ML20217H898

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Revised Application for Amends to Licenses NPF-68 & NPF-81, Revising TS Re Credit for Boron & Enrichment Increase for Fuel Storage
ML20217H898
Person / Time
Site: Vogtle  Southern Nuclear icon.png
Issue date: 08/08/1997
From: Mccoy C
SOUTHERN NUCLEAR OPERATING CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20217H901 List:
References
LCV-0849-E, LCV-849-E, NUDOCS 9708130341
Download: ML20217H898 (23)
v • d • e


Text

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C. K. McCoy Southern Nuclear Vice President Operating Company,Inc.

Vogtle Project 40 inverness Center Pa.1way P0. Box 1295 Birmingham, Alabama 35201 Tel 205.992.7122 Fax 205992.0403 August 8, 1997 SOUTHERNkh Docket Nos. 50-424 50-425 #" N " N

  • N" # #

U. S. Nuclear Regulatory Commission LCV-0849-E ATTN: Document Control Desk Washington, D. C. 20555 l l

Gentlemen:

I VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECHNICAL SPECIFICATIONS CREDIT FOR BORON AND ENRICHMENT INCREASE FOR FUEL STORAGE By letter LCV-0849 dated October 4,1996 the licensee for the Vogtle Electric Generating Plant (VEGP) proposed, in accordance with the provisions of 10 CFR 50.90 and 10 CFR 50.59, to amend the VEGP Unit I and Unit 2 Technical Specifications, Appendix A to Operating Licenses NPF-68 and NPF-81. This letter responds to the NRC's request for additional information dated October 29,1996. The proposed revision to the Technical Specifications incorporates the requirements necessary to change the basis for prevention of criticality in the fuel storage pool. The change eliminates credit for Boraflex as a neutron absorbing material in the fuel storage pool criticality analysis and supports the use of fuel with enrichments up to and including 5.0 weight percent U 235 rather than the -

current value of 4.5 weight percent U-235. ,

General Design Criterion 62 of Appendix A to 10 CFR Part 50 requires the prevention of criticality in the handling and storage of fuel. NRC guidance recommends a 5 percent suberiticality margin. Boraflex is currently used in the VEGP spent fuel racks as a nonproductive neutron absorber to reduce the reactivity of the fuel storage pool configuration. The current VEGP analyses take credit for the Boraflex to maintain the 5 //

percent margin. The proposed charge will establish an alternative method for maintaining the margin without relying on the Boraflex. I The analyses supporting the initial requested changes to the Technical Specifications were performed using the methodology developed by the Westinghouse Owner's Group and q)() /

described in WCAP-14416 which, at that time, was concurrently bcing reviewed by the NRC. As a result of the NRCs review of WCAP-14416, revisions to the methodology used for the criticality analysis were required. The revised methodology has been accepted by the NRC and published as WCAP-14416 NP-A, rev.1, Nov.1996.

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U. S. Nuclear Regulatory Commission

' Page 2 LCV-0849 E Iri response to the NRCs request for additional information dated October 29,1996, Southern Nuclear Operating Company (SNC), is submitting a revision to the request for license amendment. This revision includes the results of criticality re-analysis using the approved methodology of WCAP-14416-NP-A, re,v.1. It consists of a replacement of the enclosures ofletter LCV-0849 with revised enclosures incornorating responses to the 6 questions contained in the NRC letter dated October 29,1996.

The analyses established burnup, soluble boron concentrations and storage configurations for the fuel stored in the spent fuel racks that will assure that the 5 percent margin is maintained without reliance on the Boraflex, for fuel that is enriched up to and including 5,0 weight percent U-235. The proposed Technical Specification changes incorporate the appropriate limiting conditions for operation and surveillance requirements to assure that the fuel storage poolis maintained consistent with the analyses. Those aspects of the limits, such as checkerboard storage configurations, burnup, enrichment and interface requirements have been added to the Technical Specifications instead of the Core Operating Limits Report (COLR), in response to the NRCs request.

The proposed Technical Specifications relative to the control of boron concentration and storage configurations in the fuel storage pool are more restrictive than current VEGP requirements which allow unrestricted storage. Southern Nuclear will implement these requirements administratively as a means of assuring compliance with both the requirements of GDC 62 and the 5 percent subcriticality margin regardless of any Boraflex degradation that may occur in the VEGP fuel storage pool. Deterioration of Boraflex is accompanied by elevated silica concentrations in the fuel storage pool. The higher silica levels are an operational concern but reduction of the silica levels is believed to increase the rate of Boraflex degradation. Approval of this change will allow the reduction of silica levels and the elimination of Boraflex coupon surveillance programs which represent operational benefits. Therefore, SNC requests that the NRC approve the requested changes to the Technical Specifications by December 1,1997.

