ML20210D412
| ML20210D412 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 06/06/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20210D410 | List: |
| References | |
| NUDOCS 8706160495 | |
| Download: ML20210D412 (3) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION j
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4 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 6 TO FACILITY OPERATING LICENSE NO. NPF-47 GULF STATES UTILITIES COMPANY RIVER BEND STATION, UNIT 1 DOCKET NO. 50-458
1.0 INTRODUCTION
By letter dated January 28, 1987 as supplemented February 13 and April 16 1987, Gulf States Utilities Company (GSU) (the licensee) requested an amendment to Facility Operating License No. NPF-47 for the River Bend Station, Unit 1.
Technical Specification 2.2. Table 2.2.1-1, Reactor Protection System Instrumentation Setpoints, Item 9.b identifies the Scram Discharge Volume Water Level - High trip setpoint and allowable value for the Float Switches LSN013A, B, C and D.
This proposed amendment requests a modification to the setpoints for this function.
These setpoints, which actuate a reactor trip, are provided to detect water level in the Scram Discharge Volume Water Level - High trip setpoint and allowable value for the Float Switches LSN013A, B, C and D.
This proposed amendment requests a modification to the setpoints for this function.
These setpoints, which actuate a reactor trip, are provided to detect water level in the Scram Discharge Volume at a point high enough to indicate an accumulation of water but low enough to ensure that sufficient volume will remain to accept the water displaced from the movement of 4
control rods when they are tripped.
The licensee contends that present design of the float switches has resulted in a configuration which cannot be calibrated to the Technical Specification setpoints but can be maintained below allowable values.
During the review of the design. the licensee contends that sufficient margin is included in the original design to allow a revision of the trip setpoint although no change to the allowable value will be required.
Therefore, the licensee is requesting the trip setpoints identified above be revised to less than or equal to 48.76 inches for LSN013A and B and less than or equal to 46.88 inches for LSN013C and D.
2.0 EVALUATION
The initiation of the Reactor Protection System Trip is based on main-taining sufficient capacity in the scram discharge volume to acconrnodate the water displaced by the CRD pistons during a scram. The design function of the float switches has not changed and the minimum volume requirements have been maintained.
8706160495 870606
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PDR ADOCK 05000458 P
2-The proposed amendment changes the trip setpoint for float switches LSN013A, B, C and D, but the allowable values for these float switches remain unchanged.
The Technical Specification allowable value are those values which are determined using acceptable methodology to ensure adequate conservatism exists to prevent exceeding safety limits during normal operation and design basis operational occurrences and to assist in mitigating the consequences of accidents.
The set point methodology used at River Bend assures that the process safety limit will not be exceeded.
The licensee states and the staff agrees that this assurance is provided by the specific accounting of all inaccuracies between the process safety limit and the allowable value and by properly accounting for drift and calibration between the allowable value and the trip setpoint.
There are additional margins due to conservative assumptions and calculations between the process safety limit and the trip set point which are not considered in the safety analysis.
The requested change in trip set point modifies only this additional margin.
The margin between the allowable value and the top setpoint for L5N013A and B will be reduced from 6.18 to 4.74 inches.
The margin for L5N013C and D will be reduced from 3.56 to 2.12 inches. The design of the float switches is such that there is a zero drift in switch actuation. The calibration of the float switches is such that the accuracy of calibrating them is estimated to be approximately + 0.02 inches. Since the margin that exists between the allowable value and the trip setpoint will always be greater than the maximum inaccuracy value of one inch, the new set-points assures an adequate margin of safety.
The staff also concurs with the licensees' assessment that the proposed ll change does not involve a significant reduction in the margin of safety and does not alter the River Bend Setpoint Methodology.
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3.0 ENVIRONMENTAL CONSIDERATION
This araendment involves a change to a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. 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 this amendment involves no significant hazards consideration and there has been no public comment on such
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Accordingly, this amendment meets the eligibility criteria for i
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9 3-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 this amendment involves no significant hazards consideration and there has been no public comment on such categorical exclusion set forth in 10 CFR 51.22(c)(gibility criteria for finding. Accordingly, this amendment meets the eli 9). Pursuant to 10 CFR 51.22(b), no environmental impact statement nor environmental assessment need.be prepared in connection with the issuance of this amendment.
4.0 CONCLUSION
The staff 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, and (2) such activities will be conducted in comp 11ance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and the security nor to the health and safety of the public.
Principal Contributor:
R. Lasky Dated: June 6,1987 r
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