L-PI-10-029, Request for Revision to Reactor Vessel Material Surveillance Capsule Withdrawal Schedule

Request for Revision to Reactor Vessel Material Surveillance Capsule Withdrawal Schedule

ML100900089
Person / Time
Site:	Prairie Island
Issue date:	03/30/2010
From:	Schimmel M Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-PI-10-029
Download: ML100900089 (6)

Text

@ Xcel Energym MAR 3 O 2010 L-PI-10-029 10 CFR 50 Appendix H U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 License Nos. DPR-42 and DPR-60 Request for Revision to Reactor Vessel Material Surveillance Capsule Withdrawal Schedule for Prairie Island Nuclear Generating Plant (PINGP)

References:

1. Letter from Nuclear Management Company, LLC (NMC) to NRC, "Application for Renewed Operating Licenses", dated April 11, 2008, ADAMS Accession Number ML081130666.

Pursuant to 10 CFR 50 Appendix HI Section lll.B.3, Northern States Power Company, a Minnesota corporation (NSPM), doing business as Xcel Energy, hereby requests approval for a revision to the PINGP, Units 1 and 2, reactor vessel material surveillance capsule withdrawal schedule. In reference 1, NMC* submitted an application for a renewed operating license which would allow PINGP operation to be extended for 20 years. To support the proposed extended period of plant operations, NSPM proposes to remove Capsule N from Unit 1 during the Spring 201 1 refueling outage and remove Capsule S from Unit 2 during the Spring 2012 refueling outage. The existing removal schedule states that the remaining capsules are in "standby". The details of the proposed schedule revision are contained in Enclosure 1 to this letter. Based on the technical evaluation in Enclosure 1, NSPM concludes that the proposed withdrawal schedule complies with the requirements of the American Society for Testing and Materials (ASTM) standard ASTM E 185-82.

To support implementation of the revised withdrawal schedule, NSPM requests approval of this proposed change by April 1, 201 1.

• On September 22, 2008, NMC transferred its operating authority to NSPM, doing business as Xcel Energy. By letter dated September 3, 2008, NSPM assumed responsibility for actions and commitments previously submitted by NMC.

1717 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1121

Document Control Desk Page 2 If there are any questions or if additional information is needed, please contact Mr. Dale Vincent, P.E., at 651-388-1 121.

Summarv of Commitments This letter contains no new commitments and no revisions to existing commitments.

Mark A. Schimmel Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosures (1) cc: Administrator, Region Ill, USNRC Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC

Enclosure 1 Request for Revision to Reactor Vessel Material Surveillance Capsule Withdrawal Schedule for Prairie Island Nuclear Generating Plant (PINGP)

1. BACKGROUND Appendix H of 10 CFR Part 50 describes reactor vessel material surveillance program requirements. Paragraph (lll)(B)(3) of this Appendix states that proposed withdrawal schedules must be submitted with a technical justification per 10 CFR 50.4, and approved prior to implementation.

The design of the reactor vessel surveillance program and the withdrawal schedule must meet the requirements of the edition of American Society for Testing and Materials (ASTM) standard ASTM E 185 that is current on the issue date of the American Society of Mechanical Engineers (ASME) Code to which the reactor vessel was purchased. The applicable ASTM E 185 version for PINGP, Units 1 and 2, is ASTM E 185-70. In addition, to the extent practicable, the test procedures and reporting requirements for each capsule withdrawal must comply with ASTM E 185-

82. Tables 1 and 2, which were derived from the Pressure and Temperature Limits Report, show the withdrawal schedule for PINGP, Units 1 and 2, respectively, reactor vessel surveillance capsules.

Table 1 Unit 1 Reactor Vessel Surveillance Capsule Removal Schedule I

1 I

Capsule Vessel Location (degree)

~ e a d [ ~ ] Withdrawal Factor EFPY[~]

Fluenceral (nlcm2, E>1.0 MeV)

T 67 1.89 Standby -----

237 1.77 Standby -----

Page Iof 4

RV Capsule Withdrawal Schedule Table 2 Unit 2 Reactor Vessel Surveillance Capsule Removal Schedule 1

I Vessel Location ~ e a d [ ~ ] Withdrawal ~luence[~]

Capsule (degree) Factor EFPY[~] (nlcm2, EM.0 MeV)

