expansion regions, or the tube bulges that resulted from stress relief under locked tube conditions. In the following subsection an estimate is provided of the service performance that might reasonably be expected for sleeve installations in Series 51 SGs. 5.7 Estimated Sleeve Performance at Plant A An estimate of the sleeve performance at Plant A was performed using experience from previous programs and extrapolating the results to Plant A SG conditions. 4 Two conditions were considered. These were: (a) the tubes are completely free to expand axially upon sleeving and thermal stress relief; and (b) the tubes are rigidly fixed at the first tube support plate (TSP). 5-7
l 4 In performing the following estimates, the operating temperature of Plant A SGs (T3 , = 607'F) is taken into consideration. l All estimates of sleeve performance were based on stresses measured in prototypic mockups for j which the laser weld stress relief region experienced five minute exposures [ ]. ! l Stress relief of the upper hydraulic expansion transitions was not performed.
- Tubes Free to Exnand Axially j
In this case, following thermal stress relief of the laser weld region, the primary stresses acting I ~ on the tube-sleeve assembly in the steam generator are the remaining residual weld stress and the operating pressure stress. Doped steam accelerated corrosion tests on inockups prepared under the condition of no axial fixity have run for periods [ ]"' (average of five "{ mockups - no failures in tes;). Based on comparison with roll transition mockups, prepared of ' the same Alloy 600 material and tested at the same time, the sleeved tubes are projected to exhibit resistance to PWSCC for periods [
).e, l
For Plant A, the earliest in-service degradation due to PWSCC is estimated to have occurred after about 3.5 effective full power years (EFPY) of operation (first reported at the EOC 4 refueling outage, at 3.91 EFPY) Hence, the sleeve service performance is estimated to be adequate for much greater than [ l*## Tubes Fixed at the First Tube Supoort Plate In the Plant A Series 51 steam generators, the first TSP is at an elevation approximately 50 inches above the top of the tubesheet. For fixed conditions at this elevation, the far-field stresses after thermal stress relief of the weld will be in the range of [ l
]'#'.
Corrosion testing of mockups under this condition of stress, again from comparison with roll transition mockups exposed at the same time, indicates degradation-free sleeve performance in primary water for periods approximately twenty times those required to initiate PWSCC in roll transitions. For Plant A, operating at a relatively modest Tso, this suggests more than [ 3u A summary of the estimates for the service performance oflaser welded sleeve-repaired tubes at Plant A, for the different conditions assumed for tube fixity, is provided below.
.l 5-8 i
_ a,c.e 5.8 Outer Diameter Surface Condition Because the sleeving involves operations only on the primary side, no aspect of the sleeve installation directly involves the tube OD surfaces. In operating SGs, however, the OD surfaces undergo surface corrosion and may collect deposits. These are typically oxides or related minerals in the thermodynamically stable form of the constituent elements; in PWR secondary water, magnetite is the most prominent oxide that forms. At the temperatures experienced during sleeve welding and thermal stress relief, these compounds are stable and do not thermally decompose. All such compounds have crystal structures that are too large to permit diffusion into the lattice of the Alloy 600. Reactions between these stable oxides and minerals and the alloying elements of Alloy 600 are thermodynamically unfavorable. Consequently, their presence during sleeve installation is not expected to produce deleterious tube-sludge / scale interactions. This judgment has been evaluated by installing and laser welding sleeves into tubes removed from operating plants. Following the sleeving operations, microanalytical examinations were performed to verify the lack ofinteractions. Prior to welding, the tubes had oxide deposits which contained Cu,' Ti, Al, Zn, P and _Ca as measured by EDAX analyses on an SEM. Following
,- welding and stress relief the maximum penetrations of the OD surfaces were on the order of 7 to 8 pm (less than a grain depth).
- Additional evaluations were performed on three areas of an Alloy 600 U-bend section which was coated with sludge and heat treated in air for 10 minutes at 1350*F. The sludge was a simulant of SG secondary side sludge (Fe 3 0, Cu, CuO, ZnO, CaSO and MgCl 2) and was applied to the U-bend using acrylic paint as a binder. Post-thermal exposure evaluations indicated no general or intergranular corrosion had occurred.
