Text

Additional Responses to Request for Additional Information Regarding (1) Large Break Loss of Coolant Accident, (2) Steam Line Break, and (3) Miscellaneous Analysis
	ML11138A093
Person / Time
Site:	Watts Bar
Issue date:	05/13/2011
From:	Stinson D; Tennessee Valley Authority
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	Download: ML11138A093 (41)
	v • d • e

Enclosures 1 and 4 are to be withheld from public disclosure under 10 CFR § 2.390.

When separated from these enclosures, this letter is decontrolled.

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 May 13, 2011 10 CFR 50.4 10 CFR 2.390(b)(4)

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 NRC Docket No. 50-391

Subject:

Watts Bar Nuclear Plant (WBN) Unit 2 - Additional Responses to Request for Additional Information Regarding (1) Large Break Loss of Coolant Accident, (2) Steam Line Break, and (3) Miscellaneous Analysis

References:

1. NRC letter to TVA dated April 27, 2011, "Watts Bar Nuclear Plant, Unit 2 -Audit Report Of Westinghouse Documents Relating to Final Safety Analysis Report Accident Analyses (TAC NO. ME4620)

2. TVA letter to NRC dated April 1, 2011, "Watts Bar Nuclear Plant (WBN)

Unit 2 - Response to Large Break Loca (LBLOCA) and Over-Pressurization Request for Additional Information"

3. TVA letter to NRC dated April 29, 2011, "Watts Bar Nuclear Plant (WBN)

Unit 2 - Response to Requests for Additional Information (RAIs) Regarding Inadvertent ECCS Actuation Analysis, And Chemical & Volume Control System Malfunction Analysis" The purpose of this letter is to provide additional responses to requests for additional information (RAIs) regarding (1) large break loss of coolant accident (LBLOCA), (2) Steam Line Break (SLB), and (3) miscellaneous analysis. These RAIs were received during the NRC Audit at the Westinghouse Electric Company LLC offices in Rockville, Maryland, held during the week of March 14, 2011. The results of this NRC Audit were clarified in the Audit Report issued April 27, 2011 (Reference 1). Partial responses to these RAIs were provided in References 2 and 3. to this letter addresses the remaining LBLOCA questions (in addition to those provided in Reference 2) by providing Westinghouse document WBT-D-3108 P-Attachment, "Watts Bar 2 (WBT) Responses to remaining RAI from NRC Staff Audit Report" (Proprietary).

U.S. Nuclear Regulatory Commission Page 2 May 13, 2011 This document contains information proprietary to Westinghouse. Accordingly, TVA respectfully requests that this proprietary information be withheld from public disclosure in accordance with 10 CFR 2.390. Enclosure 2 provides the supporting affidavit signed by Westinghouse, the owner of the information. The affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of Section 2.390. U.S. Nuclear Regulatory Commission correspondence with respect to the copyright or proprietary aspects of the items listed above or the supporting Westinghouse affidavit should reference CAW-1 1-3149 and should be addressed to J. A. Gresham, Manager, Regulatory Compliance, Westinghouse Electric Company LLC, Suite 428, 1000 Westinghouse Drive, Cranberry Township, Pennsylvania 16066. provides Westinghouse document WBT-D-3108 NP-Attachment, "Watts Bar 2 (WBT) Responses to remaining RAI from NRC Staff Audit Report" (Non-Proprietary), containing non-proprietary version of the information provided in Enclosure 1. to this letter provides the response to the SLB Analysis portion of the RAIs by providing Westinghouse document WBT-D-3041 P-Attachment, "Response to March 15, 2011 NRC Audit Questions on Steam Line Break Analysis for Watts Bar Unit 2" (Proprietary).

