ML19204A051

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Final Safety Evaluation for Topical Report ANP-10342P, Revision 0, Gaia Fuel Assembly Mechanical Design
ML19204A051
Person / Time
Site: PROJ0728, 99902041
Issue date: 09/24/2019
From: Jeremy Dean
NRC/NRR/DSS/SNPB
To: Peters G
Framatome
Rowley J, NRR/DLP, 415-4053
Shared Package
ML19204A048 List:
References
CAC No. MF9078/EPID: L02016-TOP-0016 ANP-10342P, Rev. 0
Download: ML19204A051 (15)
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FINAL SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION TOPICAL REPORT ANP-10342P, REVISION 0, GAIA FUEL ASSEMBLY MECHANICAL DESIGN FRAMATOME INC.

PROJECT NO. 728/DOCKET NO. 99902041

1.0 INTRODUCTION

By letter dated December 21, 2016 (Reference 15), Framatome Inc. (Framatome, formerly AREVA Inc.) submitted for U.S. Nuclear Regulatory Commission (NRC) staff review Topical Report (TR) ANP-10342P, "GAIA Fuel Assembly Mechanical Design." Approval would permit licensees with Westinghouse Electric Company (Westinghouse or W) three-loop and four-loop nuclear power reactors that use a 17 x 17 fuel rod array to reference the generic TR for use of the GAIA fuel. The GAIA design is a conglomerate of the previous Framatome, Babcock and Wilcox Company (B&W), and Electricité de France (EdF) fuel designs with some additional new design features and optimizations focused on thermal efficiency. This TR evaluated the performance of the GAIA fuel design against the design criteria defined in the Standard Review Plan (SRP), Section 4.2, Fuel System Design (Reference 1).

Per letter request (Reference 19), Section 9.0 of the TR, has been withdrawn from consideration. This leaves the update process for GAIA to only that which is allowed per 10 CFR 50.59 and other existing regulations. Specifically, the EMF-92-116(P)(A) TR (Reference 8) is not applicable to GAIA. The NRC staff approves the use of this TR subject to the limitations and conditions (L&Cs) listed in Section 4.0 of this safety evaluation (SE).

The SE considers comments and additional information provided in References 17,18, and 19.

Throughout this document the term GAIA is meant to mean the GAIA-W17x17-264 rods fuel assembly (FA).

2.0 REGULATORY EVALUATION

Fuel designs must ensure that the reactor core will have the appropriate margin to assure that the specified acceptable fuel design limits (SAFDLs) criteria in Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix A, General Design Criterion (GDC) 10, Reactor Design, are met. Additionally, GDC 27, Combined Reactivity Control System Capability, and GDC 35, Emergency Core Cooling, require that licensees maintain control rod insertability and core coolability. Loss-of-coolant accident (LOCA) coolability requirements are contained in 10 CFR 50.46. The NRC staff review guidance for new fuel designs is contained in SRP Section 4.2.

The guidance provided within the SRP forms the basis of the NRC staffs review and ensures that the criteria of 10 CFR 50.46, GDCs 10, 27, and 35 are met.

For many of the SRP 4.2 criteria, Framatome does not address the acceptance criteria within this TR. For completeness, this SE acknowledges that those evaluations are done elsewhere and, if necessary, imposes any needed restrictions required for the safe operation of the GAIA FA where those outside analyses may be out-of-date to the current state of knowledge, requirements, or industry issues that need to be addressed.

3.0 TECHNICAL EVALUATION

The GAIA design is a conglomerate of the previous Framatome, B&W, and EdF fuel designs with some additional new design features and optimizations focused on thermal efficiency including:

  • GRIPTM bottom nozzle based upon proven FUELGAURDTM and TRAPPERTM bottom nozzles,
  • GAIA end and intermediate spacer grid based upon proven HMPTM and HTPTM spacer grid designs (respectively),
  • Intermediate GAIA Mixer grid based upon Advanced Mark-BW design,
  • Standard Reconstitutable Top Nozzle,
  • Framatome standard M5 material for the cladding,
  • Q12TM material for MONOBLOCTM guide tubes (GT) and instrument tubes (IT) [NEW FEATURE]
  • Framatome standard M5 material for both intermediate grid designs and Alloy 718 for the end grids.

Per letter request (Reference 19), Section 9.0 of the TR, has been withdrawn from consideration. This leaves the update process for GAIA to only that which is allowed per 10 CFR 50.59 and other existing regulations. Specifically, the EMF-92-116(P)(A) TR (Reference 8) is not applicable to GAIA.