5-9
Table 5-1 Summary ofImpact of Laser Welded Sleeve Operations on Stresses
- _a,c.e W M 5-10
i i i l l Table 5-2. Far-field Stress as a Function of Stress Relief Temperature ' _ a,c,e i f f I f r w I i 5-1 I
Table 5 3. Results of 750*F Doped Steam Tests for Nd:YAG Laser Weld Repaired Mockups a,c,e I 4 i P e i W W 5-12
. -. . ,-. - - . . . .. - . _.. - .. ~ - . - . . - - . - . _ .. .- . . - . -
- )
t . Table 5-4. Doped Steam Corrosion Test Results for 3/4 inch
- Tube-Sleeve Mockups Tested Without Axial Load '
i i
- - i 1
,. ,a,c,e >
5 a i 1 J f 4 a f i l 1 t h t a b 4 n i ( i l 1 l 4 U i ' e M s M 5-13
I Table 5-5. Summary of Temperatures, Stresses and Corrosion Test Results for 7/8 inch Sleeve Mockups - Tested with Applied Axial Load a,c,e { i i i 1 ' I mm - 5-14 _ . _ _ _ _ _ . . _ _ . _ . . _ . _________-_m.__ . _ _-_ . _ _ _ _ _ _ _ _ _ __ -
3 l i 1 _ a,c,e : l T l 1 I l Figure 5-1. Corrosion Test Specimen for Doped Steam Testing of a LWS Joint 5-15
~
. _ a,c.e P
i
.l l
I i 1 l 1 l 1 l l 1 Figure 5-2 Test Stand used to Fabricate 7/8 inch OD Tube /LWS Mockups under Locked Tube Conditions 5-16
.. - - . - - . . . _ - . . . . . - . _ - - _ . . . _ - _ - - . - . - - . _ . - ~ . - . - . . . - . . - . -
i 4 i _ a,c,e J i i 1 1 j l 1 i i 1
~
.I
\
i
- i r
- i s ;
e i I i I .t l 1 l
- i 1 I i !
a 1 1 1 1 1 4 i t t i i i i 2 i a. 1 ! ) Figure 5-3 Schematic of Test Assembly used for Doped Steam Testing of Tube /LWS Mockups under Conditions of Applied Axial Loading 4 5-17 i-
1
\
J [ c a,b,e . i i l i I i i i i f i f I Figure 5-4 IGSCC in Alloy 600 Tube of YAG Laser Welded Sleeve Joint after 109 Hours in 750 F Steam Accelerated Corrosion Test 5-18 , I
6.0 INSTALLATION PROCESS DESCRIPTION The following description of the sleeving process pertains to current processes used. I Westinghouse continues to enhance the tooling and processes through development programs. ^ As enhanced techniques are developed and verified they will be utilized. Use of enhanced techniques which do not materially affect the technical justification presented in this report and are considered to be acceptable for application. Section XI, Article IWB-4330 of the ASME 1 Code (Reference 8.2),is used as a guideline to determine which variables require requalification. i The sleeves are fabricated under controlled conditions, serialized, cleaned, and inspected. They 3 are typically placed in polyethylene sleeves, and packaged in protective styrofoam trays inside
- wood boxes. Upon receipt at the site, the boxed sleeves are stored in a controlled area outside i
containment and as required moved to a low radiation, controlled region inside containment. Here the sealed sleeve box is opened and the sleeve removed, inspected and placed in a protective j sleeve carrying case for transport to the steam generator platform. The sleeve packaging { ] specification is extremely stringent and, if unopened, the sleeve package is suitable for long term j storage. ] The full length tubesheet sleeve installation consists of a series of steps starting with tube end j preparation (if necessary) and progressing through tube cleaning, sleeve insertion, hydraulic expansion at both the lower and upper joint, hard rolling the lower tubesheet joint locations, welding the upper joint, visual inspection, post-weld stress relief and eddy current inspection. I The elevated tubesheet sleeve (ETS) installation consists of the same steps as the full length tubesheet sleeve (FLTS) installation. However, in the case of the ET5, the welding and rolling i
- steps are reversed in sequence. The sleeving sequence and process are outlined in Table 6-1.
l 1 These steps are described in the following sections. More information on the currently used 1
- equipment can be obtained from References 8.9,8.10 and 8.11.
