ML12354A272

Request for Additional Information and Suspension of Review of License Amendment Request for Revised Licensing Basis for High-Energy Line Breaks

ML12354A272
Person / Time
Site:	Oconee
Issue date:	12/20/2012
From:	Boska J Plant Licensing Branch II
To:	Gillespie P Duke Energy Carolinas
Boska, J P
References
TAC ME7743, TAC ME7744, TAC ME7745
Download: ML12354A272 (9)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 20, 2012 Mr. Preston Gillespie Site Vice President Oconee Nuclear Station Duke Energy Carolinas, LLC 7800 Rochester Highway Seneca, SC 29672

SUBJECT:

OCONEE NUCLEAR STATION, UNITS 1,2, AND 3 - REQUEST FOR ADDITIONAL INFORMATION AND SUSPENSION OF REVIEW OF LICENSE AMENDMENT REQUEST FOR REVISED LICENSING BASIS FOR HIGH-ENERGY LINE BREAKS (TAC NOS. ME7743, ME7744, AND ME7745)

Dear Mr. Gillespie:

By letter dated December 16,2011, Duke Energy Carolinas, LLC (Duke or the licensee) submitted a revised license amendment request (LAR) to the Nuclear Regulatory Commission (NRC) for a change to the plant licensing basis for high-energy line breaks (HELBs) for Oconee Nuclear Station, Units 1, 2, and 3 (ONS 1/2/3). By letter dated July 31, 2012, Duke stated that the implementation of the new protected service water (PSW) system had developed some issues, and requested that the schedule for implementation of the PSW system be delayed by two years. The PSW system is credited in the HELB LAR (e.g., for mitigation of certain high energy line breaks). As the PSW system had been scheduled to be operational before the end of 2012, the NRC staff had proceeded with the HELB LAR with that understanding. Now that the PSW system has been delayed, the NRC staff finds that it is not possible to approve a revised licensing basis for HELBs without the detailed knowledge of the final configuration of the PSW system. Therefore, the NRC staff has suspended the review of the HELB amendment.

Attached is a request for additional information (RAI) on the HELB LAR that had been developed prior to the suspension of the review. When the NRC has issued a license amendment approving the final configuration of the PSW system, please submit the response to this RAI and the NRC staff will resume the review of the HELB LAR.

P. Gillespie -2 If you have any questions, please contact me at 301-415-2901 or via e-mail at John. Boska@nrc.gov.

Sincerely, J hn P. Boska, Senior Project Manager lant licenSing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, 50-287

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSING BASIS FOR HIGH-ENERGY LINE BREAKS DUKE ENERGY CAROLINAS, LLC OCONEE NUCLEAR STATION, UNITS 1,2, AND 3 DOCKET NOS. 50-269, 50-270, AND 50-287 In Enclosure 3 to a letter dated December 16, 2011, Agencywide Document Access and Management System Accession No. ML120030226, Duke Energy Carolinas, LLC (Duke or the licensee) submitted a compilation of documents comprising a license amendment request (LAR) along with responses to previous requests for additional information (RAls) to the Nuclear Regulatory Commission (NRC) for a revision to the plant's licensing basis for high-energy line breaks for Oconee Nuclear Station, Units 1,2, and 3 (ONS 1/2/3). The NRC staff is reviewing the submittal and has the following questions:

RAI HELB-1 EMCB In the response to RAI 79 in the letter dated December 16, 2011, Duke states:

Surveys of postulated break locations in both the Turbine Building and Auxiliary Building indicated that no interactions with the Turbine/Auxiliary Building wall would occur from postulated breaks located in the Auxiliary Building. These same surveys indicated several interactions that could occur with the Turbine/Auxiliary Building wall from postulated breaks located in the Turbine Bui/ding.

Please provide specific information on the wall interaction and supporting justification to the statement above to include responses to the following:

• How and where have these interactions been satisfactorily documented and addressed by the licensee?

• How do the impacted target (wall) dimensions compare to the pipe(s) diameter(s) that interact with the wall? In addition, please provide a summary of the wall construction and a discussion which shows that the wall has been evaluated and can withstand applicable pipe whip loads.

RAI HELB-2 EMCB In reference to the response to RAI 79, please provide the basis for using Appendix B of ANSI ANSI 58.2 to calculate the steady state thrust forces (pipe whip) and compare these loads to the original design basis.