The enclosures to this letter replace those transmitted with LCV-0849. Enclosure 1 provides a description of the proposed changes to the Technical Specifications. Enclosure 2 provides the basis for a determination that the proposed changes do not involve significant hazards considerations. Enclosure 3 includes the marked up pages and instructions for their incorporation into the Technical Specifications. Enclosure 4 provides a conclusion concerning an environmental assessment of the proposed change. Enclosure

5 is the criticality analysis report for the VEGP Units 1 and 2 fuel storage pools.

Enclosure 6 is an assessment of events that could result in a loss of soluble boron in the fuel storage pool, which concludes that it is highly unlikely for any combination of events

U. S. Nuclear Regulatory Commission Page 3 LCV-0849.E to result in a loss of boron to the extent that the 5 percent suberiticality margin would be exceeded, Previously, enclosure 7 provided an example of the proposed COLR addition.

Enclosure 7 has been replaced because the proposed requirements are to be placed in the Technical Specifications insteac' of the COLR. Enclosure 7 responds to the questions in the NRC's letter of October 29,1996.

l Mr. C. K. McCoy states that he is a Vice President of Southern Nuclear and is authorized to execute this oath on behalf of Southern Nuclear and that, to the best of his knowledge and belief, the facts set forth in this letter and enclosures are true.

SOUTIIERN NUCLEAR OPERATING COMPANY By:

C. K. Mc oy Sworn to and subscribed before me thisy of O LM .1997.

%%1.

Notary Public 1

CKM/HWM/gmb

Enclosures:

1. Basis for Proposed Change
2. 10 CFR 50.92 Evaluation
3. Instructions for Incorporation and Revised Pages
4. Environmental Assessment
5. Criticality Analysis
6. Fuel Storage Pool Dilution Assessment
7. Responses to NRC Questions

(

1 U. S. Nuclear Regulatory Commission :

Page 4

' LCV-0849 E c(w): . Southern Nuclear

, ' Mr. J. B. Beasley, Jr.

Mr. M. Sheibani NORMS

'U. S Nuclear Regulatory Commission i Mr. L. A. Reyes, Regional Administrator _

- Mr. L. L Wheeler, Senior Project Manager, NRR Mr. C. R. Ogle, Senior Resident inspector, Vogtle  ;

State of Georgia Mr. L. C. Barrett, Commissioner, Department of Naturel Resources i

a

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l ENCLOSURE 1

.VOGTLE ELECTRIC GENERATING PLANT

{3 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION

REVISED REQUEST TO REVISE TECIINICAL SPECIFICATIONS CREDIT FOR BORON AND ENRICllMENT INCREASE FOR FUEL STORAGE BASIS FOR PROPOSED CilANGE Proposed Changes These changes to the Technical Specifications add two new Technical Specifications and associated Bases, and revise the Design Features section, to make the changes necessary >

to credit soluble boron in the fuel storage pool criticality analyses and increase the allowable fuel enrichment to 5.0 weight per cent U-235. The proposed changes are described below:

Revisions to the Technical Specifications These Technical Specification revisions are attached with Enclosure 3.

1. Revisions to the Table of Contents The Table of Contents is revised to include two additional Technical Specifications 3.7.17,

" Fuel Storage Pool Boron Concentration",3.7.18, " Fuel Assembly Storage" and figures 3.7.18-1,3.7.18-2, and 4.3.1-1 through 4.3.1-9 describing burnup credit, checkerboard configurations and interface requirements. These are being added to support crediting soluble boron in the fuel storage pool criticality analyses

2. Add Technical Specifications 3.7.17 and 3.7.18 Two Technical Specifications 3.7.17, " Fuel Storage Pool Boron Concentration" and 3.7.18, " Fuel Assembly Storage" are being added to credit soluble boron in the fuel storage poc! criticality analyses, and specify acceptable enrichment-burnup combinations for storage of fuel in the fuel storage pool.
3. Specification 4.3.1.1 Design Features Section 4.3.1.1 is revised to reflect the increased maximum enrichment assumed in the fuel storage pool criticality analyses, change the 0.95 K n requirement "if fully flooded with unborated water" to "when fully flooded with water borated to 450 ppm (Unit 1) or 500 ppm (Unit 2)," and add a requirement.to maintain K aless than 1.0 if fully flooded with unborated water, and to add a reference to Specification 3.7.18 for allowable enrichment-burnup combinations Requirements for fuel that does not meet the requirements of Specification 3.7.18, have also been added to section 4.3.1.1, including figures 4.3.1-1 through 4.3.1-9 depicting acceptable enrichment-burnup requirements and checkerboard configurations.

