ML17164A449
| ML17164A449 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 11/30/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17164A448 | List: |
| References | |
| NUDOCS 9412060290 | |
| Download: ML17164A449 (5) | |
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UNITED STATES NUCLEAR REGULATORY COMMlSSION WASHINGTON, D.C. 20555-0001 ATTACHHENT 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUS UEHANNA EXTENDED FUEL BURNUP PENNSYLVANIA POWER
& LIGHT COMPANY SUS UEHANNA STEAN ELECTRIC STATION UNITS 1
AND 2 DOCKET NOS.
50-387 50-388
- 1. 0 INTRODUCTION By letter dated Hay 31,
- 1994, Pennsylvania Power
& Light Company submitted a
request to increase the burnup limit of Siemens'x9-2 fuel from 40,000 to 45,000 HWd/HTU assembly'verage.
The technical basis for the exposure extension includes on-site fuel inspections, fuel design analyses and evaluations, and in-reactor fuel assembly extended exposure demonstration.
The demonstration assemblies were 4 previously discharged Siemens'x9-2 fuel assemblies, and were inserted into Unit 2 Cycle 6 core for irradiation to an exposure of 46,848 HWd/HTU.
During the Unit 2 refueling outage, the 4 demonstration assemblies were sipped for leakage detection.
The result showed that there was no leakage for all 4 assemblies.
The NRC staff has previously approved a similar Siemen's fuel design, 9x9-IX and 9x9-9X, in a topical report ANF-89-014(P), Revision 0, Supplement 1 up to 48,000 HWd/HTU assembly average.
The licensee indicated that the first cycle which will be designed with the higher exposure of the 9x9-2 fuel is Unit 1 Cycle 10.
The licensee analyzed the 9x9-2 fuel design up to 45,000 HWd/HTU for extended burnup irradiation.
Our evaluation follows.
9412060290 9'41130 PDR ADDCK 05000387, P
- 2. 0 EVAL'UATION
- 2. 1 Cladding Creep Collapse The design criterion on the cladding creep collapse is that there shall not be significant axial gap in the fuel column during fuel densification'ince the majority of the fuel densification occurs early in life, the fuel column will remain compressed by the plenum spring during extended burnup.
Based on the approved Siemens'x9-IX and 9x9-9X fuel design, the staff agrees that the 9x9-2 will not have a cladding creep collapse problem during extended burnup to 45,000 MWd/MTU.
2.2 Fuel Rod Axial Growth The design criterion on fuel rod growth is that the fuel rods must be properly engaged to the upper tie plate.
The licensee performed a
conservative calculation to determine the axial growth.
The result showed that there is sufficient shoulder gap existed for higher burnup exposure for Susquehanna Units I and 2.
Based on the approved Siemens'x9-IX and 9x9-9X fuel design, the staff concludes that there is sufficient shoulder gap for 9x9-2 fuel during extended burnup to 45,000 MWd/MTU.
2.3 Cladding Corrosion and Crud Buildup The fuel design criterion for cladding corrosion and crud buildup is to prevent significant degradation of cladding strength and unacceptable temperature increases.
The licensee has used a
maximum oxidation limit in fuel design.
Based on conservative calculations, the total oxidation in extended burnup is still below the maximum limit.
Since the approved Siemens'x9-IX and 9x9-9X fuel did not have problems with corrosion, we conclude that the 9x9-2 fuel will not have a problem of cladding corrosion and crud buildup in high burnup.
2.4 Centerline Temperature The fuel design criterion for fuel pellet centerline temperature is that the fuel centerline temperature shall not exceed melting temperature during normal operation and anticipated operational occurrences.
The licensee analyzed the pellet centerline temperature for high burnup exposure and showed no melting occurred.
Based on the licensee's conservative
- analysis, the staff concludes that the 9x9-2 fuel will remain below the fuel melting temperature for extended burnup operation.
2.5 Fuel Rod Internal Pressure The fuel design criteria for fuel rod internal pressure is that a limited number of fuel rods is allowed to have internal pressure exceeding the system pressure based on conservative analysis and calculation.
The licensee analyzed the rod internal pressure for high burnup, and determined that the rod pressure would exceed the system pressure,
- however, remain below a proprietary and conservative pressure limit.
Based on the conservative calculation and analysis, the staff concludes that the fuel rod internal pressure will not present a problem for extended burnup.
2.6 High Burnup Effect on Fuel Behavior
- Recently, a fuel dispersal test in a foreign country indicated a significant decrease in fuel failure and fuel dispersal thresholds beyond about 43,000 MWd/HTU peak pellet exposure.
This preliminary result prompted the staff to reassess the fuel dispersal limit of 280 cal/gm and the BWR fuel failure criterion of 170 cal/gm.
While the staff is continuing to evaluate the impact of the test, the staff has also considered its implication on the fuel burnup extension request for the Susquehanna Units.
In a letter dated November 21, 1994, the licensee presented analyses results for the control rod drop accident assuming reduced fuel failure thresholds of 30, 50 and 85 cal/gm.
The results showed that the offsite dose calculations were well
within the regulatory limits, i.e., below the 25K of 10 CFR 100 limits, even when the 30 cal/gm failure threshold was considered.
The results clearly demonstrated that a significant margin of safety was retained for the Susquehanna extended burnup applications.
Based on the licensee's conservative
- analyses, the staff concludes that there is adequate safety margin to compensate for potential reduction of the fuel failure threshold for the requested Susquehanna extended burnup application.
- 3. 0 CONCLUSION We have reviewed the licensee submittal of extended burnup of Siemens'x9-2 fuel for Susquehanna.
Based on the staff evaluation, we approve the extended burnup from 40,000 to 45,000 NWd/HTU assembly average for Siemens'x9-2 fuel for Susquehanna Units 1 and 2.
The staff 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 issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
FNCLOSURE 2
SYSTEMATIC ASSESSMENT OF LICENSEE PERFORMANCE FACILITY NAME Susquehanna Steam Electric Stations Units I and 2
SUMMARY
OF REVIEW The review is straightforward.
The submittal is sufficient for the staff review.
NARRATIVE DISCUSSION OF LICENSEE PERFORMANCE SAFETY ASSESSMENT UALITY VERIFICATION The licensee performance is satisfactory.
AUTHOR:
DATE:
S.
Wu
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