ML19318C429
| ML19318C429 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 06/24/1980 |
| From: | Hancock J FLORIDA POWER CORP. |
| To: | |
| References | |
| REF-PT21-80-230-002 3--7-A, 3-0-7-A, NUDOCS 8007010463 | |
| Download: ML19318C429 (17) | |
Text
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p i-Florida Power C O n ta e a t eo se June 24, 1980 File: 3-0-7-a Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
Docket No. 50-302 License No. DPR-72 Cry,stal River Unit #3 Dea: Sir:
The 10 CFR 21 report submitted to you on May 30, 1980 concerning Mainsteam Safety Valves which exhibited cracking in the valve disc guides, has been dispositioned.
Results of analyses of the parts which were reported as defective are appended and the parts have been determined acceptable for use as is in their current configuration.
Please advise if further discussion is required.
Very truly yours, FLORIDA POWER CORPORATION J. A. Hancock Assistant Vice President Nuclear Operations Hancock(Tb)D47 00l cc: Director 5
Office of Inspection and Enforcement f
U. S. Nuclear Regulatory Comission
///
230 Peachtree Street NW Suite 818 Atlanta, GA 30303 8 0 0 7 010e%3
.e General Office 3201 inerty-eurtn street soutn. P O Box 14042, st. Petersburg. Florica 33733 e 813-866 5151
CORRESPONDENCE
}kg INTEROFFICE H-8 Nuclear Engineering
~ tuen coa.s pmc )
Crystal River 3 SU2 JECT:
CR 3 - Eq 3-11-14 File:
June 20,1980 DATE:
T. C. Lutkehaus To:
letter We have reviewed Dresser Report SV-157 submitte k
n i
the guides and their recommendation to re nsThe location, size, and orientati i
guides removing the cracks. cracks should be documented so that some representa can be reinspected at the next refueling outage.
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DAESSEA ib__ _- _3 INDUSTRIES
.a INDUSTRIALVALVC & INSTRUMENT Divis10N O sox 14sc 0 ALEXANDRf A. LCUISl ANA 71301 Tct. sis /s4o.z a so O Twx: sio *To-s7 ss 0 TcLcx: so 64 :3 0 caste: oivio 1
June 19, 1980
.1, f
Mr. Sam Johnson Crystal River Nuclear Plant Florida Power Corp.
P.O. Box 1228 Crystal River, Florida 32629
Dear Mr. Johnson:
Enclosed per your request is a copy of Dresser Report SV-157, entitled
" Dresser Posit'.co with regard to Main Stea::: Safety Valve Guides".
Although the report along with the supporting stress analysis is self explanatory, please contact me if you have any questions.
Very truly yours, g,NN N
/
T
- d. D.
eck, P.E.
j Chief Engineer Consolidated Valves eds Attachments O
AsscaorT O w4wcoct O cowsoi.noATco O weisc o. r..... o u s,..... e.
SV-157 Juno 17, 1980 I
um 7
DAESSEA INDUSTRIES h
_f INDUSTRIA! VAI.VE & INSTRUMENT DIVISION O COX 1430 0 At.EXAN DRI A. LOUISl AN A 713 01 vci :is/s4o asso O Twx: sto 97s s733 0 TcLcx: so s4:s O cAetti civio DRESSER POSITION WITH REGARD TO i
MAIN STEAM SAFETY VALVE GUIDES On May 23, 1980 during testing of Dresser main steam safety valves type 3700 by Florida Power Corp. personnel, valves which had been removed from the Crystal River Unit 3 Nuclear Power Station were found to have indications of cracking on the upper portion of the guide.
These cracks were circumferential surface cracks located immediately beneath the flange and did not extend
-to the inside diameter which is the guiding surface.
Cracks were present with a maximum length of 4" with an apparent depth of up to.100 inches.
Two cracks in each guide were discovered diametrically opposed in a pa nicularly similar pattern.
The cracked guides were subsequently replaced with guides supplied from the Dresser Alexandria facility.
