ML19309A920
| ML19309A920 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 03/23/1973 |
| From: | Davis E SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8004010672 | |
| Download: ML19309A920 (7) | |
Text
. AEC DIS" MBUTIO[T FOR PART 50 DOCIET f AT"IAL i j ,
(TE4PORARY FORM)
CONTROL NO:
1977 FIrr FROM:
DAE OF DOC:
DATE REC'D LG iG;<0 Rpr or;ga Srcremento Municipal Utility.Dist.
Secremento, California 95813 3-23-73 3-26 x E. K. Davis l
A. Giambusso 1 signed 39 S m LOCAL PDR y
CIASS:
U/FROP IliF0
.IIiFi)T lio CYS REC'D DOC E T IiO:
40 50-312 DESCRIPIIGIi:
ENCLOSURES:
L6r re our 12 72 ler...trans. the following:
Addl Info to Final Report on Minor Imperfectioni found in pipe welds at the Rancho Seco Nuclear l Generating Station.
A000gtGB 30 NOI EV0Vi PIA!iT NAIGS:
Rancho Seco (25 cys ree'd)
FOR ACTIO:i/I.UOR'4AT:0:i 4-3-/a roo BUTLER (L)
.AICHWaiCER(L)
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YOUNGELCOD(E)
W/' Copies W/ 7 Copies W/ Copies W/ Copies CIARK(L)
STOLZ(L)
ROUSE (FM)
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W/ Copies W/ Copies W/ Copies' W/ Copies GOLLER(L)
VASSALLO(L)
. DICKER (E)
W/ Copies W/ Copies W/ Copies W/ Copies
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KNIGHTON(E)
'W/ Copies W/ Copies W/ Copies W/ Copies INTERNAL DISTRIBUTION h FI TECH REVIEW DENTCN F&M WADE E
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HENDRIE GRIMES SMILEY BROWN E
A, ROOM P-506A SCHROEDER GAMMILL NUSSBAUMER G. WILUAIG E
,,,,MUNrZING/ STAFF MACCARY KASTNER SHEPPARD
-E CASE KNIGHT (2)
BALLARD LIC ASST.
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GIAMBUSSO PAWLICKI SPANGLER SERVICE L
A/T IND BOYD SHAO VIISON L
BRAITMAN V. MOORE-L(BWR)
,,, STELID ENVIRO A OULBOURNE L SALTZMAN haDEYOUNG-L(PWR)
HOUSTON MULLER SMITH L
SKOVHOLT-L NOVACK DICKER GEARIN L
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P. COLLINS ROSS KNIGHTON DIGGS L
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LONG FROJ LEADER MAIGRET L
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,4TEELE BENAROYA HARLESS 800an3m[9 2,s v0LtxzR rwmin DTs'rHT9tmoir
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$SMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street, Box 15830, Sacra nento, California 95813; (916) 452 3211 March 23, 1973 T
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N.. t $.,9 7 l'*f Mr. Angelo Giambusso Deputy Director for Reactor Projects
/U-Directorate of Licensing L
U. S. Atomic Energy Commission
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7 Washington, D. C.
20545 Rancho Seco Nuclear Generating Station No. 1 AEC Docket No. 50-312
Dear Mr. Giambusso:
The Sacramento Municipal Utility District hereby submits twenty five (25) copies of additional information relating to the
" Final Report on Minor Imperfecti'ons Found in Pipe Welds at the Rancho Scco Nuclear Generating Stat. ion."~
This information is in response to Mr. DeYoung's letter of December 5, 1972 and demonstrates adequate fatigue strength margins exist for the subject pipe velds-.
S rely-yours, c ' h l'
f' lbbDO 9.,K. Davis General Manager i
Enclosures 9
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AN ELECTRIC SYSTEM S E R VIN G MORE THAN 600,000 IN THE HEART OF CAlff0R%iA
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QUESTION We have reviewed your report, " Final Report on Minor (Ref. AEC letter dated Dec. 5, 1972).
Imperfections Found in Pipe Welds at Rancho Seco Nuclear Generating Statica", dated August 31, 1972.
We agree with the analysis of the problem, actions taken to reduce the probability of occurrence of minor imperfections, and the basic interpretation of the results of the experimental program. We conclude that pipe welds having " minor imperfec-tions" of. the type evaluated da this report are acceptable, provided that you furnish additional assurance that such pipe welds possess adequate -
fatigue strength margins.
~
ANSWER Justification of the use of the increased value of K and K stress Indices 2
3 As a general justification we can state that:
In the piping design the pipe wall thickness is determined by the elbows.
Stress indices applicable to elbows (see Table No.1) are higher than the actual stress indices found by tests for the imperfection zone.
