ML20216H181
| ML20216H181 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/17/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20216H173 | List: |
| References | |
| NUDOCS 9803200209 | |
| Download: ML20216H181 (3) | |
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UNITED STATES a
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NUCLEAR REGULATORY COMMISSION 2
WAsHINoToN, D.c. 3065dHM01
'+9.....,o SAFETY EVALDATION BY THE OFFICE OF NUCl EAR REACTOR REGULATION RELATED TO AMENDMENT NO 228'O FACILITY OPERATING LICENSE NO. DPR-53 AND AMENDMENT WO.200rO FACILITY OPERATING LICENSE NO. DPR-69 BALTIMORE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NOS.1 AND 2 QQCKET NOS. 50-317 AND 50-318
1.0 INTRODUCTION
An Electrical Distribution System Functional Inspection (EDSFI) identified a weakness associated with the 4 kV emergency bus degraded voltage relay settings at Calvert Cliffs Nuclear Power Plant, Unit Nos.1 and 2. Based on the review of voltage calculations, the inspection determined that 75% of rated equipment voltage was not always available for starting of safety-related motors. To address the concems, the licensee, in a letter dated October 22,1997, proposed a Technical Specification change to incorporate both steady state and transient degraded voltage i
setpoints, as opposed to the current single degraded voltage selpoint. Additionally, the licensee proposed to decrease the 4 kV voltage settings to ensure that the new steady state relays are not actuated during testing of the emergency diesel generators (EDG). The licensee also proposed that the changes described with this amendment apply to the improved Technical Specifications (ITS) and submitted the affected ITS and associated bases.
2.0 DISCUSSION AND EVALUATION At Calvert Cliffs, each 4 kV emergency bus is monitored for loss of voltage and degraded voltage by eight relays. Four relays provide loss of voltage input signals to the Engineered Safety Features Actuation System (ESFAS), and the four remaining relays provide degraded voltage input signals to ESFAS. The safety function of the relays is to ensure that the preferred power source is disconnected from the 4 kV emergency buses during loss of voltage and degraded voltage conditions. The relay inputs to ESFAS also ensure that the EDGs are started and loaded. These actions ensure that the minimum terminal voltage necessary to start and run all safety-related equipment is maintained. An EDSFIidentified an apparent weakness in the adequacy of degraded voltage relay settings. The inspection determined that 75% rated i
equipment voltage was not always available for starting of safety-related motors. Design j
requirements for safety-related electrical equipment states that equipment must be capable of starting at 75% of nominal voltage. To ensure that adequate terminal voltage to all safety-related equipment is available, the licensee is replacing the existing loss of voltage and degraded voltage relays for each channel with a single three element relay for each channel. Two of the elements in each new relay monitor for loss of voltage and degraded voltage similar to the existing scheme. The third element monitors for steady state degraded voltage.
The licensee has proposed to change the degraded (transient) vol%ge setpoint from 3628 +/-25 Volts to 3710 +/-60 Volts in Current TS Table 3.3-4. Design requirements for safety-related electrical equipment states that equipment must be capable of starting at 75% of nominal 9803200209 900317 PDR ADOCK 0b000317 P
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2-voltage. Based on the most recent calculations, a minimum voltage of 3630 Volts is required to ensure at least 75% of rated equipment voltage is available to No.13 Charging pump, which is the most limiting electrical load. The new setpoint ensures that at least 75% of the required terminal voltage is available to the most limiting load.
The licensee has also proposed to revise Current Technical Specifications Table 3.3-4 to include the new Steady State Degraded Voltage element of the 3 element relay. The licensee has established the new steady state degraded voltage relay setpoint at 3900 +/-80 Volts. The setpoint ensures that there is at least 90% ofload equipment voltage available to No.13 Charging pump. The time delay associated with this actuation OS 101 +/-3.5 seconds. The time delay provides adequate time for voltage regulator to recover bus voltage following a voltage swing on the 500 kV system and time for the EDG voltage regulator to stabilize. The transient and steady state degraded voltage relay settings have been established to include calibration tolerances, potential transforraer correction factors, test equipment uncertainties, aad relay drift.
The licensee has also proposed to revise Current Surveillance Requirement 4.8.1.1.2.a.4 to require a more conservative voltage range during EDG testing. The sureeillance requirement verifies that the EDG voltage regulator is maintaining an acceptable voltage. The licensee proposed acceptable range of 4160 +/-420 Volts to 4160 +240/-100 Volts. The low end value provides adequate margin to ensure the steady state degraded voltage relays do not actuate during EDG surveillance testing. The upper end value is established at 4400 Volts and ensures that the 4 kV motors are operated within their voltage rating of 4 kV +/- 10 percent.
The licensee has also proposed to convert the above Sections of the TS to the improved Technical Specifications (ITS) NUREG-1432, " Standard Technical Specification - Combustion Engineering Plants." In the process, they identified certain changes in the electrical area that are different from the ITS. The addition of four sensor modules and measurement channels per EDG for the Steady State Degraded Voltage function and the designation of the existing degraded voltage function to Transient Degraded Voltage function and associated Basis reflect the plant-specific design. The iTS specifies two loss-of-voltage (LOV) functions; i.e., loss of voltage and degraded voltage, for each 4.16 kV vital bus. Based on the above changes, the Calvert Cliffs TS now specifies three LOVs Functions; i.e., Loss of voltage, Transient Degraded voltage, and Steady State Degraded voltage, for each 4.16 kV emergency bus.
The staff evaluated the licensee's submittal and concluded that the transient degraded voltage setpoint and new steady state degraded voltage features ensures adequate terminal voltage to all safety-related electrical equipment during steady state and transient voltage conditions and ine change is, therefore, acceptable. The staff also evaluated the new EDG voltage range and concluded that the low end value provides adequate margin to ensure that the steady state degraded voltage relays do not actuate during EDG surveillance testing and the upper end value ensures that the 4 kV motors are operated within their voltage rating and the change is, therefore, acceptable. The staff also finds that the conversion of this portion of the current TS to ITS is in accordance with the Improved Standard Technical Specifications and the Calvert Cliffs plant-specific design and is, therwore, acceptable.
3.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Maryland State official was notified of the proposed issuance of the amendments. The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendmmts change a requirement with respect to installation or use of a facility componsnt located with;n the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. 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 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 (62 FR 61838). Accordingly, the amendments meet the eligibility criteria for categorical exciusion 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.
5.0 CONCLUSION
The Commission has concluded, based on de considerations discussed above, that: (1) there is reasonable assurance that the health cod 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, 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 Contributor: Narinder K. Trehan Date:
March 17, 1998 4