Enclosure

-2 RAI HELB-3 EMCB In the response to RAI 80, Duke states:

Thermal fatigue stresses alone (i.e., secondary stresses) do not fail piping.

Therefore the original Giambusso/Schwencer break criteria based solely on SA is not appropriate, and the BTP [Branch Technical Position] MEB 3-1 break threshold is used. The current ONS Licensing basis for crack locations is a non-deterministic Giambusso criteria (worst effects). The ASME Code discussion recognizes that self-limiting (secondary) thermal stresses, even above yield, does not fail piping and therefore, for cracks, the 0.4 (Sh + SAl is an appropriate stress limit for crack postulation also taken from BTP MEB 3-1.

A. The statement that thermal fatigue stresses alone do not fail piping has been repeated several times in many of Duke's RAI responses. Please provide justification that validates this statement.

B. Please clarify how the Giambusso/Schwencer break criteria based solely on SA have been shown to be not appropriate.

C. The Duke response mentions "The ASME Code discussion ... " Please provide specific details on this "ASME Code discussion."

RAI HELB-4 EMCB In the response to RAI 80, Duke states:

"The revised outside containment ONS HELB Program does not use Leak-Before-Break methods to link crack and break locations. For rigorously analyzed piping systems, break and crack locations are based only on stress values, and then cracks and breaks are evaluated for their different effects, as required by Giambusso/Schwencer."

Please discuss how the above statement conforms with the requirement to postulate breaks at terminal ends regardless whether the piping system has been rigorously analyzed. (

Reference:

BTP MEB 3-1, Revision 2, 1987: Sections B.1.c.(1 )(a) (Class 1) and B.1.c.(2)(a) (Class 2 & 3).

RAI HELB-5 EMCB In the response to RAI 81, Duke states:

The collar/guard pipe is designed to withstand the pressure loads as a result of a break anywhere under these components. Since they surround a straight piece of 24" nominal diameter pipe, the dynamic and jet effects of a piping break under the collar/guard pipe up to and including the butt weld at the elbow will result in the same dynamic forces, the same pipe reactions and no greater consequences than those breaks initiating from under the guard pipe alone.

-3 Please provide verification that approved and final design & analysis calculations exist that support the above statement.

RAJ HELB-6 EMCB In the response to RAI 83, Duke states:

The ONS HELB criteria address the effects of breaks and cracks for piping down to 1.5 inches NPS.

BTP 3-3-9, Revision 3, March 2007, Appendix B, (Giambusso), Section 3.b. specifies criteria used to determine pipe break orientation at the specified break locations: "Circumferential breaks in piping runs exceeding 1 inch nominal pipe size."

Please verify that there exist no lines that are less than 1.5 inch NPS (Le. 1.25 inch NPS) that should have been considered from a HELB perspective but have been inadvertently excluded.

RAJ HELB-7 EMCB In the response to RAI 84, Duke states:

Duke Energy agrees that NUREGICR-2913 was initiated for the determination of jet impingement effects following a high energy line break. However, Duke Energy requests NRC approval to use the NUREG for determination of the effects from critical cracks.

Please provide information and bases for any precedent(s) that is (are) available for using NUREG/CR-2913 to define jet impingement effects from cracks.

If other plants have been approved to use this approach, provide justification for use of the same approach by Oconee. Establish similarities between any precedent plants including system operating parameters (pressure and temperature), & geometry (including variables such as nominal pipe size) to those lines affected at Oconee.

Address, as necessary, the validity of the application of NUREG/CR-2913 for lines outside the model application ranges stated in the Duke response to RAI 84: "The model ranges in application from 60 bars (870 psi) to 170 bars (2465 psig) pressure and 70 degrees Centigrade (158 degrees Fahrenheit) subcooled liquid to 0.75 (or greater) steam quality."

RAJ HELB-8 EMCB In the response to RAI 85, Duke Energy states:

The original 1973 HELB submittal (MDS OS-73.2) did not include the methodology to which HELB thrust forces and jet impingement loads were calculated. Thrust forces for systems normally in operation and for systems not normally in operation were listed in Tables 2.1-1 and 2.1-2 respectively in the MDS OS-73. 2 report. However the methodology used to determine these forces

- 4 is not included. In addition, the submittal did not include information relative to the jet lengths originating from a high energy line break or crack.

One of the reasons for submitting a new design basis for HELB was to provide sufficient documentation on the bases for break/crack postulation, determination of pipe whip and jet impingement loads, jet impingement lengths, and determination of mitigation strategies that were unclear in the 1973 submittal (MOS OS-73.2).