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ENCLOSURE 1 VOGTL.E ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TEC11NICAL SPECIFICATIONS CRED]T FOR BORON AND ENRICHMENT INCREASE FOB FUEL STORAGli BASIS FOR PROPOSED CliANGE (continued)

4. RevLions to the Table of Contents (Bases)

The Table of Contents is revised to include two additional Technical Specification Bases, 3.7.17, " Fuel Storage Pool Boron Concentration" and 3.7.18, " Fuel Assembly Storage" that are being added to support crediting soluble boron in the fuel storage pool criticality analyses.

U 5. Add Bases for Technical Specifications 3.7.17 and 3.7.18 Two Technical Specification Bases,3.7,17, " Fuel Storage Pool Boron Concentration" and 3.7.18 " Fuel Assembly Storige" are being added to credit soluble boron in the fuel storage pool criticality ape.!yses.

Basis The spent fuel rack criticality analyses have been performed taking credit for the soluble boron contained in the fuel storage pool water and not taking any credit for the Boraflex poison contained in the racks. The analyses were performed for fuel enrichments up to and including 5.0 weight percent U-235. In the fuel storage pool criticality analysis, a storage configuration has been defined to ensure that the fuel storage rack K a will be less than 1.0 including uncertainties and tolerances on a 95/95 basis without the presence of any soluble boron in the fuel storage pool. Soluble boron credit is used to provide safety margin by maintaining K ns 0.95 including uncertainties, tolerances, and accident conditions in the presence of fuel storage pool soluble boron.

New Technical Specification 3.7.17 establishes the new boron concentration requirements for the fuel storage pool water. Soluble boron has been contained in the fuel storage pool since its initial operation, therefore, the new requirement will have little effect on normal pool operations and maintenance.

New Technical Specification 3.7.18 establishes requirements for fuel storage that are consistent with the criticality analysis. Since the new limitations are administrative, they will not have any significant efTect on normal pool operations and maintenance.

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ENCLOSURE 1 VOOTLE ELECTRIC GENERATING PLANT L . RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 4

- REVISED REQUEST TO REVISE TECHNICAL SPECIFICATIONS-CREDIT FOR BORON AND ENRICHMENT INCREASE FOR FUEL STORAGE i -

4

_ BASIS FOR PROPOSED CHANGE (conti n:ed) f 1.

i The changes to the Technical Specifications are included in Enclov *- 3. Enclosure 2 is an evaluation in accordance with 10 CFR 50.92 to demonstrate that Nw changes to the l Technical Specifications do not involve any significant hazards consiuerations.

i!

j Due to degradation,- Borallex is being eliminated from the analytical basis for

demonstrating compliance with General Design Criteria 62. This has been done by
i. utilizing the methodology in WCAP.14416-NP-A; rev.1, Nov.1996. The new criticality analyses assume enrichments up to and including 5.0 weight percent U-235. The VEGP

] new fuel storage area has already been analyzed for 5.0 weight percent U-235 fuel as

[ documented in section 9.1.1.3 of the VEGP Final Safety Analysis Fmort.

The new criticality analyses take credit for a portion of the soluble boron maintained in the

! fuel storage pool, checkerboard storage configurations in the spent fuel storage racks and

.. the effects of burnup. Therefore it is appropriate to establish limiting conditions for i operation and surveillance requirements in the Technical Specifications to assure that fuel L is stored in accordance with the analytical assumptions. The checkerboard storage l configurations and burnup limits are based on analyses performed in accordance with the

! NRC approved methodology, n

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1 ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECliNICAL SPECIFICATIONS CREDIT FOR DORON AND ENRICilMENT INCREASE FOR FUEL STORAGE 10 CFR 50.92 EVALUATION Llackground This submittal proposes to take credit for the soluble beton in the fuel storage pool water to control the subcritical condition of the fuel array. It also takes credit for fuel burnup and checkerboard storage configurations in the spent fuel racks. The utilization of soluble boron, which is contained in the fuel storage pool, provides a simple, direct method of ensuring suberiticality. This control feature retains the necessary criticality safety requirements and has many benefits. Credit for soluble boron is currently used for Mode 6 reactivity control in the reactor vessel.

NRC guidance recommends a 5 percent subcriticality margin. This proposed license amendment uses an alternative method of maintaining the 5 percent shutdown margin.