6.1 Tube Preparation a There are two steps involved in preparing the steam generator tubes for the sleeving operation. These consist of rolling at the tube mouth and tube cleaning. Tube end rolling is performed only if necessary to insert a sleeve. 6.1.1 Tube End Rolling (Contingency) If gaging or inspection of tube inside diameter measurements indicate a need for tube end rolling
. to provide a uniform tube opening for sleeve insertion, a light mechanical rolling operation will be performed. This is sufficient to prepare the mouth of the tube for sleeve insertion without adversely affecting the original tube hard roll or the tube-to-tubesheet weld. Tube end rolling will be performed only as a contingency.
l 6-1
___.___.__.____._._.._______.___m . _ _ _ _ . i Testing of similar lower joint configurations in Series 27 steam generator sleeving programs at a much higher torque showed no adverse effect on the tube-to-tubesheet weld. Because the radial forces transmitted to the tube-to-tubesheet weld would be lower for a larger Series 44 and 51 tube ' than for the above test configuration, no effect on the weld as a result of the light roll is ' expected. 6.1.2 Tube Cleaning The sleeving process includes cleaning the inside diameter area of tubes to be sleeved to prepare the tube surface for the upper and lowerjoint formation by removing frangible oxides and foreign
~
material. Evaluation has demonstrated that this process does not remove any significant fraction of the tube wall base material. Cleaning also reduces the radiation shine from the tube inside diameter, thus contributing to reducing man-rem exposure.
- The interior surface of each candidate tube will be cleaned by a [
]**
- The hone brush is mounted on a flexible drive shaft that is driven by an pneumatic motor and carries reactor grade deionized flushing water to the hone brush. The hone brush is driven to a predetermined height in the tube that is greater than the sleeve length in order to adequately clean the joint area. [
]'*** The Tube Cleaning End Effector mounts to a tool delivery robot and consists of a guide tube sight glass and a flexible seal designed to surround the tube end and contain the spent flushing water A flexible conduit is attached to the guide tube and connects to the tube cleaning unit on the steam generator platform. The conduit acts as a closed loop system which serves to guide the drive shaft / hone -
brush assembly through the guide tube to the candidate tube and also to carry the spent flushing water to an air driven diaphragm pump which routes the water to the radioactive waste drain. 6.2 Sleeve Insertion and Expansion When all the candidate tubes have been cleaned, the tube cleaning end effector will be removed from the tool delivery robot and the Select and Locate End Effector (SALEE) will be installed. The SALEE consists of two pneumatic camlocks, dual pneumatic gripper assemblies, a pneumatic translation cylinder, a motorized drive assembly, and a sleeve delivery conduit. e' i 6-2 i
The tool delivery robot draws the SALEE through the manway into the channel head. It then positions the SALEE to receive a sleeve, tilting the tool such that the bottom of the tool points toward the manway and the sleeve delivery conduit provides linear access. At this point, the ; platform worker pushes a sleeve / mandrel assembly through the conduit until it is able to be gripped by the translating upper gripper. l l The tool delivery robot then moves the SALEE to the candidate tube. Camlocks are then inserted into nearby tubes and pressurized to secure the SALEE to the tubesheet. l Insertion of the sleeve / mandrel assembly into the candidate tube is accomplished by a { combination of SALEE's translating gripper assembly and the motorized drive assembly which l pushes the sleeve to the desired axial elevatien. For support plate sleeves, the support plate is l found by using an eddy current coil which is an integral part of the expansion mandrel. The l sleeve is positioned by using the grippers and translating cylinder to pull the sleeve into position to bridge the support plate. For tubesheet sleeves, the sleeve is positioned by use of a positive stop on the delivery system.
)
At this point, the sleeve is hydraulically expanded. The bladder style hydraulic expansion mandrel is connected to the high pressure fluid source, the Lightweight Expansion Unit (LEU), i via high pressure flexible cainless tubing. The Lightweight Expansion Unit is controlled by the Sleeve / rube Expansion Controller (S/TEC), a microprocessor controlled expansion box which is i an expansion control system previously proven in various sleeving programs. The StrEC { activates, monitors, and terminates the tube expansion process when proper expansion has been achieved. 1 The one step process hydraulically expands both the lower and upper expansion zones simultaneously. The computer controlled expansion system automatically applies the proper controlled pressure depending upon the respective yield strengths and diametrical clearance between the tube and sleeve. The contact forces between the sleeve and tube due to the initial hydraulic expansion are sufficient to keep the sleeve from moving during subsequent operations. At the end of the cycle, the control computer provides an indication to the operator that the expansion cycle has been properly completed. When the expansion is complete, the mandrel is removed from the expanded sleeve by reversing the above insertion sequence. The SALEE is then repositioned to receive another sleeve / mandrel
, assembly. . 6.3 Lower Joint Hard Roll (Tubesheet Sleeves) l 6.3.1 Full Length Tubesheet Sleeves I At the primary face of the tubesheet, the sleeve is joined to the tube by a mechanical interference fit joint, a.k.a. hard roll, (following the hydraulic expansion). For the generic process, the hard 6-3
l l roll is performed with a roll expander [
]
].'A' (For a site specific process, the particulars of the roll expansion will be provided in a site specific WCAP document.) The control of the mechanical expansion is maintained through l
[ !