The objectives of this fuel system safety review, as described in SRP Section 4.2, are to provide assurance that (1) the fuel system is not damaged as a result of normal operation and anticipated operational occurrences (AOOs), (2) fuel system damage is never so severe as to prevent control rod insertion when it is required, (3) the number of fuel rod failures is not underestimated for postulated accidents, and (4) coolability is always maintained. A fuel system is "not damaged" when fuel rods do not fail, fuel system dimensions remain within operational tolerances, and functional capabilities are not reduced below those assumed in the safety analyses. Fuel rod failure means that the fuel rod leaks and that the first fission product barrier (the cladding) has been breached. Coolability, which is sometimes termed coolable geometry, means that the fuel assembly retains its rod-bundle geometrical configuration with adequate coolant channels to permit removal of residual heat even after an accident.

3.1 Fuel Assembly Design The GAIA fuel assembly design is intended for use in Westinghouse three-loop and four-loop reactors which use a 17 x 17 fuel rod array, with each assembly containing 264 fuel rods. This SE documents the NRC staff basis for approving this specific design and application. If Framatome wants to develop and market a comparable GAIA product for any other design or application, it must be submitted for review. This is consistent with past practice.

Other fuel assembly designs, not discussed in ANP-10342 or considered in the NRC staff review, include the following:

  • CE14x14-176 rods
  • Palisades-216 rods
  • B&W15x15-208 rods The GAIA fuel assembly design is a conglomerate of the previous Framatome, B&W, and EdF fuel designs with some additional new design features focused on thermal efficiency. The design uses the M5 advanced alloy which has been previously approved (References 3 and 9) for cladding. Q12TM alloy (Reference 5) is used for GT and IT that is one of the first deployments of this new approved alloy. A thorough description and schematic diagrams of the fuel assembly, fuel rod, grids, top nozzle, guide tubes and instrumentation tubing, bottom nozzle, and the materials used for each component are provided in Section 4.0 of the TR.

Based on the content of the TR, the staff concludes that a satisfactory description of the fuel assembly has been provided for this review.

3.2 Lead Test Assembly (LTA) Program/Operating Experience (OPX)

The LTA program for confirming the irradiation behavior of the GAIA fuel assembly design used LTAs in locations where the LTAs saw near-peak core power conditions. The GAIA program was a global design effort within Framatome's three main regions of operation (U.S., France, and Germany), in cooperation with two customers to thoroughly test the design prior to batch implementation. Four GAIA LTAs were inserted in the core of an international reactor in 2012.

Eight GAIA LTA's were inserted in the core of a U.S. reactor in 2015. Both plants are Westinghouse 3-loop designs.

At the time of the TR submittal, the U.S. based LTAs only had one cycle of operation. During their core residency, two cycles are expected to be in high duty locations and during the third cycle, some the LTAs are to be placed on the core-periphery, a hostile hydraulic environment.

Post-irradiation examinations (PIEs) were and will be performed after every irradiation cycle to confirm that the LTAs were operating as predicted. The PIEs that have and will be performed were appropriate for confirming the performance of the fuel design and the results met expectations. Therefore, the LTA performance is acceptable but is subject to L&C #3 to ensure suffucient high burnup fuel rods have been examined prior to a full batch of GAIA fuel assemblies have reached end-of-life (EOL).

Most of the components on the GAIA FA are evolutions in design from previous components in many different FA designs. As such, a smaller LTA program is warrented based on the large OPX database composed of the earlier variants of those components. The exception to this is the Q12' material used for the GAIA GTs, but that marterial was approved outside this TR (Reference 5). The table below summarizes both the OPX of the previous variants of the components and LTA for the new components. Some values in the table are estimates/approximations (Est.).

No. of Region No. of No. of Type Year Component Component United States (U)

Reactors FA LTA/OPX Introduced s/Rods International (I)

GAIA LTA 1 4 - 1I LTA 2012 GAIA LTA 1 8 - 1U LTA 2015 M5' Fuel 84 21000 5000000 U, I (various) OPX 1995 U Rods GAIA M5' 1U 2 12 3180 LTA 2012 Fuel Rods 1I HTP' Spacer 8000 U 20 U 50 8000 Est OPX 1988 U Grid 10000 I 30 I GAIA Spacer 1U 2 12 72 LTA 2012 Grid 1I 718 HMP' 18 U 42 11000 11000 OPX 1998 Spacer Grid 24 I GAIA uses same HMP' - - - - - -

Spacer Grid W17x17 4U MSMG Spacer 12 2300 6900 OPX Not Stated 8I Grid GAIA IGM 1U 2 12 36 LTA 2012 Spacer Grid 1I W17x17 Top 7U 70 33000 33000 OPX 1996 Nozzle 63 I GAIA uses same Top - - - - - -