This document contains information proprietary to Westinghouse. Accordingly, TVA respectfully requests that this proprietary information be withheld from public disclosure in accordance with 10 CFR 2.390. Enclosure 5 provides the supporting affidavit signed by Westinghouse, the owner of the information. The affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)(4) of Section 2.390. U.S. Nuclear Regulatory Commission correspondence with respect to the copyright or proprietary aspects of the items listed above or the supporting Westinghouse affidavit should reference CAW-1 1-3136 and should be addressed to J. A. Gresham, Manager, Regulatory Compliance, Westinghouse Electric Company LLC, Suite 428, 1000 Westinghouse Drive, Cranberry Township, Pennsylvania 16066. provides Westinghouse document WBT-D-3041 NP-Attachment, "Response to March 15, 2011 NRC Audit Questions on Steam Line Break Analysis for Watts Bar Unit 2" (Non-Proprietary). This document contains the non-proprietary version of the information provided in Enclosure 4.

In addition to the clarifying information provided in Enclosure 4, the following non-proprietary information from Westinghouse is included to explain why the SLB analysis for WBN Units 1 and 2 predicts peak post trip power levels that are less than half the peak post trip power levels predicted for other Westinghouse supplied four loop plants for the same break size:

U.S. Nuclear Regulatory Commission Page 3 May 13, 2011 There are many factors that influence the peak heat flux in a steamline break analysis initiatedfrom hot zero power conditions. Watts Bar has integralflow restrictorswhich reduce the maximum break size compared to some other 4-loop plants and Safety Injection (SI) capacity which is favorable compared to some plants. The Watts Bar analysis models a minimum shutdown margin of 1.6% and many other plants have reduced their minimum shutdown margin to 1.3%. The maximum auxiliary feedwater assumption for Watts Bar is smaller than most other 4-loop plants. Reactivity feedback also highly influences the peak heat flux reached.

To be more specific, a comparison was made to two other Westinghouse designed 4-loop plants. The peak heat flux of the first plant is 15% and the peak heat flux for Watts Bar is just over 3%. The safety injection capacity of this other plant is roughly half that modeled for Watts Bar and the minimum shutdown margin modeled is 1.3%. Also, the maximum AFW is about twice the maximum AFW modeled for Watts Bar. Like Watts Bar, the analysis was done with the LOFTRAN computer code. As a result, the significantly higherpeak heat flux for this plant when compared to Watts Bar is expected.

The licensingbasis steam line break analysis for a second Westinghouse 4-lOOp plant was also examined. This plant has a 1.6% SDM and auxiliaryfeed water which is slightly less than Watts Bar.Also, the safety injection flow rates are smaller than the flow rates assumed in the Watts Bar steamline break analysis. The analysis for this plant was performed using the RETRAN code and the peak heat flux is 6.5%. The higherpeak heat flux for this plant when compared to Watts Bar is expected.

Based on these two examples, the WBN peak heat flux reached is reasonable. includes additional information regarding SLB analysis as provided in Westinghouse document WBT-D-3146 Attachment, 'Watts Bar Unit 2 Steam Line Break NRC Audit Response" (non-proprietary).

Reference 1 also requested an analysis of a bottom mounted instrument (BMI) tube failure. A response to this request will be provided in conjunction with the RAIs recently received on the Mass Addition events.

There are no new commitments made in this submittal. Ifyou have any questions, please contact Bill Crouch at (423) 365-2004.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 13th day of May, 2011.

Respectfully, David Stinson Watts Bar Unit 2 Vice President

U.S. Nuclear Regulatory Commission Page 4 May 13, 2011

Enclosures:

1. Westinghouse Document WBT-D-3108 P-Attachment, "Watts Bar 2 (WBT) Responses to Remaining RAI from NRC Staff Audit Report" (Proprietary)

2. Watts Bar Nuclear Plant Unit 2 Affidavit for Withholding Proprietary Information from Public Disclosure

3. Westinghouse Document WBT-D-3108 NP-Attachment, "Watts Bar 2 (WBT) Responses to Remaining RAI from NRC Staff Audit Report" (Non-Proprietary)