Upon dye penetrant examination of the replacement guides, indications of cracking in i
the same location (on one of the six guides), again diametrically opposed, was discovered.
i Valves were subsequently obtained from Tennes.see Valley Authority for the purpose of installation' at Crysta'. River Unit 3 to bring the unit back on line.
Examination of two valves supplied by e
I AnwenorT D wawcoce n cowsouoavro n weer
I i
Tennessee Valley Authority showed the guides once again indicat-
' ing. cracks very similar in appearance to those originally found at Crystal River.
t Dresser Industries in their Alexandria Valve Operations conducted s 7-an engineering / metallurgical investigation in order to attempt to determine the,cause of the indications.
It was postulated at Dresser that the cracking was a result of shrink occurring during the casting cooling process (the guides are sand cast and subsequently machined on their inner and most of the outer surfaces).
The assessment by Dresser Engineering personnel was that the. cracks were induced at the time of initial pouring of the casting and subsequent cooling with service conditions of alternate high heating and cooling causing the cracks to become more apparent to the point where they were visible to the naked eye.
Dresser Engineering evaluation was that the cracks, due to the method of their fo'rming, would not be liable to propagate, however, we felt that independent analysis was necessary to confirm this position.
In order to provide the independent analysis, one guide was submitted by Florida Power Corp. to Battelle Memorial Institute in Columbus,' Ohio.
This guide was reviewed by Battelle Metallurgist, Mr. John Beavers, as well as the casting expert on the Battelle staff, Mr. Don Roach.
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Battelle Memorial Institute has confirmed the initial' evaluation of Dresser b' gineering personnel in that the Battelle evaluation n
indicates the cracks are formed due to shrinkage at the time of casting and become more apparent during the operational gycling.
It is the stated opinion of the Battelle Memorial Institute Metallurgist that no propagation of the crack is indicated by the sample which was examined by him.
\\
e, Analysis has been performed which indicates the stresses applied
)
to the part are approximately 20% of the allowable stress for this material at the applied temperature.
This analysis, which is appended to this report, indicates that the crack indications can be removed, if desired, by machining and reducing the wall thickness of the part without any detrimental impact to the guide.
It is the opinion of Dresser Engineering personnel and supported by Battelle Memorial Institute that the indications of crceking in this guide (which is not a pressure retaining part) have no J
affect on the operation, functionability.
- design life of the valve.
It is therefore, our recommendation that no 10CFR Part 21 be issued since no significant safety hazard is present.
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INDUSTRIAL VALVE & INSTRUMENT DIVislON O sox 1430 0 ALEXANDRIA. LOul51ANA 71301 Tet. sis /s4o asso O Twx: sto-*7s s?is 0 Tctext so s4 23 0 casts: oivio CERTIFICATION OF ANALYSIS Report Number SV-157 Revision 0
j.
I HEREBY CERTIFY THAT I HAVE P.ERFORMED THIS ANALYSIS TO THE j
BEST OF MY ABILITY AND BELIEVE IT ACCURATELY REFLECTS THE OPERATIONAL LOADING AND STRESSES THE COMPONENT IS SUBJECTED TO.
PRODUCT ENGINEER I'8~/f80
/'
DATE I HEREBY CERTIFY THAT I HAVE REVIEWED THIS ANALYSIS TO THE BEST OF MY ABILITY AND BELIEVE IT ACCURATELY REFLECTS THE OPERATIONAL LOADING AND STRESSES THE COMPONENT IS SUBJECTED j
TO.
CHIEF PRODUCT ENGINEER /
,/}
LA 6/l<6
/
v i
[
DATE
)
o c
l I HEREBY CERTIFY THAT I HAVE REVIEWED THIS ANALYSIS TO THE BEST OF MY ABILITY AND BELIEVE IT ACCURATELY REFLECTS THE OPERATIONAL LOADING AND STRESSES THE COMPONENT IS SUBJECTED TO.
