ML20073M220
| ML20073M220 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/07/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20073M204 | List: |
| References | |
| NUDOCS 9410140190 | |
| Download: ML20073M220 (3) | |
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UNITED STATES
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WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS.30 AND 15 TO FACILITY OPERATING LICENSE N05. NPF-87 AND NPF-89 TEXAS UTILITIES ELECTRIC COMPANY COMANCHE PEAK STEAM ELECTRIC STATION. UNITS 1 AND 2
't DOCKET NOS. 50-445 AND 50-446
1.0 INTRODUCTION
By application dated November 15, 1993, Texas Utilities Electric Company (TU Electric /the licensee) requested changes to the Technical Specifications (Appendix A to Facility Operating License Nos. NPF-87 and NPF-89) for the Comanche Peck Steam Electric Station (CPSES), Units 1 and 2.
The proposed changes would revise the technical specifications (TSs) by increasing the maximum permitted power at which the post-refueling power ascension reactor coolant system (RCS) flow verification can be performed.
2.0 BACKGROUND
The TSs require that reactor coolant system flow be measured and an incore-excore detector calibration be performed during the power ascension following each refueling outage.
Surveillance Requirement (SR) 4.2.5.4'of the TS currently requires that a RCS flow verification by precision heat balance measurement be performed at a power plateau below 75 percent rated thermal-power (RTP).
Table 4.3-1, note (6), requires an incore-excore detector calibration be performed at a power plateau above 75 percent RTP. These tests therefore current'.y require two power plateaus during the post-refueling power ascension, potentially within a few percent RTP of one another.
The licensee proposes to revise SR 4.2.5.4 to require that the post-refueling precision heat balance RCS flow rate measurement be performed prior to reaching 85 percent RTP.
This would allow a single power plateau, between 75 percent and 85 percent rated thermal power, to be used to conduct both the RCS flow verification and the incore-excore detector calibration.
3.0 EVALUATION The purpose of measuring reactor coolant system flow rate after a refueling outage is to ensure that RCS flow rate is within its analyzed values for operation at up to 100 percent RTP.
This measurement ensures that activities during the refueling, such as plugging steam generator tubes and installing new fuel, have not adversely affected RCS flow rate to below its acceptance 1
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_2 criteria. The measurement is performed below 100 percent rated thermal power to provide margin to departure from nucleate boiling (DNB) in the event that RCS flow is found to be less than required.
The effect of the requested change is to reduce the available margin to DNB at the power level the test is conducted at since the licensee is proposing to perform the flow verification measurement at a higher power level.
The licensee performed an analysis, using NRC approved methodologies, to determine if any safety limits would be exceeded by performing the RCS flow verification test at 85 percent RTP instead of 75 percent RTP. This analysis evaluated the loss of forced RCS flow event, which is normally the most limiting event for DNB acceptance criteria. The key assumptions in the analysis included:
- 1) measured flow was 20 percent less than expected flow, which is verified by a RCS elbow tap differential pressure measurement prior to entering MODE 1 following the refueling outage; 2) power dependent enthalpy rise peaking factor (Fu) has been verified to be within the limits of Technical Specification 3.2.3; and 3) consideration of uncertainties on pressurizer pressure and RCS temperature. The licensee's analysis demonstrated that the DNB limit will not be exceeded if the initial power level is 85 percent RTP or less, with a 20 percent reduction in RCS flow.
In addition to the administrative and technical specification requirements noted above that were taken into account in the analysis, the licensee also administratively limits the trip setpoint of the power range neutron flux -
high reactor trip function. This reduced setpoint, typically set at 90 percent RTP, is maintained until all important parameters, including RCS flow, are verified to be within analyzed values.
The staff has evaluated the information submitted by the licensee and concluded that the RCS flow verification test can be performed at up to 85 percent RTP and still have sufficient margin to DNB. The analysis was i
performed with conservative assumptions and demonstrated that tM DNB limit would not be exceeded under those assumptions.
Furthermore, the iicenae has administrative controls in place, as described above, that provide additional i
margin to DNB.
Therefore, the proposed change is acceptable.
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4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Texas State official was notified of the proposed issuance of the amendments.
The State official had no comments.
l 5.0 [NVIRONMENTAL CONSIDERATION The amendments change a surveillance requirement. The NRC staff has determined that the amendments involve 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 i
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 l
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(59 FR 17606). Accordingly, the amendments meet 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 the amendments.
6.0 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, i
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 Centributor:
T. Bergman Date: October 7, 1994 i