Nozzle W17x17 6U Bottom Nozzle 70 33000 33000 OPX 1996 64 I (TRAPPER')

W17x17 1U Bottom Nozzle 2 12 12 LTA 2012 1I (GRIP')

MONOBLOC' 10 U 90 38000 570000 Est. OPX 1998 GT 80 I 1U Q12' GT 11 380 Not Stated LTA/OPX 2010 10 I

3.3 Design Evaluation The fuel system design bases must reflect these four objectives: (1) the fuel system is not damaged as a result of normal operation and AOOs, (2) fuel system damage is never so severe as to prevent control rod insertion when it is required, (3) the number of fuel rod failures is not underestimated for postulated accidents, and (4) coolability is always maintained. To satisfy these objectives, acceptance criteria are needed for fuel system damage, fuel rod failure, and fuel coolability. The design basis for each criterion remains the consistent with those in the Advanced Mark-BW fuel assembly (Reference 10).

3.3.1 Fuel System Damage Criteria The design criteria relating to the fuel system damage should not be exceeded during normal operation including AOOs. Fuel rod failure should be precluded and fuel damage criteria should ensure that fuel system dimensions remain within operational tolerances and that functional capabilities are not reduced below those assumed in the safety analysis. Each damage mechanism listed in SRP Section 4.2 will be reviewed to confirm that the design criteria are not exceeded during normal operation for the GAIA design.

3.3.1.1 Stress The design criteria for stress are that the stress intensities for GAIA fuel assembly components shall be less than the stress limits based on the American Society of Mechanical Engineers Code,Section III criteria (Reference 7). These design criteria are consistent with the acceptance criteria of SRP Section 4.2; therefore, the stress criteria are acceptable for application to the GAIA fuel design.

A deterministic method is used to obtain the most limiting stress value provides the most conservative stress value for each fuel assembly component. Positive margin to the design criteria is shown for each of the fuel assembly components; therefore, the NRC staff concludes that the fuel assembly design satisfies the design criteria for design stress.

3.3.1.2 Cladding Strain The design criterion for strain is that the GAIA fuel rod transient strain (elastic plus plastic) limit should not exceed 1 percent for Condition I and II events. This criterion is intended to preclude excessive cladding deformation during normal operation and AOOs. This design criterion is consistent with the acceptance criteria of SRP Section 4.2; therefore, the strain criterion is acceptable for application to the GAIA fuel design.

The analysis of the cladding strain uses the approved COPERNIC code (Reference 2) to determine the cladding strain by evaluating the cladding circumferential changes before and after a linear heat rate (LHR) transient. The 1 percent strain limit corresponds to a transient LHR that is greater than the maximum transient the fuel rod is expected to experience Condition I and II events. Therefore, the NRC staff concludes that the fuel assembly design criteria for cladding strain are met.

3.3.1.3 Cladding Fatigue The design criterion for cladding fatigue is that the GAIA maximum fuel rod fatigue usage factor shall not exceed 0.9. This design criterion is consistent with the acceptance criteria of SRP Section 4.2; therefore, this cladding fatigue criterion is acceptable for application to the GAIA fuel design.

The methodology used for determining the cladding fatigue is outlined in Reference 3. The analysis used a fuel rod life of 10 years and a vessel life of 40 years; therefore, the fuel rod will experience 25 percent of the number of transients that the vessel will. The analysis uses all the Condition I and II events and one Condition III event to determine the total cladding fatigue usage factor. The maximum fatigue usage factor was determined to be well below the design criteria limit. Since the methodology is consistent with the guidance in SRP Section 4.2 and the maximum fatigue is well below the design criteria limit, it is demonstrated that the cladding fatigue acceptance criterion has been met.

3.3.1.4 Fretting The design criteria for fretting are that the GAIA fuel assembly design shall be shown to have no failure due to fretting (Reference 9). This criterion is conservative with the acceptance criteria of SRP Section 4.2; therefore, the fretting criteria are acceptable for application to the GAIA fuel design.

Framatome performed extensive autoclave testing using expected EOL condition for the GAIA fuel assemblies. Fretting wear and performance testing were performed at the HERMES-P (Cadarache, France) and PHFT (Richland, Washington) flow test facilities. 1000 hour0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> endurance flow tests were performed and followed up by additional tests at the PETER loop (Erlangen Germany). Additionally, an individual component pressure drop tests were performed at MAGALY test loop (Le Creusot, France). Evaluations of this extensive testing showed that the GAIA fuel assembly is expected to meet all criteria though EOL. Therefore, Framatome has demonstrated that the GAIA fuel has the ability to meet this criterion.