}a,c.c 6.3.2 Elevated Tubesheet Sleeves '
As discussed in Section 2, this sleeve is elevated approximately 15 inches from the primary face ~l of the tubesheet. However, the ETS MIF lowerjoint is fabricated by the same types of processes ; which are used to fabricate the FLTS lower joints, i.e., hydraulic expansion and roll expansion. *i In this case, the joint processes are performed at the proper elevation by extensions of the j hydraulic and roll expanders from the tubesheet bottom face. i 6.4 I General Description of Laser Weld Operation Welding of the upper tubesheet sleeve joint and the upper and lower tube support plate sleeve , joints will be accomplished by a specially developed laser beam transmission system and rotating ! weld head. This system employs a Nd:YAG laser energy source located in a trailer outside of I containment. The energy of the laser is delivered to the steam generator platform junction box through a fiber optic cable. . The fiber optic contains an intrinsic safety wire which protects personnel in the case of damage to the fiber. ~ The weld head is connected to the platform junction box by a pre-aligned fiber optic coupler. Each weld head contains the necessary optics, i fiber termination and tracking device to correctly focus the laser beam on the interior of the j sleeve. ' The weld head / fiber optic assembly is precisely positioned within the hydraulic expansion region using the SALEE (described earlier) and an eddy current coil located on the weld head. At the initiation of welding operations, the shielding gas and laser beam are delivered to the welding 3 head. During the welding process the head is rotated around the inside of the tube to produce l the weld. A motor, gear train, and encoder provide the controlled rotary motion to deliver a 360 ' degree weld around the sleeve circumference. The welding parameters, qualified to the rules of the ASME Code, are computer controlled at the weld operators station. 6.5 Rewelding Under some conditions, the initial attempt at making a laser weld may be interrupted before completion. Also, the ultrasonic test (UT) examination of a completed initial weld may result in the weld being rejected. In these cases, if the sleeve / tube has not been perforated by the initial I weld, up to two rewelds, having the same nominal characteristics as the initial weld, will be made j at the same nominal elevation of the initial weld (refer to Figure 6-1). If the three welds at the 1 6-4
initial elevation are unacceptable, and if a perforation of the sleeve is suspected at the initial weld i elevation, up to two rewelds, having the same nominal characteristics as the original weld, will
- be made in the expansion zone inboard of the initial weld. l f,
j; 6.6 Post-Weld Heat Treatment )t Based on the results of corrosion tests of as-welded laser weld-repaired mockups, it has been 3 clearly established that optimum resistance to corrosion requires the use of a post-weld thermal .
- ) stress relief. The effect of the stress reliefis to reduce the high peak stresses at the laser weld and hydraulic expansion locations while minimizing the far-field stresses that may develop in the i
(, parent tube. These effects and means to minimize them, were discussed in Section 5. The data i presented there clearly support the prudence of post-weld thermal stress relief. j Since stress corrosion cracking is related to a large extent to residual stresses, a reduction in the j residual welding stress level will enhance the corrosion resistance of the LWS. The l !- Westinghouse development program determined that a stress reliefin the [ j ]**# reduces the level of residual stress without significant microstructural
- changes. Accordingly, upon completion of all of the welds, the weld sites are stress relieved using a quartz lamp with sufficient power to maintain the tube temperature in the desired range
{ for[ ]**. The value of the heating power is established based on tube surface emissivity information derived from pulled tubes, operating history, visual observation, and prior heat treat programs. This_ post-weld heat treatment (PWHT) is effective over a tube length sufficient to cover the actual weld length as well as any heat affected zone. l . 6.7 Lower Joint (Elevated Tubesheet Sleeves) i In the tubesheet, the sleeve is joined to the tube by a hard roll, a.k.a. roll expansion (following l the hydraulic expansion), performed with a roll expander [ ]*** 1 i [ 1 1 i i a,c.e J. 6.8 Inspection Plan In order to verify the final sleeve installation, inspections will be performed on sleeved tubes to j verify installation and to establish a baseline for future eddy current examination of the sleeved tubes. Specific NDE processes are discussed in Section 7.0. I i j Ifit is necessary to remove a sleeved tube from service as judged by an evaluation of a specific i sleeve / tube configuration, tooling and processes are available to plug the tube. 4 1 6-5
@ I
)
Table 6-1 Sleeve Process Sequence Summary I TUBE PREPARATION 1) Light Mechanical Roll Tube Ends (if necessary)
- 2) Clean Tube inside Surface (Optional)
SLEEVE INSERTION 3) Insert Sleeve / Expansion Mandrel Assembly
- 4) Hydraulically Expand Sleeve, Top and Bottom "I Joints TUBESHEET SLEEVE 5)* Roll Expand Tubesheet Sleeve i LOWER JOINT FORMATION Lower End P WELD OPERATION 6)* Weld Tubesheet Sleeve Upper Joints
- 7) Weld Upper and Lower Support Plate Sleeve Joints INSPECTION 8) Visually Inspect Lower Tubesheet Sleeve Weld
- 9) Ultrasonically Inspect Sleeve Welds (Free span welds only on a sample plan) !