' N 237 1.72 Standby -----

I 57 1.72 Standby -----

L .

a. Updated in Capsule S dosimetry analysis

b. Effective full power years (EFPY) from plant startup

c. Plant specific evaluation d Updated in Capsule P dosimetry analysis PROPOSED REVISION TO THE WITHDRAWAL SCHEDULE The proposed schedule is to withdraw Unit 1 Capsule N during the Spring 201 1 outage, and Unit 2 Capsule S during the Spring 2012 outage. Unit 1 Capsule T and Unit 2 Capsule N will remain in standby. As shown below in Section 3, the proposed withdrawal schedules satisfy the requirements of ASTM E 185-70, the version that was current at the time the reactor vessels were purchased and ASTM E 185-82.

Therefore, the withdrawal schedules satisfy the requirements of Appendix H to 10 CFR Part 50.

TECHNICAL JUSTIFICATION Northern States Power Company, a Minnesota corporation (NSPM), doing business as Xcel Energy, submitted an application for renewal of the PINGP operating licenses (Reference I ) , which proposed to extend plant operation for an additional 20 years. To account for license renewal, NSPM proposes to withdraw one of the two remaining capsules from each unit after the capsule receives a neutron fluence equivalent to the 60-year vessel fluence. The remaining spare capsules (one per unit) will stay in the reactor vessel to provide meaningful metallurgical data for potential future license renewals.

The proposed surveillance capsule withdrawal schedule is based on the requirements specified in ASTM E 185-82, Section 7.6. Six surveillance capsules were installed in each unit at PINGP. Four capsules have been removed per the Page 2 of 4

RV Capsule Withdrawal Schedule established withdrawal schedule. The last capsule to be removed from Unit 1 was Capsule S at 18.12 EFPY and the last capsule removed from Unit 2 was Capsule P at 17.24 EFPY. In accordance with the requirements of ASTM E 185-82, Section 7.6.2, NSPM proposes to withdraw one of the remaining capsules from each unit when its neutron fluence exposure exceeds the new peak end-of-life (EOL) (54 EFPY) vessel fluence, but prior to exceeding twice that fluence exposure.

The maximum reactor vessel fluence at 54 EFPY for Unit 1 is projected to be 5.162E19 n/cm2 (Esl .O MeV), and for Unit 2 is projected to be 5.196E19 n/cm2 (E>1.0 MeV). Per the requirements of ASTM E 185-82, Section 7.6, the surveillance capsules should be removed when their neutron fluence exceeds the new peak EOL vessel fluence (i.e., 5.162E19 nlcm2for Unit 1 at 54 EFPY, and 5.196E19 nlcm2for Unit 2 at 54 EFPY), but prior to exceeding twice that fluence exposure (i.e.,

1.032E20 n/cm2for Unit I , and 1.039E20 nlcm2for Unit 2). Calculations have been performed to determine the earliest withdrawal times for the remaining capsules which are shown in Table 3.

Table 3 Earliest Withdrawal Times Removal Time Unit Capsule Lead Factor (2EFPY) 1 T 1.89 24.2 N 1.77 26.5 As of August I,2009, the total lifetime performance of Unit 1 was 30 EFPY and of Unit 2 was 29.9 EFPY. Additional calculations have been performed to estimate the neutron fluence of each capsule at the time of the proposed next withdrawal. The results are shown in Table 4.

Page 3 of 4

RV Capsule Withdrawal Schedule Table 4 Projected Fluences Projected Unit Capsule Proposed EFPY Fluence Removal (nlcm2) 1 T Standby 31.6 6.292E19 N Spring 201 1 31.6 5.893E19 2 N Standby 32.2 5.739E19 1 S I Spring 2012 1 32.2 1 5.739E19 1 After capsule removal, the surveillance specimens will be tested in accordance with the requirements of 10 CFR 50, Appendix H and ASTM E 185-82. The results of materials testing, fluence analysis, and effective full power years (EFPY) from startup are used to predict the effects of neutron embrittlement through the end of extended life.

4. REFERENCES

1. Letter from Nuclear Management Company, LLC (NMC) to NRC, "Application for Renewed Operating Licenses", dated April 11, 2008, ADAMS Accession Number ML081130666.

Page 4 of 4