AEP-NRC-2014-51, Response to Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916), Dated May 6, 2014

Response to Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916), Dated May 6, 2014

ML14189A102
Person / Time
Site:	Cook
Issue date:	07/03/2014
From:	Lies Q American Electric Power, Indiana Michigan Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
AEP-NRC-2014-51, TAC MF2916
Download: ML14189A102 (9)

Text

INDIANA Indiana Michigan Power MICHIGAN Cook Nuclear Plant l*1!IER One Cook Place A unit of American Electric Power lndianaMichiganPower.com July 3, 2014 AEP-NRC-2014-51 10 CFR 50.90 Docket No.: 50-315 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk' Washington, DC, 20555-0001 Donald C. Cook Nuclear Plant Unit 1 Response to "Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916)," dated May 6, 2014

References:

1. Letter from J. P. Gebbie, Indiana Michigan Power Company (I&M), to U. S. Nuclear Regulatory Commission (NRC) Document Control Desk, "Donald C. Cook Nuclear Plant Unit 1 Docket No. 50-315, License Amendment Request Regarding Restoration of Normal Reactor Coolant System Operating Pressure and Temperature Consistent with Previously Licensed Conditions," dated October 8, 2013, Agencywide Documents Access and Management System (ADAMS) Accession Number ML13283A121.

2. Letter from T. J. Wengert, NRC, to L. J. Weber, I&M, "Donald C. Cook Nuclear Plant, Unit 1, Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure And Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916)"" dated March 31, 2014, ADAMS Accession Number ML14066A311.

3. Letter from J. P. Gebbie, I&M, to NRC Document Control Desk, "Donald C. Cook Nuclear Plant Unit 1, Response to 'Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916),"' dated April 29, 2014, ADAMS Accession Number ML14121A422.

4. Letter from T. J. Wengert, NRC, to L. J. Weber, I&M, "Donald C. Cook Nuclear Plant, Unit 1 - Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916)," dated May 6, 2014, ADAMS Accession Number ML14099A450.

5. Letter from J. P. Gebbie, i&M, to NRC Document Control Desk, "Donald C. Cook Nuclear Plant Unit 1, Response to 'Request for Additional Information on the Application

U. S. Nuclear Regulatory Commission AEP-NRC-2014-51 Page 2 for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916),"' dated June 5, 2014.

By letter dated October 8, 2013 (Reference 1), IKdiana Michigan Power Company (I&M) submitted an application for a license amendment to restore the normal reactor coolant system operating pressure and temperature consistent with previously licensed conditions for the Donald C. Cook Nuclear Plant (CNP), Unit 1. The U.S. Nuclear Regulatory Commission (NRC) staff provided a Request for Additional Information (RAI):(Reference 2) to complete the review of Reference 1. I&M responded to Reference 2 by Reference 3. By letter dated May 6, 2014, the NRC provided an additional RAI (Reference 4) to complete the review of Reference 1.. Reference 5 was I&M's response to the RAIs contained in Reference 4, with the exception of Containment and Ventilation Systems Branch (SCVB) RAI-3(c), SCVB RAI-9(a), and SCVB RAI-9(b). This submittal provides I&M's response to the RAts contained in Reference 4 which were not included in Reference 5.

Also, during its review of Reference 5, the NRC discovered an error in I&M's response to SCVB-RAI-1O(b). In I&M's response, the first sentence states: "To ensure the calculated NPSH-required value is conservatively maximized under all conditions, the CNP Unit 1 NPSH AOR (Reference 3) for the ECCS pumps and CTS pumps uses bounding design inputs rather than relying on specific containment conditions associated with specific M&E releases or pump flow rates associated. with specific flow requirement scenarios." In fact, the Net Positive Suction Head (NPSH)-required (NPSHR) is provided by the pump vendor. The NPSH-available. (NPSHA) is obtained by NPSH analysis using conservatively biased inputs that maximize the sump water temperature (to maximize the vapor pressure), ýmaximize the piping and strainer head loss, and minimize the sump static head. Therefore, the first line should, instead, state: "To ensure the calculated NPSH-available value is conservatively minimized. under all conditions,....." This correction was, entered into CNP's corrective action process; revieyw determined that the remainder of the response is accurate. to this letter provides an affirmation statement. Enclosure 2 provides an overview of responses to RAIs: SCVB RAI-3(c), SCVB .RAI-9(a), and SCVB RAI-9(b). Enclosure 3 provides non-proprietary responses to RAts: SCVB RAI-3(c), SCVB RAI-9(a), and SCVB RAI-9(b).

