ML12342A383

Regulatory Audit Summary and Request for Additional Information, Round 2, License Amendment Request to Revise Technical Specification 3.7.4, Atmospheric Dump Valves (Advs)

ML12342A383
Person / Time
Site:	Palo Verde
Issue date:	12/13/2012
From:	Lauren Gibson Plant Licensing Branch IV
To:	Edington R Arizona Public Service Co
Gibson L
References
TAC ME6566, TAC ME6567, TAC ME6568
Download: ML12342A383 (7)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 December 13, 2012 Mr. Randall K. Edington Executive Vice President Nuclearl Chief Nuclear Officer Mail Station 7602 Arizona Public Service Company P.O. Box 52034 Phoenix, AZ 85072-2034

SUBJECT:

PALO VERDE NUCLEAR GENERATING STATION, UNITS 1,2, AND 3 REGULATORY AUDIT

SUMMARY

AND REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATION 3.7.4, "ATMOSPHERIC DUMP VALVES (ADVS)"

(TAC NOS. ME6566, ME6567, AND ME6568)

Dear Mr. Edington:

By letter dated June 22, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML11182A908), as supplemented by letters dated December 9, 2011 (ADAMS Accession No. ML11356A088), and January 27, 2012 (ADAMS Accession No. ML12046A649), Arizona Public Service Company, the licensee for Palo Verde Nuclear Generating Station Units 1, 2, and 3, requested a license amendment that would revise Technical SpeCification (TS) Limiting Condition for Operation (LCO) 3.7.4, "Atmospheric Dump Valves (ADVs)." The proposed change would require four ADV lines to operable in MODES 1, 2, and 3, and, when a steam generator is relied upon for heat removal, MODE 4.

The U.S. Nuclear Regulatory Commission (NRC) staff conducted a regulatory audit onsite November 27-29, 2012, to assist in the review of this application. The NRC staff conducting the audit were Lauren Gibson, licensing project manager, Benjamin Parks from the Reactor Systems Branch, and Stanley Gardocki, from the Balance of Plant Branch. All are in the Office of Nuclear Reactor Regulation. Any information identified during the audit that the NRC staff would like to use in the review is being requested formally on the docket through the enclosed request for additional information.

During the audit, the licensee presented the history of the licensing basis for this particular TS LCO. Then, the licensee presented computer analyses of various accident scenarios with different availabilities of the ADVs. The NRC staff discussed those analyses in depth with the licensee. The NRC staff also reviewed procedures relating to the scenarios. Furthermore, the NRC staff observed a simulator crew responding to accident scenarios with ADVs declared inoperable. Along with a resident inspector, the NRC staff toured the equipment relative to this review.

As a result of the audit, the NRC staff determined that the additional information identified in the enclosure to this letter is needed in order for the NRC staff to complete its review. The draft copy of the request for additional information was provided to Mr. Robert Roehler of your staff

R. Edington - 2 via e-mail onDecember3.2012(ADAMSAccessionNo.ML12339A069). The responses to this request are due January 25, 2013.

If you have any questions, please contact me at (301) 415-1056 or via e-mail at lauren.gibson@nrc.gov.

Sincerely, Lauren K. Gibson, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-528, STN 50-529, and STN 50-530

Enclosure:

As stated cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST RELATED TO REVISION OF TECHNICAL SPECIFICATION 3.7.4, "ATMOSPHERIC DUMP VALVES (ADVS)"

ARIZONA PUBLIC SERVICE COMPANY PALO VERDE NUCLEAR GENERATING STATION. UNITS 1. 2. AND 3 DOCKET NOS. STN 50-528, STN-50-529. AND STN-50-530 By letter dated June 22, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML11182A908), as supplemented by letters dated December 9,2011 (ADAMS Accession No. ML11356A088), and January 27,2012 (ADAMS Accession No. ML12046A649), Arizona Public Service Company (APS), the licensee for Palo Verde Nuclear Generating Station Units 1, 2, and 3, requested a license amendment that would revise Technical Specification (TS) Limiting Condition for Operation (LCO) 3.7.4, "Atmospheric Dump Valves (ADVs)." The proposed change would require four ADV lines to operable in MODES 1, 2, and 3, and, when a steam generator is relied upon for heat removal, MODE 4.

The U.S. Nuclear Regulatory Commission (NRC) staff conducted a regulatory audit onsite November 27-29,2012. As a result of that audit, the NRC staff identified that the following additional information is required to complete the review.

1. The following questions pertain to the steam generator tube rupture (SGTR) evolution and supplemental analyses that are discussed in APS's response to NRC's request for additional information (RAI) 3, provided by letter dated January 27,2012.

a. Please provide a tabulated sequence of events for the supplemental analysis.

b. Please provide a comparison of the Henry-Fauske break flow model to the Homogenous Equilibrium model including a plot of steam generator (SG) tube flow versus time that compares the design basis analysis to the supplemental analysiS. Provide this comparison for a period of time that extends to the time that the atmospheric dump valves (ADVs) are assumed to actuate in the design basis analysis and discuss the effect that any other significant differences aside from the break flow model have on the compared results.

c. Please provide plots of the following parameters as functions of time:

i. Leak flow rate ii. Pressurizer pressure iii. Pressurizer volume iv. RCS subcooling

v. Steam generator pressure vi. Steam generator level (wide range)

