ML20209D899
| ML20209D899 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/02/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20209D896 | List: |
| References | |
| NUDOCS 8609090512 | |
| Download: ML20209D899 (3) | |
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UNITED STATES g
NUCLEAR REGULATORY COMMISSION j
WASHINGTON, D. C. 20555 S
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...,s SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO.120 TO FACILITY OPERATING LICENSE NO. DPR-50 METROPOLITAN EDISON COMPANY JERSEY CENTRAL POWER AND LIGHT COMPANY PENNSYLVANIA ELECTRIC COMPANY GPU NUCLEAR CORPORATION THREE MILE ISLAND NUCLEAR STATION, UNIT NO. 1 DOCKET NO. 50-289 INTRODUCTION By letter dated July 16, 1986, GPU Nuclear Corporation (GPU or the licensee) requested amendment to the Technical Specifications (TSs) appended to Facility Operating License No. DPR-50 for the Three Mile Island Nuclear Station, Unit No. 1 (TMI-1). The proposed amendment (titled Technical Specification Change Request No.159) would allow the withdrawal of the axial power shaping) rods (APSRs) fron the core as early as 240 effective full power days (EFPDs into the current Cycle 5.
Withdrawing the APSRs will extend Cycle 5 from 280 EFPDs to 290 15 EFPDs. A change to the quadrant tilt Technical Specification 3.5.2.4 was also included in the submittal, but this subject q
will be addressed by a separate evaluation. The staff has reviewed the i-proposed changes and prepared the following evaluation.
EVALUATION The APSRs at THI-1 are part length control rods used to shape the axial power distribution if an axial xenon transient occurs. These rods do not trip during a reactor scram since their movement may add positive or negative l
reactivity to the total control rod worth, depending on their position at the time of reactor trip. The APSRs would be fully withdrawn at 250 i 10 EFPDs to the end of cycle (E0C) 5 now estimated to be 290 15 EFPDs. The increase in Cycle 5's length is caused, primarily, by a net increase in core reactivity of about 0.5% delta k/k when the APSRs are fully withdrawn from the core. The main issues involved in APSR withdrawal from the core are (1) the effect on axial power shape control, (2) the effect on reactor core parameters (e.g., moderator temperature coefficient), (3) the effect on accident and transient analyses, and (4) the effect on fuel and thermal design.
I Even though the APSRs are fully withdrawn from the core, the axial power shape can easily be maintained to either prevent or control any axial xenon transient. The axial xenon stability index was calculated to be -0.0387 per hr., therefore any xenon transient induced power oscillation will be damped.
Moreover, many PWRs operate without part length control rods indicating the efficacy of various power distribution control schemes.
From an analysis 8609090512 e60902 PDR ADOCK 05000289 p
. of power distribution control, the licensee determined that the current rod index limits still maintain the shutdown margin and ejected rod worth criteria.
The licensee determined new power / imbalance / flow Technical Specification setpoints to meet power peaking factor limits for near E0C 5 operation with the APSPs fully withdrawn. These setpoints are less restrictive than the original Cycle 5 limits which were established with the intention of bounding future cycles. These new setpoints provide the plant with greater operational flexibility. The staff concludes that the licensee's evaluation of the rod index limits and power / imbalance / flow setpoints is acceptable since previously approved methods have been used in the analysis.
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The licensee evaluated the effect of APSR withdrawal from the core on the reactor core parameters. The results indicate that only slight change in various parameters and coefficients will occur. The largest change occurs
-2.63 x 10 grator temperature coefficient (MTC). The MTC changed from for the mod
-2.51x10"jdeltak/k/ Fat 17ppmofboronwiththeAPSRsinsertedto delta k/k/*F at 17 ppm of boron with the APSRs fully withdrawn.
The Cycle 5 startup tests indicated that the reactor design agreed well with the test measurements and confirmed the adequacy of the Cycle 5 design methodology. The staff concludes that the licensee's evaluation of E0C 5 nuclear design with the APSRs removed is acceptable.
The licensee evaluated the effect of the change in core parameters on the accident and transient analyses. The only FSAR events directly affected by the changes in core parameters are overcooling transients (steam line break and cold water accident) and a dropped control rod.
For the steam line break, the E0C 5 would result in a less severe accident than reported in the FSAR due to the less negative MTC. The effect of other parameters on the accident would be negligible. Similarly, a cold water accident would be less severe than reported in the FSAR because of the less negative MTC. The dropped rod is dependent, primarily, on rod worth and the MTC. A review of these parameters indicates that the consequences of a dropped rod would be less severe than the FSAR analysis. The staff concludes that the licensee's assessment of the effect of E0C 5 APSR withdrawal on transients and accidents is acceptable since the FSAR analyses of the affected accidents and transients remained more limiting.
l The effect of the increased cycle burnup has no significant effect on the fuel and thermal design. No previous assumptions or criteria on the fuel design were exceeded, including those for cladding collapse and internal pin pressure. The thermal hydraulic design is not affected by the small Cycle 5 burnup extension. Previous assumptions for the rod bow penalty remain bounding. The staff concludes that the licensee's assessment of the fuel and thermal design for the increased Cycle 5 burnup is acceptable.
The staff concludes that the proposed Technical Specifications associated with the withdrawal from the core ' f the APSRs near E0C 5 and the resultant o
Cycle 5 extension are acceptable.
ENVIRONMENTAL CONSIDERATION This amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
We have determined that the amendment involves no significant increase in the amounts, and 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 nccupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the issuance of this amendment.
CONCLUSION We have 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 the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Dated: September 2,1986 Principal Contributors: D. Fieno l
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