This letter contains no. new or revised commitments' Should you have any questions, please contact Mr. Michael K. Scarpello, Regulatory Affairs Manager, at (269) 466-2649.

Sincerely, Q. Shane Lies.

Engineering Vice President, Indiana Michigan Power JMT/amp

U. S. Nuclear Regulatory Commission AEP-NRC-2014-51 Page 3

Enclosures:

1. Affirmation

2. Overview of Responses to SCVB RAI-3(c), SCVB RAI-9(a), and SCVB RAI-9(b)

3. Westinghouse Letter, LTR-PL-14-24, "Westinghouse Responses to NRC, "Donald C. Cook Nuclear Plant Unit 1 - Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916) Set #2, Part I1," dated June 19, 2014 c: T. A. Beltz, NRC Washington DC J. T. King, MPSC MDEQ - RMD/RPS NRC Resident Inspector C. D. Pederson, NRC Region III A. J. Williamson, AEP Ft. Wayne, w/o enclosure

ENCLOSURE 1 TO AEP-NRC-2014-51 AFFIRMATION I, Q. Shane Lies, being duly sworn, state that I am Engineering Vice President of Indiana Michigan Power Company (I&M), that I am authorized to sign and file this request with the U. S. Nuclear Regulatory Commission on behalf of I&M, and that the statements made and the matters set forth herein pertaining to I&M are true and correct to the best of my knowledge, information, and belief.

Indiana Michigan Power Company Shane Lies Engineering Vice President, Indiana Michigan Power DANIELLE BURGOYNE SWORN TO AND SUBSCRIBED BEFORE ME Notary Public, State of Michigan County of Berrien DAY OF 2014 My commission Expires 04-04-2018 THIS Acting in the County of y CNotaEpirs - "

My Commission Expires _,*- L\

ENCLOSURE 2 TO AEP-NRC-2014-51 Overview of Responses to SCVB RAI-3(c), SCVB RAI-9(a), and SCVB RAI-9(b)

Introduction Containment and Ventilation Systems Branch (SCVB) Request for Additional Information (RAI)-3(c), RAI-9(a), and RAI-9(b) question the direction of conservatism for initial containment temperature in various containment temperature and pressure analyses that support the normal operating pressure/normal operating temperature (NOP/NOT) License Amendment Request (LAR) (Reference 1). Enclosure 3 provides specific responses to these RAls and describes results of the Westinghouse evaluations and assessments supporting the responses.

As discussed in Enclosure 3, Westinghouse identified that the historical assumption that low initial containment temperatures should be used is not always conservative. This finding adversely impacts the containment integrity analysis-of-record (AOR) for Donald C. Cook Nuclear Plant (CNP) and the NOP/NOT analysis and evaluations for loss-of-coolant accident (LOCA) and Steam Line Break (SLB) included in WCAP-17762-NP (Reference 2).

The purpose of this overview is to provide perspective on the new Westinghouse sensitivity analyses and to identify actions that have been taken, and that will be taken, by Indiana Michigan Power Company (I&M) to collectively address the adverse analysis impacts in a way that supports the NOP/NOT LAR. Finally, it is noted that this new issue is being addressed in CNP's Corrective Action Program.