4. Westinghouse Document WBT-D-3041 P-Attachment, "Response to March 15, 2011 NRC Audit Questions On Steam Line Break Analysis for Watts Bar Unit 2" (Proprietary)

5. Watts Bar Nuclear Plant Unit 2 Affidavit for Withholding Proprietary Information from Public Disclosure

6. Westinghouse Document WBT-D-3041 NP-Attachment, "Response to March 15, 2011 NRC Audit Questions On Steam Line Break Analysis for Watts Bar Unit 2" (Non-Proprietary)

7. Westinghouse Document WBT-D-3146 Attachment, "Watts Bar Unit 2 Steam Line Break NRC Audit Response" (Non-Proprietary) cc (Enclosures):

U. S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 NRC Resident Inspector Unit 2 Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381

Enclosure 2 TVA Letter Dated May 13, 2011 Additional Responses to Request for Additional Information Regarding (1) LBLOCA, (2) Steam Line Break (SLB), and (3) Miscellaneous Analysis Watts Bar Nuclear Plant Unit 2 Affidavit for Withholding Proprietary Information from Public Disclosure

CAW-I 1-3149 AFFIDAVIT COMMONWEALTH OF PENNSYLVANIA:

ss COUNTY OF BUTLER:

Before me, the undersigned authority, personally appeared J. A. Gresham, who, being by me duly sworn according to law, deposes and says that he is authorized to execute this Affidavit on behalf of Westinghouse Electric Company LLC (Westinghouse), and that the averments of fact set forth in this Affidavit are true and correct to the best of his knowledge, information, and belief:

A. A. Gresham, Manager Regulatory Compliance Sworn to and subscribed before me this 2nd day of May 2011 Notary Public COMMONWEALTH OF PENNSYLVANIA Notarfal Seal Cynthia Olesky, Notary Public Manor Boro, Westmoreland County Commyssion Expie July 16, 2014.

M@MW, Mffif RiW MHlAtlen ef Notaries

2 CAW-] 1-3149 (1) I am Manager, Regulatory Compliance, in Nuclear Services, Westinghouse Electric Company LLC (Westinghouse), and as such, I have been specifically delegated the function of reviewing the proprietary information sought to be withheld from public disclosure in connection with nuclear power plant licensing and rule making proceedings, and am authorized to apply for its withholding on behalf of Westinghouse.

(2) I am making this Affidavit in conformance with the provisions of 10 CFR Section 2.390 of the Commission's regulations and in conjunction with the Westinghouse Application for Withholding Proprietary Information from Public Disclosure accompanying this Affidavit.

(3) I have personal knowledge of the criteria and procedures utilized by Westinghouse in designating information as a trade secret, privileged or as confidential commercial or financial information.

(4) Pursuant to the provisions of paragraph (b)(4) of Section 2.390 of the Commission's regulations, the following is furnished for consideration by the Commission in determining whether the information sought to be withheld from public disclosure should be withheld.

(i) The information sought to be withheld from public disclosure is owned and has been held in confidence by Westinghouse.

(ii) The information is of a type customarily held in confidence by Westinghouse and not customarily disclosed to the public. Westinghouse has a rational basis for determining the types of information customarily held in confidence by it and, in that connection, utilizes a system to determine when and whether to hold certain types of information in confidence.

The application of that system and the substance of that system constitutes Westinghouse policy and provides the rational basis required.

Under that system, information is held in confidence if it falls in one or more of several types, the release of which might result in the loss of an existing or potential competitive advantage, as follows:

(a) The information reveals the distinguishing aspects of a process (or component, structure, tool, method, etc.) where prevention of its use by any of Westinghouse's

3 CAW- 11-3149 competitors without license from Westinghouse constitutes a competitive economic advantage over other companies.

(b) It consists of supporting data, including test data, relative to a process (or component, structure, tool, method, etc.), the application of which data secures a competitive economic advantage, e.g., by optimization or improved marketability.

(c) Its use by a competitor would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing a similar product.