3.3.1.5 Oxidation, Hydriding, and Crud Buildup The design criteria for oxidation, hydriding, and crud buildup are that the GAIA fuel rod cladding best-estimate corrosion shall not exceed 100 microns. There is not a defined limit on hydrogen pickup for the cladding. The M5 cladding material fuel rods are expected to have less than 50 microns of oxidation at peak rod burnup of 62-gigawatt day per metric tons of uranium (GWd/MTU). Hydrogen pickup is a material dependent property that is driven by the alloying elements and accelerated by thicker oxide layers. Initial hydrogen pickup is limited by smart manufacturing processes that remain unchanged for GAIA. Additionally, the M5 cladding material has an optimized resistance to hydrogen pickup due to its alloying and excellent oxidation layer buildup performance.

These criteria are intended to preclude potential fuel system damage mechanisms. The SRP does not specify limits on cladding oxidation and crud but does specify that their effects should be accounted for in the thermal and mechanical analyses performed for the fuel accounts for the corrosion based on a database established for the M5 cladding material from the in-reactor performance. This performance is based upon a long history of the M5 cladding material,

which remains unchanged in its application to the GAIA FA. It is, therefore, not a subject of detailed review in this TR. The methodology and limits defined in Reference 2 are applicable and acceptable in the evaluation of the GAIA FA. Additionally, this is acceptable because it uses realistic data that is representative of the material and burnup limits for the GAIA fuel assembly design.

Based on the data for M5 cladding material under prototypical irradiation conditions, the oxidation and hydrogen pickup rates are well below the criteria limit. Because crud is included as part of the oxidation measurement, the crud is also limited and well within the total acceptable range. Therefore, it is demonstrated that the oxidation, hydriding, and crud buildup for the GAIA fuel assembly design have met the acceptance criteria.

3.3.1.6 Fuel Rod Bow The design criterion for fuel rod bow is that the fuel rod bowing shall be evaluated with respect to the mechanical and thermal-hydraulic performance of the fuel assembly. There is not a specific limit for fuel rod bow specified in SRP Section 4.2; the SRP only requires that rod bow be included in the design analysis.

The methodology for fuel rod bow was approved in Reference 12. This database is representative of Zircaloy clad fuel. Because M5 cladding grows at a lower rate under irradiation conditions, the database for Zircaloy is conservative relative to the M5 performance.

This approach remains unchanged and has been previously approved in Reference 9.

Therefore, the NRC staff concludes that use of this database for predicting the rod bow of M5 clad fuel and continuing use of the penalty generated by the Zircaloy database for M5 fuel is conservative and acceptable for use.

3.3.1.7 Axial Growth The design criteria for axial growth are that the GAIA fuel assembly-to-reactor internals gap allowance and the fuel assembly top nozzle-to-fuel rod gap allowance shall be designed to provide positive clearance during the assembly lifetime. These design criteria are consistent with the acceptance criteria of SRP Section 4.2; therefore, the axial growth criteria are acceptable for application to the GAIA fuel design.

Tolerances are combined in an appropriate manner and treated consistently. The lowest clearance values are/will be obtained at EOL and in all evaluations, positive clearance remained at EOL under the worst conditions. Axial growth of the GAIA FA is driven by the irradiated growth of the FAs GTs, in this case Q12'. The irradiated growth performance for Q12' was reviewed and approved in Reference 5. Therefore, the NRC staff concludes that the GAIA fuel design meets the axial growth acceptance criteria subject to completion of L&C #3 to validate that the LTA EOL measurements are within the expected range of performance.

3.3.1.8 Fuel Rod Internal Pressure The design criterion for fuel rod internal pressure is that the fuel system will not be damaged due to excessive internal pressure. Fuel rod internal pressure is limited to that which would cause (1) the diametral gap to increase due to outward creep during steady-state operation or (2) reorientation of the hydrides in the radial direction in the cladding. These design criteria

have been applied in previous fuel assembly designs (Reference 10) and will continue to be valid since the parameters used in the methodology remain unchanged. Therefore, these criteria are acceptable for application to the GAIA fuel design.

The fuel rod internal pressure analysis uses the COPERNIC code with the methodology approved in Reference 2. This analysis, performed on a plant-specific basis, includes the use of the most limiting manufacturing variations and a bounding power history for that plant. If the bounding analysis does not meet the fuel rod internal pressure criteria, then on a cycle-specific basis a rod-specific analysis using the actual power history and manufacturing data for that rod can be performed to demonstrate that the internal rod pressure criteria are satisfied. These dual analysis paths using the approved methodology are acceptable for use because they will demonstrate that the fuel rod internal pressure criterion is met.

