ML071630521

Response to NRC Questions Regarding Kewaunee Request for Approval of Topical Report DOM-NAF-5, Application of Dominion Nuclear Core Design and Safety Analysis Methods to the Kewaunee Power Station (Kps)

ML071630521
Person / Time
Site:	Kewaunee
Issue date:	06/12/2007
From:	Gerald Bichof Dominion, Dominion Energy Kewaunee
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
06-578D, DOM-NAF-5
Download: ML071630521 (11)

Text

Ilominion Energy Kewaunee, Inc.

W O O [)ominion Boulevard, Glen Allcn, VA 13O1,O June 12, 2007 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 k

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'Dominion Serial No. 06-578D NL&OS/CDS: R4 Docket No. 50-305 License No. DPR-43 DOMINION ENERGY KEWAUNEE. INC.

KEWAUNEE POWER STATION RESPONSE TO NRC QUESTIONS REGARDING KEWAUNEE REQUEST FOR APPROVAL OF TOPICAL REPORT DOM-NAF-5. "APPLICATION OF DOMINION NUCLEAR CORE DESIGN AND SAFETY ANALYSIS METHODS TO THE KEWAUNEE POWER STATION (KPS)"

In a January 31, 2006, public meeting with Nuclear Regulatory Commission (NRC) staff, Dominion Energy Kewaunee, Inc. (DEK) presented a conceptual approach and implementation strategy for application of existing NRC-approved nuclear core design and safety analysis methods to Kewaunee Power Station (KPS) (reference 1). These design and analysis methods are already in use within the remainder of the Dominion fleet. Fundamental to the proposed approach was creation of a composite topical report (DOM-NAF-5) that would document the application of the relevant methodologies to KPS.

On August 16, 2006, DEK submitted Dominion Topical Report DOM-NAF-5 without attachments A and B (reference 2). Attachment A to DOM-NAF-5, containing Core Management Systems benchmark analysis results, was submitted on December 6, 2006 (reference 3). On April 16, 2007, DEK submitted Attachment B to DOM-NAF-5, containing RETRAN benchmark analysis results (reference 4).

This submittal, in conjunction with References 2 and 3, provided the complete contents of DOM-NAF-5.

On May 4, 2007, DEK submitted the KPS plant specific application of the NRC approved Dominion Topical Report VEP-NE-2-A, "Statistical DNBR Evaluation Methodology," for KPS cores containing Westinghouse 422V+ fuel assemblies with the VIPRE-DNVRB-1 code correlation (reference 15).

Subsequently, the (NRC) staff communicated two questions regarding these submittals.

These questions and DEKs responses are provided in Attachment 1.

Should you have any questions, please contact Mr. Craig D. Sly at 804-273-2784.

Very truly yours, G. T. Bischof w

Vice President - Nuclear Engineering

Serial No. 06-578D Response to NRC Questions Page 2 of 4

References:

1. Summary of Meeting on January 31, 2006,, "To Discuss the Applicability of Dominion Safety and Core Design Methods to Kewaunee Power Station (TAC No. MC 9566),"

(ADAMS Accession Number ML060400098).

2. Letter from G. T. Bischof (DEK) to NRC, "Request for Approval of Topical Report DOM-NAF-5, 'Application of Dominion Nluclear Core Design and Safety Analysis Methods to the Kewaunee Power Station (KPS),"' dated August 16, 2006 (ADAMS Accession Number ML062370351 ).

3. Letter from G. T. Bischof (DEK) to NRC, "Attachment A to Topical Report DOM-NAF-5, 'Application of Dominion Nuclear Core Design and Safety Analysis Methods to the Kewaunee Power Station (KPS),"' dated December 6, 2006 (ADAMS Accession Number ML0063410177).

4. Letter from G. T. Bischof (DEK) to NRC, "Request for Approval of Topical Report DOM-NAF-5, 'Application of Dominion Nuclear Design and Safety Analysis Methods to the Kewaunee Power Station (KPS),"' dated April 16, 2007.

5. Letter from G. T. Bischof (DEK) to NRC, "Implementation of the Dominion Statistical DNBR Methodology with VI PRE-DNVRB-1 at Kewaunee Power Station," dated May 4, 2007.

Attachment:

1. Response to NRC Request for Additional Information Regarding Kewaunee Request for Approval of Topical Report DOM-NAF-5, "Application of Dominion Nuclear Core Design and Safety Analysis Methods to the Kewaunee Power Station (KPS)."