A. How many more breaks and cracks have been postulated under the "new" methodology and evaluation than were considered in the original evaluation and submittal from 1973?

B. How are the new analyses (submittal designated HELB LARs, Report ONDS-351 Rev 2) establishing a new licensing basis (e.g., show they are as conservative as the original analyses (Report designated MDS OS-73.2) or meet current NRC criteria) based upon the table data (steady state thrust force and steady state thrust coefficient) provided in the response to RAI 85?

C. Duke stated that the original methodology was not included in MDS OS-73.2. Please provide the basis for the following statement: "However, the overall methodology for determining steady state thrust forces appears to be the same."

D. Considering both of the tables included in the Duke response to RAI 85, provide justification for the steady state thrust coefficient that was "back calculated from the IVIDS OS-73.2 thrust force."

E. If other comparisons of steady state thrust forces were made beyond those examples provided in the response to RAI 85, why were they not included? If no other comparisons were made, provide justification as to why.

F. The response to RAI 85 also states:

The portions of ANSIIANS 58.2 regarding assumptions related to jet expansion modeling that may lead to un-conservative assessments ofjet impingement loads from postulated pipe breaks on SSCs located in the zone of influence were not used in the revised ONS HELB licensing basis.

Please clarify what specific assumptions or portions of ANSIIANS 58.2 that may lead to un conservative assessments of jet impingement loads were not used.

G. Address, as necessary, the validity of the application of NUREG/CR-2913 for lines outside the model application ranges stated in the Duke response to RAI 84: "The model ranges in application from 60 bars (870 psi) to 170 bars (2465 psig) pressure and 70 degrees Centigrade (158 degrees Fahrenheit) subcooled liquid to 0.75 (or greater) steam quality."

H. Provide justification that the jet impingement loads calculated in accordance with NUREG/CR-2913 and used to evaluate the structural components are at least as conservative as those used in the original analyses. Please include in the justification a

- 5 summary of jet impingement loads derived by application of NUREG/CR-2913 compared to loads at the same locations used in the original analyses.

RAI HELB-9 EMCB In the response to RAI 86, Duke states:

Per UFSAR Section 3.6. 1. 1 (2), "All penetrations are designed to withstand line rupture forces and moments generated by their own rupture as based on their respective design pressures and temperatures." This is interpreted to mean that each ONS containment penetration is designed for a postulated rupture of the piping running through that penetration. The postulated rupture could be either inside or outside containment. However, the postulated rupture would be adjacent to the anchor point of the penetration. Since the focus of the HELB LAR is for high energy line breaks outside containment, the location of the postulated terminal end breaks at the containment penetrations are outside of the concrete envelope of the reactor building. The locations were previously documented in the original HELB submittal (MDS OS-73.2) and these locations remain the same in the revised ONS HELB licensing basis. Jet impingement loads on each penetration would be bounded by individual line rupture loads given the distributed load characteristic associated with the jet expansion and the small area of the penetration(s).

A. Please verify that documentation exists that shows that the stated interpretation is correct.

B. In the October 23, 2009 Duke response to RAI 9 (b), Duke states that "any postulated break at the containment penetrations (at the terminal end) would result, by definition, in a loss of containment integrity." How is the loss of containment integrity addressed?

RAI HELB-10 EMCB In RAI 87, the following sketch is included:

Sketch RAHl7

- 6 The location of the break (shown outside the containment wall) is being considered as the break location conforming to requirements of Giambusso/Schwencer as described in the Duke response to RAI 87. However, the RAI 87 break location shown in the sketch has the potential to impact the liner plate which Duke acknowledges as an integral part of the Reactor Building containment.

How has the integrity of the liner plate in that location (and others with similar arrangements) been addressed for potential pipe breaks?

Does the licensee assert that a break could not occur at the location labeled "Break Location for RAI 87" in the sketch accompanying RAI 87?

ML12354A272 .. See memo dated 4/11/12 OFFICE DORLlLPL2-1/PM DORLlLPL2-1/LA DE/EMCB/BC" NAME JBoska SFigueroa MMurphy DATE 12119/12 12/19/12 4111112 OFFICE DORLlLPL2-1/BC DORLID DORLlLPL2-1/PM NAME RPascarelli MEvans JBoska DATE 12/19/12 12/20/12 12/20/12