ML19347F049
| ML19347F049 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Quad Cities  |
| Issue date: | 04/30/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19347F043 | List: |
| References | |
| NUDOCS 8105150134 | |
| Download: ML19347F049 (4) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D. C. 20555
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.[ * * # _. SAFETY EVALUATION.RY.THE OFFICE OF NUCLEAR. REACTOR REGULATION SUPPORTING AMENDMENT N0. 59 TO PROVISIONAL OPERATING LICENSE NO. OPR-19 AMENDMENT _ NO. 52 TO FACILITY OPERATING LICENSE NO. DPR-25, AMENDMENT NO. 70 TO FACILITY OPERATING LICENSE N0. DPR-29, AND AMENDMENT NO. 64 TO FACILITY OPERATING LICENSE NO. DPR-30 COMMONWEALTH EDISON COMPANY AND IONA-ILLIN0IS GAS AND ELECTRIC COMPANY DRESDEN STATION UNIT NOS. 2 AND 3 QUAD CITIES STATION UNIT NOS. 1 AND 2 DOCKET NOS. 50-237, 50-249, 50-254, 50-265
1.0 INTRODUCTION
By letter dated November 1,1979 (Reference 1), Commonwealth Edison Company (CECO, the licensee) proposed amendments to Appendix A, Technical Specifications for Operating License Nos. DPR-19, DPR-25, DPR-29 and DPR-30 for Dresden Units 2 and 3 and Quad Cities Units 1 and 2, respectively.
The change involves a modified power / flow line, which provides more operating flexibility during power ascension while adhering to procedures aimed at reducing fuel pellet-clad interaction.
2.0 DISCUSSION The power / flow restrictions result from the analysis of abnormal operating transients with degraded scram reactivity characteristics that are dependent on fuel exposure. The power / flow restrictions assure acceptable pressure and thermal margins during postulated transients.
The proposed power / flow line will follow the proposed APRM rod block line up to an intercept point and then along a linear path to the 100%
power /100% flow (100/100) point. The proposed APRM rod block line is represented by the following equation:
S < 0.58 WD + 50 81 % 350l %
.. Where: S = setting in. percent. of rated. power.
WD = percent of drive flow required to produce a rated core flow of 98 Mlb/hr The intercept point was chosen by the licensee at 85% power /61% flow
(_85/61 ). This value establishes the highest power level permitted when operating on the APRM rod block line.
It is sufficiently high to provide the desired operational flexibility during power ascension, but low enough to ensure adequate margin to the permissible operational limits for plant operation. The licensee has provided safety analysis demonstrating that nowhere along the proposed power / flow line could more severe transients or accidents occur than those analyzed at the 100/100 point.
3.0 EVALUATION Ceco has performed the following safety analyses and evaluation of the conditions specified in the discussion:
(1)
The most conservative value for the scram reactivity insertion function occurred at end of cycle. This value was consequently used in analyzing the most limiting abnormal operational transients; load rejection without bypass, turbine trip without bypass, loss of feedwater heating, and rod withdrawal error. Each transient was analyzed to show that the highest value of the change in critical power ratio was obtained at the 100/100 point and that the existing operating limits for mir.imum critical power ratio (MCPR) were applicable to the new power / flow line and are therefore acceptable.
(.2 )
The compliance of the proposed technicai specification amendment with the ASME pressure vessel code was verified by analyzing the flux scram caused by a closure of the main steam isolation valve
(.MSIV).
It was shown that the pressure rise produced by the most limiting transient, occurring at the rated power / flew point, was 62 psi below the allowable pressure limit for the reactor vessel, and is therefore acceptable.
(3)
A reanalysis of the rod withdrawal accident was performed.
It was demonstrated that the lowest value of MCPR occurred at the 100/100 point. However, with the rod block monitor setpoint at 108% of full power, the rod withdrawal would be blocked before the permissible safety limit for CPR could be reached. The rearalysis of the rod withdrawal accident is therefore acceptable.
(4)
A statistical analysis was performed to determine the partload s
safety MCPR requirement along the APRM rod block line.
It was shown that small increases in the MCPR requirement due to lower load conditions are adequately compensated by the conservatism i
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factors used in the analysis and by the small changes in in Kf CPR occurring during abnormal transients and rod withdrawal errors at part load conditions. The MCPR requirements under the special stated conditions are therefore acceptable.
(.5)
A thermal hydraulic stability analysis was performed for the new limiting power / flow line. The decay ratios determined from the limiting reactor core stability conditions show the reactor to be well below the ultimate stability limit at the intersection-of the natural circulation and extrapolated rod block lines.
In addition, operation in the natural circulation mode at significant power levels is not a normal mode of operation, thus there is additional margin to the stability limit. The reactor core stability conditions are therefore acceptable.
On the basis of the foregoing considerations, the changes proposed by the licensee will allow reactor power ascension to proceed safely along the modified power / flow line, and are acceptable.
4.0 ENVIRONMENTAL CONSIDERATION
We have determined that these amendments do not authorize a change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determination, we have further concluded that these amendments involve an action which is insignificant from the standpoint of environmental impact, and pursuant to 10 CFR Section 51.5(d)(4) that an environmental impact statement, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of these amendments.
5.0 CONCLUSION
We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probability or conseque ices of accidents previously considered and do not involve a significant decrease in a safety margin, the amendments do not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (3) such activities will be conducted in compliance with the Comnission's regulations and the issuance of these amendments will not be inimical to the connon defense and security or to the health and safety of the public.
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REFERENCES
~(I) '"' Commonwealth ' Edison Coihpa'n) lefter' to* Director"of N'uclesN'ReactW~ ^~ ~ "
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.Regulaticn, "Dresden Station Units 2 and 3, Quad-Cities Station Units 1 and 2, Proposed Amendment to Facility Operating License Nos. DPR-19,
- 25, 29 and 30 Associated with Expanding the Power /Flov Operating Region, NRC Docket Nos. 50-237/249/254/265," dated November 1,1979.
-(2)-
NRC letter (). L. Ziemannl to Northeast Nuclear Energy Company (W. G.
Counsil), " Amendment No. 52 to Provisional Operating License No. DPR-21 for the Millstone Nuclear Power Station Unit No.1," dated July 11, 1978.
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