ML20085E983
| ML20085E983 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 10/04/1991 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20085E980 | List: |
| References | |
| NUDOCS 9110210306 | |
| Download: ML20085E983 (4) | |
Text
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o UNITED STATES
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'n NUCLEAR REGULATORY COMMISSION
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,E WASHINGTON, D. C 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLLAR REACTOR REGULATION RELATED TO AMENDMENT NO. 47 TO FACILITY OPERATING LICENSE NPF-68 AND AMENDMENT NO. 26 TO FACILITY OPERATING LICENSE NPF-81 GEORGIA POWER COMPANY.ET AL.
V0GTLE ELECTRIC GENERATING PLANT UNITS 1 AND 2 DOCKET NOS. 50-424 AND 50-425
1.0 INTRODUCTION
By' letter dated June 3,1991, Georgia Power ampany, et al. (GPC or the licensee),
proposed-amendments to the operating licenses for the Vogtle Electric Generating Plant.(VEGP)} Units 1and2.
The amendments would change the Technical Specifi-cations,(TSs toallowtheuseoftwoWestinghouseVANJgGE-5 fuel: assemblies, each:containing_uptotwelvefugrodscladwithZ1RLO
, an advanced zirconium alloy cladding material. ZIRLO is proposed for limited use in VEGP reload core designs to obtain additional operational # :perience with the cladding's improved corrosion-resistant per_formance under VEGP-specific reactor conditions.
ThisTSchangeis'proposedtosgportthelicensee'splantoload;twofuel assemblies containing the Z1RLO clad fuel rods beginning with the initial introduction of VANTAGE-5 fuel into Unit 1, scheduled for late September 1991.
Previously, on May-13, 1987, the NRC staff approved a similar application for the Northgnna. Unit 1reactortoJsetwodemonstrationfuelassembliescontaining Z1RLOT ' clad fuel rods. The North Anna fuel assemblies began irradiation in June 1987._
The NRC. staff also previously determined that exemptions _to 10 CFR 50.44, 10CFR50.46,10gFR51.52,andAppendixKto10CFR50wererequiredtoallow T
the use of Z1RLO. Exemptions to these regulations were issued on October 3, 1991.
This Safety Evaluation covers the staff's review of the proposed changes to L
VEGP TS.5.3.1, " Fuel Assemblies," reflecting changes to the relohd core designs:
beginning with Cycle 4 for Unit 1.
E 2.0 EVALUATION
-2.1. Fuel-Mechanical Design i
L Currently, VEGP Units 1 and 2 utilize the Westinghouse 17x17 low-parasitic
~(LOPAR) fuel. Beginning with Unit 1 Cycle 4 and Unit 2 Cycle 3, reload fuel l
will consist of the Westinghouse VANTAGE-5 fuel design, which was approved by the staff in Amendments 43 and 44 (Unit 1) and 23 and 24 (Unit 2). GPC plans to insert up to two-Westinghouse VANTAGE-5 fuel assemblies, each containing up to twelvefuel rods clad with. the advanced zirconium alloy cladding material (Z1RLO
-). into Vogtle reload core designs.
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. D The chemical conposition of the ZIRLO cladding is similar to Zircaloy-4 u cept for slight reductions in the cor. tent of tin, iron, chromium, and zirconium, and the addition of a nomical one percent niobium.
This nominal amount of niobium provides greater corrosion resistance as cor. pared to Zircaloy-4. The physical and mechanical properties are very similar to Zircaloy-4 while in the same metallurgical phase. However,thetemperaturesatwhichge metallurgicalphasesghangearedifferentforZircaloy-4andZIRLO Further aspects of the ZlRLO clad performance, includina its performance under loss-of-coolantaccident(LOCA) conditions,andthefg1roddesignbasesand criteria which are particularly affected by the ZIRLO clad, are described in WCAP-12610, "Vantace-5 Fuel Assembly Reference Core Report," June 1990.
This WCAP was reviewed and approved by the NRC staff on July 1,1991.
Basedontheabove,theNRCstaffconcludesthatthemechgicalaspectsofthe proposed fuel design, with its proposed use of some ZIRLO clad fuel rods, are acceptable for use in VEGP Units 1 and 2, 2.2 Nuclear Design WCAP-10444-P-A, " Vantage-5 Fuel Assembly Reference Core Report," September 1985, showsthatthegsignandpredictednuclearcharacteristicsofeachfuelrod clad with ZIRLO are similar to those of VANTAGE-5 clad with Zircaloy-4 The licensee has performed evaluations using NRC-approved g thodology and has shown thatthenucleardesignbasesforfuelcladwithflRLO are satisfied.
The licensee has also shown that the change to ZlRLO will not affect the use of standard nuclear design analytical models and methods to accurgely u.cribe the neutronic behavior of fuel.
