ML20031D184
| ML20031D184 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 09/30/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20031D180 | List: |
| References | |
| NUDOCS 8110130054 | |
| Download: ML20031D184 (4) | |
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NUCLEAR REGULATORY COMMISSION t,
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PELATED TO AMENDMENT NO. 69 TO FACILITY OPERATING LICENSE NO. DPR-39 l
COMMONWEALTH EDISON COMPANY ZION STATION UNIT 1 DOCKET NO. 50-295 Introduction By.telecopied letter dated September 4,1981, the Commonwealth Edison Company (CECO) requested a temporary change to the Technical Specifications appended to Facility Operating License No. DPR-39 for the Zion Station, Uni t No.1.
The change would add the following exemption to Table 4.1-1, Reactor Protection System Testing and Calibration Requirements.
i "The Channel Calibration and Channel Functional test for items 14 and 15, RCP (Reactor Coolant Pump) Bus Undervoltage and RCP Bus Underfrequency (Reactor Trips), scheduled for the Spring 1981 refueling outage will be performed the next time these reactor coolant pamps are de-energized or the first unit i
shutdown after September 11, 1981, whichever is earlier."
Background
4 On September 4,1981, it was discovered that the required calibration check of the undervoltage and underfrequency trips on the reactor coolant pump bures had not been performed during the preceding refueling outage (Spring 1981). These protective channels had been calibraced last on November 25, 1979. These channels are designed to allow calibration 4
only when the buses e.e de-energized (i.e., during plant shutdown).
Wher, the protective channel's have not been calibrated, tested, or checked according to the prescribed schedule, the channels are considered by Technical Specifications to be inoperable.. With multip'e channels inoperable, the facility Technical Specifications require that a plant shutdown be initiated if the situation is not corrected within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
Faced with an immedir.te plant shutdown, the licensee requested a one-titre extension of this surveillance requirement, i.e., an emergency Technical Specification change.
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. Evaluation The Zion plant is a Westinghouse-designed PWR that has several diverse types of protective instrumentatio'n provided for postulated loss-of-flow accidents:
a) low reactor coolant flow.
b) pump bus low voltage.
c) pump bus low frequency.
d) pump electrical breaker position.
e) overpower delta-T.
These diverse sets of instrumentation provide protection for a wide l
spectrum of loss-of-flow situations including:
loss of flow in a single loop, pump seizure, and loss of flow in multiple loops.
For all postulated accidents, except one, the undervoltage/underfrequency trips are not the primary protection. That is, adequate protection is provided by other protective channels (e.g., coolant flow channels),
with the undervoltage/underfrequency trips serving either a non-essential anticipatory role or a backup role.
There is one postulated accident for which the undervoltage/underfrequency trips are the primary protective instruments - the multiple-loop loss-of flow situation. This type of accident can be generated credibly only by gross electrical power problems affecting all pumps. Such problems
, could arise from electrical grid disturbances that cause total loss of all offsite power or rapid system frequency decay. Such gross distur-bances, however, are not highly likely. Therefore, the need for the undervoltage/underfrequency trips as the primary protection is not frequent.
Further, in the remote event that these features should not function properly, the coolant ficw channels serve as backup protection and would be expected to trip at about 1.8 seconds into such an event.
Similarly, the delta-T channels would trip at abcut 4 seconds. While a CNBR criteria of 1,30 may be violated, these backup levels of protection are adequate to prevent clad damace.
In discussing with the licensee the capabilities of the undervoltage/
underfrequency trips at this time, we determined that they are exp(cted to function if needed and to function at a value that is most likely within the calibration specifications, even though the calibration checks were not performed. The channels were functionally tested on the prescribed schedule and performed satisfactorily. A review of previous calibration results confirmed that the setpoints of these.i; rip units are quite stable. The resident inspector verified that the calibration checks showed that the actual setpoints have remained within specifications and did not need any adjustment for the past four years.
7 In consideration of the unlikely need for these undervoltage/underfrequency trips to function in the next few months and the availability of backup diverse protective channels, but based primarily upon the demonstrated reliability of these particular trip units, we determined that these calibration checks did not warrant a special unscheduled plant shutdown.
In our review, we considered providing additional protection by increasing the setpoints on the coolant flow channels, an adjustment that could be made without' shutting down the plant. We determined that changes of this type could introduce the possibility of errors that might outweigh the potential benefit.
We did express our. concern that the calibration checks not be deferred until the next refueling outage (April 1982) if an opportunity to perform these calibrations should arise before then.
In discussing this matter with the licensee, they agreed in principle to perform the calibration at the next plant shutdown but raised a procedural concern. The calibration procedures presently are written to be performed at Cold Shutdown. To revise the procedures to perform these calibrations at Hot Standby and to QA the procedures would require about a week. We believe it would not be prudent to require that these calibrations be performed before the revised procedures are well checked out.
Therefore, the licensee has agreed to perform the calibrations at the first plant shutdown that occurs after September 11, 1981.
Sunenary We have determined that the likelihood of needing the undervoltage/under-frequency trips is not great, diverse backup instrumentation channels are provided, the undervoltage/underfrequency trips will most likely function within specifications, and the licensee has agreed to perform the calibrations at the first opportunity that does not require a special plant shutdown exclusively for that purpose. We find this Technical Specification change to be acceptable.
Environmental Consideration We have determined that the amendment does not authori:e 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 th'e amendment involves an action which is insignificant from the standpoint of environmental impact and, persuant to 10 CFR 551.5(d)(4), that an environmental impact statement or negative declaration and environ-mental impact appraisal need not be prepared in connection with the issuance of this amendment.
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. 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 ano security or to the health and safety of the public.
Date:
September 30, 1981 References 1.
Letter, T.R. Tramm, Commonwealth Edison, t'o H.R. Denton, NRC, September 4, 1981, 2.
Zion FS AR, Section 7.2.
3.
Topical Report WCAP-7306, " Reactor Protection System Diversity in Westinghouse Pressurized Water Reactors."
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Letter, T. Novak, NRC, to L.O. DelGeorge, Commonwealth Edison Ccmpany, dated September 8,1981.
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