ML20077S343
| ML20077S343 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Crane |
| Issue date: | 12/21/1978 |
| From: | Giacobbe F GENERAL PUBLIC UTILITIES CORP. |
| To: | Skuchas E GENERAL PUBLIC UTILITIES CORP. |
| Shared Package | |
| ML20077S281 | List: |
| References | |
| FOIA-83-349 NUDOCS 8309220028 | |
| Download: ML20077S343 (4) | |
Text
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Subiect Continusd Operation, of he THI #1 DH-V-1 (sTI.0006) fo -
E. G. SKUCEAS Locatiort Reading
)
At the request of Metropolitan Edison Company, a re-evaluation was performed assessing the possibility of stress corrosion cracking occurring in the #1 decay heat valve because of the presence of fur =4.te., In c
making, this evaluation the.following para =aters were established:
51.
The valve body, which is the critical component in contact with the ~
furmanij;e is cast 316 SS (Table I).
2.
The Itd=perature in' the vicinity of the furm= rite is,140*--150*F.
~ (Data supplied by E. G. Skuchas).
~
'3.
The stresses in the valve body are +7,920 psi circumferential, +14,573 psi, longitudinal,,dth a M-m st'ress of +16,773 psi. (Data supplied by E.
G. Skuchas from original calculations performed by MPR Associates.)
4.
Ihe' chloride levels for the furcanite used in the DH-V-1 are:
.i
~
8 ppr-leachable - GPU Analysis *
~
100 ppm' total 50 ppm Icachable - MPR Analysis Analyring 'the above data there appears to be little propensity for stress corrosion for the-following reasons.
First of all, observations over the
~
ydars have shown that fully annealed castings have rarely. displayed cracking in chloride environ =ents.1 In addition, Fontana2 found 'that increasing the
~
~ ferrite content in stainless steels raises the threshold stress level for
. cracking to occur.
Calculated ferrite levels for the valve body is approxi.
mately 20% (Table I), which is a significant amount.
Next, an.extreEely critical parameter which enters into the decision is..
temperature.
At 140*-150* F, which is the lower limit for cracking to occur, cracking has been observed in highly stressed (90% Y.S.) 304 SS; however, there is no data. on cast 316 SS in a similar environment.
The literature in ~.
f general suggests, th,ough, that c ist 316 SS would be significantly more resistant
~
However, as the tc.msi.erature increases, the propensity for cracking, as well as the time for crack initiation increases; therefore, it is of prime impcrtance that the temperature be maintained at" the icwest level practicable.
In regard to chlorides, at the low levels we are dealing with certain factors appear to be key as to whether cracking will occur.
The prime factor l
is whether concentration of chlorides will occur.
MPR Associates, in their i
letter to Mr. S. H. Bailey dated November 3,1977, has indicated that chlorides would not concentrate unless a leak develops.
This statenent is correct provide I the surface is not alternately wetted and dryed.
It is best to keep,the surfaces wetted e pecially when temperatures are above ambient. *
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8309220028 830728
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Lastly, as the pH value increases towards the alkaline end of the scale
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'the tendency,for cracking is ' reduced.
The normal water chenistry range around pH 9 appears to-be the most favorable.
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. Conclusion,-
Since the initial avah.uation by D. A. Mitchell in March 1977'the' e has r'
been no significant < bngen in the state-of-the-art regarding enviroc.ments which can produce SCC in case 316 SS (CF8M).
Analysis of available data.
would stin, therefore, indicate that SCC is improbable, but, this is based.
on inference rather than hard data relating.to our specific s.et of conditions.
for this reason I would suggest that in addition to the periodic metallurgical
' review, that the feasibility of non-destructive exanination of the' valve body '
to detect cracking be considered.
It would appear that ultrasonic inspection:
is the most likely method to accomplish this.
Because there is a low probability that cracking will occur, plus'd.f cracks would initiate the crack propogation rate would be slow due to, the "high ferrite levels, an inspection frequency tied in with the refueling outage would be adequai:e.
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. SCOTI GIAC.0BBE FSG:bk.
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J. L. C. Bachofer, Jr.
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. R. M. Snith
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H. E. Bodden.
J. A. Janiszewski R. M. Klinga=an L. L.. Lawyer G. J. Troffer' R. Earley J. Seelinger D. E. Hetrick
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1 R. D. Hopkins
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Part: Valve Body
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' Material:
AS'IM A-351 Gr CF8M -
Heat:
413 j
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.. Chemical Analysis
.t.
S' d'.015
.066 C
.014 *
..P
.'2.35 Cr 20.00-No 9.50 Ni SL
- 82
. 44' Mn
. Nickel Equivalent ' =~ (% Ni) + (30 z '% C) + (.5 x % Mn)
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9.50 = (30.x.06.6) '+ (.5 x.44)
=
9.50,+ 1.98 +.'220 l..
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.= 11.70 4
diromium Equivalent = (% Cr) +' (% Mo) + 1.5 'x % Si)
= 20.00 + 2.35 + (1.5 x.82)
= 20.00 + 2.35 + 1.23
= 23.58
. Percent Perrite #20%' as determined by the Schaeffler Diagram...
Mechanical Properties. -
' Tensile Strength 83,750 psi
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Yield' Strength 38,750 psi -
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% Elongation 39.5%
Percent of YieM Strength Under Operating Stresses
.i 38,750 - 16,773 x 100 = 57%..... -
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1.
G. E. Moller, " Designing with Stainless Steels for Service In Stress Corrosion Environments", NACE Corrosion /76.
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J. W. Flowers, F. H. Beck & M. G. Fontana, " Corrosion and Aga Hardening Studies o,f Some Cast Stainless Alloys Cont =hhg.
Ferrite", corrosion, Vol.19, No. 5, May 1963, pp 186t-198t.
3
.R. M. Latanision, R. W., Staelh.e, " Stress Corrosion. ci acking 3.
o'f Iron--Nickel--Chromium Alloys", Proceeding of Corference,
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Fundamezital Aspects of Stress Corrosion Cracking, Sept.1967.
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