The proposed license amendment takes credit for a portion of the soluble boron maintained in the fuel storage pool. The storage configurations have been dermed using La calculations, as described in WCAP-14416 -NP-A, rev.1, Nov.1996 (Reference 4),

and Enclosure 5, to ensure that the spent fuel rack Ka will be less than 1.0 including uncertainties and tolerances on a 95/95 basis without the presence of any soluble boron in the fuel storage pool (No Soluble Boron 95/95 Kn conditions). Soluble boron credit is used to provide margin by maintaining K.a 5 0.95 including uncertainties, tolerances, and accident conditions in the presence of fuel storage pool soluble boron. The Vogtle Units 1 and 2 fuel storage pool configurations were analyzed utilizing the Westinghouse Spent Fuel Rack Criticality Analysis Methodology described in WCAP-14416 -NP-A, rev.1 (Reference 4).

The Vogtle Units I and 2 spent fuel racks have been reanalyzed to allow storage of Westinghouse 17x17 fuel assemblies with enrichments up to and including 5.0 weight percent U-235 in the allowable storage cell locations using soluble boron credit, burnup and checkerboard storage configuration. This analysis also ignores the presence of the spent fuel rack Boraflex poison panels.

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECHNICAL SPECIFICATIONS CREDIT FOR BORON AND ENRICHMENT INCREASE FOR FUEL STORAGE 10 CFR 50.92 EVALUATION (continued)

The analysis considered storage of fuel in all storage locations,3-out-of-4 checkerboard and 2-out-of-4 checkerboard configurations. Additionally, the Unit 2 storage racks were analyzed for a 3x3 checkerboard storage configuration. The enrichment for each storage configuration was determined and the required equivalent burnup for 5.0 weight percent U-235 fuel was determined. Burnup versus enrichment requirements for each checkerboard configuration were developed as described in Enclosure 5 and shown in the revised Technical Specifications. These took credit for soluble boron in accordance with WCAP-14416 NP-A, rev.1. The highest boron concentration required for maintaining K,a 50,95 in the specified checkerboard configurations was 450 ppm (Unit 1) and 500 ppm (Unit 2). An additional boron concentration was determined to assure that the 0.95 limit would be met for a dropped or misplaced assembly, these concentrations were determined to be 1150 ppm (Unit 1) and 1250 ppm (Unit 2). The bounding boron concentration to account for misplacement of a fuel assembly er other events that could affect La is 1250 ppm because the two fuel storage pools are normally connected. The typical concentration of boron in the fuel storage pool is greater than 2400 ppm. The proposed Tectaical Specification limit of 2000 ppm allows margin for any credible circumstances that could dilute the boron concentration and is well within the nomially maintained concentration of the pools. Since a misplaced assembly and a dilution event are independut events, conservative margin exists between the normal condition concentration and the concentration for maintaining Kg 50.95. Therefore, no credible dilution event or accidental misplacement of a fuel assembly can result in La greater than 0.95.

Deterministic calculations were performed (Enclosure 6) in order to define the dilution times and volumes for Vogtle. The dilution sources available at Vogtle were also compiled and evaluated against the dilution volume calculated, to determine the potential of a fuel storage pool dilution event. The deterministic evaluations show that a large volume of water (more than 535,000 gallons for a single pool or 1,070,000 gallons when the pools are connected, which is the normal configuration)is necessary to dilute the fuel storage pool to a soluble boron concentration where a La of 0.95(500 ppm) would be approached in the Vogtle Units 1 and 2 fuel storage pools.

A dilution event large enough to result in a significant reduction in the fuel storage pool boron concentration would involve the removal of a large quantity of water from a dilution source and a significant increase in fuel storage pool level, which would ultimately overflow the pool. Such a large water volume turnover, and the likely overflow of the fuel storage pool, would be readily detected and terminated by plant personnel.

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVlisti ThulNICAL SPECIFICATIONS 1 CREDIT FOR BORON AND ENRICHMENT INCREASE FOR FUE.L STORAGE -

l i

10 CFR 50.92 EVALUATION (continued)

In addition, because of the very large quantities of water required, and the fuel storage pool level and sump alarms, any dilution of the fuel storage pool would be detected and eliminated before a significant dilution could occur.

The evaluations in Enclosure 6, combined with the No Soluble Boron 95/95 Ka calculation, which shows that the spent fuel rack La will remain less than 1.0 when flooded with unborated water demonstrate a level of safety comparable to the conservative criticality analysis methodology described in References 1,2, and 3.

Proposed Change The proposed changes to the Technical Specifications are described in Enclosure 1, and the specific wording of changes are shown in Enclosure 3.

Safety Eva!uation .

