ML20247B120
| ML20247B120 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 05/10/1989 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20247B115 | List: |
| References | |
| NUDOCS 8905240012 | |
| Download: ML20247B120 (8) | |
Text
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UNITED STATES
[ } ).g. ([gg NUCLEAR REGULATORY COMMISSION r,,,
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
j RELATED TO AMENDMENT NO. 37 TO FACILITY OPERATING LICENSE NO. DPR-80 AND AMENDMENT NO. 36 TO FACILITY OPERATING LICENSE NO. DPR-82 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 DOCKET NO. 50-275 AND 50-323
1.0 INTRODUCTION
By letter dated November 29, 1988, as supplemented by letters dated December 9, 1988 and February 17,1989(ReferenceLAR88-08),PacificGas and Electric Company (PG&E or the licensee) requested amendments to the combined Technical Specifications (TS) for the Diablo Canyon Nuclear Power Plant, Unit Nos. I and 2.
The amendments revise the TS to permit core reload and operation with Westinghouse 17x17 VANTAGE 5 fuel assemblies.
Both units are presently operating with Westinghouse 17x17 low-parasitic (LOPAR) fuel assemblies.
The transition from a complete LOPAR core to a complete VANTAGE 5 core will be accomplished over three cycles in each unit.
The proposed revisions to the Technical Specifications support operation with each of the transition cores and all subsequent cores using only VANTAGE 5 fuel.
The submittals dated December 9, 1988 and February 17, 1989 provided additional analyses and information to support the TS changes and did not alter the action noticed or affect the initial determination.
The major design features of the VANTAGE 5 fuel relative to the current LOPAR fuel include the following:
(1) integral fuel burnable absorber (IFBA), (2) intermediate flow mixer (IFM) grids, (3) reconstitutible top nozzles, (4) axial blankets, (5) six intermediate zircaloy grids, (6) optimized (smaller) diameter fuel rods, guide thimbles, and instrumentation tubes, and (7) extended burnup capability. Changes to the Technical Specifications are required due to the use of VANTAGE 5 fuel and use of the following analytical methods and assumptions:
(1) TheImprovedThermalDesignProcedure(ITDP);
1 (2) The WRB-1 and WRB-2 departure from nucleate boiling (DNB) correlations; (3) Large break loss-of-coolant accident (LOCA) analyses using the 1981 evaluation model and the BASH model; (4) Small break LOCA analyses using the NOTRUMP model; and (5) Heat flux hot channel factor, F (z), surveillance.
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The licensee has stated that safety analyses for the transition cores and.
the full VANTAGE 5 core were performed at a thermal power level of
'3338 MWt for Unit I and 3411 MWt for Unit 2 with conservative assumptions 1
including (1) a full power nuclear enthalpy hot channel factor (Fdelta-H c
of 1.62 for the~LOPAR fuel and 1.65 for the VANTAGE 5 fuel, (2) a maximum heatfluxhotchannelfactor(F)of2.45,(3)fifteenpercentsteam g
I generator tube plugging, and (4) a positive moderator temperature coefficient (MTC) of.+5 pcm/ degree F.from O to 70% power, which then decreases linearly to 0 from 70 to 100% power.
The.. VANTAGE 5 fuel design has been previously reviewed and approved by the NRC staff on a generic basis. The staff's generic safety. evaluation for VANTAGE 5 fuel is appended to WCAP-10444-P-A, " Westinghouse Reference Core Report VANTAGE 5 Fuel Assembly," by S. L. Davidson and W. R. Kramer, September 1985. However, several conditions are defined by the staff in its safety evaluation that must be addressed in each specific application to use VANTAGE 5 fuel.
3.0 EVALUATION
.In its generic safety evaluation of the VANTAGE 5 fuel design that is included in WCAP-10444-P-A, the NRC staff identified several plant-specific conditions that must be resolved by each licensee using VANTAGE 5 fuel. 'PG&E addressed each of these conditions in its letter dated February 17, 1989. The-NRC staff's evaluation of the acceptability of these conditions for Diablo Canyon is given below.
(1) Statistical Convolution Method In its generic safety evaluation of VANTAGE 5 fuel, the NRC staff stated that the statistical method should not be used to evaluate the fuel rod shoulder gap in VANTAGE 5 fuel.
The licensee indicated that the statistical convolution method was not used for the VANTAGE 5 fuel design and the currently approved method was used for evaluating fuel rod shoulder gap.
Therefore, this item is acceptable to the staff.
