ST-HL-AE-5622, Application for Amends to Licenses NPF-76 & NPF-80,revising Tech Specs 5.3.1, Fuel Assemblies & 6.9.1.6, COLR, to Allow Use of Alternate zirconium-based Fuel Cladding,Zirlo & Limited Substitution of Fuel Rods by ZIRLO Filter Rods

Application for Amends to Licenses NPF-76 & NPF-80,revising Tech Specs 5.3.1, Fuel Assemblies & 6.9.1.6, COLR, to Allow Use of Alternate zirconium-based Fuel Cladding,Zirlo & Limited Substitution of Fuel Rods by ZIRLO Filter Rods

ML20138A940
Person / Time
Site:	South Texas
Issue date:	04/22/1997
From:	Cloninger T HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20138A944	List: ML20138A947 ST-HL-AE-5622, Application for Amends to Licenses NPF-76 & NPF-80,revising Tech Specs 5.3.1, Fuel Assemblies & 6.9.1.6, COLR, to Allow Use of Alternate zirconium-based Fuel Cladding,Zirlo & Limited Substitution of Fuel Rods by ZIRLO Filter Rods
References
ST-HL-AE-5622, NUDOCS 9704280288
Download: ML20138A940 (9)

Text

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The Light company Houston tightmg & Power South Texas Project Electric Generstlag Station P.O. Bos 289 Wadsworth, Texas 77483 April 22,1997 l ST-HL-AE-5622 File No.: G20.02.01 10CFR50.90 10CFR50.92 10CFR51 N(

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U. S. Nuclear Regulatory Commission I Attention: Document Control Desk i Washington, DC 20555 South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Proposed Amendment of Technical Specifications 5.3. land 6.9.1.6 to Allow Use of ZlRLO Fuel Claddine and Limited Substitution of ZIRLO Filler Rods

Reference:

Letter from L. W. Myers to the Nuclear Regulatory Commission Document Control Desk, dated January 17,1995 (ST-HL-AE-5266, LER 95-013-00)

The South Texas Project proposes to amend Facility Operating Licenses NPF-76, Unit I and NPF-80, Unit 2 by incorporating revisions to Technical Specifications 5.3.1, Fuel Assemblies, and 6.9.1.6, Core Operating Limits Report, to allow use of an alternate zirconium-based fuel cladding, ZIRLO, and limited substitution of fuel rods by ZIRLO filler rods.

The South Texas Project and the South Texas Project's fuel supplier, Westinghouse, are working to remediate the phenomenon ofincomplete Rod Insertion, which the South Texas Project has experienced as described in the referenced letter. The cause of Incomplete Rod Insertion has been determined to be high in-vessel compressive loading of the fuel assembly skeletons. This compressive loading was exacerbated by irradiation growth of the fuel assembly guide tubes. The material of the guide tubes is being changed to ZIRLO for better dimensional stability and corrosion resistance. While this change alone is not viewed as the complete solution to Incomplete Rod Insertion, it is an action that can be incorporated in the next refueling outage for South Texas Project Unit 1, scheduled to begin September 13, 1997,to improve rod insertion performance.

280072 1n an erfort to improve incomplete Rod Insertion performance as quickly as possible, the South Texas Project has purchased Westinghouse " VANTAGE + Fuel with Performance +

Features" for the next Unit I refueling outage, using ZIRLO guide tubes, instrument tubes and i fuel cladding. The South Texas Project requests that the Nuclear Regulatory Commission l Staff review and approve this license amendment request with high priority and not later than i l

etwmmac-wxtrsc4m622 p Project Manager on Behalf of the Participants in the South Texas Project sTI 20 mon 9704280288 970422 PDR ADOCK 05000498 ll l[ll lhllllll ll

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Houston Lighting & Power Company  ;

South Texas Project Electric Generating Station i ST-HL-AE-5622 i File No.: G20.02.01 Page 2 August 15,1997, to support receipt of new fuel with ZIRLO cladding for the next Unit 1 ,

refueling outage.

