ML20236M751
| ML20236M751 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 07/09/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20236M743 | List: |
| References | |
| NUDOCS 9807140244 | |
| Download: ML20236M751 (5) | |
Text
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2006M001 gs...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.121 TO FACILITY OPERATING LICENSE NO. NPF-43 DETROIT EDISON COMPANY FERMI 2 4
DOCKET NO. 50-341
1.0 INTRODUCTION
By letter dated January 28,1998 (NRC-98-0002), the Detroit Edison Company (DECO or the licensee) requested an amendment to the Technical Specifications (TS) appended to Facility Operating License No. NPF-43 for Fermi 2. The licensee plans to replace the Division ll 130/260-volt direct current (Vdc) battery during the sixth refueling outage. The proposed amendment would revise TS surveillance requirements (SRs) 4.8.2.1.a.2,4.8.2.1.b, and 4.8.2.1.c.4 for the battery to accommodate the design of the replacement battery. Because the implementation date for the amendment is tied to the outage, the NRC requests that you submit a letter informing the staff when the amendment is implemented.
2.0 BACKGROUND
The de electrical power system at Fermi 2 provides dc emergency power via the 130/260-Vdc systems and the 24/48-Vdc system. The function of the Class 1E 130/260-Vdc system is to provide de power to Class 1E de loads and for the control and switching of Class 1E systems.
This power is provided through two sets (Divisions I and il) of 130/260-Vdc Category 1 station batteries with full capacity battery chargers. The Division 11260-volt battery (2PB) censists of two 130-volt batteries (2B-1 and 28-2) connected in series.
j The present Division il batteries are designed with sufficient capacity to support the Fermi design-basis accident load profile. However, the licensee has identified a decreasing trend in battery capacity during battery performance discharge testing. A recent battery performance test indicated increased signs of degradation in battery capacity of approximately 7 percent for the 130-Vdc battery 2B-1 and over 2 percent for the 130-Vdc battery 2B-2. The licensee has indicated that, even with this degradation, the existing batteries meet the present design requirements for assuring the batteries are capable of performing their functions and will be l
maintained above the criteria for battery replacement until they are replaced.
l l-The current Division il 260-Vdc battery is furnished by C&D Power Systems, Inc. (C&D). This battery is a KC-17 type, lead calcium battery containing 120 cells (includes two 130-Vdc batteries containing 60 cells each) with a 1.215 specific gravity. This battery will be replaced with a higher capacity battery fumished by C&D. The new battery will be an LCR-21 type, lead calcium battery containing 116 cells (includes two 130-Vdc batteries containing 58 cells each)
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s with a 1.215 specific gravity. The battery is scheduled to be replaced during the sixth refueling outage (RF06).
The battery replacement will not change the existing battery system configuration (other than adjustments for the smaller number of cells). The new Division il 260-Vdc battery will remain located in the Auxiliary Building Division 11 Battery Room and will continue to supply de power through a set of 130-Vdc station batteries. The battery replacement will change the battery capacity and number of cells per battery system.
The licensee has indicated that the replacement of the Division ll 130/260-Vdc battery will provide benefits for the de power system. The benefits include providing more capacity than the present batteries and reducing the potential of tripping the Division 11 battery chargers on high voltage shutdown by reducing the equalizing charge voltage.
3.0 EVALUATION l
As a first step in evaluating the amendment request, the staff performed a comparison of the replacement battery to the old battery. One key parameter that the replacement battery must satisfy is that the minimum battery voltage at the end of discharge must be greater than or I
equal to 210 Vdc. The discharge would occur if the associated chargers were not available to supply the de loads. For the old battery,210 Vdc translated to a minimum cell voltage of:
210 Vdc + 120 cells = 1.75 volts per cell (V/ cell)
For the replacement battery, the minimum cell voltage is:
- 210 Vdc + 116 cells = 1.81 V/ cell Maintaining the same minimum system voltage at the end of discharge ensures that the r.ew battery will have sufficient capacity to power essential loads if power to the battery chargers is lost.
Battery capacity is measured in ampere-hours, the cumulative product of discharge current over the discharge period.. For the Division ll battery, the plant design requires a discharge period of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The existing battery had a capacity of 560 ampere-hours for a 4-hour discharge with a minimum cell voltage of 1.75 V. The replacement battery will have a capacity of 1200 ampere-hours for a 4-hour discharge with a minimum cell voltage of 1.81 V. Therefore, the new battery provides a higher capacity, in terms of ampere-hours, for the 4-hour discharge.