3.3.1.9 Assembly Liftoff The design criteria for assembly liftoff are that the GAIA fuel hold down springs must be capable of maintaining fuel assembly contact with the lower support plate during normal operating, Condition I and II events, except for the pump over-speed transient. The fuel assembly top and bottom nozzles shall maintain engagement with reactor internals and the holddown springs shall maintain positive holddown margin after a pump overspeed event. These design criteria are consistent with the acceptance criteria of SRP Section 4.2, except for the exclusion of the pump over-speed transient. However, it has been previously approved to exclude this transient; therefore, the assembly liftoff criteria are acceptable for application to the GAIA fuel design.

It should be noted that the NRC staff was not able to find a comprehensive evaluation of this exemption in past approvals. Since the precedent has been set and without cause to show a substantial increase in safety the NRC staff has no basis to reverse this exemption for the pump over-speed transient. The generic fuel assembly liftoff evaluations for GAIA does not show assembly lift but would be allowed in a plant specific evaluation consistent with this precedent.

Framatome performs a combination of deterministic and statistically based analysis and can demonstrate that during all conditions considered, except for the pump over-speed transient, the fuel assembly liftoff criteria are met. During the pump over-speed transient, the lift is small, and the hold-down spring deflection is less than the worst-case normal operating cold-shutdown condition. The hold-down spring is not compressed to a solid height for any operating condition.

Therefore, the NRC staff concludes that for the GAIA fuel assembly design, the fuel assembly liftoff criteria are met.

3.3.2 Fuel Rod Failure Criteria The design criteria relating to the fuel rod failure are applied in two ways. When they are applied to normal operation including AOOs, they are used as limits (SAFDLs) since fuel failure should not occur. When they are applied to postulated accidents, fuel failures are permitted and must be accounted for in the fission product releases. Fuel rod failure is defined as the loss of fuel rod hermeticity. Each fuel rod failure mechanism listed in SRP Section 4.2 will be reviewed to confirm that the design criteria are not exceeded during normal operation and are properly accounted for during postulated accidents for the GAIA design.

Whether or not fuel rod failure is allowed during a Condition III transient is a plant specific criterion regardless of the methodology applied. If a plant is restricted to no fuel failure based upon its licensing basis, then Framatome must demonstrate that criterion is satisfied, or the plant may need to submit a license amendment request (LAR) to remove that restriction, or to change the American national Standards Institute/American Nuclear Society event categorization for a specific event, based upon Framatomes methodology and/or to justify the change in consequences for the event.

3.3.2.1 Internal Hydriding The design criterion for internal hydriding is that the internal hydriding shall be precluded by appropriate manufacturing controls. For the GAIA assembly design, hydriding is prevented by keeping the level of moisture and hydrogenous impurities within the fuel to very low levels.

Framatome maintains the fabrication level for total hydrogen in the fuel pellets to a level that is lower than the SRP Section 4.2 value of 2 parts per million. This design criterion is consistent with the acceptance criteria of SRP Section 4.2 and is acceptable.

Framatome maintains the low hydrogen levels in the fuel rod through manufacturing controls.

Because these controls will remain in place for the GAIA fuel assembly design and the limits are lower than the SRP Section 4.2 values, the design criteria will continue to be met with the GAIA fuel assembly design.

3.3.2.2 Cladding Collapse The design criterion for cladding collapse is that the predicted creep collapse life of the fuel rod must exceed the maximum expected in-core life. The SRP states that if axial gaps in the fuel pellet column occur due to densification, the cladding has the potential to collapse into a gap.

Because of the large local strains that accompany this process, any collapsed cladding is assumed to fail. Because the design criterion is consistent with the acceptance criteria of SRP Section 4.2, it is acceptable for application to the GAIA fuel assembly design.

Framatome uses their approved creep collapse methodology (Reference 4), to determine the potential for creep collapse of the GAIA fuel assembly design. This methodology uses conservative values to determine the creep collapse life of the fuel rod. Creep collapse is assumed when either the rate of creep ovalization exceeds 0.1 mils/hr or the maximum fiber stress exceeds the unirradiated yield strength of the cladding. Based on these definitions of creep collapse, the creep collapse lifetime was shown to be greater than 62 GWd/MTU.

Therefore, the GAIA fuel assembly design is adequately designed to prevent creep collapse for a service life up to 62 GWd/MTU.

3.3.2.3 Overheating of Cladding The design criterion for overheating of the cladding is that for a 95/95 tolerance level, DNB will not occur on a fuel rod during normal operation and AOOs. The SRP states that it has been traditional practice to assume that failures will not occur if the thermal margin criteria (i.e., DNB ratio) are satisfied. Because the design criterion is consistent with the acceptance criteria of SRP Section 4.2, it is acceptable for application to the GAIA fuel assembly design.

