ML20080G217
| ML20080G217 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/31/1995 |
| From: | Richard Anderson NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9502060326 | |
| Download: ML20080G217 (5) | |
Text
e, Northem States Power Company Prairie Island Nuclear Generating Plant 1717 Wakonade Dr. East Welch, Minnesota $5089 January 31, 1995 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 Interim Report on Westinghouse Alloy 600 Steam Generator Mechanical Tube Plues Installed at Prairie Island Units 1 and 2 The following status is provided as requested by the NRC Staff during the NRC/NEI/ Utility / Westinghouse meeting on December 22, 1994 about recent field experience with Westinghouse Alloy 600 mechanical plugs heat number NX2387.
This letter provides the NRC staff with our response to the latest field data and our schedule for submitting to the NRC our action plan.
Backcround In December 1994, Westinghouse notified us of recent field exp9rience with Alloy 600 mechanical plugs that requires a revision to the corrosion algorithm presented in WCAP-12244 Rev. 3.
This revision in the corrosion algorithm affects our previously developed schedule and action plan for addressing all remaining Alloy 600 mechanical plugs in service in our steam generators.
Westinghouse has communicated to us that they intend to issue Addendum 3 to WCAP-12244 Rev. 3 in January 1995.
In the interim the original basis for a Justification for Continued Operation provided to us by Westinghouse continues to apply to the next Unit 2 Refueling outage (May 1995) and the next Unit 1 Refueling Outage (January 1996). This issue does not pose an immediate concern about the health and welfare of the public.
Response
We will comply with the recommendai. Ions set forth in the Westinghouse Owner's Group letter OG-94-107 dated December 30, 1994.
At present, there are 104 plugs in the cold legs and 59 plugs in the hot legs of the Prairie Island Unit 1 steam generators. At present, there are 145 plugs in the cold legs and 104 plugs in the hot legs of the Prairie Island Unit 2 steam generators, t
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4 USNRC NORTHERN STATES POWER COMPANY January 31, 1995 Page 2 Table " Plug Life Revision January 1995, Prairie Island" attached provides the current status of the Westinghouse Alloy 600 mechanical plugs in each steam generator.
None of the plugs can cause a tube rupture from a tube plug top release event because the Prairie Island steam generator tubes all have a partial depth (2.75 inches) expansion at the bottom of the tube sheet.
Our planned activities are to remove the remaining Alloy 600 plugs from the hot leg of each steam generator during the next scheduled refueling outage for each unit. The plugs will be replaced with Alloy 690 plugs. Addendum 3 of l
WCAP-12244 Rev. 3 will be reviewed to determine if a different course of action is required, in which case Northern States Power will submit an action plan to the NRC staff 30 days prior to the next schedule refueling outages.
During the operating period remaining prior to the next scheduled refueling outages, safe operation is assured for Prairie Island Units 1 and 2.
The basis for acceptability for continued operation is the validation of the previously developed Justification for Continued Operation present in Section 3.0 of WCAP-12244 Rev. 3.
Based on a current review of the plant j
configuration and operating conditions, we have concluded the Justification
{
for continued Operation is applicable to Prairie Island Units 1 and 2 during the time period when the plug calculated repair / replacement dates are t
exceeded.
The bases for the Justification for Continued Operation are summarized below:
- 1. Plug Top Release event can not cause a tube rupture at Prairie Island.
- 2. If the Plug Top Release could occur, the population of tubes which are in Rows 1 through 4 are 6 tubes in 12 Steam Generator and one tube in 21 Steam Generator, i
- 3. Should perforation occur, the primary to secondary leakage consequences are limited.
- 4. There is a low probability that multiple plugs could be in a i
conditions that would be capable of resulting in Plug Top Releases.
- 5. The plant Emergency Response Guidelines are adequate to bring the plant to a safe shutdown condition, j
- 6. All of the steam generator tubes at Prairie Island have partial depth roll expansions.
The actions being taken are consistent with NRC Bulletin 89-01 and its supplements.