When the new battery is installed, the licensee proposes to change a number of the setpoints associated with the battery. The existing setpoints (which would remain in effect for the Division I battery) and the new setpoints are listed below:
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3-Division ll Batterv Charaer Setooints Setpoint Description Existing Setpoint New Setpoint High Voltage Shutdown 138.5 Vdc (2.31 V/ cell) 138.5 Vdc (2.39 V/ cell)
Equalize Charge Voltage 137.5 Vdc (2.29 V/ cell) 135.5 Vdc (2.34 V/ cell)
High Voltage Alarm 136.0 Vdc (2.27 V/ cell) 134.0 Vdc (2.31 V/ cell)
Float Voltage 133.0 Vdc (2.22 V/ cell) 129.0 Vdc (2.22 V/ cell)
Low Voltage Alarm 128.5 Vdc (2.14 V/ cell) 124.2 Vdc (2.14 V/ cell)
The lower value for the equalize charge voltage increases the margin between that voltage and the high voltage shutdown, decreasing the likelihood of an unnecessary battery charger shutdown.
Because of the changes in the Division ll battery charger setpoints, SRs 4.8.2.1.a.2,4.8.2.1.b, and 4.8.2.1.c.4 will be revised. The SRs under 4.8.2.1.a are performed at least once per 7 days.
The current SR 4.8.2.1.a.2 requires the licensee to verify that:
Total battery terminal voltage is greater than or equal to 130 volts on float charge.
The revised SR 4.8.2.1.a.2 would require the licensee to verify that:
Total battery terminal voltage is greater than or equal to 130 volts for Division I and greater than or equal to 125.7 volts for Division ll on float charge.
For Division 11, the revised minimum voltage provides the same cell voltage (2.167 V/ cell) for the new battery as the current minimum voltage provides for the current batteries. Maintaining the battery voltage at or above this value provides assurance that the battery charger is working effectively and that the batteries are capable of performing their design function. Therefore, this change is acceptable.
Currently, the SRs under 4.8.2.1.b are performed at least once per g2 days and within 7 days after a battery discharge with battery terminal voltage less than 105 Vdc or battery overcharge
. with battery terminal voltage greater than 150 Vdc. The revised version of 4.8.2.1.b would L
require the same SRs to be performed. However, the vabe of overvoltage at which action
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would be required for Division ll would be reduced to 145 Vdc. This lower battery voltage corresponds to the same cell voltage (2.5 V/ cell) as the current overvoltage limit for the current batteries. A voltage of 2.5 V/cellis slightly greater than the maximum continuous recommended equalize charge voltage (for both the old and new batteries) of 2.38 V/ cell. No immediate
- damage would be expected at this cell voltage. Therefore, this change is acceptable.
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% The SRs ui: der 4.8.2.1.c are performed at least once per 18 months. The current SR 4.8.2.1.c.4 i
requires the licensee to verify that:
The battery charger will supply at least 100 amperes at a minimum of 129 volts for at least 4
4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, j
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. The revised SR 4.8.2.1.c.4 would require the licensee to verify that:
The battery charger will supply at least 100 amperes at a minimum of 129 volts for Division I and at a minimum of 124.7 volts for Division ll for at least 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.
For Division ll, the revised minimum voltage provides the same cell voltage (2.15 V/ cell) for the new battery as the current minimum voltage provides for the current batteries. This value of the cell voltage is greater than the minimum cell float voltage of 2.13 V/ cell required by TS Table 4.8.2.1-1, " Battery Surveillance Requirements." Maintaining the battery voltage at or above this value provides assurance that the battery charger can maintain the batteries.
Therefore, this change is acceptable.
Because of similarities between the old and the new batteries (e.g., same specific gravity (1.215), similar physical configuration), the balance of the SRs and the parameters in Table i
4.8.2.1-1 are unaffected by the replacement of the batteries.
l Therefore, the staff concludes that the changes to SRs 4.8.2.1.a.2,4.8.2.1.b, and 4.8.2.1.c.4 l
proposed by the licensee are acceptable for the replacement batteries.
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4.0 STATE CONSULTATION
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In accordance with the Commission's regulations, the Michigan State official was notified of the
- proposed issuance of the amendment. The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
The amendment changes TS surveillance requirements. The staff has determined that the amendment involves 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 amendment involves no significant hazards consideration and there has been no public comment on such finding (63 FR 9597). Accordingly, the amendment meets 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 amendment.
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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, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
1 Principal Contributor Andrew Kugler l
Date: July 9, 1998 i
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