U. S. Nuclear Regulatory Commission (NRC) RAI SCVB RAI-3(c)

Correction of Submittal Error During the Westinghouse investigation of SCVB RAI-3(c), it was discovered that summary information presented in WCAP-17762-NP regarding the effects -of the containment air recirculation fan delay and containment spray system (CTS) delay on containment pressure was not extracted correctly from the corresponding calculation notes. Specifically, in Section 5.4.2.5, "Results," and Section 5.4.2.6, "Conclusions," the combined effect of the two delay parameters was reported as an increase of 0.0300 pounds per square inch (psi) when it should have been reported as an increase of 0.0486 psi. Correction of this error increases the reported evaluated peak pressure from 11.7184 pounds per square inch gauge (psig) to 11.7370 psig. The overall conclusion that "the containment design limit of 12 psig is not exceeded" is not affected by this documentation error. The complete text of corrected Sections 5.4.2.5 and 5.4.2.6 is included on Pages NP-2 and NP-3 of Enclosure 3. Westinghouse and I&M have entered this error into their respective corrective action programs.

Table SCVB-RAI-3(c)-1 summarizes relevant containment analysis results to clarify the impact of the documentation error. The current values for containment peak pressure documented in Updated Final Safety Analysis Report (UFSAR) (Reference 3) Section 14.3.4.1.3.1.6 are also provided for comparison.

to AEP-NRC-2014-51 Page 2 Table SCVB-RAI-3(c)-I Containment Pressure Item UFSAR, AOR WCAP-17762-NP, Correction of Error Revision 25 Revision 1 in WCAP-1 7762-NP Long Term Ice Condenser (LOTIC) 11.42 11.4184 11.4184 11.4184 calculated value Adjustments per 0.27 0.2700 0.2700 0.2700 UFSAR Penalty per UFSAR 0.06 (Note 1)

Hydrogen Skimmer Fans (CEQ) and CTS --- --- 0.0300 0.0486 delayed start Total peak pressure 11.75 11.6884 11.7184 11.7370 Design pressure 12.00 12.0000 12.0000 12.0000 Note 1 - Westinghouse informed I&M during the recent investigation that this previously assessed penalty is not applicable to CNP; it will be removed in an upcoming UFSAR update Findings Related to SCVB RAI-3(c)

The stated assumption in the RAI that the containment response evaluations performed for NOP/NOT used the same initial containment temperatures as the AOR is correct. As presented in WCAP-17762-NP, Section 5.4.2, "Long-Term LOCA Mass & Energy Releases and Containment Response," no new LOCA mass and energy (M&E) analyses were performed for the NOP/NOT program. An evaluation was performed to determine if the current LOCA M&E and containment integrity AOR support operation of CNP Unit 1 at NOP/NOT conditions. For the LOCA M&E analysis, this effort was accomplished by comparing the CNP Unit 1 NOP/NOT conditions to the inputs assumed in the current LOCA M&E AOR. For the containment integrity analysis, this effort was completed by evaluating the effects of increased delay times for CTS actuation and containment air recirculation fan actuation on the LOCA containment integrity analysis.

With regard to the specific question regarding initial containment temperature bias, Westinghouse determined that low initial temperatures have historically been used because of the density effect on air mass. To respond to SCVB RAI-3(c), Westinghouse performed a sensitivity analysis on the CNP AOR while assuming the Technical Specification (TS) 3.6.5 maximum temperature of 100 degrees Fahrenheit (OF) in the upper volume and 120°F in the lower volume. This sensitivity analysis identified increases in calculated containment pressure.

Investigation has determined that the direction of conservatism for initial temperature is also influenced by the timing of ice bed melt, which is affected by initial ice mass, containment spray operation, and M&E release.

The results of the sensitivity analysis using high initial containment temperature indicate that the calculated peak containment pressure is higher than the AOR case, increasing by 0.72 psi, i.e.,

to AEP-NRC-2014-51 Page 3 from 11.6884 psig (including adjustments) to 12.4084 psig (including adjustments). Adding the effect of delayed actuation times for CTS and CEQ for Unit 1 NOP/NOT operation increases the peak pressure value to 12.4570 psig. In both the AOR and NOP/NOT cases, the elevated pressure would exceed the containment design pressure limit of 12 psig specified in TS Basis B3.6.4.

