ML20212E535
| ML20212E535 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 01/29/1987 |
| From: | Hicks J, Pitka W BABCOCK & WILCOX CO. |
| To: | |
| Shared Package | |
| ML20212E483 | List: |
| References | |
| 51-1167330, 51-1167330-00, TAC-63083, NUDOCS 8703040370 | |
| Download: ML20212E535 (4) | |
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- i m=m ammy ENGINEERING INFORMATION RECORD DocumentidentlAur51 1167330-00 Title Materials-Chemistry Assessment for Internals Vent Valve PREPARED BY:
REVIEWED BY:
Name Jack Hicks Name L y d i.,. I).W, Signat::re O !,
Date //2d8 7 Signaturebihum3h0)
_DateMJ-,h 1
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7 Technical Manager Statement: Initials Revieweris independent.
Remarks:
The attached document provides a technical assessment of the chemistry materials considerations to support a Rancho Seco request to the MRC for delaying the testing of the reactor internals valves.
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- Page 2 of-4
- Material skhemist'rv' Assessment for Internal s ' Vent Val ve
- Backoround~
- The " reactor internals vent valves are requi red - to be'. tested :for: operational.
capability on a scheduled basis.
Rancho Seco would-like to delay the-testing.
b'eyond :-the oilmit - of
- the present schedule range.
This document - prov ides a itechnical assessment of the
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chemistry-materials considerations to support-a request to the NRC ~for delaying the testing.
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Chemistrv Review --
- The vent valve was last tested during the refueling outage in the spring of'1985.
- 'Since that time there have been two periods (about one month.one time and about
- two ' months another time), when the plant was at power operating conditions. For
'the-remainder of the' time, the plant has been at: cold : shutdown conditions with
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periods when the RCS-conditions were such that reactor coolant had low ~ oxygen levels and periods when high oxygen : levels - existed (up to saturated conditions) which for the most part related to a partially drained RCS where the vent valves were above the water level.-
A review of the RCS chemistry data indicates that tne pH, B, 0, C1, and F were 2
' generally within the specifications or expected values for the conditions that existed in't.he RCS.
On several occasions (a day or so in each case)'during cold shutdown, the C1!and F exceeded the tech spec limit of 0.15 ppm max for each (up
. to 0.24 ppm for C1 and ' up to 0.19 ppm for F).
In one instance during power operation, ~ a 0.52l ppm value was recorded for F.
However,- analyses of samples taken on the day before and after the high value, indicated that the F was < 0.04 l:
ppm on both occasions.
'In March 1986i sulfur monitoring was. initiated.
The analysis results for the i.
fi rst few days indicated that the sulfur, as 50 ", was as high as 1.4 ppm and W:
then was < 0.08 ppm for the most of April.
Frombay 1 to July 15, the sulfur as sul fate was consistently high, ranging form 0.12 to 1.1 ppm and averaging about 0.29 ppm.
Some analyses were.also performed which indicated that most of the p
total sulfur was in the form of sul fate rather than reduced species.
Materi als Cor rosion Asses ent
.The - material s of construction for the vent valves are listed in Reference 1.
There are.two types of cormsion that could af fect the operability of the vent valves:
general cormst on and accele rated corrosion due to the presence of contam inant s.
From.the general cormston standpoint the materials of interest are the shaft, bu sh ing, and body, which are constructed respectively of Type 431 martensitic
. stainless steel, Stellite #6, and Type 304 austenttic stainless steel. Ava il able
- data for RCS hot operating conditions indicate that the corrosion rates for these
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51-1167330-00 Page 3 of 4
' ma'terials arelin Ethe range of- 0.05 mils per year or )less and that the corrosion rates _ are comparable to these values at RCS cold shutdown conditions (References'
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'2-5).
' According to. Reference l' the cold clearance gap -dimensions are as follows:
= Bushing:ID 0.010 to 0.020 inches
&' Shaft 00 (10-20 mils)
Body _ID 0.003 to 0.010 inches
& Bushing 00 G-10 mils)
Assuming a uniform 'cormston rate ofl0.05 mils per year, the gap would not close to hinder the operation. of the valve during the design life of the plant.
For the accelerated cormsi_on issue (e.g., stress cormston), the iten of-concern
.is-the ~ ef fect of chloride, fluoride, and sulfur on austenttic stainless steel.
.The. level s at which -' chloride and fluoride induce stres s co r ro sion are
'significantly higher -than those that existed in the RCS at Rancho Seco.
4 (Refers.ces 6 and - 7.)
.The ~su',ceptibility-to these forms of 1 cormston 1s.also related to the degree of sensitization of the material (References 6 and 7).
The material s in the vent valve have not been subjected to treatments which would -
sensitize the materials.
' Sulfur-induced stress cormston of austenitic stainless is also related to the -
Ldegree of sensitization of the material and to the type of reduced sulfur soecies present-(e.g., S0 "' S"' S 0 =).
(References 8-11).
The sulfur analyses of the 3
23 reactor coolant indicate that the sulfur has been mainly in the form of sulfate 1(SO ") which is an oxidized specie rather than a : educed specie.
In addition, 4
when the reactor coolant system has been partially drained, the reactor coolant has high oxygen -levels which is conducive to producing an oxidizing envimnment rather than a reducing envimnment. With an oxidizing envimnment, the sulfur is more apt.to be in the form of sul fate.
From the above, it. is concluded that the contaminant envimnments that have existed in the RCS have not affected the operability of the vent valves.
Refe rences 1.
B&W Document 51-1167259-00 "SMUD Vent Valve Material and Hinge Clearances."
2.
'W.
E. Ber ry, Cormston in Nuclear. Applications, John Wiley and Sons, New York, New York, 1971.
3.
J.
F.
Hall, Literature Survey of Fastener Cormsion in PWR Plants, EPRI Report NP-3784, 1984.
4.
R. L. Dillon and A. B. Johnson, J r., Corrosion Product Generation in Water Reactors, Cor rosion Resea.ch & Engineering Section, Battel le Northwest, Richland, Wash ington.
f c,. e..
E 51-1167330-00 Page 4 of 4 5.
W. D. ' Fletcher, Primary Coolant Chemistry of PWR's Nuclear Energy Systems,-
Westinghouse Electric Corporation, Intemational Water Conference,1970.
.6.
_ E. L. - Hidlebrand, Corrosion 12, (10), 73 (1956).
7.
A. Dravnteks and C. H. Samans, J. Am. Pet. Inst., 31, (III),100, (1957).
8.
F. Zucchi,- A. Frighani, G. Trabanelli, and M. Zucchini, La Metallurgia Itali ana, No. 4 188 (1976).
9.
A. - J. Brophy, Materi als Performance,13., (5), 9 (1974).-
10.
S. Dhawale, G. Cragnolino, and D. D. MacDonald,. Stress Corrosion Cracking of Sensitized Stainless Steel in Boric Acid Solutions Containing Sul fur.
Species, Section 4, EPRI-NP-2531, Ohio State University, August 1982.
11.
.I.
M a ts uch ima, Proc. 6th Int. ' Concres s Met al li c Co r ro si o n, Sydney (Australia) 1975, Paper 2-20.
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