View source for RBG-25714, Forwards Addl Info Re 870128 Application for Amend to License NPF-47,revising Tech Specs Re Scram Discharge Vol Instrumentation Setpoints

{{Adams
| number = ML20213A488
| issue date = 04/16/1987
| title = