NG-17-0241, Supplemental Response to Request for Additional Information, Fifth Inservice Inspection Interval Program Plan, Relief Request RR-03

Supplemental Response to Request for Additional Information, Fifth Inservice Inspection Interval Program Plan, Relief Request RR-03

ML17341A852
Person / Time
Site:	Duane Arnold
Issue date:	12/07/2017
From:	Dean Curtland NextEra Energy Duane Arnold
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NG-17-0241
Download: ML17341A852 (5)

Text

NEXTera.

EN ERGY~

DUANE ARNOLD December 7, 2017 NG-17-0241 10 CFR 50.55a U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Duane Arnold Energy Center Docket No. 50-331 Renewed Op. License No. DPR-49 Supplemental Response to Request for Additional Information, Fifth lnservice Inspection Interval Program Plan, Relief Request RR-03

References:

1) Letter, Curtland (NextEra) to U.S. NRC, "Fifth lnservice Inspection Interval Program Plan," dated March 7, 2017 (ML17069A172)

2) Electronic Communication, Request for Additional Information -

Duane Arnold Energy Center - Relief Request No. RR Alternative Requirements for Nozzle Inner Radius and Nozzle-To-Shell Welds, dated August 8, 2017(ML17220A333)

3) Letter, Curtland (NextEra) to U.S. NRC, "Response to Request for Additional Information, Fifth lnservice Inspection Interval Program Plan, Relief Request RR-03," dated October 26, 2017 (ML17300A195)

In the Reference 1 letter, NextEra Energy Duane Arnold, LLC (hereafter NextEra Energy Duane Arnold) submitted our Fifth lnservice Inspection Interval Program Plan pursuant to 10 CFR 50.55a. The NRC Staff requested, via Reference 2, additional information regarding Relief Request RR-03 which is contained in Reference 1. NextEra Energy Duane Arnold provided the additional information in Reference 3. Subsequent discussion with the NRG Staff has identified the need for a supplemental response regarding Relief Request RR-03.

The Enclosure to this letter contains Structural Integrity Associates, Inc. Report No. 1701150.401.RO which includes the requested supplemental information.

This report provides context for the Probable Fracture Mechanic results for the NextEra Energy Duane Arnold , LLC, 3277 DAEC Road, Palo, IA 52324

Document Control Desk NG-17-0241 Page 2 of 2 low temperature over pressure condition and the normal operation condition; specifically, the differences in the methods used to determine these results and the context in which each value can be illustrative.

This letter does not contain any new or revised commitments.

If you have any questions or require additional information, please contact J. Michael Davis at 319-851-7032.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on December 7, 2017 Dean Curtland Site Director NextEra Energy Duane Arnold, LLC Enclosure cc: NRC Regional Administrator NRC Resident Inspector NRC Project Manager

Enclosure to NG-17-0241 Supplemental Response to Request for Additional Information, Fifth lnservice Inspection Interval Program Plan, Relief Request RR-03 Structural Integrity Associates, Inc. Report No. 1701150.401.RO 2 pages follow

SJ Structural Integrity Associates, Inc.

5215 Hellyer Ave.

Suite210 San Jose, CA 95138-1025 Phone: 408-978-8200 Fax: 408-978-8964 www.structintcom wwong@structint.com November 29, 2017 Repo1tNo. 1701150.401.RO Quality Program: [ZI Nuclear D Commercial

Subject:

Normal Operating Probability of Failure for Code Case N-702 Using VIPERNOZ SI Calculation No. 1701150.301Revision1 determined that probability of failure (PoF) per reactor year due to a Low Temperature Over Pressure (LTOP) event for the nozzle-to-she)l-weld and nozzle blend radii in the Duane Arnold Nl nozzles are below the acceptance criterion of 5x 1o-6 per year. The work was performed usfo.g the same methodology and computer program used in BWRVIP-108, which is the technical basis for ASME Code Case N-702 and similar to the work in BWRVIP-05. However, during sensitivity studies performed for the Safety Evaluation Report (SER) ofBWRVIP-108, the results for nmmal operating conditions were requested for sensitivity comparison, even though it was not the focus ofBWRVIP-108. The reported PoF due to normal operation was higher than the PoF due to an LTOP event for one of the sensitivity study cases.

The purpose of this report is to explain why reporting the PoF due to normal operation in the application of Code Case N-702 using the VIPERNOZ program is not required.

There are no acceptance criteria for PoF due to normal operation. The 5x1 o* 6 PoF limit for the LTOP event is obtained from NUREG-1806 for pressurized thermal shock screening.

In addition, since the VIPERNOZ program was designed to give a proper LTOP PoF number, the program only considers linear elastic fracture mechanics (LEFM). This is appropriate for analyzing the conditions during an LTOP event, but overly conservative for vessel material behavior at normal operating temperatures where materials have significantly higher ductility.

The number reported in the BWRVIP-108 SER for normal operation PoF was used for comparative info1mation purposes only.

Other than for comparative information purposes, the PoF due to normal operation is irrelevant because when the plant stays within the required pressure-temperature (PT) curve limits the regulatory required margin to failure is met. The intent of the BWRVIP-05 and BWRVIP-108 work was to evaluate the PoF due to a postulated LTOP event, where the low temperature and high pressure can result in failure due to brittle fracture. The PT curves assure that plant startup, shutdown, and other normal operating conditions are within the bounds for prevention of brittle failure. Accordingly, a PoF value for nonnal operating conditions calculated using the LEFM method in VIPERNOZ is not appropriate for comparison to the PoF acceptance criterion.

Toll-Free 877-474- 7693 Akron, OH Ausun,TX Charlotte, NC Chattanooga, TN 330-899*9753 512*533*9191 704-597-5554 423-553*1180 Chicago, IL Denver, co san Diego, CA San Jose, CA state College, PA Toronto, Canada 877-474-7693 303:792-0077 858-455-6350 408-978-8200 814-954-7776 905-829-9817

November 29, 2017 ReportNo. 1701150.401.RO Page 2 of2 In addition, the PoF for the LTOP event in the sensitivity study reported in the SER of BWRVIP-108 is actually two orders of magnitude higher (1.19x 1o-4) than the normal operation condition (l.98xI0-6). It's only when the conditional probability of the LTOP event is accounted for that the comparison showed a closer relationship. This confinns the original assessment in BWRVIP-05 and concurred in the SER ofBWRVIP-108, that the LTOP event is the governing event that should be evaluated for PoF.

Therefore, the PoF due to normal operation in the application of Code Case N-702 is not required because it's calculated using overly conservative methods, is already addressed in PT curve limits, and is governed by the LTOP event.

Prepared by: Verified by:

11/29/17 #~ 11/29/17 Wilson Wong Date S.S. Tang Date Senior Engineer Associate Reviewed by:

11/29/17 Terry J. Herrmann, P.E. Date Senior Associate Approved by:

11/29/17 Wilson Wong Date Senior Engineer SJ Structural Integrity Associates, /n9.