STRESS RELIEF 10) Post Weld Stress Relief Sleeve Welds INSPECTION 11) Baseline Eddy Current Sleeves ;
- e For full length tubesheet sleeves, this is the nominal sequence for these two steps; the roll is -
performed after stress relief for elevated tubesheet sleeves. t i i 6-6 d
i _ a.c.a i l 1 4 I I 1 l i Figure 6-1 Full Length Tubesheet Sleeve with Reweld 6-7 l 1
.- - --~ .- . . . - _ - - . _ - - - - _ . . . - - . - . . . . _ . . - _ . - -
i b 4 7.0 NDE INSPECTABILITY < 1 The welding parameters are computer controlled at the weld operator's station. The essential ; l variables, per ASME Code Case N-395, produce repeatability of the weld process. In addition,
- two non-destructive examination (NDE) capabilities have been developed to evaluate the success !
of the sleeving process. One method is used to confirm that the laser welds meet critical process j dimensions related to structural requirements. The second method is then applied to provide the i necessary baseline data to facilitate subsequent routine in-service inspection capability. i ! 7.1 Inspection Plan Logic j- 7.1.1 The basic tubesheet sleeve inspection plan shall consist of: j, A.' Ultrasonic Inspection (Section 7.2) [ ]**# or alternate methods l (Section 7.4). I 1 j 1. Verify minimum required weld width. i j B. Eddy current examination (Section 7.3) [ ].* *#
- 1. Demonstrate presence of upper and lower hydraulic expansions.
i 1
- 2. Demonstrate lower roll joint presence.
l { 3. Verify weld is located within the hydraulic expansion.
- 4. Verify presence of a post weld heat treatment.
- 5. Record baseline volumetric inspection of the sleeve, the sleeve / tube joint, and the parent tube in the vicinity of the welded sleeve joint for future inspections.
i l C. Weld Process Control [ ].* *#
- 1. Demonstrate weld process parameters comply with qualified weld process specifications.
i 7.1.2 The basic tube support plate sleeve inspection plan shall consist of: lo A. Ultrasonic Inspection (Section 7.2) [ ]'*# or alternate methods (Section 7.4).
- 1. Verify minimum required weld width.
i a i 7-l
i B. ' Eddy current examination (Section 7.3) [ ] .'" f
- 1. Demonstrate presence of upper and lower hydraulic expansions.
- 2. Demonstrate lower joint presence !
- 3. Verify welds are located within the hydraulic expansions.
- 4. Verify presence of a post weld heat treatment. I J
- 5. Record baseline volumetric inspection of the sleeve, the sleeve / tube joint, and the ,l parent tube in the vicinity of the welded sleeve joint for future inspections.
