ML20245B270
| ML20245B270 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 06/14/1989 |
| From: | Larson C NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-89-001, IEB-89-1, NUDOCS 8906230107 | |
| Download: ML20245B270 (6) | |
Text
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1 Northem Giates Power Company 414 Nicollet Mall Minneapolis Minnesota 55401-1927.
Telephone (612) 330-5500 June 14, 1989 NRC Bulletin 89-01 Director of Nuclear Reactor Regulation U S Nuclear Regula*.ory Commission Attn: Document Cortrol Desk Washington, DC. 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos, 50-282 License Nos. DPR-42 50-306 DPR-60 Response to NRC Bulletin 89-01 Our response to NRC Bulletin No. 89-01, "Tailure of Westinghouse Steam Generator Tube Mechanical Plugs", is attached.
Please contact us if you have any questionu related to our response to this NRC Bulletin.
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C E Larso Vice President Nuclear Generation c: Regional Administrator Region III, NRC Senior Resident Inspector, NRC NRR Project Manager, NRC G Charnoff l
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e UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PIANT DOCKET NO. 50-282 50-306 i
I RESPONSE TO NRC BULLETIN 89-01 Northern States Power Company, a Minnesota corporation, with this letter ir
. submitting information requested by NRC Bulletin 89-01.
This' letter contains no restricted or other defense information.
NORTH TATES POWER COMPANY By E Larson Vice President Nuclear Generation
,/Nibeforemeanotarypublicinandforsaid On this ay of utc__ -
County, personally appeared C E Larson, Vice President Nuclear Generation, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and be-lief the statements made in it are true and that it is not interposed for delay.
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Page 1 of 4 RESPONSE TO NRC BULLETIN 89-01 Actions ReouesteG and Responses 1 Action Reauested #1 Addressees are. requested to verify that information contained in References 1 and 2 relating specifically to their plants is correct for plugs supplied from heat numbers 3279, 3513, 3962, and 4523.
The specific information to be verified is the number of Westinghouse mechanical plugs installed in the hot and cold legs broken down by steam generator number, heat number, and date of installation.
If information from these references is incorrect, appropriate corrections shoulc be identified. Addressees are requested to so state if their plants have not installed Westinghouse mechanical plugs from the subject heats.
Resocnse The information contained in References 1 and 2 of NRC Bulletin 89-01 has been reviewed. One error was found: On pages C-10 and C-14 of WCAP-12244, the
- correct number of plugs installed in No. 12 Steam Generator hot leg and cold leg during April of 1987 is 6 instead of 7 as shown. Westinghouse has been j
informed of this discrepancy. No other errors were found.
Action Recuested #2 Addressees are requested to take the following actions, to be implemented initially during any refueling outage or extended outage (greater than four weeks) which ends 30 days or more following receipt of this bulletin and during all future refueling outages.
1 a)
Steam generator tube plug lifetime for plugs from heats 3279, 3513, 3962, 1
I and 4523 should be estimated using the methodology from References 1 and 2 and should be based on the Millstone Unit 2 benchmark subject to any corrections per item 1 above.
Lifetime estimates in Reference 2 for plugs fabricated from heat 4523 are based on the Farley Unit 2 benchmark.
l These estimates should be adjusted to reflect the Millstone Unit 2
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benchmark using the methodology described in Section 4.1.2 of Reference 1.
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!b). Addressees should implement appropriate remedial actions (i.e., repair and/or-replacement) for all plugs whose estimated lifetimes in 2a above do not extend to the next refueling outage.
If operation is planned
- beyond a refueling outage that represents the last outage before any plu:
. exhausts the predicted lifetime, an alternative schedule with the-
. appropriate technica1 Justification should be submitted to the NRC at Lleast 30. days before the end of this refueling outage.
.c)'
Prior to any plug repairs or replacement, addressees are reminded that their responsibilities under ALARA require analysis of the various plug repair.or replacement methods available to determine Which method will result in the lowest overall personnel radiation exposure While still remaining cost-effective.
In choosing a plug repair or replacement method, the licensee should consider the accessibility of the plugs and
.the dose reduction benefit of using robotic. manipulators.
Prior to plug repair or replacement, the licensee should consider steam generator decontamination'and/or local shielding to reduce working area dose rates.
d)
Installation of Westinghouse mechanical plugs from heats 3279, 3513, 3962, and 4523 should be discontinued.
e)
Westinghouse mechanical plugs removed from steam generators, regardless of heat number, should be examined for PWSCC on a sample basis for each heat. Addressees should maintain a record of these examinations and the results should be provided to Westinghouse to improve the database concerning the susceptibility of plugs to PWSCC.
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Response
i a) The estimated tube plug lifetimes for all of the susceptible plugs in Unit 1 will be exceeded prior to the next Unit i refueling outage planned for January 1990. The estimated tube plug lifetimes for all of the-susceptible plugs, except heat 4523, in Unit 2 will be exceeded prior to the next Unit 2 refueling outage planned for September 1990. The estimated tube plug lifetimes were calculated based on the Millstone Unit l
2 benchmark.
The most recent extended' outage at Prairie Island was the refueling outage for Unit 2 Which ended April 29, 1989.
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l Page 3 of 4 b) All of the Prairie Island steam generator tubes are partially-depth-expanded (approximately 2 1/4 inches) in the lower tubesheet. region and as such remedial actions are being deferred until the next refueling outage on each unit (Unit 1 - January 1990, Unit 2 -
i September 1990).
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c). The Prairie Island Steam Generator Committee will consider the various f
plugging and replacement options in a joint meeting with Westinghouse in i
June 1989. Most of the susceptible plugs installed at Prairie Island are at the periphery of the tubesheet regions where manual and remote repair actions are more difficult.
Sixteen of the plugs installed in No. 12 i"
Steam Generator are candidates to be pulled and replaced by sleeves. All cost-effective means will be' evaluated in order to conduct repairs in a manner which will ensure as low as reasonably achievable radiation
- exposure, d) The installation of Westinghouse mechanic _.1 plugs from heats 3279, 3513, 3962, and 4523 has been discontinued at Prairie Island, e) Westinghouse mechanical plugs removed from Prairie Island steam
-generators, regardless of heat number, will be examined for PWSCC on a sample basis. Records of these examinations will be maintained by NSP and the results of the examinations will be providad to Westinghouse.
Action Reauested #3 Remedial actions at plants where the steam generator tubes are partially-depth-expanded within the tubesheet as described above may be deferred on a one time basis to the next scheduled refueling outage if the outage that immediately'follows receipt of this bulletin ends before October i
1, 1989.
Response
As discussed in the response to Required Action #2 above, all of the Prairie Island steam generator tubes are partially-depth-expanded (approximately 2 1/4 j
inches) in the' lower tubesheet region and es such remedial actions will be taken during the January 1990 refueling outage on Unit 1 and the September 1990 refueling outage for Unit 2.
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- Page'4'of 4
- 1 PAction Reauestied #41 N
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Remedialiactions for " sentinel-related" mechanical plugs described.above may Lbe deferred on a'oneitime basis to the.next refueling' outage if the' outage '
..that.immediately followsl receipt.of!this. bulletin ends before October.1, 1989.
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Response
Prairie Island has'no " sentinel related" mechanical plugs installed.
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