CHIEF DEVELOPMENT ENGINEER /
DATE t
e
/
AswenorT O wAwcocic 0 cowsouo4Tro O weisc
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Report No. SV-157 Rcv. 0
SUMMARY
By assuming the wall thickness of 0.5" in the upper half of the disc guide, calculated resultant stress in the dise'
. guide due to safety valve opening is well below the yield strength of guide material at operating temperature.
W t
1 i
j 0
o
+
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1
+
I Disc Guide Material:
ASTM B584 Alloy 978 Leaded Nickel Bronze t
Sy = 20,000 psi Su'= 37,000 psi @ 4000F
[1]
Loading:
(1)
AP = 300 psi (2)
Spindle side thrust Fe,- 4500# (assumed)
(3) t 50 psi pressure pulsation with 120 Hz.
(I)
Natural frequencies The dimensions of the guide was given on page 2.
The natural frecuencies of the structure are computed as follows:
(1)
Transversal vibration mode
<,,,,,,.,n<
,i,,,
,,,,////
N N
s s
?^
\\
For conservatism, the disc NN N
I s
s s
i s
A N
guide was modelled as a s
s s
s s
3-stepped beam structure.
)N
()E 2
s The mass of the upper ring
[N s
was lumped into the step s
N ys 3
s, s
no. 2. - The structural
[
s properties of each step were computed as i
[1] Metal Handbook, 8th Edition, Vol. 1, American Society for Metals, P.P. 1050-1051
2
.j s,.
g
/.*i
=.
i/
x y,
\\'
\\ \\\\
,,\\
\\
\\\\
m' s r:.
2 e
e l
4 er I
s s
4 hs m
=
qu e e
e 7.
ey s
[l
'l 0) t)
4 m
s l
t
~.
N ge 5
e 4
9 f
I N
i D
5 O
tt)
O'
%s g
r N
w
- 4 6
~~
7 "O
'e a.
O
'. l... '
3 Sten 1:
l = g [(9.646)' - (8.646)4] = 150.6 in' I
2 1 = A p/(32.2 x 12) = 0.'0167089747 lbm sec /in l
11 = 3.375" 1=y[(10.125)2-(8.640)2]=21.886in2 (conservative)
A 3
p
= 0.295 lb/in '
(weight density)
Step 2:
2 " [k [(9.75)4 - (8.646)4] = 169.293 in' I
2 p2 " ^2p / (32. 2 x 12.) = 0.040516 lbm-sec /in 2 " 4[(9.75)2 - (8.640)2] = 16.0323 in 2
A A2=A2 + upper ring (37.03665888) 22 = 5.0" Step 3:
13 = JL [ (9.197)
- (8.646)4] = 76.8969 in4 64 2
p3 = A p/(32.2 x 12) = 0.005230? lbm-sec /in 3
1
- eme.e.e.*-w--.a
,-4
_ _-<=._
o w -*
- ,*+*e
+v
.-+e
- e =
- to. - e e w
4 (8.640)2] = 7.083095 in2
-A3 = E [ (9.197) 4 6
23 = 6.0" E - 28 x 10 psi 1
By Rayleigh-Ritz method, the first mode natural frequency is obtained [2]
f.= 7,201 Hz a
(ii)
Shell vibration mode For simplicity and conserva-tism, the disc guide was
' ' ' ' l ' ' ' ' ' ' ' di # 5 s
s modelled as a uniform Mlh%
s s
s s_
L cylindrical shell.
Its s;I s
s s s dimensions was given in
's
']1 2d
'N the figure.
It was s'i s s treated as an infinite long cylinder with half wave length of 6" long, and mean radius of 4.599".
The natural frequency equa-tion of the structure is 2
2 2
a 2
2 a
[A n
- n 3g(y_y)A gA 2_
2_,(n
+n 2 + 1))
+ 4 (1 + v )"2,2) + 4(1 + v)"2 2 2 an
=0 3
7
[ 2][ 3]
[ 2] Handbook of Engineering Mechanics, FlBgg McGraw-Hill, 1962 P.P.61-25-28 m
_m
.._....--a-.
mae___
---.~_m.
y
_.,g
. \\... *. -
5 where v = 0.3 = Poission's ratio, a = mean radius, n = circumferential wave number L = half wave length = 6" h
The lowest mode occurs at n = 9, and corresponding A = 0.107.