The design basis for preventing criticality in the fuel storage pool is that, including uncertainties, there is a 95 percent probability at a 95 percent confidence level that the La of the fuel storage array will be less than 0.95 with full density moderation. Compliance with GDC 62 v ithout credit for soluble boron is demonstrated by assuring that the No Soluble Boron 95/95 Ka is less than 1.0. The baron concentration is then determined to assure that Ka is less than or equal to 0.95 including boron uncertainties. The actual boron concentration is significantly higher than that required to maintain Ka less than or equal to 0.95, thus assuring that the 5 percent suberiticality margin recommended by the NRC will be maintained.

For the storage of fuel m the spent fuel storage racks, the acceptance criteria for criticality requires the effective neutron multiplication factor, Kn ,be less than or equal to 0.95, including uncertainties. The criticality analysis performed for the Vogtle Units I and 2 fuel storage configurations shows that the acceptance criteria for criticality is met for the storage of 17xl7 fuel assemblies under both normal and accident conditions with soluble boron credit, no credit for the spent fuel rack Boraflex poison panels, and the storage configurations and enrichment limits described in Enclosure 5.

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORh1ATION REVISED REQUEST TO REVISE TEClINICAL SPECIFICATIONS l CREDIT FOR BORON AND ENRICHh1ENT INCREASE FOR FUEL STORAGE 10 CFR 50.92 EVALUATION (continued) l i

The Vogtle Units 1 and 2 spent fuel storage racks were analyzed utilizing the  !

Westinghouse Spent Fuel Rack Criticality Analysis hiethodology described in WCAP-14416-NP-A, rev.1 (Reference 4). The analytical methods used in the analysis conform with ANSI N18.2-1973, " Nuclear Safety Criteria for the Design of Stationary Pressurized Water Reactor Plants", Section 5.7, Fuel Handling System; ANSI 57.2-1983, " Design .

Objectives for LWR Spent Fuel Storage Facilities at Nuclear Power Stations", Section l 6.4.2; ANSI N16.91975, " Validation of Calculation hiethods for Nuclear Criticality l Safety", and the NRC Standard Resiew Plan, Section 9.1.2, " Spent Fuel Sterage". The  ;

methodology uses an alternative method (relative to credit for the presence of soluble boron in the fuel storage pool) to that stated in ANSI 57.2-1983 (Reference 3) and the NRC position paper for spent fuel storage (Reference 7).

While this License Amendment Request proposes use of credit for soluble boron in the fuel storage pool criticality analyses, storage configurations have been dermed using No Soluble Boron 95/95 K.a assumptions to ensure that the K awill be less than 1.0 with no soluble boron under normal storage conditions. Soluble boron credit provides significant negative reactivity in the criticality analysis, which is used to provide suberitical margin such that the fuel storage pool K.a is maintained less than or equal to 0.95. Soluble boron credit and storage configuration were also used to offset the reactivity increase when ignoring the presence of the spent fuel rack Boraflex poison panels.

New Technical Specirication 3.7.17 establishes the new boron concentration requirements for the fuel storage pool water. Because soluble baron is normally contained in the fuel storage pool, the new requirement will have little effect on normal pool operations and maintenance.

New Technical Specification 3.7.18 establishes the requirements for the fuel storage configurations. Since the pool storage configuration iimitations are administrative, the new limitations will only have limited efTects on normal pool operations and maintenance.

Fuel storage pool systems, instrumentation, and supporting systems are not modified as a result of the proposed license amendment. The operations involving fuel storage pool water cooling and cleanup do not change. The procedures related to the fuel storage pool will be upgraded as necessary to ensure that the pool boron concentration is maintained.

The procedures will ensure that the proper provisions, precautions, and instructions exist to control the fuel storage pool boron concentration.

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECHNICAL SPECIFICATIONS '

CREDIT FOR BORON AND ENRICHMENT INCREASE FOR FUEL STORAGE 10 CFR 50.92 EVALUATION (continued) l The Vogtle Units I and 2 spent fuel rack criticality analysis also addressed postulated I

. accidents in the fuel storage pool. The accidents that can occur in the fuel storage pool and their consequences are not significantly affected by taking credit for the soluble boron present in the pool water as a major suberiticality control element.

Most fuel storage pool accident conditions will not result in an increase in Lt. Examples l of such accidents are the drop of a fuel assembly on top of a rack, or between rack modules and the pool wall.

From a criticality standpoint, a dropped assembly accident occurs when a fuel assembly in its most reactive condition is dropped onto the storage racks. The rack structure from a criticality standpoint is not excessively deformed. Previous accident analysis with unborated water showed the dropped assembly which comes to rest horizontally on top of the rack has sufficient water separating it from the active fuel height of stored assemblies to preclude neutronic interaction. The rack continues to provide suaicient separation to prevent neutronic interaction even with the assembly enrichment increased to 5.0 weight percent U-235. For the borated water condition, the interaction is even less because the water contains boron, an additional thermal neutron absorber. The radiological consequences of a dropped assembly accident in the fuel storage pool are unaffected by

this proposed change to the Technical Specifications.