(d) It reveals cost or price information, production capacities, budget levels, or commercial strategies of Westinghouse, its customers or suppliers.

(e) It reveals aspects of past, present, or future Westinghouse or customer funded development plans and programs of potential commercial value to Westinghouse.

(f) It contains patentable ideas, for which patent protection may be desirable.

There are sound policy reasons behind the Westinghouse system which include the following:

(a) The use of such information by Westinghouse gives Westinghouse a competitive advantage over its competitors. It is, therefore, withheld from disclosure to protect the Westinghouse competitive position.

(b) It is information that is marketable in many ways. The extent to which such information is available to competitors diminishes the Westinghouse ability to sell products and services involving the use of the information.

(c) Use by our competitor would put Westinghouse at a competitive disadvantage by reducing his expenditure of resources at our expense.

4 CAW- 11-3149 (d) Each component of proprietary information pertinent to a particular competitive advantage is potentially as valuable as the total competitive advantage. If competitors acquire components of proprietary information, any one component may be the key to the entire puzzle, thereby depriving Westinghouse of a competitive advantage.

(e) Unrestricted disclosure would jeopardize the position of prominence of Westinghouse in the world market, and thereby give a market advantage to the competition of those countries.

(f) The Westinghouse capacity to invest corporate assets in research and development depends upon the success in obtaining and maintaining a competitive advantage.

(iii) The information is being transmitted to the Commission in confidence and, under the provisions of 10 CFR Section 2.390; it is to be received in confidence by the Commission.

(iv) The information sought to be protected is not available in public sources or available information has not been previously employed in the same original manner or method to the best of our knowledge and belief.

(v) The proprietary information sought to be withheld in this submittal is that which is appropriately marked in "Watts Bar 2 (WBT) Responses to Remaining RAI from NRC Staff Audit Report" (Proprietary), for submittal to the Commission, being transmitted by Tennessee Valley Authority letter and Application for Withholding Proprietary Information from Public Disclosure, to the Document Control Desk. The proprietary information as submitted by Westinghouse is that associated with the NRC review of the Watts Bar Unit 2 license application.

This information is part of that which will enable Westinghouse to:

(a) Assist the customer in obtaining NRC review of the Watts Bar Unit 2 license.

5 CAW-1 1-3149 Further this information has substantial commercial value as follows:

(a) Westinghouse plans to sell the use of this information to its customers for purposes of plant specific LOCA analysis for licensing basis applications.

(b) Its use by a competitor would improve their competitive position in the design and licensing of a similar product for LBLOCA analyses.

(c) The information requested to be withheld reveals the distinguishing aspects of a methodology which was developed by Westinghouse.

Public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Westinghouse because it would enhance the ability of competitors to provide similar calculations and licensing defense services for commercial power reactors without commensurate expenses. Also, public disclosure of the information would enable others to use the information to meet NRC requirements for licensing documentation without

.purchasing the right to use the information.

The development of the technology described in part by the information is the result of applying the results of many years of experience in an intensive Westinghouse effort and the expenditure of a considerable sum of money.

In order for competitors of Westinghouse to duplicate this information, similar technical programs would have to be performed and a significant manpower effort, having the requisite talent and experience, would have to be expended.

Further the deponent sayeth not.

Proprietary Information Notice Transmitted herewith are proprietary and/or non-proprietary versions of documents furnished to the NRC in connection with requests for generic and/or plant-specific review and approval.

In order to conform to the requirements of 10 CFR 2.390 of the Commission's regulations concerning the protection of proprietary information so submitted to the NRC, the information which is proprietary in the proprietary versions is contained within brackets, and where the proprietary information has been deleted in the non-proprietary versions, only the brackets remain (the information that was contained within the brackets in the proprietary versions having been deleted). The justification for claiming the information so designated as proprietary is indicated in both versions by means of lower case letters (a) through (f) located as a superscript immediately following the brackets enclosing each item of information being identified as proprietary or in the margin opposite such information. These lower case letters refer to the types of information Westinghouse customarily holds in confidence identified in Sections (4)(iiXa) through (4)(ii)(f) of the affidavit accompanying this transmittal pursuant to 10 CFR 2.390(b)(1).