C. Weld Process Control [ ]'" y
- 1. Demonstrate weld process parameters comply with qualified weld process ;
specifications. t 7.2 General Process Overview of Ultrasonic Examination. The ultrasonic inspection process is based upon field proven techniques which have been used l on laser welded sleeves installed by Westinghouse. The inspection process developed for i application to the laser welds uses the transmission of uhrasound to the interface region (the ! sleeve OD / tube ID boundary) and analysis of the amount of reflected energy from that region. j An acceptable weld joint should present no ' acoustic reflectors from this interface above a predetermined threshold. { 1 Appropriate transducer, instrumentation and delivery systems have been designed and techniques established to demonstrate the ability to identify welds.with widths below the structural requirements. The entire weld interface (100 per cent of the axial and circumferential extent) will be examined. Acceptance of welds is based upon application of criteria which is qualified by destructive examination of marginal welds. 7.2.1 Principle of Operation and Data Processing of Ultrasonic Examination. 5 The ultrasonic examination of a laser-weld is schematically outlined in Figure 7-1. An ultrasonic j wave is launched by application of an electrical pulse to a piezoelectric transducer. 'Ihe wave propagates in the couplant medium (water) until it strikes the ID of the sleeve. Ultrasonic energy i is both transmitted and reflected at the boundary. The reflected wave returns to the transducer where it is converted back into an electrical signal which is amplified and displayed on the UT ~l 4 display. I 3 i j The transmitted wave propagates in the sleeve until it reaches the sleeve OD. If fusion between a the sleeve and tube exists, the wave continues to propagate through the weld joint into the tube. This wave then reaches the outer wall (backwall) of the tube and is reflected back to the 7-2 i
=_, _ _ _ - - - , . _. .-
1 transducer. The resulting UT display from a sound weld joint is a large signal from the sleeve ID, followed by a tube backwall " echo" spaced by the time of travel in the sleeve-tube-weld i assembly (Ti .u). If no fusion between the sleeve and the tube exists, another pattern is observed with a large signal from the sleeve ID followed by a reflection from the sleeve OD. The spacing of these echoes depends on the time of travel in the sleeve alone (T i.2). Additional reflections j after the sleeve OD reflections are considered " multiples" of the sleeve OD reflection. These are
-caused as the sound energy reflected off the sleeve OD bounces back and forth between the sleeve ID and OD, and decays over time.
[ ja.c.e Criteria for the acceptance of a laser weld is based upon combination of the observed ultrasome > response at the at the weld surface, the sleeve / tube interface, and the tube OD. j An automated system is used for digitizing and storing the UT wave forms (A-Scans). [ l
]'" The ultrasonic response from the weld is then digitized for l each pulse. A typical digitized A-scan is shown in Figure 7-2. Time intervals known as " gates" are set up over the signals of interest in the A-Scan so that an output known as a "C-Scan" can be generated. The C-Scan is a developed view of the inspection area which maps the amplitude of the signals ofinterest as a function of position in the tube. A combined C-scan which shows the logical combinations conditions of signals in two gates with respect to predetermined threshold values can also be displayed. Figure 7-3 shows the A, B, C, and combined C-scan display for a weld in a calibration standard.
7.2.2 Laser Weld Test Sample Results Ultrasonic test process criteria are developed by [ 1 e L.C.8 l 7-3
Field application requires calibration to establish that the system essential variables are set per the same process which was qualified. Elements of the calibration are to: 1 Set system sensitivity (gain).-Provide time of flight reference for sleeve ID, OD and tube OD signals. I i l Verify proper system function by scanning of the standard. ' Figure 7-4 depicts a calibration standard for the sleeve weld UT exam. -7.2.3 Ultrasonic Inspection Equipment and Tooling . The Probe is delivered with the Westinghouse ROSA III zero entry system. The various -
~
subsystems include the water couplant, UT, motor control, and data display / storage. 1 The prebe motion is accomplished via rotary and axial drives which allow a range of speeds and axial advances per 360' scan of the transducer head (pitch). The pitch provides a high degree of j overlapping coverage without sacrificing resolution or sensitivity. The controls and displays are configured for remote location in a trailer outside of containment. The system.also provides for periodic calibration of the UT system on the steam generator ! platform. - 7.3 Eddy Current Inspection.