The South Texas Project has reviewed the attached proposed amendment pursuant to ,

10CFR50.92 and determined that it does not involve a significant hazards consideration. In  ;

addition, the South Texas Project has determined that the proposed amendment satisfies the criteria of 10CFR51.22(c)(9) for categorical exclusion from the requirement for an  ;

environmental assessment. The South Texas Project Nuclear Safety Review Board has reviewed and approved the proposed changes.

The required affidavit, along with a Safety Evaluation and No Significant Hazards Consideration Determination associated with the proposed changes, and the marked up i Technical Specifications pages are included as attachments to this letter.  !

In accordance with 10CFR50.91(b), South Texas Project is providing the State of ,

Texas with a copy of this proposed amendment.

If you should have any questions concerning this matter, please call Mr. A. W. 1 Harrison at (512) 972-7298 or myself at (512) 972-8787.

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. H. lonin Vic Pre ' ent, N 1 E inee 'ng LLS/

Attachments: 1. Affidavit

2. Safety Evaluation and No Significant Hazards Consideration Determination

3. Proposed Change to Technical Specifications 5.3.1 and 6.9.1.6 l

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Houston Lighting & Power Company South Texas Project Electric Generating Station ST-HL-AE-5622 File No.:G20.02.01 Page 3 Ellis W. Merschoff Rufus S. Scott Regional Administrator, Region IV Associate General Counsel U. S. Nuclear Regulatory Commission Houston Lighting & Power Company 611 Ryan Plaza Drive, Suite 400 P. O. Box 61067 Arlington, TX 76011-8064 Houston, TX 77208 Thomas W. Alexion Institute of Nuclear Power Project Manager, Mail Code 13H3 Operations - Records Center U. S. Nuclear Regulatory Commission 700 Galleria Parkway Washington, DC 20555-0001 Atlanta, GA 30339-5957 David P. Loveless Dr. Bertram Wolfe Sr. Resident Inspector 15453 Via Vaquero c/o U. S. Nuclear Regulatory Comm. Monte Sereno, CA 95030 P. O. Box 910 Bay City, TX 77404-0910 Richard A. Ratliff Bureau of Radiation Control J. R. Newman, Esquire Texas Department of Health Morgan, Lewis & Bockius 1100 West 49th Street 1800 M Street, N.W. Austin, TX 78756-3189 Washington, DC 20036-5869 J. R. Egan, Esquire M. T. Hardt/W. C. Gunst Egan & Associates, P.C.

City Public Service 2300 N Street, N.W.

P. O. Box 1771 Washington, D.C. 20037 San Antonio, TX 78296 J. C. Lanier/M. B. Lee U. S. Nuclear Regulatory Commission City of Austin Attention: Document Control Desk Electric Utility Department Washington, D.C. 20555-0001 721 Barton Springs Road Austin, TX 78704 Central Power and Light Company ATTN: G. E. Vaughn/C. A. Jolmson P. O. Box 289, Mail Code: N5012 Wt:dsworth, TX 77483 E \WP.NL\NRC WKTT5C-97\S622 wp ST) 30243041

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Attachment 1 l ST-HL-AE-5622 i Page 1 of 1 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of ) i

) l Houston Lighting &' Power ) Docket Nos. 50-498 Company, et al., ) 50-499

)

South Texas Project )

Units 1 and 2 -)

AFFIDAVIT I, T H. Cloninger, being duly sworn, hereby depose and say that I am Vice President, t Nuclear Engineering, of Houston Lighting & Power Company; that I am duly authorized to sign and file with the Nuclear Regulatory Commission the attached revised pages to Technical Specifications 5.3.1 and 6.9.1.6; that I am familiar with the content thereof; and that the matters set forth therein are true and correct to the best of my knowledge and belief.

.H. Cl ninge Vice resic t, Nu ear ngineerin STATE OF TEXAS )

)  !

COUNTY OF MATAGORDA )

Subscribed and sworn to before me, a Notary Public in and for the State of Texas, this ) day of Ap ell ,1997.