3.3.2.4 Overheating of the Fuel Pellets The design criteria for overheating of the fuel pellets are that fuel pellet centerline melting shall not occur during normal operation and AOOs. These design criteria are consistent with the acceptance criteria of SRP Section 4.2; therefore, they are acceptable for application to the GAIA fuel assembly design.

SRP Section 4.2 states that this analysis should be performed for the maximum linear heat generation rate anywhere in the core, including all hot spots and hot channel factors, and should account for the effects of burnup and composition on the melting point. Framatome uses the COPERNIC computer code and fuel melt methodology (Reference 2) to determine the local LHR throughout the fuel rod lifetime that could result in centerline temperature predictions exceeding the limit. The typical generic fuel centerline melt LHR is higher than any expected LHR at the most limiting time of the cycle. If the peak LHR is not at BOL then the time in life must be determined and thermal conductivity degradation must be accounted for the centerline temperature predictions. Therefore, this analysis demonstrated that for the GAIA fuel assembly design the acceptance criteria are met.

3.3.2.5 Pellet Cladding Interaction (PCI)

There are no generally applicable criteria for PCI failure in SRP Section 4.2. The two criteria that should be applied in accordance with SRP Section 4.2 are that the uniform strain of the cladding should not exceed 1 percent and fuel melting should be avoided. Since both of these criteria were addressed previously in this SE, the criteria for PCI are satisfied and acceptable for the GAIA design.

3.3.2.6 Cladding Rupture There is not a specific design limit associated with cladding rupture other than the requirements in 10 CFR 50.46, Appendix K. The cladding rupture correlation and supporting data were reviewed and approved for LOCA emergency core cooling system (ECCS) analyses in References 3, 9, and 16. Because this correlation was developed specifically for use in analyzing M5 cladding, the use of this correlation will provide the appropriate cladding rupture evaluations for the GAIA fuel assembly design under accident conditions.

Clad swelling and rupture requirements following a postulated LOCA are included in the NRC-approved ECCS evaluation models. Emergency core cooling performance is addressed in plant-specific analyses using NRC-approved methods.

3.3.3 Fuel Coolability For postulated accidents in which severe damage might occur, core coolability must be maintained as required by GDC 27 and 35. Coolability, or coolable geometry, has traditionally implied that the fuel assembly retains its rod bundle geometry with adequate coolant channels to permit the removal of residual heat.

Section 4.2, Appendix B of Reference 1 provides interim limits for reactivity insertion accidents (RIAs). The new guidance being developed by the NRC is contained in draft RG (DG) 1327, Pressurized Water Reactor Control Rod Ejection and Boiling Water Reactor Control Rod Drop Accidents. A licensee should consider the most up-to-date guidance and analytical limits at the

time of submittal. Alternative means to demonstrate compliance will be considered on a case-by-case basis.

These criteria will be met as long as Framatome or licensee uses NRC approved methods for RIAs and demostrates that the appropiate limits are met including radiological consequences (L&C #5).

3.3.3.1 Cladding Embrittlement To meet the requirements of 10 CFR 50.46, as it relates to LOCA, acceptance criteria of 2200 degrees Fahrenheit on peak cladding temperature and 17 percent on maximum cladding oxidation must be met. Framatome has demonstrated through high-temperature oxidation and quenching tests that the M5 cladding can meet these limits. The data and analysis to support this conclusion were reviewed and approved in Reference 3. Further, Reference 3 concluded that the Baker-Just correlation is conservative for determining high-temperature M5 oxidation for LOCA analysis and; therefore, is acceptable for LOCA ECCS analyses. Since the Baker-Just correlation is conservative and is required in accordance with 10 CFR 50.46 Appendix K, these criteria will be met without any modification needed to the applicable ECCS evaluation models.

If Framatome chooses to use their best-estimate plus uncertainty realistic large break LOCA methodology (Reference 16) and utilize the Cathcart-Powell (CP) oxidation correlation, then the associated limitation on the oxidation criterion, 13 percent, applies to the evaluation of the GAIA fuel assembly design. Cladding embrittlement evaluations are done outside of the methodology discussed in this TR. Emergency core cooling performance is addressed in plant-specific analyses using NRC-approved methods.

3.3.3.2 Violent Expulsion of Fuel In severe RIAs, such as a rod ejection event, the large and rapid deposition of energy in the fuel can result in melting, fragmentation, and dispersal of fuel.