(2) Seismic and LOCA Loads In its generic safet/ evaluation of VANTAGE 5 fuel, the NRC staff stated that for each plant application, it must be demonstrated that the fuel assembly will maintain its coolable geometry under combined seismic and LOCA loads. The licensee stated that Diablo Canyon Units 1 and 2 were not bounded by the analysis described in WCAP-9401, " Verification, Testing and Analyses of the 17x17 Optimized Fuel Assembly," 5. L. Davidson, et. al., March 1979.
- Instead, plant-specific analyses with approved methodology were performed to
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demonstrate structural integrity of fuel assemblies, in accordance with Section 4.2 of NUREG-0800, " Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants," (SRP). The licensee analyzed mixed (transition) cores of VANTAGE 5 and LOPAR fuel and a full core of VANTAGE 5 fuel. The results showed that limited grid deformation in some peripheral fuel assemblies was predicted for the mixed cores during combined seismic and LOCA loads.
However, further evaluation showed that peak cladding temperature in these assemblies still remained below 2200*F, thereby meeting the coolable geometry criteria described in SRP Section 4.2.
For other fuel assembly components such as thimble tubes and fuel rods, the licensee demonstrated that the loadings on these components were significantly below the allowable stress limits.
Therefore, the licensee concluded that both VANTAGE 5 and LOPAR fuel meet all structural integrity criteria described in Appendix A to SRP 4.2 that are applicable to seismic and LOCA conditions.
Based on the licensee's acceptable results, the NRC staff concludes that the structural integrity and coolable geometry will be maintained, and the appropriate criteria for seismic and LOCA loads are satisfied.
(3)
Irradiation Demonstration Program In its generic safety evaluation of VANTAGE S fuel, the NRC staff required that an irradiation program be performed to confirm the VANTAGE 5 fuel performance. The licensee stated that Virgil C. Summer Unit I has four VANTAGE 5 demonstration assemblies irradiated up to an assembly average burnup of 30 GWD/MT.
Post-irradiation examinations showed all four assemblies to be of good mechanical integrity. These four assemblies have been reinserted for continued irradiation.
On this basis, the NRC staff concludes that the VANTAGE 5 fuel will perform satisfactorily in Diablo Canyon Units 1 and 2.
(4)
Improved Thermal Design Procedure (ITDP)
In its generic safety evaluation of VANTAGE 5 fuel, the NRC staff stated that its approval of the use of the Westinghouse improved thermal design procedure (ITDP) was subject to certain restrictions which should be applied to the VANTAGE 5 fuel design. The use of the ITDP is discussed in the licensee's letter dated December 9, 1988.
In its letter of February 17, 1989, the licensee stated that it complied with the appropriate restrictions on the use of ITDP in its analysis of Diablo Canyon Units 1 and 2.
Based on this, the NRC staff concludes that this condition has been met.
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(5) DNBR Limit In its generic safety evaluation of VANTAGE 5 fuel, the NRC staff stated that plant-specific analysis should be performed to show that the DNBR limit is not violated with the higher value of Fdelta-H' The licensee examined all the transient analyses related to DNBR calculations (using 1.65 for both transition cores and a full core of VANTAGE 5 fuel), and concluded that there were no DNBR limit violations in Diablo Canyon Units 1 and 2.
The NRC staff finds this acceptable.
(6) Reactor Coolant Pump Shr't Seizure In its generic safety evaluation of VANTAGE 5 fuel, the NRC staff stated that the mechanistic approach in determining the fraction of fuel failures during the reactor coolant pump shaft seizure accident was unacceptable. The fuel failure criterion should be the 95/95 DNBR limit. The licensee indicated that the mechanistic method was not used and an analysis of this accident was done using approved methodology for Diablo Canyon. The results showed that the number of fuel failures was less than 10% of the total fuel rods in the core l
based on the 95/95 DNBR limit. This fuel failure has been used in the dose calculation for radiological impact assessment. Based on the acceptable fuel failure criterion of 95/95 DNBR limit, the staff concludes that the reactor coolant pump shaft seizure accident is satisfactorily addressed for VANTAGE 5 fuel at Diablo Canyon.
(7) Positive Moderator Temperature Coefficient In its generic safety evaluation of VANTAGE 5 fuel, the NRC staff stated that if a positive moderator temperature coefficient (MTC) is expected, the same positive MTC should ae used in the plant-specific analysis. The licensee indicated that a positive MTC was considered in the analyses, and all the appropriate safety criteria were met.
On this basis the NRC staff considers this to be acceptable for Diablo Canyon.
