ML20062F340
| ML20062F340 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 11/27/1978 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20062F320 | List: |
| References | |
| NUDOCS 7812180081 | |
| Download: ML20062F340 (6) | |
Text
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NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 41 TO FACILITY OPERATING LICENSE NO. DPR-40 OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION, UNIT NO. 1 Introduction By letter dated August 30, 1978, Omaha Public Power District (the i
licensee) requested an amendment to Facility Operating License No.
DPR-40 for the Fort Calhoun Station, Unit No.1.
The amendment would add requirements for operation and surveillance of emergency power systems as proposed in the design description provided by the August 30, 1978 letter.
The proposed emergency power system modifications were provided in response to NRC letter dated June 2,1977.
The NRC letter of June 2,1977, requested that the licensee assess the susceptibility of the safety-related electrical equipment to:
1.
Sustained degraded voltage conditions at the offsite power source; and 2.
Interaction between the offsite and onsite emergency power systems.
Discussion The licensee proposed to modify the energency power system by:
1.
Installation of second level undervoltage relays with a higher i
undervoltage setpoint and a time delay to detect sustained degradation of voltage on the safety-related 4160 volt buses; and 2.
Design change to prevent load shedding from the emergency buses once the onsite power source is supplying power to the all sequence loads on the emergency buses.
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. The licensee proposed to change the Technical Specifications to:
1.
Set the second level undervoltage relay trip setpoint at a value of 90 - 92% of the rated voltage 4160 volts, with time delay maximum of 8.0 seconds on the 4160 volt buses; and 2.
Require calibration and testing of the second level undervoltage protection systems and equipment.
Design Basis Criteria The design basis criteria that were applied by the NRC in determining the acceptability of the system nodifications to protect the safety-related equipment from degradation of grid voltage are:
I 1.
General Design Criterion 17 (GDC 17), " Electrical Power Systems,"
of Appendix A, " General Design Criteria for Nuclear Power Plants,"
of 10 CFR Part 50; 2.
IEEE Std. 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations;"
3.
IEEE Std. 308-1974, " Class IE Power Systems for Nuclear Power Generating Stations;" and 4.
NRC staff positions as detailed in June 2,1977 letter sent to the licensee.
Evaluation of Proposed Design Modifications The licensee proposes to install a second level of undervoltage protection system for each of the two 4160 volt safety-related buses from a sustained degradation of grid voltage which exceeds the design value for the safety 4
equipment and systems under abnormal condition.
The second level under-voltage protection consists of an undervoltage relay and a timer.
The voltage monitoring circuit of the second level undervoltage protection automatically indicates the disconnection of offsite power sources when voltage degrades below the safety operating voltage level and after a preset time delay. This undervoltage monitor will have a trip setpoint at about 90% of the rated voltage, i.e., 4160 volts, with an eight second time delay.
This monitor will be designed to a two-out-of-four coincidence logic per bus.
The proposed modifications associated with the second level of under-j voltage protection satisfy the following requirements in our position:
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1.
The undervoltage setpoint and the allowable time duration for a degraded voltage condition shall not result in failure of safety related systems and/or equipment (the 8 second timed setpoint at Fort Calhoun would not result in any damage to the systems or equipment because of the equipment thermal l
capability);
I 2.
The time delay shall minimize the effect of short duration disturbances from reducing the availability of power to the safety-related systems and equtoment (the 8 second timed setpoint j
fulfills this requirement);
3.
The time delay of power to safety related equipment shall not exceed the maximum time delay (30 seconds) considered in the accident analysis section of the Final Safety Analysis Report l
(FSAR) (the 8 second timed delay at Fort Calhoun is short enough to allow power to the safety related equipment within the above 30 second margin);
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4 The undervoltage protection shall include coincidence logic to i
preclude spurious tripping of either the offsite or onsite J
power source (the two out of four system logic at Fort Calhoun
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satisfies this requirement);
5.
The time delay shall override voltage dips on emergency buses due to the sequenced pick-up of loadby a diesel generator (the 8 second delay at Fort Calhoun prevents spurious trips due to short duration voltage transients); and 6.