1 Three accidents can be postulated for each storage configuration which could increase reactivity beyond the analyzed condition. The first postulated accident would be an increase in temperature beyond that considered in the analysis (50 F to 185 F). The second would be the dropping of a fuel assembly into an already loaded cell. The third would be the misloading of a fuel assembly into a cell for which the restrictions on location, enrichment or burnup are not satisfied.

An increase in the fuel storage pool water temperature causes a decrease in water density which would normally result in an addition of negative reactivity. However, since Boraflex is not considered to be present, and the fuel storage pool water has a high concentration of boron, a density decrease causes a positive reactivity addition. This event was evaluated for temperatures up to 240 F, and it was determined to be bounded by the misload accident.

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECilNICAL SPECIFICATIONS l CREDIT FOR BORON AND ENRICllMENT INCREASE FOR FUEL STORAGE  !

10 CFR 50.92 EVALUATION (continued)

For the accident of dropping a fuel asserably into an already loaded :clI, the upward axial leakage of that cell will be reduced, however the overall effect on the rack reactivity will be insignificant. This is because the total axialleakage in both the upward and downward directions for the entire fuel array is worth about 0.003 AK. Thus, minimizing the upward-only leakage ofjust a single cell will not cause any significant increase in i reactivity. Furthermore, the neutronic coupling between the dropped assembly and the l already loaded assembly will be low due to several inches of assembly nozzle structure which would separate the active fuel regions. Therefore, this accident would be bounded by the mistoad accident.

The fuel sssembly misloading accident involves having restricted storage locations based on initial enrichment and burnup requirements. Administrative controls are placed on the placement of assemblies into these restricted locations. The misloading of an assembly constitutes not meeting the enrichment and burnup requirements of that restricted location. The result of the mistoading is to add positive reactivity, increasing Kn.

The amount of soluble boron required to offset each of these postulated accidents was evaluated for all of the proposed storage configurations. That evaluation established the amount of soluble boron necessary to ensure that the spent fuel rack Le will be maintained less than or equal to 0.95 should a loss of fuel storage pool coolinr a fuel assembly be dropped into an already loaded storage cell, or a fuel assembly e ,d occur.

The reactivity addition due to the misloading an assembly bounds those of an .asembly dropped into an already filled storage location or an increased temperature.

An event or sequence of events that reduces the amount of soluble boron in the fuel storage pool would add positive reactivity, thus increasing Kg. Significant dilution of the fuel storage pool requires two elements: (1) the inflow of a large volume of water from a source of water with a boron concentration less than that of the pool, and (2) a location or place to which the large volume of pool bo;ated water goes when it is removed from the pool.

Deterministic calculations were performed (Enclosure 6) in order to define the dilution times and volumes for Vogtle: The di!ution sources available at Vogtle were compiled and evaluated against the dilution volume calculated, to determine the potential for a fuel storage pool dilution event. Inadvertant dilution and the misplacement of a fuel assembly -

are considered independant events. The deterministic evaluations show that a large volume of water is necessary to dilute the fuel storage pool to a soluble boron concentration where the K,g would approach 0.95 when fuel assemblies are stored in 4

accordance with the analysis (500 ppm for Unit 2 and 450 for Unit 1).

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION j REVISED REQUEST TO REVISE TECHNICAL SPECIFICATIONS CREDIT FOR BORON AND ENRICHMENT IN_ CREASE FOR FUEi STORAGE 10 CFR 50.92 EVALUATION (continued)

A dilution event large enough to result in a significant reductica in the fuel storage pool boron concentration will involve the removal of a large quantity of water from a dilution source and a significant increase in fuel storage pool level, which would ultimately result in pool overflow. Such a large water volume turnover, and the likely overflow of the fuel storage pool, would be readily detected and terminated by plant personnel. In addition, because of the very large quantities of water r: quired, and the fuel storage pool level and sump alarms, any dilution of the fuel storage poolis expected to be detected and terminated before a significant dilution could occur.

Therefoie, it is highly unlikely that any dilution event in the fuel storage pool could result in the reduction of the fuel storage pool boron concentration to less than the value for maintaining Kg s 0.95.

No safety-related equipment, safety function, or plant operations will be altered as a result of the boron concentration limits or storage configurations. The Technical Specifications will require operation of the fuel storage pool within limits calculated by NRC-approved methodologies. The effects of the proposed fuel storage pool limits are administrative in nature. Appropriate actions to be taken if the limits are not met will be contained in the Technical Specifications.