(8) LOCA Analysis In its generic safety evaluation of VANTAGE 5 fuel, the NRC staff stated that the plant-specific LOCA analysis should be performed to show that the applicable requirements of 10 CFR Part 50 are mot. The licensee analyzed large break LOCA and small break LOCA using the approved Westinghouse LOCA Evaluation Model with a F of 2.5.
The g
results show that all the requirements in 10 CFR 50.46 and Appendix K to 10 CFR Part 50 were met for Diablo Canyon Units 1 and 2.
On this basis, the NRC staff concludes that this condition is satisfied for the VANTAGE 5 fuel in Diablo Canyon.
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In summary, the licensee has addressed the plant-specific conditions identified in the staff's generic safety evaluation approving the use of VANTAGE 5 fuel.
On this basis, the NRC staff finds the use of VANTAGE 5 fuel in Diablo Canyon to be acceptable, both for the transition cores and the all-VANTAGE 5 cores.
4.0 TECHNICAL SPECIFICATION CHANGES Specifically, the amendments change the following Technical Specifications in order to accommodate the use of VANTAGE 5 fuel:
(1) Core Safety Limits (TS 2.1.1, Figures 2.1-la and 2.1-Ib);
(2) Reactor Coolant Flow-Low Trip Setpoint and Allowable Values (TS 2.2.1, Table 2.2-1);
(3) Overtemperature delta-T and Overpower delta-T Reactor Trip Setpoints (TS2.2.1, Table 2.2-1);
(4) DNB Correlations, DNBR Limits, Fower Range Neutron Flux High Rate, and F m
needaindes (Bases 2.1.O; delta-H (5) Rod Drop Time (TS 3.1.3.4);
(6) AxialFluxDifference(TS3/4.2.1);
(7) Heat Flux Hot Channel Factor - F (Z) (TS 3/4.2.2, Bases 3/4.2.2);
9 (8) RCS Flow Rate and Nuclear Enthalpy Rise Hot Channel Factor, Fdelta-H (TS 3/4.2.3, Figures 3.2-3a, 3.2-3b, and 3.2-3c);
(9) DNBParameters(TS3/4.2.5, Table 3.2-1, Bases 3/4.2.5);
(10) ESFAS Instrumentation Trip Setpoints (TS 3/4.3.2, Table 3.3-4);
(11) Group Height, Insertion, and Power Distribution Limits (TS 3/4.10.2);
and (12) Radial Peaking Factor Limit Report (TS 6.9.1.8).
The NRC staff evaluation of each of these TS changes is given below. All the proposed TS changes were found to be acceptable.
(1) Core Safety Limits (TS 2.1.1, Figures 2.1-la and 2.1-1b)
The core safety limits are revised to reflect the use of VANTAGE 5, ITDP, WRB-1 (LOPAR fuel) and WRB-2 (VANTAGE 5 fuel) DNB correlation, and F f 1.66.
Based on the approved WCAP-10444-P-A, ITDP delta-H method, and DNBR correlations, the NRC statf concludes that the revised core safety limits are acceptable.
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(2) Reactor Coolant Flow Trip-Low Setpoint and Allowable Values (T5 2.2.1, Table 2.2-1)
TS Table 2.2-1, Item 12 " Reactor Coolant Flow-Low" is revised based on the ITDP calculations to reflect the VANTAGE 5 fuel design. The NRC staff has reviewed this change and finds it acceptable.
(3) Overtemperature delta-T and Overpower delta-T Reactor Trip Setpoints (TS 2.2.1, Table 2.2-1)
Overpower and overtemperature setpoints are revised to maintain consistency with the non-LOCA accident analyses. Since the revised setpoints are based on the approved methods in WCAP-8745 " Design Bases for the Thermal Overpower Delta-T and Thermal Overtemperature Delta-T Trip Functions," the NRC staff finds the revised overpower and overtemperature setpoints to be acceptable.
(4) DNB Correlations, DNBR Limits, Power Range Neutron Flux High Rate, and F Limit Uncertainties (Bases 2.1.1) delta-H TS Bases 2.1.1 " Reactor Core" is revised to address the DNB correlations and design and safety analysis DNBR limits for the VANTAGE 5 fuel. The NRC staff finds these changes acceptable, since they are appropriate for VANTAGE 5 fuel.
(5) Rod Drop Time (TS 3.1.3.4)
TS Section 3.1.3.4 " Rod Drop Time" is revised to increase the rod drop time from 2.2 seconds to 2.7 seconds. This change is the result of an increase in the core hydraulic resistance due to the VANTAGE 5 fuel design. All relevant reload transient and accident analyses were redone using this value.