UNDA RITamRRY A fhQ Notary Public in and for the 9

! *** 8"* d '* State of Texas 3>, wc up . ica"m ]

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Attachment 2 ST-HL-AE-5622 j Page 1 of 6 SAFETY EVALUATION AND NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION -

Safety Evaluation  ;

Descriotion of the Proposed Channes l The South Texas Project proposes to revise Technical Specifications 5.3.1, Fuel Assemblies, I and 6.9.1.6, Core Operating Limits Report, to allow use of an alternate zirconium-based fuel  !

cladding, ZIRLO, for South Texas Project Units 1 and 2. Limited substitution of fuel rods by j ZIRLO filler rods would also be permitted. The marked up Technical Specifications pages '

for the proposed changes are provided in Attachment 3. A discussion of the proposed  ;

changes follows. j Description and Bases of the Current Reauirement Technical Specification 5.3.1 requires fuel rods to be clad with Zircaloy. Fuel rods may be i substituted by filler rods consisting of Zircaloy or stainless steel, ifjustified by a cycle-specific reload analysis. Technical Specification 6.9.1.6 lists the analytical methods, which r have been reviewed and approved by the NRC, that are used to determine the core operating {

limits. l The fuel system is designed so that: (a) the fuel system will not be damaged as a result of i normal operation and anticipated operational occurrences; (b) fuel dunage during postulated accidents will not be severe enough to prevent control rod insertion when it is required; and (c) core coolability will always be maintained, even after severe pcstulated accidents. The current fuel design thereby meets the related requirements of: 10CFR50.46; 10CFR50, Appendix A, General Design Criteria 10,27 and 35; 10CFR50, Appendix K; and 10CFR100.

Ilescription and Bases of the Reauested Revision

The South Texas Project proposes to revise Technical Specification 5.3.1 and 6.9.1.6 to allow j fuel rods to be clad with ZIRLO. The proposed change would allow a limited number of fuel l rods to be substituted by ZIRLO filler rods in addition to the currently licensed stainless steel '

or Zircaloy, ifju':tified by a cycle specific reload analysis. Westinghouse report, WCAP-12610-P-A, " VANTAGE + Fuel Assembly Reference Core Report," has been added to Technical Specification 6.9.1.6 to reflect the methodology used for the rod heatup calculation m the Loss of Coolant Accident (LOCA) Evaluation models with ZIRLO clad fuel.

I The proposed change is intended to remediate the pl'enomenon of Incomplete Rod Insertion, which has been experienced at the South Texas Project. The cause ofIncomplete Rod

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5 Attachment 2 ST-HL-AE-5622 Page 2 of 6 Insertion has been determined to be high in-vessel compressive loading of the fuel assembly skeletons. This compressive loading was exacerbated by irradiation growth of the fuel assembly guide tubes. The material of the guide tubes is being changed to ZlRLO for better dimensional stability and corrosion resistance.

i in accordance with the manufacturer's experience, the fuel rod cladding material is simultaneously being changed to ZIRLO for compatibility with the assembly skeleton, as well as for improved corrosion and dimensional stability properties.

The change is consistent with 10CFR50.44 and 10CFR50.46. The change is also consistent with NRC-approved topical report WCAP-13060, " Westinghouse Fuel Assembly Reconstitution Evaluation Methodology," which meets the intent of Supplement 1 of Generic Letter 90-02, " Alternative Requirements for Fuel Assemblies in the Design Section of Technical Specifications." NUREG-1431, " Standard Technical Specifications for Westinghouse Plants," specifically includes ZlRLO as an acceptable cladding material.

Imnact of the Pronosed Chances The NRC revised the acceptance criteria in 10CFR50.44 and 10CFR50.46 relating to evaluations of combustible gas control and emergency core cooling systems applicable to Zircaloy-clad fuel to include ZIRLO-clad fuel. ZlRLO is a preferred cladding material since it provides a significant improvement in corrosion margin and fuel integrity. The NRC noted that the revision to include ZlRLO as an acceptable zirconium-based cladding material along with Zircaloy will reduce the licensee burden but will not reduce the protection of the public health or safety.