The natural frequency is j[Ghge,
]Dge' = 8645 Hz 1
x f
'na p
2na p
p
= 0.295 lb/in3 = 0.000763 slug /in3 h
= 0.5 (thickness)
E 6
G 10.77 x 10 psi
=
=
2(1+v) ge = 386.4 lbm-in/lbf-sec2 (II)
Stresses due to AP = 300 psi The pressure load produces the side thrust on the disc guide as shown in the
'3/ ' > > > > ' " > > " d_
figure.
For conserva-
--+
,/
'40c f 55 "
tism, the total pressure load is computed as I
F = 300 x Ap = 21,690#
where A is the projection area = 73 in2 p
[3] Theory of Sound, J. W. Rayleigh,~;uw York Dover Publications, Vol.
1, P.O. 402-405
- p__...--
.s s.<--
sn...-e-...se
.-.....o.e.-
.,..e-
6 The maximum bending moment occurs at the. built-in
- end, M=fF(6)=65,070"-#
The bending stress and shearing stress are ob = M/Z = 2,083 psi F/A = 1,510 psi t
=
where j
Z 32 [ (9.646)' - (8.646)4]/ (9.646) = 31.239 in JL 3
=
n[(9.646)2 - (8.646)2]/4 = 14.366 in2 j
A
=
(III) Stresses due to Fe - 4,500#
l The spindle side thrust is assumed acting at the bottom end of the disc guide.
The stresses at the built-in end are computed as:
ob = M/Z = 864 psi F /A = 313 psi T
=
e M
F (6) = 27,000"-#
=
e l
l (IV)
Stresses due to dynamic pressure load i
Pd = 50 sin 2nft f = 120 Hz Two types of dynamic pressure load acting on the disc l
l
(
a 7
guide:
(i) transversal harmonic force, and (ii) radial harmonic force.
A (i)
Transversal harmonic force Since the natural frequency
/ / /// / //////W/
of the disc guide for the transversal vibration is much higher than the fre-h quency of forcing fune. tion.
50 M M fi)
Therefore, the amplification factor of the system can be assumed as 2
AMF = 1/[ 1- (w /wn) 3 U 1 For conservatism, the system is considered as a SDOF as shown in the figure.
L/ ' '..//1EL-1 p-50 Ap = 50(73) = 3650#
F Therefore, the response of the system is
=h F=E E M )
f x = Xsin 2nft X = (AMF)(X ) = 0.0000505 o_
where F23 P
Xo = 3EI
= 0.0000505 I
=
" [ (9. 64)0 (8.646)4] = 185.9 in4 64
i Total maximum force at the disc guide is 22 p + M l' l = 3650 + m (4n f X) = 3654#
F=F x
f =.1274615896 m = total mass =
1 1 + E 2 (#2 ~ # ) + 43(#3-22 2
1 The stresses are ob = E = 702 psi Z
= F/A = 254. psi r
(iii) Radial harmonic force For conservatism, the AMF for radial vibration is given as AMF = 1/[1 w/wn] '- 2 (assumed)
_. / ;.o j i i ;;,-
The response of the system is
~
(AMF)yo = 0.0001163184" y
=
e 2
yo = PR (1-0.5v)/(CE) = 0.0000582" where 3, g.,
t = 0.5 (average thickness)
\\ k G N
v = 0.3
/
s R = 4.599" (mean radius)
]
// !m Total pressure load will be 22 P = 50 + p(4n f y) = 50.03 psi w
_ _ _-.., y y -.
e - - -. -
.r w,.
..~..
f;....
~
.I 9
where 2
= mass per unit area = 0.000735 slug /in The stresses are S2 = ER = 208 psi 2t Sr = PR/t = 417 psi (V)
Resultant Stresses Maximum total stresses at the built-in end are e
= 3,857 psi n
r
= 2,077 psi Maximum primary membrane-plus-bending stress is P +L = 5,669 psi m
'w,-