Conclusion:

The combination of the following provide a level of safety comparable to the conservative criticality analysis methodology required by References 1,2, and 3:

1 The No Soluble Boron 95/95 Kg calculation, shows that the Kg will remain less than 1.0 when flooded with unborated water.

2. The large volumes of water that are necessary to dilute the fuel storage pool and operator response times, assure that credible events will not result in dilution of the fuel storage pool to a boron concentration where Kg exceeds 0.95.

Therefore, Southern Nuclear believes there is reasonable assurance that the health and safety of the public will not be adversely affected by the proposed Technical Specification changes.

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECHNICAL SPECIFICATIONS CREDIT FOR BORON AND ENRICHMENT INCREA_SE FOR FUEL STORAGE 10 CFR 50.92 EVALUATION (continued)

Determination of Significant flazards:

j The proposed change:: to the Operating License have been evaluated to determine whether they constimte a significant hazards consideration as required by 10 CFR 50, Section l 50.91 using the standards provided in Section 50.92. This analysis is provided below:

1. The proposed change dcas not involve a significant increase in the probability or consequences of an accident previously evaluated.

The radiological consequences of 5.0 weight percent U-235 fuel on accidents previously evaluated in the Vogtle FSAR are not significant, increasing the enrichment up to and including 5.0 weight percent U-235 has minor effects on the radiological source terms and subsequently the potential releases both normal and accidental are not significantly affected. Evaluations performed (WCAP-12610-P-A, Reference 5) considered the source term, gap fraction, and the accident doses for a maximum fuel enrichment of 5.0 weight percent U-235, it was concluded that operating with and storing fuel with 5.0 weight percent U-235 enrichment may result in minor changes in the normal annual releases of long half-life fission products that are not significant. Also, the radiological consequences of accidents are minimally affected due to the very small changes in the core inventory and the fact that the currently assumed gap fractions remain bounding The use of the slightly higher enrichment for VEGP fuel will not result in burnups in excess of those currently allowed for VEGP. The cycle design methods and limits will remain the same as are currently licensed. Therefore, the use of fuel with the higher enrichment will not result in conditions outside those currently allowed for VEGP.

There is no increase in the probability of a fuel assembly drop accident in the fuel storage pool wian considering the presence of soluble boron in the pool water for criticality control. The handling of the fuel assemblies in the fuel storage pool has always been performed in borated water.

Fuel assembly placement will be controlled pursuant to approved fuel handling procedures and will be in accordance with the spent fuel rack storage configuration limitations in the Technical Specifications. The consequences of a misplaced assembly have been included in the analysis supporting this revision to the Technical Specifications.

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECilNICAL SPECIFICATIONS CREDIT FOR BORON AND ENRICllMENT INCREASFlOR FUEL STORAGE 10 CFR 50.92 EVALUATION (continued)

There is no increase in the consequences of the accidental misic:. ding of a fuel assembly into the fuel storage pool racks because criticality analyses demonstrate that the pool will remain subcritical following an accidental mistoading of an assembly. There are no credible dilution events that reduce the suberiticality margin below the 5% margin recommended in NRC guidance (references 1,2, and 3). Even if the fuel storage pool were diluted to a boron concentration of 0 ppm the No Soluble Boron 95/95 analysis de:aonstrates that the pool will remain subcritical. The proposed Technical Specifications limitations will ensure that an adequate fuel storage pool boron concentration will be maintained.

There is no increase in the probability of the loss of normal cooling to the fuel storage pool water due to the presence of soluble boron in the pool water for subcriticality control, because a concentration of soluble boron similar to the proposed limit has always been maintained in the fuel storage pool water.

The loss of normal cooling to the fuel storage pool will cause an increase in the temperature of the fuel storage pool water. This will cause a decrease in water density which we,uld normally result in an addition of negative reactivity. Ilowever, since Botaflex is not considered to be present, and the fuel storage pool water has a high concentration of boron, a density decrease causes a positive reactivity addition. The amount of soluble boron required to offset this postulated accident was evaluated for the allowed storage configurations. The amount of soluble boron necessary to mitigate these accidents and ensure that the Km will be maintained less than or equal to 0.95 has been included in the fuel storage pool boron concentration. Because adequate soluble boron will be maintained in the pool water, the consequences of a loss of normal cooling to the fuel storage pool will not be increased.

Therefore, based on the conclusions of the above analysis, the proposed changes will not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. The praposed change daes not create the possibility of a new or different kind of accident kom any accident previously analyzed.