The staff has reviewed this change and finds it acceptable.
(6) Axial Flux Difference (TS 3/4.2.1)
The axial power distribution control is revised to follow the recommendation of the Relaxed Axial Offset Control (RA0C) procedure.
Since the RAOC procedure is described in the approved report WCAP-10215-P-A " Relaxation of Constant Axial Control - Fq Surveillance Technical Specification," the NRC staff considers this revision acceptable.
Also, the surveillance requirement in TS Section 4.2.1.1 is revised to reflect the RAOC procedure.
The staff considers this change to be acceptable.
/g, (7) Heat Flux Hot Channel Factor - F (Z) (TS 3/4.2.2, Bases 3/4.2.2) 9 Because of increased thermal margin available from the use of VANTAGE 5 fuel, the peaking factor F has been increased to 2.45 to g
allow greater operational flexibility.
Since the licensee has performed all the analyses based on the F of 2.45, the NRC staff O
finds this revision acceptable.
For Surveillance Requirements in TS Section 4.2.2, the licensee proposes to use F surveillance to replace the current F,,
g surveillance.
Since the F surveillance is described in the approved q
report WCAP-10215-P-A, the staff finds this change to be acceptable.
(8) RCS Flow Rate and Nuclear Enthalpy Rise Hot Channel Factor, Fdelta-H (TS 3/4.2.3, Figures 3.2-3a, 3.2-3b, and 3.2-3c)
The peaking factor F has been increased (to allow for greater delta-H operational flexibility) due to the use of VANTAGE 5 fuel. This change is similar to F, and the staff finds this change acceptable q
also.
The associated Bases in TS Section 3/4.2.3 has been revised to be consistent with the specification changes. The NRC staff finds this change acceptable.
(9) DNB Parameters (TS 3/4.2.5, Table 3.2-1, Bases 3/4.2.5)
I The limits of the DNB parameters, T,yg and pressurizer pressure, are revised to be consistent with the new analyses due to the use of VANTAGE 5 fuel. The staff finds these changes acceptable.
TS Bases 3/4.2.5 is revised to add the new DNBR limits used for VANTAGE 5 and LOPAR fuel. The staff finds this change acceptable.
(10) ESFAS Instrumentation Trip Setpoints (TS 3/4.3.2. Table 3.3-4)
TS Table 3.3-4 is revised to change the allowable values for
-Low-Low. Because this change is consistent with the use of l
T,yfAGE5 fuel VAN
, the flRC staff considers it acceptable.
l (11) Group Height, Insertion and Power Distribution Limits (TS 3/4.10.2)
TS Section 3/4.10.2 and the associated Surveillance Requirements are revised to reflect the use of F surveillance. The staff finds these q
changes acceptable.
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'.O (12)RadialPeakingFactorLimitReport(TS6.9.1.8)
TS Section 6.9.1.8 is revised to include the W(Z) function associated with the F surveillance requirements. A report requirement g
concerning the W(Z) function is also addressed.
The staff finds these changes acceptable.
5.0
SUMMARY
OF STAFF EVALUATION The NRC staff has reviewed the use of VANTAGE 5 fuel and the associated changes to the Diablo Canyon Nuclear Power Plant, Unit Nos. I and 2 combined Technical Specifications proposed by PG&E letter dated November 29, 1988, as supplemented by letters dated December 9, 1988 and February 17, 1989. These submittals describe the VANTAGE 5 fuel design and the associated TS changes for transition cores of VANTAGE 5 and LOPAR fuel and all-VANTAGE 5 cores. Based on the previously-approved generic topical report WCAP-10444, and acceptable plant-specific analyses, the NRC staff finds the use of VANTAGE 5 fuel in Diablo Canyon and the associated Diablo Canyon Technical Specification changes to be acceptable.
6.0 ENVIRONMENTAL CONCLUSION Pursuant to 10 CFR 51.21, 51.32, and 51.35, an Environmental Assessment and Finding of No Significant Impact has been prepared and published in the Federal. Register on May 4, 1989 at 54 FR 19264. Accordingly, based upon the environmental assessment, the Commission has determined that the issuance of these amendments will not have a significant effect on the quality of the human environment.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the Commission's regulations and (3) the issuance of these amendments will not l
be inimical to the common defense and security or to the health and safety of the public.
1 Principal Contributors:
S. L. Wu H. Rood Dated: May 10, 1989 f
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