ML20037B433
| ML20037B433 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 07/10/1978 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20037B431 | List: |
| References | |
| NUDOCS 8009260717 | |
| Download: ML20037B433 (2) | |
Text
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UNITED STA TES NUCLEAR REGULATORY COMMisslON g(
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WASHINGTON, D, C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 26 TO FACILITY OPERATING LICENSE NO. DPR-2 COMMONWEALTH EDIS0N COMPANY DRESDEN UNIT NO. 1 DOCKET N0. 50-10 Introduction By letter dated November 25, 1975, as supplemented by letters dated April 15, 1976, August 19, 1976, September 9,1977, and October 18, 1977, the Cc monwealth Edison Company (the licensee) requested an amendment to Facility Operating License No. DPR-2 to incorporate changes to the Dresden Unit 1 pressurization heatup and cooldown limitations. The requested changes relate to requirements of Appendix G, Fracture Toughness Require-ment of 10 CFR Part 50.
During our review of the proposed changes, we found that certain modifications to the proposal were necessary to meet regulatory requirements.
These changes were discussed with and agreed to by the licensee and have been incorporated into the amendment.
Evaluation In their submittal of November 25,1975, the licensee proposed operating limits for the elevated minimum pressurization temperature applicable to Dresden Unit 1.
A fracture mechanics analysis was used to determine adequate vessel toughness, using the criteria of ASME Code Section III, Appendix G.
Additional calculations were performed in accordance with ASME Code Section III, to show that the vessel could tolerate stresses due
- the pressure increase and wall thermal gradients as the vessel is heated
- the minimum pressurization temperatures.
However, upon completion of our rsview, we determined that the proposal did not meet all of the requirements cf 10 CFR 50, Appendix G, and was therefore unacceptable.
By letter dated October 18, 1977, the licensee submitted revised pressure-2 temperature operating limits calculated for a fluence of 1.4 x 1039 N/cm,
which corresponds to -2.4 x 10 6 MW days of operation. The degree of radiation damage (changes in RTNDT) on vessel beltline material is based c-data obtained from the Dresden Unit 1 material surveillance program.
- 'nerials, includino both eld and base material, were subjectsd to fluences as high as 1.5 x 1020 N/cm. The limiting material in the Dresder. Unit 1 reactor vessel.as determined to be base material, so base material orcperties
-i e used in arr. :ng at the pressure-temperature operatir.g limits.
8009260 7/ 7
We have completed our review of the pressure-temperature operating limits-proposed in the October 18, 1977 submittal and find that they are in con-fomance with Appendix G of 10 CFR 50, and are acceptable for operation up to 2.4 x 106 K4 days thermal power.
These operating limits do not permit heatup with the core critical below a temperature of 235'F.
Below this temperature, heatup will be accomplished by the use of heating boilers and recirculation pumps. The maximum heatup rate of 11*F/ hour by this method is low, but is not an unwarranted burden on plant operation.
Compliance with 10 CFR 50, Appendix G, establishes safe operating limitations and will ensure adequate safety margins during operation, testing, maintenance and postulated accident conditions and constitute an acceptable basis for ~ satisfying the requirements of General Design Criterion 31, Appendix A, 10 CFR Part 50.
Environmental Consideration We have determined that the amendment does 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 the amendment involves an action which is insignificant from the standpoint of environmental impact and pursuant to 10 CFR !i51.5(d)(4) that an environmental impact statement, or negative declaration and environmental impact appraisal,
need not be prepared in connection with the issuance of this amendment.
~
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendment does 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 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:
July 10, 1978