Copyright Notice The reports transmitted herewith each bear a Westinghouse copyright notice. The NRC is permitted to make the number of copies of the information contained in these reports which are necessary for its internal use in connection with generic and plant-specific reviews and approvals as well as the issuance, denial, amendment, transfer, renewal, modification, suspension, revocation, or violation of a license, permit, order, or regulation subject to the requirements of 10 CFR 2.390 regarding restrictions on public disclosure to the extent such information has been identified as proprietary by Westinghouse, copyright protection notwithstanding. With respect to the non-proprietary versions of these reports, the NRC is permitted to make the number of copies beyond those necessary for its internal use which are necessary in order to have one copy available for public viewing in the appropriate docket files in the public document room in Washington, DC and in local public document rooms as may be required by NRC regulations if the number of copies submitted is insufficient for this purpose. Copies made by the NRC must include the copyright notice in all instances and the proprietary notice if the original was identified as proprietary.

Enclosure 3 TVA Letter Dated May 13, 2011 Additional Responses to Request for Additional Information Regarding (1) LBLOCA, (2) Steam Line Break (SLB), and (3) Miscellaneous Analysis Westinghouse Document WBT-D-3108 NP-Attachment, "Watts Bar 2 (WBT) Responses to Remaining RAI from NRC Staff Audit Report" (Non-Proprietary)

Westinghouse Non-Proprietary Class 3 Page I of 11 WBT-D-3108 NP-Attachment Watts Bar 2 (WBT) Responses to Remaining RAI from NRC Staff Audit Report Westinghouse Electric Company 1000 Westinghouse Drive Cranberry Township, Pennsylvania 16066

Page 2 of 11 WBT-D-3108 NP-Attachment RAI 1: Provide the refueling water storage tank (RWST) temperature.

The RWST temperature range applied in the ASTRUM analysis is based on the Technical Specifications (60-105°F). [

]a"C The limiting Peak Cladding Temperature (PCT) and Maximum Local Oxidation (MLO) case from the ASTRUM analysis (presented in the FSAR) sampled a RWST temperature of

78. 1F.

RAI 2: An explanation of how condensation was treated in this event was requested and whether condensation maximized?

Validation and treatment of Emergency Core Cooling System (ECCS) condensation in Westinghouse Best-Estimate LOCA methodologies is discussed in detail in Section 15-3 and Section 25-9 of WCAP-12945-P-A (Reference 1).

]a,c ECCS condensation is not maximized, [

]a,c The subcooling in various regions of the downcomer for the Watts Bar 2 limiting PCT/MLO case is inspected during the period of downcomer boiling (and corresponding cladding heatup), which occurs from about 100 seconds to 280 seconds (Figures 1 and 2).

ac

]ac RAI 3: The effect of time step on the results was also required and whether this included time steps down to and including 0.001 sec.

WCOBRA/TRAC timestep studies were documented in Section 22-5 of WCAP-12945-P-A, with the final timestep limits for PWR calculations provided in Table 22-5-4. The timestep sizes used in the Watts Bar Unit 2 ASTRUM analysis are in compliance with the limits provided Table 22-5-4. Therefore, the usage condition in the USNRC Safety Evaluation Report (SER) for WCAP-12945-P-A was met. It is noted that

Page 3 of 11 WBT-D-3108 NP-Attachment Section 13-3-1 of WCAP-16009-P-A states that the timestep usage condition remains applicable with ASTRUM. As such, no plant specific timestep studies have been performed.

RAI 4: Confirm correct conductivity in the downcomer walls.

The conductivity in the downcomer walls has been confirmed. The vessel wall is modeled using carbon steel with a stainless steel cladding, and the core barrel and neutron pads are modeled using stainless steel.

