ML20012C992
| ML20012C992 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 03/19/1990 |
| From: | Cockfield D PORTLAND GENERAL ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-002, IEB-88-2, NUDOCS 9003260261 | |
| Download: ML20012C992 (10) | |
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, u David W. Cockheid Vice President', Nuc' ear 4
March 19, 1990 i
- Trojan Nuclear Plant Docket 50-344
. License NPF-1.
U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk-t
-Washington DC 20555
Dear Sirs:
7 Nuclear: Regulatory Commission (NRC)Bulletin 88-02, Rapidly Propa$ sting Fatigua Cracks-in-Steam Generator Tubes By letter dated December 23 1988, Portland General Electric Company-(PCE)
.provided the final report evaluating actions necessary to minimize the potential:for a steam generator tube rupture caused by high-cycle fatigue
-such as occurred at' North' Anna Unit l'in 1987, Our letter included-enclosure of.both proprietary (WCAP-12024)~and nonproprietary l(WCAP-12023)
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versions of the' report entitled; " Trojan Plant. Evaluation for Tube -
Vibration-Induced Fatigue"'.-
By letter dated January 30. 1990, the NRC requested additional information.
that is needed for completion of the review and closeout of the' NRC Bulletin 88-02 issue for Trojan. Attached are responses to your~ requests.
All four tubes questioned in your January 30' letter have been shown to be acceptable for continued service.
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Document Control Desk March 19, 1990 Page 2 please note that information contained in the attachment is proprietary to Westinghouse Electric Corporation.
It is respectfully requested that the information be withheld from public disclosure in accordance with Title 10 of l
the Code of Federal Regulations, Section 2.790 (10 CFR 2.790) as requested and provided for in our letter of December 23, 1988.
Sincerely, I
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Attachment
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c:.Mr. John B. Martin Regional Administrator, Region V i
U.S. Nuclear Regulatory Commission Mr. David Stewart-Smith State of Oregon Department of Energy, w/o Attachment Mr.~R. C. Barr-NRC Resident Inspector Trojan Nuclear. plant subscribed and sworn to before me this 19th day of March 1990.
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i Westinghouse Proprietary Class 2 Trojan Nuclear Plant Document Control Desk Docket 50-344 March 19, 1990 License NPF-1 Attachment Page 1 of 8 RESPONSES TO REQUESTS FOR INFORMATION REGARDING WCAP-12024 TROJAN PLANT EVALUATION FOR TUBE VIBRATION-INDUCED FATIGUE By lett.er dated December 23, 1988, Portland General Electric Company (PGE) provided WCAP-12024 as the final report evaluating actions necessary to minimize the potential for a steam generator tube rupture caused by high-cycle fatigue such as occurred at North 1.nna Unit 1 in 1987.
By letter dated January 30, 1990, the Nuclear Regulatory Commission (NRC) requested additional information that is needed for completion of the review and closecut of the NRC Bulletin 88-02 issue for Trojan.
In response to your request, a~ detailed reevalustion'of the.four tubes of concern was performed, and our specific responses are provided below.
Request 1 - Tube Row 9, Column 35 (R9C35), Steam Generator (SG) A:
In WCAP-12024. Table 8-7, this tube has been assigned a flow peaking factor of 1.37.
This flow peaking factor appears to correspond to idealiced Anti-Vibration Bar (4VB) Configuration of as pictured in Figure 8-7.
The steff' notes, however, that idealized AVB Configuration 4f differs from the actual AVB ccnfiguration associated with Tube '9C35 in one-possibly significant manner. Namely, the centerline ot the AVB between Columns 36 and 37 penetrates the gap between R7C36 and R7C37, thus rastricting flow between these tubes. Note that the centerline of the
-i subject AVB projects to the 7.2 position, and' the bottom surf ace of the
- AVB is close to the 7.0 position.
In view of the significant flow restriction between R7C36 and R7C37, the staff believes that idealized AVB Configuration 4f is potentially non-conservative for Tube R9C35 and that the actual flow peaking factor for this tube may substantially exceed 1.37.
A peaking factor significantly in excess of 1.37 could cause the fatigue usage factor for the subject tube to exceed 1.0.
PGE Responne:
AVB insertion depths for the columns near SG A Tube R9C35 have been revised as shown in Figure 1.
This tube was originally assigned a flow peaking factor of 1.37 corresponding to AVB Configuration Af.
The revised map as shown in Figure 1 differs from Configuration 4f and other configurations already tested. Therefore a new configuration corresponding to this tube and called 8r was tested at the Westinghouse Science and Technology Center. The peaking factor for Configuration 8r (Figure 2) was 1.28.
Therefore, this tube has a lower stress ratio than reported in the reference and may be kept in service.
t A
Westinghouse Proprietary Class 2 Trojan Nuclear Plant Document Control Desk Docket 50-344 March 19, 1990 License NPF-1 Attachment Page 2 of 8-Request 2 - Tube R8C25 SG A:
WCAP-12024. Table 8-7, has assigned a flow peaking factor of 1.16 to this tube. This appears to correspond to idealleed AVB Configuration 4a.
This appears to be a reasonable assumption provided that one or more of the AVBs between Columns 22 and 23, 23 and 24, 26 and 27, and 27 and 28 do'not penetrate far enough into the bundle to restrict flow between Row 7 tubes.
(The AVB projection value where there may begin to be some flow restriction around Row 7 tubes is about 7.4.)
Unfortunately, Figure 6-2 of WCAP-12024.
does not show how far down these AVBs project. The staff notes that if some L
of these AVBs do in fact project to Row 7, the flow peaking factor could approach or even exceed 1.58, potentially leading to a significant f atigue p
usage factor.
l PCR Response:
The revised AVB map for SG A Tube R8C25 (Figure 3) shows that this tube is supported and is not subject to tube vibration-induced f atigue.
Requent 3 - Tube R8C64, SG B:
L Similar comment as Item 2 above.
PGE Response:
The revised AVB map for SG B Tube R8C64 (Figure 4) shows that this tube is supported and is not subject to tube vibration-induced fatigue..
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Request 4 - Tube R8C60, SG D:
l Similar comment as Item 2 above.
PGE Response:
The revised AVB map for SG D Tube R8C50 is shown in Figure 5.
The Configuration lu as shown in Figure 6 is a good match for this tube and has a flot peaking factor of 1.02.
Thus, from Tables 8-7 and 9-2 of WCAP-12024 it t
L can be concluded that this tube has a relative stability ratio less than 0.623 and may remain in service.
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