4 Changing to ZlRLO cladding will provide greater resistance to in-core fuel red corrosion, which is of concern for higher burnup fuel and longer cycles. Future core designs may feature longer cycles, higher capacity factors, and ultimately, higher discharge bumups. Using higher discharge burnups in the reactor core design will reduce the number of fuel assemblies required per reload. The South Texas Project will benefit by paying less for fuel fabrication and by using less spent fuel storage space.

. Ai. analysis of the safety implications is provided in a NRC letter to Westinghouse, dated i

July 1,1991, " Acceptance for Referencing of Topical Report WCAP-12610, ' VANTAGE +

Fuel Acsembly Reference Core Report' (TAC NO 77258)." The report supports the following conclusivis:

(1) The mechanical design bases and limits for the ZIRLO clad fuel assembly design are the same as those for the previously licensed Zircaloy clad fuel assembly design, except those for clad corrosion.

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4 l Attachment 2 ST-HL-AE-5622 Page 3 of 6 j (2) The neutronic evaluations have shown that ZIRLO clad fuel nuclear design bases are satisfied and that key safety parameter limits are applicable. The nuclear design j models and methods accurately describe the behavior of ZlRLO clad fuel.

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(3) The thermal and hydraulic design basis for the ZIRLO clad fuel is unchanged.

l (4) The methods and computer codes used in the analysis of the non-LOCA licensing basis ,

events are valid for ZIRLO clad fuel, and all licensing basis criteria will be met. ]

i 1 (5) The large break LOCA evaluation model was modified to reflect the behavior of the *

ZIRLO clad material during a loss of coolant accident. Consequently, the revised

, evaluation model satisfies 10CFR50.46 and Appendix K of 10CFR50.-

i

! Accident Analyses

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I l The limiting design basis accidents described in the South Texas Updated Final Safety l Analysis Report (UFSAR) Chapter 15 were evaluated to determine the affect on the results of  ;

j using ZlRLO cladding fuel rod cladding. The limiting design basis accidents are a large break LOCA, Reactor Coolant Pump shaft seizure (locked rotor), and Rod Cluster Control Assembly ejection.

l l For South Texas Project Units 1 and 2, bounding large break LOCA rod heatup cases were

evaluated and all acceptance criteria are met, including those in 10CFR50.46. Adequate margm to the peak clad temperature limit of 2200 F is maintained.

l The effect of ZlRLO on a locked rotor transient for South Texas Project Units 1 and 2 is

. insignificant. Sensitivity analyses performed by Westinghouse demonstrate that the impacts of l ZlRLO on peak cladding temperature and the metal-water reaction in the locked-rotor transient results are insignificant.

The Rod Control Cluster Assembly ejection was analyzed at hot full power and hot zero j i

power. The analysis demonstrated that any consequential damage to the core or the reactor I coolant system would not prevent long term core cooling and that off-site dose would remain

within the guidelines of 10CFR100. WCAP-12610 includes results of sensitivity analyses performed by Westinghouse that demonstrate that the impact of ZIRLO on Rod Control Cluster Assembly ejection analyses is an insignificant change in both the fraction of fuel melted at the hot spot as well as the peak fuel stored energy. Therefore, the current off-site dose analysis for the Rod Control Cluster Assembly ejection remains bounding, and the dose

limits of 10CFR100 are not exceeded. j i

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. . 1 Attachment 2 ST-HL-AE-5622 Page 4 of 6 Fuel configuration, size, enrichment and cladding material will be limited to those designs that have been analyzed with applicable NRC-approved codes and methods, and shown by test or cycle specific reload analyses to comply with all fuel safety design bases. The use of ZlRLO fuel cladding will be justified by a cycle specific reload analysis, in accordance with NRC-approved applications of fuel rod configurations.

WCAP-13060 delineates the methodology used to evaluate applicable design criteria associated with reconstituted fuel assemblies that have solid filler rods replacing uranium filled fuel rods. Evaluations and analyses of fuel assembly reconstitution will be performed on a cycle specific basis whenever reconstituted fuel assemblies are used in the reactor core.

