ML12347A040
| ML12347A040 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 12/19/2012 |
| From: | Gibson L K Plant Licensing Branch IV |
| To: | Edington R K Arizona Public Service Co |
| Gibson L K | |
| References | |
| TAC ME8160, TAC ME8161, TAC ME8162 | |
| Download: ML12347A040 (5) | |
Text
UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555*0001 December 19, 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 PALO VERDE NUCLEAR GENERATING STATION, UNITS 1,2, AND REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO ELIMINATE THE USE OF THE TERM CORE ALTERATION (TAC NOS. ME8160, ME8161, AND ME8162) Dear Mr. Edington: By letter dated March 8, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 12076A045), as supplemented by letter dated October 11. 2012 (ADAMS Accession No. ML 12286A330). Arizona Public Service Company (APS, the licensee) submitted a license amendment (LAR) for Palo Verde Nuclear Generating Station, Units 1, 2, and 3. The proposed amendment would eliminate the use of the term CORE ALTERATION from the Technical Specifications. The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided by the licensee and 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 in two parts to Mr. Robert Roehler of your staff via e-mail on December 5,2012. A clarifying conference call was held on December 13.2012. Mr. Roehler agreed to provide a response by January 31, 2013.
R. Edington -If you have any questions, please contact me at (301) 415-1056 or via e-mail at Lauren. Gibson@nrc.gov. Sincerely, Docket Nos. STN 50-528, STN and STN Enclosure: As stated cc w/encl: Distribution via Listserv REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST TO ELIMINATE THE USE OF THE TERM CORE ALTERATION IN THE TECHNICAL SPECIFICATIONS ARIZONA PUBLIC SERVICE COMPANY PALO VERDE NUCLEAR GENERATING STATION. UNITS 1. 2. AND 3 DOCKET NOS. 50-528. 50-529. AND 50-530 By letter dated March 8, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 12076A045), as supplemented by letter dated October 11, 2012 (ADAMS Accession No. ML 12286A330), Arizona Public Service Company (APS, the licensee) submitted a license amendment (LAR) in which it proposed to remove the use of the term CORE ALTERATION from the Technical Specifications (TSs) including TS 3.9.2, "Nuclear Instrumentation," for the Palo Verde Nuclear Generating Station, Units 1, 2, and 3 (PVNGS). The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the submitted information and has determined that the following additional information is required to complete the review. 1. For PVNGS, current TS 3.9.2 (for Mode 6), "Nuclear Instrumentation", requires that (1) Core Alterations be suspended and (2) positive reactivity activities be terminated if the required source range nuclear instrumentation is determined to be inoperable. The licensee proposed to remove the required action of suspending Core Alterations from the TS 3.9.2 while maintaining the required action of suspending positive reactivity activities. At PVNGS, the source range monitors (SRMs) are used during refueling operations to monitor the core reactivity conditions. The SRMs provide a signal to operator of unexpected changes in core reactivity such as a boron dilution event and a misloaded fuel assembly event. These detectors are located external to the reactor vessel and detect neutron leaking from the core. The licensee stated in its submittal that for the conditions that one SRM is inoperable, the required action of suspending positive reactivity additions is sufficient to preclude an accident criticality. Based on the current definitions in TS 1.1, "CORE ALTERATION shall be the movement or manipulation of any fuel, sources, or reactivity control components [excluding control assemblies (CEAs) withdrawal into the upper guide structure], within the reactor vessel with vessel head removed and fuel in the vessel. Suspension of CORE ALTERATIONS shall not preclude completion of movement of a component to a safe position". With the removal of the TS required action of suspending CORE ALTERATION, the only TS 3.9.2 restriction is the required action to suspend positive reactivity operations. Enclosure
-Since the withdrawal of fuel assemblies from the core may not contribute to the addition of positive reactivity to the core, it is not prohibited by the proposed TS 3.9.2. The NRC staff is concerned that the SRM could be decoupled from the nuclear response when the fuel assemblies are withdrawn out of the core. For example, the withdrawal of fuel assemblies could result in a condition where fuel assemblies reside in a half of the core opposite the operable SRM. Another example is removal of a source assembly from a decayed core. Under these conditions, the remaining operable SRM may not be able to effectively detect the neutron reactivity. Thus, there may not be an SRM to adequately detect the occurrence of the boron dilution or misloaded fuel assembly event, resulting in an unanalyzed condition. Please address whether the operable SRM could be decoupled from the neutron fluxes during a fuel assembly withdrawal in Mode 6. If the SRM-neutron decouple is determined to be a non-credible phenomenon, please provide the rationale in support of the determination. If the SRM-neutron decouple is determined to be a credible phenomenon, please justify the proposed change to remove CORE ALTERATION from the TSs. The justification should include information addressing the compliance with: Acceptance criterion in NUREG-0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition," (SRP) Section 15.6.4, "Radiological Consequences of Main Steam Line Failure Outside Containment (BWR)," that requires that at least 30 minutes is available from the time the operator is made aware of the unplanned boron dilution event to the time a total loss of shutdown margin (criticality) occurs during refueling (Mode 6), and Guidance of Item 4 on page 15.4.6-8 of SRP Section 15.6.4, Revision 2, March 2007, that specifies that redundant alarms should be available for the operator to identify and terminate the unplanned boron dilution within the required time. The NRC staff is concerned that, without a prior criticality analysis, it could be difficult to determine whether shuffling an assembly (change the core geometry) causes a positive or negative reactivity change. By restricting core alteration, rather than just positive reactivity addition, current TS 3.9.2 explicitly delineates components that cannot be moved, and this TS restriction of core alteration could prevent the operator from misjudging the reactivity of the fuel assembly movement. Please describe how the licensee determines whether shuffling an assembly would cause a positive or negative reactivity change.
R. Edington -2 If you have any questions, please contact me at (301) 415-1056 or via e-mail at Lauren.Gibson@nrc.gov. Docket Nos. STN 50-528, STN 50-529, and STN 50-530 Enclosure: As stated cc w/encl: Distribution via Listserv DISTRIBUTION: PUBLIC LPLIV r/f RidsAcrsAcnw _MaiICTR Resource RidsNrrDorlLpl4 Resource RidsNrrDssSrxb Resource RidsNrrLAJ Burkhardt Resource RidsNrrPMPaloVerde Resource RidsOgcRp Resource RidsRgn4MailCenter Resource SSun, NRRlDSS/SRXB Sincerely, IRA by Brian Benney forI Lauren K. Gibson, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation ADAMS Accession No. ML 12347 A040 *b memo dated NRRlDORULPL4/PM NRRlDORULPL4/LA NRRlDSS/SRXBlBC LKGibson (BSingal for) 12/17112 JBurkhardt CJackson* 12/17/12 11/16/12 NRRlDORULPL4/BC NRRlDOR MMarkley 12/19/12 LKGibson (BBenney for) 12/19/12 OFFICIAL RECORD COpy