Fuel cladding failure may occur almost instantaneously during the prompt fuel enthalpy rise (due to PCMI) or may occur as total fuel enthalpy (prompt + delayed), heat flux, and cladding temperature increase. For calculating fuel enthalpy for assessing PCMI failures, the prompt fuel enthalpy rise is defined as the radial average fuel enthalpy rise at the time corresponding to one pulse width after the peak of the prompt pulse. For assessing high cladding temperature failures, the total radial average fuel enthalpy (prompt + delayed) should be used.

This criterion will be met as long as Framatome or Licensee uses NRC-approved methods for RIA and demostrates that the appropiate limits are met including radiological cosequences (L&C #5).

3.3.3.3 Fuel Rod Ballooning To meet the requirements of 10 CFR 50.46, as related to the evaluation of ECCS performance during accidents, burst strain and flow blockage caused by ballooning of the cladding must be accounted for in the analysis of the core flow distribution. Framatome developed new ballooning and flow blockage models for M5 cladding which were reviewed and approved in

Reference 3. Since these models were developed specifically for use in analyzing M5 cladding, the use of these models will provide the appropriate fuel rod ballooning for the GAIA fuel assembly design.

Emergency core cooling performance is addressed in plant-specific analyses using NRC-approved methods.

3.3.3.4 Fuel Assembly Structural Damage from External Forces Earthquakes and postulated pipe breaks in the reactor coolant system would result in external forces on the fuel assembly. During these events, fuel system coolability should be maintained and damage should not be so severe as to prevent control rod insertion when required. The design criteria for fuel assembly structural damage from external forces are divided into three categories:

  • Operating Basis Earthquake (OBE) - Allow continued safe operation of the fuel assembly following an OBE event by ensuring the fuel assembly components do not violate their dimensional requirements.
  • LOCA or SSE+LOCA - Ensure safe shutdown of the reactor by maintaining the overall structural integrity of the fuel assemblies and a coolable geometry within deformation limits consistent with the ECCS and safety analyses.

These design criteria are consistent with SRP Section 4.2 guidance; therefore, they are acceptable for application to the GAIA fuel assembly design.

Framatome used the methodology in Reference 6 to perform generic evaluations of the structural damage from external forces. These analyses considered the horizontal and vertical impacts on the fuel assembly. The analysis shall include generic evaluations of the impact on the GAIA fuel assembly design when it is located in a mixed core on a plant specific basis at the time the licensee implementation. Various core loading patterns and locations in the core were utilized for the mixed core analysis impact. The results showed that the combined loads on the GAIA fuel assembly were small enough that coolable geometry is always maintained. The analysis results demonstrate that coolable geometry can be maintained under all the analyzed conditions; therefore, demonstrate that the acceptance criteria are met.

Any deformation that goes from the linear to the non-linear range is not acceptable currently. A supplement to Reference 6 will be needed to extend acceptable deformation in the non-linear region.

3.4 Design Update Process Per letter request (Reference 19), Section 9.0 of the TR, has been withdrawn from consideration. This leaves the update process for GAIA to only that which is allowed per

10 CFR 50.59 and other existing regulations. Specifically, the EMF-92-116(P)(A) TR is not applicable to GAIA.

4.0 LIMITATIONS AND CONDITIONS The NRC staff approves the the use of this TR subject to the following L&Cs:

1) This GAIA fuel assembly design is approved for use with low enrichment uranium (LEU) fuel, which has been enriched to less than or equal to 5 percent.
2) The GAIA fuel assembly design is licensed for a maximum fuel rod burnup of 62,000 Megawatt-days/metric ton of Uranium.
3) The final LTA program PIE report shall be submitted to NRC staff prior to any reload batch of GAIA assemblies reaching the third cycle of operation.
4) (Removed)

Per letter request (Reference 19), Section 9.0 of the TR, has been withdrawn from consideration. This leaves the update process for GAIA to only that which is allowed per 10 CFR 50.59 and other existing regulations. Specifically, the EMF-92-116(P)(A) TR (Reference 8) is not applicable to GAIA.

5) As part of the plant-specific LAR implementing GAIA, the licensee must demonstrate acceptable performance of GAIA under RIA conditions, including fuel damage, coolable geometry, and radiological consequences, using approved methods. Current guidance and analytical limits are found in SRP 4.2 Appendix B. Newer guidance is expected soon (e.g., DG-1327). The licensee should consider the most up-to-date guidance and analytical limits at the time of submittal. Alternative means to demonstrate compliance will be considered on a case-by-case basis.

5.0 CONCLUSION

The NRC staff reviewed the acceptance criteria and generic and proposed analysis methodology presented by Framatome in TR ANP-10342(P), Revision 0, "GAIA Fuel Assembly Mechanical Design," and determined that the criteria and proposed analysis methods are performed in accordance with the guidance provided in SRP Section 4.2. The NRC staff finds the criteria and proposed analysis methods outlined in this TR acceptable based on the determinations provided in the technical evaluation section of this SE and concludes that the TR is acceptable for referencing by licensees.