S M600, doc l
i USNRC NORTHERN STATES POWER COMPANY January 31, 1995 Page 3 l
In this letter we have made the following new Nuclear Regulatory Commission commitments:
We will comply with the recommendations set forth in the Westinghouse Owner's Group letter DG-94-107 dated December 30, 1994.
Our planned accivities are to remove the remaining Alloy 600 plugs from the hot leg of each steam generator during the next scheduled refueling outage for each unit. The plugs will be replaced with Alloy 690 plugs.
Addendum 3 of WCAP-12244 Rev. 3 will be reviewed to determine if a different course of action is required, in which case Northern States Power will submit an action plan to the NRC staff 30 days prior to the next schedule refueling outages.
Please contact Jack Leveille (612 388-1121, Ext. 4662) if you have any questions related to this letter.
['
Roger O Anderson Director Licensing and Management ssues c: Regional Administrator - Region III, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC J E Silberg
Attachment:
Plug Life Revision January 1995, Prairie Island (2 pages)
SC4600. TOC I
i
Plug Life Revision January 1995, Prairie Island Remain Mon-Year Number In EFPD to to Repair Plug Service as Plug inst No. of Plug Heat SG Ref Calc min using
- Plugs, Plugs Year Heat of Dec 31, Date Plugs No.
Date Actual EF Actual EF R&Rd R&R No.
1994 UNIT 1 HOT LEG 7/15/80 1
9789 12 12/31/94
-623
< Ref Date 9789 1
9/15/81 25 1989 11 12/31/94
-304
< Ref Date 1
9001 1989 24 9/15/81 2
1989 12 12/31/94
-304
< Ref Date 1
9001 1989 1
12/15/83 10 2205 11 12/31/94 390 Mar-1996 2205 10 12/15/83 8
2205 12 12/31/94 3M Mar-1996 3
9001 2205 5
10/15/84 2
2387 11 12/31/94 390 Mar-1996 2387 2
10/15/84 7
2387 12 12/31/94 390 Mar-1996 2
9001 2387 5
1/15/85 7
2387 11 12/31/94 733 Apr-1997 2387 7
1/15/85. 6 2387 12 12/31/94 733 Apr-1997 2
9001 2387 4
3/15/86 5
3962 11 12/31/94
-1943
< Ref Date 5
9001 3962 0
3/15/86 10 3962 12 12/31/94
-1943
< Ref Date 10 9001 3962 0
2/15/87 19 3962 12 12/31/94 1943
< Ref Date 19 9001 3962 0
4/15/87 5
3513 11 12/31/94
-1604
< Ref Date 5
9001 3513 0
4/15/87_
6 3513 12 12/31/94
-1604
< Ref Date 6
9001 3513 0
5/15/87 1
3513 12 12/31/94
-1604
< Ref Date 1
9001 3513 0
9/15/88 9
5222 11 12/31/94
-944
< Ref Date 9
9001 5222 0
9/15/88 7
5222 12 12/31/94
-944
< Ref Date 7
9001 5222 0
Unit 1 HL Total to be Replaced 59 UNIT 1 COLD LEG 7/15/80 1
9789 12 12/31/94 48046
> 2078 9789 1
9/15/81 25 1989 11 12/31/94 48364
>2078 1989 25 9/15/81 2
1989 12 12/31/94 48364
> 2078 1
9001 1989 1
12/15/83 10 2205 11 12/31/94 49058
> 2078 2205 10 12/15/83 8
2205 12 12/31/94 49058
> 2078 3
9001 2205 5
10/15/84 2
2387 11 12/31/94 49058
> 2078 2387 2
10/15/84 7
2387 12 12/31/94 49058
> 2078 2
9001 2387 5
1/15/85 7
2387 11 12/31/94 49402
> 2078 2387 7
i 1/15/85 9
2387 12 12/31/94 49402
> 2078 2
9001 2387 7
)
3/15/86 5
3962 11 12/31/94 8523 Mar-2021 3962 5
3/15/86 10 3962 12 12/31/94 8523 Mar-2021 6
9001 3962 4
2/15/87 19 3962 12 12/31/94 8523 Mar-2021 15 9001 3962 4
4/15/87 5
3513 11 12/31/94 8862 Apr 2022 3513 5
4/15/87 6
3513 12 12/31/94 8862 Apr-2022 3513 6
5/15/87 1
3513 12 12/31/94 8862 Apr-2022 3513 1
9/15/88 9
5222 11 12/31/94 12453 Apr 2033 5222 9
9/15/88 8
5222
'12 12/31/94 12453 Apr-2033 1
9001 5222 7
Unit 1 CL in Service 104 1
1/28/95 Page 1 PLGLIF95.XLS
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Plug Life Revision January 1995, Prairie Island Remain Mon-Year Number in EFPD to to Repair Plug Service as Plug inst No. of Plug Heat SG Ref Calc min using
- Plugs, Plugs Year Heat of Dec 31, t
Date Plugs No.