Relying on documented generic conservatism in the LOCA M&E methodology, the Westinghouse response (Enclosure 3) provides justification that the non-conservative initial containment temperature input does not result in a substantial safety hazard. This newly discovered issue has been entered into CNP's Corrective Action Program and will be resolved in conjunction with other issues currently affecting the CNP containment analysis, specifically, NSAL 11-5 (Reference 4) and NSAL 14-2 (Reference 5), as addressed in the earlier response to SCVB RAI-5(b) (Reference 6). The cumulative effect of the known errors in the containment analysis is approximately 3.2 psi, comprised of 2.3 psi (CNP-specific) for NSAL-1 1-5, 0.2 psi for NSAL-14-2, and 0.7 psi for the initial containment temperature issue, leaving approximately 2.8 psi of the 6 psi generic conservatism in the LOCA M&E methodology.

Although current operability and operability under proposed NOP/NOT conditions are assured using the generic conservatism in the methodology, the specific adverse impact of the initial temperature assumption will be addressed for Unit 1 prior to implementation of NOP/NOT. As part of the recent sensitivity analysis, Westinghouse determined that either of two independent actions can be taken to mitigate the specific 0.72 psig peak pressure impact associated with assuming higher initial containment temperatures:

• Decreasing the maximum assumed Residual Heat Removal (RHR) containment spray actuation time from 4500 seconds to 4200 seconds, which provides a benefit of approximately one psi

" Crediting additional ice in the ice condenser above the TS minimum value; crediting an additional ice mass of 25,000 pounds-mass provides a benefit of approximately 0.7 psi The selected approach to offset this penalty for the Unit 1 NOP/NOT amendment request is to ensure that a revised accident analysis input assumption for RHR spray initiation time of 4200 seconds can be supported.

Containment spray from the RHR system is only actuated if one train of CTS is unavailable. In the event RHR spray is needed to mitigate an event, Emergency Operating Procedures (EOP) direct that RHR spray not be placed into service prior to 50 minutes after event initiation to ensure that sufficient core heat has been removed to bring the remaining decay heat to within the removal capability of one charging pump and one safety injection pump. The EOP background documents indicate that within the following 25 minutes (total of 75 minutes from initiation of the event) one train of RHR should be placed in the containment spray mode to assist in maintaining containment pressure below the design limit after ice bed melt-out. The 75-minute maximum time for placing RHR spray in service is included in the Time Critical Action (TCA) program (Reference 7 and Reference 8). A recent validation and verification exercise in the Unit I simulator confirmed that an operating crew can perform this action in less than three minutes (less than 53 minutes from event initiation). Prior to implementation of Unit 1 NOP/NOT, the EOP background documents and TCA program will be updated to reflect a revised maximum time of 70 minutes (4200 seconds) for placing RHR spray in service.

to AEP-NRC-2014-51 Page 4 Table SCVB-RAI-3(c)-2 provides a comparison of the corrected peak containment pressure from Table SCVB-RAI-3(c)-I with the peak containment pressure assuming high initial containment temperature and actuation of RHR sprays at 4200 seconds.

Table SCVB-RAI-3(c)-2 Containment Pressure Item Correction of Error SCVB RAI-3(c) in WCAP-17762-NP Response LOTIC calculated value 11.4184 11.4184 Adjustments per UFSAR 0.2700 0.2700 CEQ and CTS delayed 0.0486 0.0486 start High initial temperature --- 0.7200 Earlier RHR spray --- -1.0000 Total peak pressure 11.7370 11.4570 Design pressure 12.0000 12.0000 NRC RAI SCVB RAI-9(a) and RAI-9(b)

Past practice for LOTIC3 containment analysis of SLB has been to minimize the upper compartment temperature and maximize the lower compartment temperature. In response to SCVB RAI-9(a) and RAI-9(b), Westinghouse performed sensitivity analyses using the Unit 1-specific containment model for SLB and assuming the maximum TS 3.6.5 upper compartment temperature limit of 1000 F for the air mass and heat sinks.