)
Upon conclusion of the sleeve installation process, a final eddy current inspection is performed i on every installed sleeve to meet the process verification and baseline inspection requirements outlined in Sections 7.1,1 B and 7.1.2 B. The combined Cecco-5/ bobbin probe is utilized towards this end to provide an enhanced baseline inspection without sacrificing data acquisition speed. The bobbin probe provides the inspection to verify the presence and location of the expansions, - as well as weld location. The Cecco-5 probe provides baseline examination of the sleeve and ( tube. 7.3.1 Cecco-5/ Bobbin Principles of Operation. f The standard bobbin probe configuration consists of two circumferentially wound coils which are displaced axially along the probe body. The coils are connected in the differential mode; that is, . the system responds only when there is a difference in the properties of the materials surrounding l the two coils. . The Cecco-5 (CS) design operates as a transmit-receive probe. The C5 configuration is designed to provide detection of both circumferential and axial degradation. There are two bracelets of coils, each consisting of an array of transmit-receive sets. Each bracelet is capable of achieving 50 percent coverage of the circumference of the tube. This is due to the fact that there is no i 7-4 j
coverage directly underneath the coils of a transmit receive probe. For this reason, the second bracelet is offset relative to the first to achieve full coverage. Transmit-receive probes are, by nature of their operational principles, less sensitive to lift-off effects than a comparable impedance coil. By virtue of this feature, probes can be designed in such a fashion that the coils do not have to ride the surface of the tube in order to achieve a reasonable level of detectability in a region of geometric change. The coupling of the probes with instrumentation and software designed to take advantage of their specific design features makes transmit-receive probes an attractive technology for the inspection of sleeved tubes. The calibration standard used for Cecco-5 sleeve inspection includes various axial and circumferential notches as depicted on Figure 7-5. Notches are located in the expansion transitions as well as in the tube and sleeve free span. Figure 7-6 depicts a 20 channel strip chart plot of the calibration standard. The analysis software allows the data from the two bracelets and the bobbin coil to be displayed in an aligned fashion. The channels may be selected so that data from each sensing point is viewed, enabling viewing of an entire tube circumference on a single screen. Figures 7-7 and 7-8 show the response of the Cecco 5 probe to [
] '" notches in the parent tube at the sleeve expansion transition.
Cecco-5 Probes have been qualified to EPRI Appendix H requirements for detection in 3/4 inch and 7/8 inch sleeved tubing. 7.4 Alternate Post Installation Acceptance Methods Ultrasonic and eddy current inspection are the prime methods for post-installation weld quality evaluation, with eddy current examination being used as the prime in-service examination technique. However, there are cases, due [
) .e
[
).
In support of accepting UT indeterminate welds, several alternate strategies will be applied, as agreed to by the implementing utility and Westinghouse. While this summary is not meant to preclude other methods, it is included to provide an indication of the rigor of the alternate methods. 7-5
i 7.4.1. Bounding Inspections [
). e
[ i
) ,,
7.4.2 Workmanship Samples [
]
]a.c.e 7.4.3 Other Advanced Examination Techniques As other advanced techniques become available and are proven suitable, Westinghouse may elect, with utility concurrence, to alter its post-installation inspection program. [
}'
[ l l i l' In summary, Westinghouse proposes to apply alternate inspection techniques with utility l concurrence as they become available. It is intending that this licensing report not preclude the use of these inspections as long as they can be demonstrated to provide the same degree or greater of inspection rigor as the initial use methods identified in this report. l 7.5 Inservice Inspection Plan for Sleeved Tubes The need exists to perform periodic inspections of the supplemented pressure boundary. The inservice inspection program will consist of the following:
- a. The sleeve will be eddy current inspected upon completion ofinstallation to obtain a baseline signature to which all subsequent inspections will be compared.
7-6
- b. Periodic inspections will be performed to monitor sleeve and tube wall conditions in accordance with the inspection section of the individual plant Technical Specifications.
- The inspection of sleeves will necessitate the use of an eddy current probe that can pass through the sleeve ID. For the tube span between sleeves, this will result in a reduced fill factor. The possibility for tube degradation in free span lengths is extremely small, as plant data have shown ,
that this area is less susceptible than other locations. Any tube indication in this region will ' require further inspection by alternate techniques (i.e., surface riding probes) prior to acceptance of that indication. Otherwise the tube shall be removed from service by plugging. Any change in the eddy current signature of the sleeve and sleeve / tube joint region will require further ; inspection by alternate techniques prior to acceptance. Otherwise the tube containing the sleeve j in question shall be removed from service by plugging. ' e 7-7
a.c.e j
-4 i
i 1 t i r
!i ;
l 1 l 4 E I I i t-
?