Enclosure

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d. Since licensed operators are trained and expected to mitigate SGTRs, please characterize the agreement between a simulator projection of an SGTR and a CENTS 1 analysis of an SGTR, given a roughly analogous scenario executed with each tool.

e. Please describe how plant personnel mitigate an SGTR coincident with loss of offsite power (LOP) event when ADVs are not available for operation from the control room. Include a discussion of applicable procedures, and provide procedure excerpts for the steps leading up to and after establishing reactor coolant system (RCS) cooldown using the steam bypass control system, contingency actions (including Appendix 18 - Local ADV actuation), and main steamline isolation. Please explain how these procedures are implemented in regards to maintaining availability of required equipment to cooldown.

f. During mitigation of an SGTR, please discuss the possibility of overfilling a steam generator if an RCS cooldown/depressurization is delayed. Please discuss the potential for a liquid release to the environment through the main steam safety valves. Please describe the timing and possible delays in the operator's ability to commence an RCS cooldown/depressurization in the event the ADVs are aU inoperable. Please describe defense-in-depth measures to control the liquid inventory in the steam generator until a method is available to commence a cooldown.

2. The following questions pertain to the main steam line break evaluation and supplemental analysis that is discussed in APS's response to NRC RAI 3, by letter dated January 27,2012.

a. Please provide a table of results that includes key system attributes such as peak RCS pressure, maximum and minimum pressurizer level, and the sequence of events. Identify the acceptance criteria for pressurizer fill and for water entrainment in the pressurizer safety valve (PSV) effluent.

b. Please provide plots of the following parameters as functions of time. The NRC staff acknowledges that some plots may need to be truncated if a stable or quasi stable condition is reached. If this is done, please describe the system behavior for the period that is not included.

i. Instantaneous safety-injection (SI) flow ii. Total SI flow iii. Pressurizer pressure iv. Pressurizer volume

v. Subcooling margin vi. Steam generator pressure vii. Steam generator level 1 CENTS is an interactive computer code for simulation of the nuclear steam supply system and related systems. It is described in WCAP-15996.

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3. The following questions pertain to the feedwater line break (FWLB) evaluation and supplemental analysis that is discussed in APS's response to NRC RAI 3, by letter dated January 27,2012.

a. Please provide a table of results that includes key system attributes such as peak RCS pressure, maximum and minimum pressurizer level, and the sequence of events. Also include relevant acceptance criteria.

b. Please provide plots of the following parameters as functions of time. The NRC staff acknowledges that some plots may need to be truncated if a stable or quasi stable condition is reached.

i. Instantaneous charging flow Ii. Total charging flow iii. Pressurizer pressure iv. Pressurizer volume

v. Steam generator pressure vi. Steam generator level

c. Please discuss how, in the context of an FWLB event and associated control room procedures, operators will ensure that the charging pumps are secured independently of taking action to open ADVs slightly. Also, please identify how procedures differ from the supplemental analysis assumptions, and explain why this is the case. For example, while the analysis assumes that charging pumps are secured within 20 minutes, operators may attempt to control pressurizer level and pressure using auxiliary spray from the charging pumps. Please explain such deviations between procedures and analysis.

d. In a control room simulator scenario where an FWLB occurs with a coincident loss of offsite power (LOP), and ADVs are unavailable, please characterize the pressurizer level and pressure response that an operator may see.

4. The RAI response refers to the use of the non-safety-related steam bypass control valves (SBCVs) as a defense in depth measure while the plant is in the 24-hour condition statement with all four ADVs inoperable and a design basis event such as an SGTRLOP occurs. The Final Safety Analysis Report (FSAR) describes two SBCVs as atmospheric relief valves with the same relief capacity as an ADV. However, the atmospheric SBCVs are non-safety-related valves located in the turbine building, downstream of the main steam isolation valves (MSIVs).

a. Please describe why the 1007/1008 SBCVs would be available as a defense-in depth measure when there are no ADVs available to mitigate accidents and transients described in its FSAR. Please include a description of the means to control operation of the valve (i.e., control power, medium to physically reposition valve, and remotellocallmanual capabilities).

b. Since the atmospheric SBCVs are downstream of the MSIVs, please describe whether the SBCVs will be available during transients and accidents or if the

-4 SBCVs can be made available through operator actions in a reasonably short period of time to provide accident mitigation and whether sufficient flow can be achieved through these normal/alternate/bypass lines.

c. In the event the ADVs are not available during an accident, the atmospheric SBCVs may be used to conduct aRCS cooldown. Please describe how operators will execute steps in the SGTR procedures related to use of the SBCVs and closing the MSIVs, and achieving the use of the SBCVs with the MSIVs closed in feed line break and main steam line procedures.

d. Please determine whether any measures are necessary or in place to assure that the 1007/1008 SBCVs are available for accident mitigation prior to entering TS Condition statement for all four ADVs not available.

R. Edington -2 via e-mail on December3,2012(ADAMSAccession No. ML12339A069). The responses to this request are due January 25, 2013.

If you have any questions, please contact me at (301) 415-1056 or via e-mail at lauren.gibson@nrc.gov.

Sincerely, IRA!

Lauren K. Gibson, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-528, STN 50-529, and STN 50-530

Enclosure:

As stated cc w/encl: Distribution via Listserv DISTRIBUTION:

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