For SCVB RAI-9(a), results of the sensitivity analyses demonstrate that the assumption of low upper compartment temperature remains conservative for double-ended rupture scenarios.

However, use of a higher value for containment initial temperature for split break scenarios yields an increase of approximately 0.3°F in peak containment temperature. To offset the adverse impact of the 0.3 0 F increase in maximum temperature, an additional sensitivity study found that a reduction in the overly conservative assumption of 100 percent (%) relative humidity (RH) to 75% RH fully offsets the impact of the increased upper compartment initial temperature.

I&M has determined that 65% RH is a conservative upper bound at the maximum temperature of 100°F. Consequently, the peak containment temperature reported in WCAP-17762-NP remains bounding.

For SCVB RAI-9(b), results of the sensitivity analysis demonstrate that higher upper compartment temperature produces a minimal change in the early peak pressure and a decrease in the long-term pressure transient. Notwithstanding those findings, the containment pressure transient for LOCA defines the limiting pressure response and easily bounds the pressure responses for a SLB.

to AEP-NRC-2014-51 Page 5 Summary During preparation of the responses to SCVB RAI-3(c), RAI-9(a), and RAI-9(b), it was learned that the assumption of low initial containment temperature for LOCA and SLB M&E-containment analyses and evaluations is not always conservative. As a result, actions have been taken by I&M to offset the adverse effects and restore the analysis margins previously identified in the NOP/NOT LAR.

Although the 6 psi margin that has been documented to exist in the LOTIC methodology for LOCA M&E-containment pressure can accommodate the 0.72 psi increase in containment pressure as a result of the higher initial temperature in upper containment, I&M plans to revise plant documentation to support reducing maximum RHR spray actuation time from 4500 seconds to 4200 seconds. The recent sensitivity analysis demonstrates that this change will more than offset the predicted pressure increase in containment and will serve to maintain a reasonable margin to the 12.0 psig containment design pressure limit.

The 0.3°F increase in containment peak temperature in the SLB M&E containment analysis resulting from using the maximum upper compartment initial temperature has been completely offset by documenting the basis for using a reduced maximum RH value inside containment.

References for Enclosure 2

1. Letter from J. P. Gebbie, Indiana Michigan Power Company (I&M), to U. S. Nuclear Regulatory Commission (NRC) Document Control Desk, "Donald C. Cook Nuclear Plant Unit 1 Docket No. 50-315, License Amendment Request Regarding Restoration of Normal Reactor Coolant System Operating Pressure and Temperature Consistent with Previously Licensed Conditions," October 8, 2013, Agencywide Documents Access and Management System (ADAMS) Accession Number ML13283A121.

2. WCAP-17762-NP, Revision 1, "D. C. Cook Unit I Return to Reactor Coolant System Normal Operating Pressure/Normal Operating Temperature Program - Licensing Report,"

September 2013 (previously submitted as Enclosure 6 of Reference 1).

3. D. C. Cook Nuclear Plant Updated Final Safety Analysis Report, Version 25; September 9, 2013.

4. Nuclear Safety Advisory Letter (NSAL)-1 1-5, "Westinghouse LOCA Mass and Energy Release Calculation Issues," July 25, 2011.

5. NSAL-14-2, "Westinghouse Loss-of-Coolant Accident Mass and Energy Release Calculation Issue for Steam Generator Tube Material Properties," March 31, 2014.

6. Letter from J. P. Gebbie, I&M, to NRC Commission Document Control Desk, "Donald C.

Cook Nuclear Plant Unit 1, Response to "Request for Additional Information on the Application for Amendment to Restore Normal Reactor Coolant System Pressure and Temperature Consistent with Previously Licensed Conditions (TAC No. MF2916),"

June 5, 2014.

7. 12-EHP-4075-TCA-001, Revision 4, "Operator Time Critical Actions," August 27, 2013.

8. PMP-4075-TCA-001, Revision 7, "Time Critical Action Validation and Verification," July 2, 2013.