Furthermore, the use of ZIRLO fo
.e two assemblies will not affect the safety lim" characteristics of the VANTAGE-5 fuel design.
The staff has-previously reviewed the licensee's avait tions in WCAP-12610. By letter dated July 1, 1991, the NRC staff approved the evaluations which had used approved methods. Therefore, the proposed nuclear aspects of the proposed fuel design are acceptable for use in VEGP Units 1 and 2.
2.3 Thermal-Hydraulic Design WCAP 10444-P-A also showsfhat the thermal and hydraulic design bases for fuel rods clad with ZIRLO ere identical to those of the VANTAGE-5 design.
TheegluationsintheWCAPusedapprovedmethodology. Since the use of the ZIRLO clad fuel does not affect the parar.;eters which are major contributors in this area (i.e., DNB, core flow, and rod bow), the design bases of the VANTAGE-5 design remain valid as previously approved. Therefore, the staff findsthethermal-hygaulicaspectsoftheproposedfueldesign,withsomefuel rods clad with ZIRLO, to be acceptable for VEGP Units 1 and 2, 2.4 Transient and Accident Analyses The licegee identified two non-LOCA accidents potentially affected by the use of ZIRLO clad material in the Final Safety Analysis Report (FSAR). These are the locked rotor / shaft break accident and the rod cluster control assembly
,. - ~. - - -
. (RCCA) ejection accident.
For the locgd rotor /shaf t break accident, the licensee has determined that the ZIRLO cladding results in a very small increase in peak clad temperature (PCT) of about 2'F, and that the difference in the effect on the methl-to-water reaction rate is negligible when compared to Zircaloy-4 A sufficient margin exists in the Vogtle safety analysis associatedwiththeVANTAGE-5fueltransitiontoacepodatethesmallPCT increase.
For the RCCA ejection accident, the Z'9L0 cladding results in a small reduction in both the fraction of fuel mel ing at the fuel's hot spot and the. fuel's peak c+ored energy when compared to the results for Zircaloy-4 LOCA analyses for the VANTAGE-5 fuel in the VEGP units were performed by the
-licensee using the 1981 Evaluation Model with BASH (large-break LOCA) and the NOTRUMP Evaluation Model (small-break LOCA). Tgevisions to these evaluation models for use in analyses of fuel with ZIRLO cladding were identified and reported in WCAP-12610. The revisions include the cladding specific heat, high-temperature creep (swelling), burst temperature, burst strain, and assembly blockage. Calculationspgformedwiththerevisedevaluationmodelsshowed that the effects of ZIRLO cladding on large break and small break LOCA analyses results are relatively minor, such that existing acceptance criteria continue-to be met.
The licensee has stated that, prior to insertion of the two fuel assemblies, the fuel rod heatup analyses for the limiting large break and small break cases from the 'Vogtle VANTAGE-5 fuel-analyses would be verified as part gf the standard T
reload design process and would reflect the behavior of the ZIRLO clad material during a LOCA as described in WCAp-12610. -The licensee's analyses would consider the gxpected peaking ' factor margin between the Zircaloy-4 clad T
rods-and the ZIRLO clad fuel rods which will be located in the low peaking factor regions.
Since the LOCA analyses are performed with the approved Westinghouse ECCS evaluation model and the results are within acceptable limits, and the fuel rod heatup-analyseswi1}gbe verified prio to insertion of the two fuel assemblies containing the ZIRLO clad fuel' rods, the NRC staff concludes that the analyses are acceptable.
2.5'- Technical Specification Changes The proposed amendments would modify TS 5.3.1 which requires that the core's
-fuel assemblies contain 264 fuel rods " clad with Zircaloy-4," This TS will be supplementedbyadding,"exceptfortwofue}Massemblies which may each contain-
.up to twelve.(12) fuel rods clad with ZIRLO Thus, the_ change reflects the insertion of two Westinghouse VANTAGE-5 fuel assemblies,eachcontaininguptotwelvefuelrodscladwiththeadvanced zirconium alley cladding. material (ZIRLO ) into VEGP reload core designs.
This change is acceptable because it is consistent with the evaluations described above. The amendments implementing this TS change are in accordance with-the-Commission's regulations, except as exempted by the NRC's letter dated October 3,
- 1991, for 10 CFR 50.44, 10 CFR 50.46, 10 CFR 51.52, and Appendix K to 10 CFR 50.
}
3.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Georgia State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change requirements with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendments involve no significant increase in the amounts, ar.d no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (56 FR 29277). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.?2(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 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, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors:
T. fluang, SRXB L.-Raghavan, PDII-3/0Rp/1/II Date:- October 4, 1991 I