?
i f i
\
i l 4 ,- 1 I Figure 7-1 Ultrasonic Inspection of Welded Sleeve Joint l a i 7-8
R f i h D 5[ 4 6
)
I 1 I i f-i I i l E a ,
#. 1 i
~ e 6
D '$ O iI IT e
$I t% l
'S '
.tP ,
ci N
.k!
a. A h 6
)
e i 1
.i
-, . - ~ - . , ..- - - , - _ . .-
i a,c.e l 1 i i
.i l
Figure 7-3 A, B, C, and Combined C-Scan Display for Weld in UT Calibration Standard 7 - 10
a,c.e f-l l l , i i l i. I 'O 1 l l I i l i i i ! l i i l 1 i t . i; - _ _ Figure 7-4 i UT Calibration Standard 7 - 11 i i P
8,C ,C Figure 7-5 Cecco-5 Sleeve Calibration Standard 7 - 12
- . . .. . . _ . . . .- --. -- -- -- - ~ -- -. ----- - - - - - - - . - .
1
~
a,c.e l l l l I I Figure 7-6 Strip Chart Display for Cecco/ Bobbin Data 7 - 13
, _ . . . . .. . . _ - - . . . . . . - - ... . . . . - -. . . . ~ . . . . - _ . - . - - -
@ l l
- a.c.e !
- 1 1
4 i r i i ! ! l l l e-l l 1 l l l l l l l l l i Figure 7-7 Response of Cecco-5 Probe to 60% OD Axial Notch in Parent Tube Located at Expansion Transition 7 - 14 l I
4 a.c.e f 1 i i i O I t e
~
Figure 7-8 Response of Cecco-5 Probe to 60% OD Circumferential Notch in Parent Tube Located at Expansion Transition i i 7 - 15
no men- wma.+-msmsn+maa ma n _-_m_um.amm,m,, . _ _ , ____ p,,__,p ,_ ,, __ _ _ ___ l l t l 1 4 i 1 S 0
-. --. ._ , _ _ _ . . ..-_ _ . _ _ _ . __ . . ._ . . , _ _ _ _._..__.. _ _,,.._.,.___ , _m_ . _ . , , _ _ _ - _ - _.,
8.0 REFERENCES
8.1 Design Specification 412A19, " Plants with Series 44 and 51 Steam Generators, Steam Generator Heat Transfer Tube Sleeving, ASME Boiler and Pressure Vessel Code, Section III, Code Case 1 Safety Class 1", Revision 0, December 17,1972. 8.2 "ASME Boiler and Pressure Vessel Code, Section III, " Rules For Construction of Nuclear Power Plant Components", The American Society of Mechanical Engineers. 8.3 USNRC Regulatory Guide 1.121, " Bases for Plugging Degraded PWR Steam Generator g Tubes (For Comment)", August 1976. o 8.4 "American Electric Power D. C. Cook Unit 1 Steam Generator Sleeving Report - (Mechanical Sleeves)", WCAP-12623, Revision 0, June 1990. 8.5 1. F. Harvey, Theory and Design of Modem Pressure Vessels, Second Edition, Van Nostrand Reinhold Company, New York, NY,1974. 8.6. WNET-142, Volume 8 "Model D4-2 Steam Generator Stress, Report Divider Plate Analysis", Westinghouse Tampa Division, September,1977. 8.7. Timoshenko, S., Strength ofMaterials, Part II, Third Edition, Van Nostrand Company, j Princeton, NJ,1956.
)
8.8 " Alloy 690 for Steam Generator Tubing Applications", EPRI Report NP-6997-SD, Final Report for Program S408-6, October 1990. 8.9 Boone, P. J., " ROSA III, A Third Generation Steam Generator Service Robot Targeted at Reducing Steam Generator Maintenance Exposure," CSNI/UNIPEDE Specialists i Meeting on Operating Experience with Steam Generator, paper 6.7, Brussels, Belgium, September 1991. 8.10 Wagner, T. R., VanHulle, L., " Development of a Steam Generator Sleeving System Using Fiber Optic Transmission of Laser Light," CSNI/UNIPEDE Specialists Meeting on Operating Experience with Steam Generators, paper 8.6, Brussels, Belgium, September e 1991. 7
- 8.11 Wagner, T. R., " Laser Welded Sleeving in Steam Generators," AWS/EPRI Seminar, Paper
! IID, Orlando, Florida, December 1991. 8.12 Stubbe, J., Birthe, J., and Verbeek, K., " Qualification and Field Experience of Sleeving Repair Techniques: CSNI/UNIPEDE Specialist Meeting on Operating Experience With Steam Generators", Paper 8.7, Brussels, Belgium, September 1991. 8-1}}