Since the pipe wall thickness is equal to the wall thickness required for the elbows, the piping system is designed for a higher stress index and for a greater fatigue life than the values indicated by tests for-girth butt welds.
4 Nuclear Class 1 Lines A. Stainless Steel As an illustrative example we compute the Usuage Factor for line No. 26524 for which the " Stress Report for East and West Core Flooding Pipelines" indicates the highest stress condition at com-ponent number 2 and joint number 2.
The usage factor for this weld is computed by using 1.1 for the three K factors.
This corresponds to a girth butt weld ground flush. With these stress indices, at the weld considered, the usage
. factor is U1 = 0.1780.
i To 'see the effect of the increased value of the K2 and K3 stress i.
indices we first compute the usage factor at the above indicated -
t point, by assuming th'at the weld is "as welded", then we compute the usage factor at the same point using the increased value of K2'and K -
3 Using the numerical values g'iven in the above indicated Stress Report for Equation 11 of Paragraph 1-705.2 of the Nuclear Piping Code (B31.7) we can write G
y -
.~
^
()
[
Po
-(2 1.406)
=
4 8856.81 Do Mi 14.00 141.2787x10
=
=
2I (2) (1116.6)
(1-v ) laT 36 8.3
= 42980.61
=
1 2
6{9.64x369.6-9.62x354.9 10-6 =4002.88 E ab "a T "b Tb
= 26.9x10 a
Then Equation 11 P
+ K2 C2 M
+
C1 2
Sp=K1 i
2 (1-v )
C E T
~ "b Tb,+ 1-v 2'
+K3 3 ab, "a a
with the use of K1 = 1.2 C1 = 1.1 K2 = 1.8 C2 = 1.0 K3 = 1.7 C3 = 1.0 we can write (1.1) (1.2)
(10007.11) + (1.8) (1.0)
(8856.81) +
S
=
p
+ (1. 7) - (42980.61) + (1.0) (1.7) (4002-.88) + (368.3) (126.1) 155466.1 PSI S
=
p
- Sn)
Sp + A (Sp Salt " i 3 m 1
"5 155466.1 + 0.7 (155466.1 - 74870) 5 36 Salt = 154436 PSI
~ n = 330
0.727 ui
3 with the use of K1 = 1.2 C1 = 1.1 K2 = 2.0 C2 = 1.0 K3 = 2.0 C3 = 1.0 we.can write S
= (1,1) (1.2) (10007.11) + -(2.0) (1.0) (8856.81 &
p
+ (2.0) (42980.61) + (1.0) (2.0) (4002.88) + ( '8.3) (126.1)
]
Iy fi,
+
171332 PSI S
=
p alt. "2
[171332 + 0.7 (171332 - 74870) ]
S 5 360 Salt = 174096 PSI n = 250
= 0.960 ui = 250 0.960 - 0.727 The increase of usage factor 00 = 32%.
0.727 Assuming that the increase of K2 and K3 factors for ground flush welds is the same as for "as welded" butt welds, then the actual usage factor of the weld at component number 2 and joint number 2 is ui = 0.178x1.32 = 0.235 Hence, we conclude that the piping is still adequate by a large margin.
B.
Carbon Steel
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w 7.g The only Nuclear Class 1 carbon steel lines are the systems of the Primary Coolant Loop. These carbon steel pipes are over-layed on the inside surface with stainless steel. They are large lines and are walded from both inside and outside. The welding procedure used precluded the formation of Minor Imper-fections studied in the Report.
Nuclear Class 2 Lines Table 10A-1 furnished with Amendment 10 of the FSAR gives maximum stress levels for both carbon steel and stainless steel piping in the Nuclear Class i
2 category. These lines have been analyzed for fatigue behavior in accord-ance with the Code requirements for this class of piping. The allowable stress values shown are higher in all cases than the actual computed stresses..
The allowable stress values were computed by using the a value of.f = 1.0 for the Stress Range Reduction Factor, which corresponds, in accordance with.
Table 102.3.2(c) of the Power Piping Code (B31.1.0) to a Number of Equiva-lent Full Temperature Cycle of N = 7000. Since this number of cycles is considerably higher than the 240 cycles required for start-up and shu* -down full cycle temperature. variation, the slight effect of the minor imperfec-tions in all cases can be considered as negligible.
Nuclear Class 3 Lines i
Lines in this category are not submitted to accumulative cyclic loads and therefore fatigue analysis is not necessary.
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Non-Nuclear. Seismic Class 1 Lines These are carbot) steel pipes conveying cooling water for safety related equipment. Here again cyclic loading of sufficient magnitude is not present and the fatigue life of these lines is not calculated.
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