ML20198N544
| ML20198N544 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 12/29/1998 |
| From: | Sorensen J NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-97-01, GL-97-1, NUDOCS 9901060153 | |
| Download: ML20198N544 (5) | |
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Northern States Power Company Prairie Island Nuclear Generating Plant 1717 Wakonade Dr. East Welch. Minnesota 55089 December 29,1998 10 CFR 50.54(f)
Generic Letter 97-01 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 Response to Request for Additional Information Concerning Northern States Power Company's Response to Generic Letter (GL) 97-01, " Degradation of CRDM/CEDM Nozzle and Other Vessel Closure Head Penetrations" Per letter dated October 1,1998, the U.S. Nuclear Regulatory Commission (NRC) issued a Request for Additional Information (RAI) to Northern States Power Company (NSP) as a follow up to NSP's 120 day response to Generic Letter 97-01 for the Prairie Island Nuclear Generating Plant (PINGP). The NRC asked NSP to respond to the RAI within 90 days. NSP's response to the RAI is provided in the attachment to this i
submittal.
l NSP is a member of the Westinghouse Owners Group (WOG) and has participated in the WOG integrated program to address GL 97-01 issues. The questions comprising
/[/Tg the RAI submitted for the PINGP are addressed in the Nuclear Energy Institute (NEI) response delivered to NRC staff on December 11,1998. NSP has not identified any deviations from the WOG integrated program that are specific to the PINGP.
9901060153 981229
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l USNRC NORTHERN STATES POWER COMPANY December 29,1998 Page 2 We have made no new Nuclear Regulatory Commission commitments in this letter.-
Please contact Jeff Kivi (651-388-1121)if you have any questions related to this letter.
Joel P. Sorensen y
Plant Manager Prairie Island Nuclear Generating Plant 1
L c: Regional Administrator-Region Ill, NRC Senior Resident inspector, NRC NRR Project Manages, NRC J E Silberg t
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ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION CONCERNING-
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1 Attachment December 29,1998 Page1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION CONCERNING NORTHERN STATES POWER COMPANY'S RESPONSE TO GENERIC LETTER 97-01
- 1. In WCAP-14901 WEC did not provide any conclusions as to what the
. probabilistic failure model would lead the WOG to conclude with respect to the assessment of primary water stress corrosion cracking (PWSCC) in WEC-designed vessel head penetrations. With respect to the probabilistic susceptibility model (e.g., probabilistic failure model) provided in WCAP-14901:
a.
Provide the susceptibility rankings compiled for the WOG member plants for which WCAP-14901 is applicable. In regard to the other WOG member plants to which WCAP-14901 is applicable, include the basis for establishing the ranking of your plants (s) relative to the others.
See enclosure 2, response to question 4 of the December 11,1998, NEl response.
b.
Describe how the probabilistic failure model in WCAP-14901 for 4
assessing postulated flaws in vessel head penetration nozzles was bench-marked, and provide a list and discussion of the standards the model was bench-marked against.
See enc l;sure 2, response 2.b to question 2 of the December 11,1998, NEl response.
c.
Provide additional information regarding how the probabilistic failure i
models in WCAP-14901 will be refined to allow the input of plant specific Inspection data into the models analysis methodology.
See enclosure 2, response 3.b to question 3 of the December 11,1998, NEl response, d.
Describe how the variability in product forms, material specifications, and heat treatments used to fabricate each CRDM penetration nozzle at the WOG member utilities are addressed in the probabilistic crack initiation and growth models described or referenced in Topical Report No. WCAP-14901 97-01 RA1. doc'
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j Attachment December 29,1998 Pago 2 See enclosure 2, response 1.b to question 1 of the December 11,1998, i
NEl response.
- 2. Table 1-2 in WCAP-14901 provides a summary of the key tasks in WEC's vessel head penetration nozzle assessment program. The table indicates that l
the Tasks for (1) Evaluation of PWSCC Mitigation Methods, (2) Crack Growth i
Data and Testing, and (3) Crack initiation Characterization Studies have not been completed and are still in progress. In light of the fact that the probabilistic susceptibility models appear to be dependent in part on PWSCC l
crack initiation and growth estimates, provide your best estimate when these tasks will be completed by WEC, and describe how these activities relate to and will be used to update the probabilistic susceptibility assessment of VHP nozzles at your plant (s).
See enclosure 2, response to question 5 of the December 11,1998, NEl response.
l
- 3. In the NEl letters of January 29,1998 (Ref.1), and April 1,1998 (Ref. 2), NEl j
indicated that inspection plans have been developed for the VHP nozzles at i
the Farley Unit 2 plant in the year 2002, and the Diablo Canyon Unit 2 plant in g
the year 2001, respectively. The staff has noted that although you have endorsed the probabilistic susceptibility model described in WCAP-14901, Revision 0, other WOG member licensees have endorsed the probabilistic susceptibility model developed by an alternate vendor of choice. The WOG's proposal to inspect the VHP nozzles at the Farley Unit 2 and Diablo Canyon Unit 2 plants appears to be based on a composite assessment of the VHP nozzles at all WOG member plants. Verify that such a composite ranking assessment has been applied to the evaluation of the VHP nozzles at your plant (s). If composite rankings of the VHP nozzles at WOG member plants have been obtained from the composite results of the two models, Justify why application of the probabilistic susceptibility model described in WCAP-14901, Revision 0, would yield the same comparable relative rankings of the VHP nozzles for your plant (s) as would application of the alternate probabilistic susceptibility model used by the WOG member plants not subscribing to WCAP-14901, Revision 0. Comment on the suscep;ibility rankings of the VHP nozzles at the Farley Unit 2 and Diablo Canyon Unit plants.
See enclosure 5 section 11, response to question 1 of the December 11,1998, NEl response.
97-01 RA!. doc.
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