There were no requests for additional information questions issue as part of this review. The missing evaluation sections, that are required per Reference 1 were accommodated by the issuance of L&Cs on this TR or by the additional information provided in Reference 18.

Therefore, on the basis of the above review and justification, the NRC staff concludes that the GAIA fuel assembly design is acceptable for use in Westinghouse three-loop and four-loop design reactors which use a 17 x 17 fuel rod array with LEU fuel subject to the L&Cs included in this SE.

6.0 REFERENCES

1) NUREG-0800 - Chapter 4, Section 4.2, Revision 3, Fuel System Design, U.S. Nuclear Regulatory Commission, March 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML070740002).
2) BAW-10231P-A, Revision 1, COPERNIC Fuel Rod Design Computer Code, Framatome ANP, Inc., January 2004 (ADAMS Package Accession No. ML042930233).
3) BAW-10227P-A, Revision 1, Evaluation of Advanced Cladding and Structural Material (M5) in PWR Reactor Fuel, Framatome ANP, Inc. June 2003 (ADAMS Package Accession No. ML15162B043).
4) BAW-10084P-A, Revision 3, Program to Determine ln-Reactor Performance of BWFC Fuel Cladding Creep Collapse, B&W Nuclear Technologies, July 1995 (ADAMS Accession No. ML14191B170, nonpublic).
5) ANP-10334P-A, Revision 0, Q12' Structural Material, AREVA Inc., September 2017 (ADAMS Package Accession No. ML17320A119).
6) ANP-10337P-A, Revision 0, PWR Fuel Assembly Structural Response to Externally Applied Dynamic Excitations, Framatome Inc., April 2018 (ADAMS Package Accession No. ML18144A816).
7) American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section Ill, Nuclear Power Plant Components, 1992 Edition
8) EMF-92-116P-A, Revision 0, Generic Mechanical Design Criteria for PWR Fuel Designs, Siemens Power Corporation, February 1999 (ADAMS Accession No. ML003681168, nonpublic).
9) BAW-10240P-A, Revision 0, Incorporation of M5' Properties in Framatome ANP Approved Methods, Framatome ANP Inc., May 2004 (ADAMS Package Accession No. ML042800308).
10) BAW-10239P-A, Revision 0, Advanced Mark-BW Fuel Assembly Mechanical Design Topical Report, Framatome ANP Inc., July 2004 (ADAMS Package Accession No. ML042820190).
11) ANF-89-060(P)(A) and Supplement 1, Generic Mechanical Design Report High Thermal Performance Spacer and Intermediate Flow Mixer, Advanced Nuclear Fuels Corporation, March 1991.
12) XN-75-32P-A, Supplements 1, 2, 3, & 4, Computational Procedure for Evaluating Fuel Rod Bowing, Exxon Nuclear Company, Inc., October 1983 (ADAMS Accession No. ML081710709, nonpublic).
13) BAW-10243P-A, Statistical Fuel Assembly Hold Down Methodology, Framatome ANP Inc., September 2005 (ADAMS Package Accession No. ML053610044).
14) Regulatory Guide 1.77, "Assumptions Used for Evaluating a Control Rod Ejection Accident for Pressurized Water Reactors," U.S. Atomic Energy Commission, May 1974 (ADAMS Accession No. ML003740279).
15) Letter from Gary Peters to the USNRC, Request for Review and Approval of ANP-10342P, GAIA Fuel Assembly Mechanical Design," AREVA Inc., December 2016 (ADAMS Accession No. ML16362A278).
16) EMF-2103P-A, Revision 3, Realistic Large Break LOCA Methodology for Pressurized Water Reactors, AREVA Inc., June 2017 (ADAMS Accession No. ML16286A579).
17) Letter from Gary Peters to the USNRC, Response to Request for Comment on Draft Safety Evaluation for ANP-10342, GAIA Fuel Assembly Mechanical Design, Framatome, December 20, 2018 (ADAMS Accession No. ML18360A171).
18) ANP-10342Q1P, Revision 0, GAIA Fuel Assembly Mechanical Design Additional Information, December 2018 (ADAMS Accession No. ML18355A067).
19) Letter from Gary Peters to the USNRC, Additional Information Regarding ANP-10342P, GAIA Fuel Assembly Mechanical Design , Framatome, September 6, 2019 (ADAMS Accession No. ML19253A050)

Attachment:

Comment Resolution Principal Contributor: J. Dean, NRR/DSS Date: September 24, 2019

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