The conductivity of each material modeled in WCOBRA/TRAC as a function of temperature is shown in Table 1 and Table 2.

Table 1: Stainless Steel Conductivity Modeled in WCOBRA/TRAC a,c Table 2: Carbon Steel Conductivity Modeled in WCOBRA/TRAC

Page 4 of 11 WBT-D-3108 NP-Attachment RAI 5: Confirm the values for the lateral k-factors in the downcomer (were they based on Idlechik?).

Responses to similar questions recently transmitted to the USNRC for D.C. Cook Unit 2 are generally also applicable to Watts Bar Unit 2. Information regarding how the lateral k-factors are modeled in the downcomer and comparisons to Idel'chik calculations on a plant specific basis are provided therein.

[

]ac Base on the physical nature of this argument, similar conclusions can be drawn for Watts Bar Unit 2.

References:

1. Bajorek, S. M., et al., March 1998, "Code Qualification Document for Best Estimate LOCA Analysis," Volume 1 Revision 2, and Volumes 2 through 5, Revision 1, WCAP-12945-P-A (Proprietary).

2. Nissley, M. E., et al., January 2005, "Realistic Large-Break LOCA Evaluation Methodology Using the Automated Statistical Treatment of Uncertainty Method (ASTRUM)," WCAP-16009-P-A (Proprietary).

Page 5 of 11 WBT-D-3108 NP-Attachment Figure 1: Peak Clad Temperature a,c

Page 6 of 11 WBT-D-3108 NP-Attachment Figure 2: Vessel Fluid Inventory a,c

Page 7 of 11 WBT-D-3108 NP-Attachment Figure 3: Average Liquid Subcooling in the Downcomer at the Nozzle Elevation a,c

Page 8 of 11 WBT-D-3108 NP-Attachment Figure 4: Average Liquid Subcooling in the Downcomer at Vessel Section 5 a,c

Page 9 of 11 WBT-D-3108 NP-Attachment Figure 5: Average Liquid Subcooling in the Downcomer at Vessel Section 4 a,c

Page 10 of 11 WBT-D-3108 NP-Attachment Figure 6: Average Liquid Subcooling in the Downcomer at Vessel Section 3 (Mid-Core) a,c

Page 11 of 11 WBT-D-3108 NP-Attachment Figure 7: Watts Bar 2 Vessel Noding Diagram a,c

Enclosure 5 TVA Letter Dated May 13, 2011 Additional Responses to Request for Additional Information Regarding (1) LBLOCA, (2) Steam Line Break (SLB), and (3) Miscellaneous Analysis Watts Bar Nuclear Plant Unit 2 Affidavit for Withholding Proprietary Information from Public Disclosure

CAW- 11-3136 AFFIDAVIT COMMONWEALTH OF PENNSYLVANIA:

ss COUNTY OF BUTLER:

Before me, the undersigned authority, personally appeared J. A. Gresham, who, being by me duly sworn according to law, deposes and says that he is authorized to execute this Affidavit on behalf of Westinghouse Electric Company LLC (Westinghouse), and that the averments of fact set forth in this Affidavit are true and correct to the best of his knowledge, information, and belief:

4.A. Gresham, Manager Regulatory Compliance Sworn to and subscribed before me 01" this 8f day of April 2011

- Notary Public COMMONWEALTH OF PENNSYLVANIA Notarial Seal Cynthia Olesky, Notary Public Manor Boro, Westmoreland County My Commisson Expires July 16, 2014 Member. Pennsylvania Association of Notaries

2 CAW-1 1-3136 (1) I am Manager, Regulatory Compliance, in Nuclear Services, Westinghouse Electric Company LLC (Westinghouse), and as such, I have been specifically delegated the function of reviewing the proprietary information sought to be withheld from public disclosure in connection with nuclear power plant licensing and rule making proceedings, and am authorized to apply for its withholding on behalf of Westinghouse.