ML20213A420

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Proposed Tech Specs,Reflecting Revised Scram Discharge Vol Water Level Setpoints
ML20213A420
Person / Time
Site: River Bend Entergy icon.png
Issue date: 01/28/1987
From:
GULF STATES UTILITIES CO.
To:
Shared Package
ML20213A392 List:
References
NUDOCS 8702030268
Download: ML20213A420 (4)
v • d • e


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ENCLOSURE 1 I. PROPOSED REVISION 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 as:

Float Trip Allowable Switches Setpoint Value LSN013A and B 5 47.32 in, f 53.50 in.

LSN013C and D $ 45.44 in. 1 49.00 in.

This change 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 control rods when they are tripped.

The 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. The difficulties in obtaining the setpoint were identified in a Notice of Violation, attached to NRC Region IV Inspection Report No.

50-458/85-71. During the review of the design to resolve this concern, it was established 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, GSU is requesting the trip setpoints identified above be revised to n 48.76 in for LSN013A and B and 5 46.88 in for LSN013C and D.

These requested setpoints are consistent with the River Bond Station design and the commitments in the Final Safety Analysis Report (FSAR). Both the RBS Facility Review Committee and the Nuclear Review Board have reviewed this proposed revision and found acceptable as required by Technical Specifications 6.5.1.6 and 6.5.3.7.

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II. JUSTIFICATION As described in FSAR Section 7.2.1.1.2.h, high water level in-the scram discharge volume is an indication that control rod insertion may be hindered. The automatic insertion of control rods upon reaching the high water level setpoint places the plant in the shutdown condition. The design of this system includes diverse initiation signals provided by float switches and independent level transmitter systems.

Original level setpoints of the float switches are based on system design requirements by the reactor vendor, industry standards and Regulatory Guide 1.105. These setpoints were conservative with regard to the final design of River Bend Station, but in this instance the final configuration does not accommodate the original -

setpoint, although it will maintain a value within the allowable limits. The proposed change will maintain the criginal design requirements and standards.

The allowance between the process safety limit (the physical level in the Scram Discharge Instrument Volume (SDIV) at which there is sufficient available volume to receive all the water from the top of the control rod drive pistons) and the Limiting Safety System Setting (LSSS) or Technical Specification Allowable Value is determined by combining the switch actuation accuracy, the switch calibration accuracy, and other effects using accepted methodology. Some additional general conservatism is also included between the process safety limit and the LSSS. The trip setpoint is determined from the LSSS by considering changes that might occur due to seismic and specific gravity fluctuations,

! installation tolerance and some additional general l conservatism.

I f This request removes some of the additional general i conservatism without affecting any calculated allowances

that were included. The process limit did not change,
nor did the LSSS (Allowable Value). The revised '

i Technical Specification Trip Setpoint allows calibration j which accounts for the actual float switch physical i arrangement.

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III. SIGNIFICANT HAZARDS CONSIDERATION The proposed amendment to the Technical Specifications would not involve a significant increase in the probability or consequences of an accident previously evaluated because there is no change in the physical design or performance of plant systems or components from those evaluated in the Final Safety Analysis Report (FSAR). The proposed revision is consistent with the accident analyses described in the FSAR.

The initiation of the Reactor Protection System Trip is based on maintaining sufficient capacity in the scram discharge volume to accommodate the water displaced by the CRD pistons during a scram. The design function of the float switches has not changed and the setpoints are to be increased to allow the system to be calibrated.

The minimum volume requirements have been maintained.

The proposed change does not create the possibility of a .

new or different kind of accident from any accident previously evaluated because this change does not involve a change in the operating mode of existing equipment and the original design requirements are maintained. Thus, no new accident scenario is introduced, f

The proposed change does not involve a significant reduction in the margin of safety because this change affects only the setpoint, the allowable value which assure the safety basis of the Technical Specification is maintained, therefore, the margin of safety is not significantly reduced.

Since the proposed amendment does not change any approved description or analysis described in the FSAR, the proposed amendment does not create the possibility of a new or different kind of accident. Finally, GSU concludes that the proposed change does not involve the significant reduction in a margin of safety because there will be no detrimental changes in the availability, operability or reliability of the systems. -

IV. Revised Technical Specification The requested revision is provided as Enclosure 2.

V. Schedule for Attaining Compliance As indicated in Item III above, River Bend Station is currently in compliance with the applicable Technical Specification allowable values.

VI. Notification of State Personnel A copy-of this amendment application is being provided to the State of Louisiana, Department of Environmental Quality -- Nuclear Energy Division.

VII. Environmental Impact Appraisal Revision of these setpoints does not result in an environmental impact beyond that previously analyzed.

Therefore, the approval of - this amendment does not result in a significant environmental impact nor does it change any previous environmental impact statements for River Bend Station.

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