Commitments made in this letter: None

Serial No. 06-578D Response to NRC Questions Page 3 of 4 cc:

Regional Administrator U. S. Nuclear Regulatory Commission Region Ill 2443 Warrenville Road Suite 21 0 Lisle, Illinois 60532-4352 Ms. M. H. Chernoff Senior Project Manager U.S. Nuclear Regulatory Commission Mail Stop 8 G9A Washington, D. C. 20555 Mr. S. C. Burton NRC Senior Resident Inspector Kewaunee Power Station

Serial No. 06-578D Response to NRC Questions Page 4 of 4 COMMONWEALTH OF VIRGINIA

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COUNTY OF HENRICO 1

1 The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Gerald T. Bischof, who is Vice President - Nuclear Engineering of Dominion Energy Kewaunee, Inc. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this /a* clay of 9-

,2007 My Commission Expires: &t

31. ado8 I

MARGARET 8. BENNE I T Notory Publlc Commonwealth of Virginla My Commlulon Explrer Aug 3 1. 2008 i (SEAL

Serial No. 06-578D ATTACHMENT 1 Response to NRC Questions Regarding Kewaunee Request for Approval of Topical Report DOM-NAF-5, "Application of Dominion Nuclear Core Design and Safety Analysis Methods to the Kewaunee Power Station (KPS)"

KEWAUNEE POWER STATION DOMINION ENERGY KEWAUNEE, INC.

Serial No. 06-578D Page 1 of 6 R ~ S D O ~ S ~

to NRC Questions Reaardina Kewaunee Reauest for A D D ~ O V ~ ~

of To~ical ReDot't DOM-NAF-5. "A~~lication of Dominion Nuclear Core Desian and Safetv Analvsis Methods to the Kewaunee Power Station (KPS)"

On August 16, 2006, Dominion Energy Kew,aunee (DEK) submitted Dominion Topical Report DOM-NAF-5 without attachments A and B (reference 2) to the NRC.

On December 6, 2006, Attachment A to DOIM-NAF-5, containing Core Management Systems benchmark analysis results, was submitted (reference 3). On April 16, 2007, DEK submitted Attachment B to DOM-NAF-5, containing RETRAN benchmark analysis results (reference 4). This submittal, in conjlunction with references 2 and 3, provided the complete contents of DOM-NAF-5.

On May 4, 2007, DEK submitted the KPS plant specific application of the NRC approved Dominion Topical Report VEP-NE-2-A, "Statistical DNBR Evaluation Methodology," for KPS cores containing Westinghouse 422V+ fuel assemblies with the VI PRE-DNVRB-1 code correlation (reference 15).

Subsequently, the (NRC) staff communicated two questions regarding these submittals.

These questions and DEKs responses are provided below.

NRC Question 1 In the August 16, 2006, submittal, a brief explanation (on page 12 of 34), and a summary (on page 14 of 34) is provided for the relaxed power distribution control methodology. However, no analysis results are provided. Please provide "before" and "after" results of the bounding analyses cond'ucted with the VEP-FRD-42 methodology, demonstrating continued adherence to the respective limits.

Dominion Response The question above was clarified during a teleconference with NRC staff members on May 15, 2007.

During the teleconference it was determined that before and after analysis results are not currently available and providing them was not practicable.

Dominion agreed to provide a comparative analysis showing the Dominion relaxed power distribution (RPDC) methodology, when applied to Kewaunee Power Station, will produce similar results to those provided by the Westinghouse relaxed axial offset control (RAOC) methodology currently in US~-(WCAP-I 0216-P, Revision 1 A (reference 7)).

Dominion expects that the cycle-specific RPDC analysis to be performed for KPS will support similar delta4 limits to those that are calculated using the Westinghouse RAOC methodology. Delta-l is defined as the difference in power generated in the top and

Serial No. 06-578D Page 2 of 6 bottom halves of the core (in percent of rated thermal power). The two methodologies are very similar to each other and the physics codes (ANC (Westinghouse) and CMS (Dominion)) used in the main calculations should generate a similar set of axial power shapes. This expectation is based on Dominion's experience with RPDC implementation for the North Anna units and informal comparisons to generic RAOC analysis results.

To further illustrate the similarity of the two methods, Table 1 presents a side-by-side comparison of key elements for both meth~d~ologies. This table provides greater detail about items a) through h) listed on page 14 of 34 of the August 16, 2006 submittal (reference 2). Since Table 1 illustrates that the key elements of the RPDC methodology are directly comparable to the elements of the RAOC methodology, it may be concluded that the RPDC results obtained during the KPS reload analysis will be essentially the same.

Serial No. 06-578D Page 3 of 6 Table 1 Comparison of Key Elements of Dominion Relaxed RPDC and Westinghouse ROAC Methodology Category Element Westing house RAOC Dominion RPDC Comparison Technical Specification /

COLR Limits Operating Axial Flux Difference (AFD) limits Axial Flux Difference (AFD) limits Same Limits versus reactor power versus reactor power FQ Surveillance Non-RAOC applies a cycle specific RPDC applies a cycle specific N(z)

Essentially the equilibrium W(z) factor to the measured FQ to factor to the FQ limit to account for same conditions account for non-equiiiisrium non-equiiibrium operation.

operation.

Condition I Analysis RAOC methodology populates a xenon shape library using a xenon reconstruction model.

The reconstruction model is dependent on several parameters Xenon whose ranges are determined by Distributions xenon transient analysis.

Parameters for a given xenon shape are retained only if Delta-l control can be maintained for those shapes within a tentative limit.