The potential for criticality accidents in the fuel storage pool are not new or difTerent types of concerns The rotential criticality accidents have been reanalyzed in the Criticality Analysis report (Enclosure 5) to demonstrate that the pool remains suberitical E2-9

ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECilNICAL SPECIFICATIONS

- CREDIT FOR BORON AND ENRICliMENT INCREASE FOR FUEL STORAGE 10 CFR 50.92 EVALUATION (continued)

Soluble boron has been maintained in the fuel storage pool water since its initial operation.

The possibility of a fuel storage pool dilution is not affected by the proposed change to the Technical Specifications. Therefore, the implementation of Technical Specification controls for the soluble boron will not create the possibility of a new or different kind of accidental pool dilution.

With credit for soluble boron now a major factor in controlling suberiticality, an evaluation of fuel storage pool dilution events was completed. The results of the evaluation concluded that no credible events would result in a reduction of the criticality margin below the 5% margin recommended by the NRC in addition, the No Soluble Boron 95/95 criticality analysis assures that dilution to O ppm will not result in criticality.

Proposed Technical Specifications 3.7.17,3.7.18 and 4.3.1.1 which ensure the maintenance of the fuel storage pool boron concentration and storage configuration, do not represent new concepts. The actual boron concentration in the fuel storage pool has been maintained at a higher value than the proposed limits for the Unit I and 2 fuel storage pools for refueling purposes. The criticality analysis (Enclosure 5) determined that a boron concentration of 450 ppm (Unit 1) and 500 ppm (Unit 2) results in a K,n 5 0.95.

There is no significant change in plant configuration, equipment design, or usage of plant equipment. The safety analysis for dilution accidents has been expanded; however, the criticality analyses assure that the pool will remain suberitical with no credit for soluble boron. Therefore, the proposed changes will not create the possibility of a new or different kind of accident.

3. The proposed change does not result in a significant reduction in the margin of safety.

Proposed Technical Specifications 3.7.17,3.7.18, and 4.3.1.1 and the associated fuel storage pool boron concentration and storage requirements will provide adequate margin to assure that the fuel storage array will always remain subcritical by the 5% margin recommended by the NRC. Those limits are based on the criticality analysis (Enclosure 5) performed in accordance with the Westinghouse fuel storage rack criticality analysis methodology described in Reference 4.

While the criticality analysis utilized credit for sc,luble boron, the storage configurations have been defined using K,a calculations to ensure that the spent fuel rack K.a will be less than 1.0 with no soluble boron.

E210

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECilNICAL SPECIFICATIONS CREDIT FOR BORON AND liNRICllMENT INCREASE FOR FUEL STORAGli l 10 CFR 50.92 EVALUATION (continued)

Soluble boron credit is used to offset off normal conditions (such as a misplaced assembly) and to provide suberitical margin such that the fuel storage pool Kn is maintained less than or equal to 0.95.

The combination of the No Soluble Boron 95/95 K.a calculation which shows that the Kn will remain less than 1.0 when flooded with unborated water and the unavailability of the large volumes of water which are necessary to dilute the Fiel storage pool to a La of >

0.95, provide a level of safety comparable to the conservative criticality analysis methodology required by References 1,2, and 3.

Therefore, the proposed changes in this license amendment will not result in a significant reduction in the plant's margin of safety.

Conclusion:

Based on the evaluation above, and pursuant to 10 CFR 50, Section 50.91, Southern Nuclear has determined that cperation of the Vogtle Electric Generating Plant in accordance with the proposed license amendment request does not involve ar.y significant hazards considerations as defined by NRC regulations in 10 CFR 50, Section 50.92.

References:

1. USNRC Star.dard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants, LWR Edition, NUREG-0800, June,1987.
2. USNRC Spent Fuel Storage Facility Design Bases (for Comment) Proposed Revision 2,1981, Regulatory Guide 1.13.
3. ANS, " Design Requirements for Light Water Reactor Spent Fuel Storage Fe::iliues ut
Nuclear Power Stations", ANSI /ANS-57.2-1983.
4. WCAP-14416-NP-A, rev.1, " Westinghouse Spent Fuel Rack Criticality Analysis Methodology", rev.1, November 1996.
5. WCAP-12610-P-A, " Vantage + Fuel Assembly Reference Core Report", April,-1995.

E2-Il

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ENCLOSURE 2 VOGTLE ELECTRIC GENERATING PLANT -

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REVISED REQUEST TO REVISE TECHNICAL SPECIFICATIONS CREDIT FOR BORON AND ENRICHMENT INCREASE FOR FUEL STORAGE 10 CFR 50.92 EVALUATION (continued)

6. Nuclear Regulatory Commission, Letter to All Power Reactor Licensees from B. K.

Grimes, OT Position for Review and Acceptance of Spent Fuel Storage and Handling Applications, April 14,1978, i

E212 :

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