Date Actual EF Actual EF R&Rd R&R No.
1994 UNIT 2 HOT LEG 3/15/81 4
1989 21 12/31/94 483
< Ref Date 4
9202 1989 0
3/15/81 37 1989 22 12/31/94
-483
< Ref Date 1989 37 9/15/81 1
1989 22 12/31/94
-483
< Ref Date 1989 1
6/15/82 15 2387 21 12/31/94 121
< Ref Date 2387 15 6/15/82 12 2387 22 12/31/94 121
< Ref Date 2387 12 9/15/83 5
2205 21 12/31/94 250_
Oct 1995 2205 5
9/15/83 15 2205 22 12/31/94 2 F 0' Oct 1995 2205 15 i
9/15/85 7
2387 21 12/31/94 886 Sep-1997 2387 7
l 9/15/85 12 2387 22 12/31/94 886 Sep 1997 2387 12 4
10/15/86 4
3962 21 12/31/94 1793
< Pef Date 4 9009 3962 0
10/15/86 20 3962 22 12/31/94 1793
< Ref Date 20 9009 3962 0
1/15/88 2
4523 21 12/31/94 1396
< Ref Date 2 9009 4523 0
1/15/88 3
4523 22 12/31/94 1396
< Ref Date 3 9009 4523 0
I 4/15/89 3
6323 21 12/31/94 703
< Ref Date 3 9202 6323 0
4/15/89 5
6323 22 12/31/94
-703
< Ref Date 5 9202 6323 0
Unit 2 HL Tota. to be Replaced 104 UNIT 2 COLD LEG 3/15/81 4
1989 21 12/31/94 48186
> 2078 1989 4
3/15/81 37 1989 22 12/31/94 48186 N2078 1989 37 9/15/81 1
1989 22 12/31/94 48186
> 2078 1989 1
6/15/82 15 2387 21 12/31/94 48548
>2078 2387 15 6/15/82 12 2387 22 12/31/94 48548
> 2078 2387 12 9/15/83 5
2205 21 12/31/94 48918
>2078 2205 5
9/15/83 1
1989 22 12/31/94 48918
> 2078 1989 1
9/15/83 14 2205 22 12/31/94 48918
>2078 2205 14 i
9/15/85 7
2387 21 12/31/94 49555
> 2078 2387 7
9/15/85 12 2387 22 12/31/94 49555
>2078 2387 12 10/15/86 4
3962 21 12/31/94 8674 May 2021 3962 4
10/15/86 20 3962 22 12/31/94 8674 May-2021 3962 20 1/15/88 2
4523 21 12/31/94 9070 Aug-2022 4523 2
1/15/88 3
4523 22 12/31/94 9070 Aug-2022 4523 3
4/15/89 3
6323 21 12/31/94 13531 Feb-2036 6323 3
4/15/89 5
6323 22 12/31/94 13531 Feb 2036 6323 5
Unit 2 CL in Service 145 4
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1/28/95 Page 2 PLGLIF95.XLS i
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