The RPDC xenon shape library is built by reducing Doppler feedback in the base neutronics model and allowing a divergent xenon oscillation to occur. Actual xenon distributions are sampled and saved from this transient. No consideration is given during the transient calculation to whether or not the shapes are obtainable during normal operation Both methodologies generate axial xenon distributions that cover essentially the same delta4 space.

Serial No. 06-578D Page 4 of 6 Category Element Westinghouse RAOC Dominion RPDC Comparison A range of power levels between Minimum of three power levels, 50% and 1 00% power with small Power 100%, 50%, and an intermediate enough increments to ensure an Essentially the Levels power are required.

adequate number of power same distributions are being analyzed (typically 10% power intervals).

Range of control rod positions Range of control rod positions from Control Rod from ARO to power dependent ARO to power dependent Rod Same Rod Insertion Limits (RILs).

Insertion Limits (RILs).

Burnups BOL, MOL, EOL BOL, MOL, EOL Same FQ Analysis Each power shape generated for Condition I is analyzed to Loss of determine if LOCA constraints are Coolant met or exceeded. For each Accident power level the results of this (LOCA) analysis will indicate a tentative range of delta-l in which there are no violations of the LOCA limits.

Normal operation power distributions are evaluated relative Loss Of Flow to the assumed limiting normal Accident operation power distribution, (LOFA) typically the 1.55 cosine, used in the accident analysis The FQ x Power for each shape is compared to the LOCA FQ x Power x K(z) limit at each power level to Essentially the determine which axial shapes approach the LOCA limit, thereby same establishing a preliminary allowable delta-l versus power band.

The entire set of axial power distributions from the normal operation analysis are evaluated Essentially the against the 1.55 cosine design axial power distribution for the LOFA same analysis with the applicable thermal-hydraulic code(s) and correlation(s).

Serial No. 06-578D Page 5 of 6 Category Element Westinghouse RAOC Dominion RPDC Comparison Condition II Analysis Analyzed Accidents Cooldown Accident, Control Rod Cooldown Accident, Control Rod Withdrawal, Boration 1 Dilution Withdrawal, Boration 1 Dilution Same Initial statepoints for Condition II statepoints for Condition II Shape analysis are limited to the Condition I axial power analysis are limited to the Condition I axial power distributions that fit Same Selection distributions that fit within tentative delta-I bands.

within tentative delta4 bands.

Serial No. 06-578D Page 6 of 6 NRC Question 2 On page 26 of 34, Section 3.6.1 addresses the conditions and limitations associated with VIPRE-D. In section 3.6.2, parts 1.C and 1. D allude to various models being used without stating when and how these models are used. Please provide additional information regarding the model selection process, e.g., when one particular model is chosen, how that choice is made, and who makes the decision.

Dominion Response The model selection process is controlled by NRC approved Dominion Fleet Report DOM-NAF-2-A, "Reactor Core Thermal-Hydraulics Using the VIPRE-D Computer Code" (reference 6). Dominion will develop and use VIPRE-D models for Kewaunee cores that strictly follow the modeling guidelines and usage requirements specified in DOM-NAF-2-A. DOM-NAF-2-A prescribes the specific constitutive models to be selected for use in the VIPRE-D models for two-phase flow models and correlations, heat transfer correlations, and turbulent mixing models. DOM-NAF-2-A allows no flexibility to select different options for these constitutive models. These VIPRE-D models are used to analyze the non-LOCA, DNB-related transients and accidents as listed in DOM-NAF A.

References:

1. Summary of Meeting on January 31, 2006, "To Discuss the Applicability of Dominion Safety and Core Design Methods to Kewaunee Power Station," (TAC No. MC 9566),

(ADAMS Accession Number ML 0604OOO!38).

2. Letter from G. T. Bischof (DEK) to NRC, "Request for Approval of Topical Report DOM-NAF-5, 'Application of Dominion Nuclear Core Design and Safety Analysis Methods to the Kewaunee Power Station (KPS),"' dated August 16, 2006 (ADAMS Accession Number ML062370351 ).

3. Letter from G. T. Bischof (DEK) to NRC;, "Attachment A to Topical Report DOM-NAF-5, 'Application of Dominion Nuclear Core Design and Safety Analysis Methods to the Kewaunee Power Station (KPS),"' dated December 6, 2006 (ADAMS Accession Number ML0063410177).

4. Letter from G. T. Bischof (DEK) to NRC, "Request for Approval of Topical Report DOM-NAF-5, "Application of Dominion Nuclear Design and Safety Analysis Methods to the Kewaunee Power Station (KPS)," di3ted April 16, 2007.

5. Letter from G. T. Bischof (DEK) to NRC, "Implementation of the Dominion Statistical DNBR Methodology with VIPRE-DNVRB-1 at Kewaunee Power Station," dated May 4, 2007.

6. Dominion Fleet Report DOM-NAF-2-A, "Rteactor Core Thermal-Hydraulics Using the VIPRE-D Computer Code," August 2006.

7. WCAP-10216-P-A, Revision 1 A, "Relaxation of Constant Axial Offset Control FQ Surveillance Technical Specification," February 1994.