The voltage sensors shall be designed to satisfy the applicable l
requirements of IEEE Std. 279-1971 (Fort Calhoun sensors meet 279-1971 requirements).
In additon to the existing first level undervoltage protection which has a setpoint at a value of about 72% of the rated voltages, the proposed second level will provide a means for detecting an unacceptable i
sustained degradation of the offsite power voltage that could j
adversely affect safety-related equipment and systems. Moreover, the proposed modifications will not degrade the availability of the of fsite power system below an acceptable level and will increase the i
capability of the onsite power system to provide power to safety-related equipment.
3 The proposed modifications block the undervoltage detecting system whenever the diesel generators have been started and have energized their respective 4160 volt emergency buses. This satisfies the requirements of General Design Criterion 17. " Electrical Power System,"
and IEEE Std. 308-1974, " Class IE Power Systems for Nuclear Power Generating Stations". General Design Criterion 17 requires provisions i
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. to minimize the probability of losing electrical power from any of the remaining supplies as.a result of or coincident with the loss of power generated by the nuclear power unit, the loss of power from the transmission network, or the loss of power from the onsite electric power supplies. IEEE Std. 308-1974 requires availability of the standby power supply following the loss of the preferred power supply within a time consistent with the requirements of the engineered safety features and the shutdown systems under both nomal and accident conditions.
4 Evaluation of Proposed Technical Specifications The proposed Technical Specifications reflect the design modifications, establish the trip setpoints for the undervoltage protection sensors and the associated time delay devices (Table 2-1), and provide the redundancy requirements (Table 2-3).
The proposed changes establich i
surveillance requirements as shown on Table 3-2.
The proposed changes to the Technical Specifications satisfy our requirements with respect to tests for emergency power system which 4
require:
(1) simulating a loss of offsite power; (2) simulating a loss of offsite power in conjunction with an engineered safety i
feature actuation signal; and (3) simulating interruption and subsequent reconnection of the onsite power source to their respective buses.
Conclusion The proposed modifications and Technical Specifications meet the re-quirements of IEEE Std. 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations;" IEEE Std. 308-1974, " Class IE Power Systems for Nuclear Power Generating Stations;" and 10 CFR 50, Appendix A, General Design Criteria 17, " Electric Power Systems."
Also, based on our evaluation of the information provided by the licensee, we find that the proposed design modifications and Technical Specifications are in confomance with the Comission's requirements (GDC 17 and NRC letter dated June 2, 1977) with regard to:
(1) sustained degraded grid voltage conditions; and (2) interaction between the of fsite and onsite emergency power systems. Therefore, we conclude that the proposed modiff-cations and Technical Specifications are acceptable.
We have detemined 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 enviror. mental impact. Having made this detemination, we have further concluded that the amendment involves an action which is insignificant from the standpoint of environmental impact and, pursuant to 10 CFR 651.5(d)(4), that an environmental impact statement, or negative declaration and environ-mental impact appraisal need not be prepared in connection with the i
issuance of this amendment.
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We have concluded, based on the considerations discussed above, that:
i (1) because the amendment does not involve a significant increase in.
I 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 i
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:
November-27, 1978 i
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REFERENCES 1.
10 CFR 50, Code of Federal Regulations, General Design Criterion 17.
1 2.
IEEE Std. 279-1971, " Criteria for Protection Systems for Nuclear Power Generating Stations."
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3.
IEEE Std. 308-1974, " Criteria for Class IE Power Systems for Nuclear Power Generating Stations."
4.
Letter from G. E. Lear (NRC) to T. E. Short, Omaha Public Power j
District, Re: Fort Calhoun Station, Unit No.1, dated June 2,1977.
5.
Letter from T. E. Short (0 PPD) to G. E. Lear (NRC), dated -
July 29, 1977.
6.
Letter from T. E. Short (0 PPD) to R. W. Reid (NRC), dated July 12,1978.
7.
Letter from Attorneys for OPPD to H. R. Denton (NRC), Re:
Application for Amendment of Operating License, dated August 30, 1978.
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