The WCAP includes proposed Technical Specification changes based on the conclusions in the WCAP and on the guidelines of Generic Letter 90-02.

NO SIGNIFICANT IIAZARDS CONSIDERATION DETERMINATION The South Texas Project proposes to revise Technical Specification 5.3.1, Fuel Assemblies, and 6.9.1.6, Core Operating Limits Report, to allow use of an alternate zirconium-based fuel cladding, ZIRLO, and limited substitution of fuel rods by ZIRLO filler rods. The South Texas Project has evaluated this proposed amendment and determined that it involves no significant hazards considerations as follows:

A. The proposed changes do not involve a significant increase in the probability or consequences of an accident previously evaluated.

The methodologies used in the accident analyses remain unchanged. With the exception of a reduction in the heat flux hot channel factor (Fn ), the operating limits will not be changed. The proposed changes will not result in any equipment exceeding its design limits under normal or accident conditions. The calculated doses presented in the UFSAR will remain bounding. Other than the changes to the fuel assemblies, there are no physical changes to the plant associated with this Technical Specification change. A reload safety analysis will continue to be performed for each cycle to demonstrate compliance with fuel safety design bases.

VANTAGE + fuel assemblics with ZIRLO clad fuel rods meet the same fuel assembly and fuel rod design bases as VANTAGE 5H fuel assemblies. Since the original design criteria are met, the ZlRLO clad fuel rods will not be an initiator for any new accident. The clad material is similar in chemical composition and has similar l

physical and mechanical properties to Zircaloy. Thus, cladding integrity is maintained and the strustural integrity of the fuel assembly is not affected. ZIRLO cladding improves corrosion performance and dimensional stability. No concerns have been E \WP\NL\NRC-% K\TSC.970622 wP STI 30243043

Attachment 2 ST-HL-AE-5622 Page 5 of 6 identified with respect to the mixed core of Zircaloy and ZIRLO clad assemblies.

Also, no concerns have been identified with respect to the use of an individual assembly containing a combination of Zircaloy and ZlRLO clad fuel rods.

Therefore, the proposed changes do not involve a significant increase in the probability or consequences of an accident previously evaluated. I l

B. The proposed changes do not create the possibility of a new or different kind of accident from any accident previously evaluated.

The proposed changes do not result in ar>y equipment exceeding its design limits under nonnal or accident conditions. All design and performance criteria continue to be met and no new failure mechanisms have been identified. The ZIRLO cladding material offers improved corrosion resistance and structural integrity.

The proposed changes do not affect the operation of any system or component in the plant. The safety functions of the related structures, systems, or components are not changed, nor is the reliabnity of any structure, system, or component reduced. The changes do not affect the manner by which the facility is operated and do not change any facility design feature, structure, or system. No new or different type of equipment will be installed. Since there is no other change to the facility or operating procedures, and the safety ftmetions and reliability of structures, systems, or components are not affected, the proposed changes do not create the possibility of a new accident or an accident different from those previously evaluated.

C. The proposed chaises do not involve a significant reduction in a margin of safety.

Use of ZIRLO fuel claddmg material will not result in any equipment exceeding its design or licensing bases limits under nonnal or accident conditions. VANTAGE 5H reload design and safety analysis limits are unchanged. For each cycle reload core, the fuel assemblies will be evaluated using NRC-approved reload design methods, including consideration of the core physics analysis peaking factors and core average linear heat rate effects. ZlRLO fuel assemblies will be assessed for use under conditions consistent with normal core operating conditions allowed in the Technical Specifications. Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Therciore, based on the above evaluation, South Texas Project has concluded that these changes do not involve significant hazards considerations.

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Attachment 2 ST-HL-AE-5622 Page 6 of 6 Imolementation Schedule The South Texas Project is planning to load fuel with ZIRLO cladding during the next refueling outages for Units 1 and 2, scheduled for September 13,1997 and October 3,1998, respectively. The South Texas Project requests NRC approval of the amendment by August 15,1997, to support the receipt of fuel for the September refueling of Unit 1.

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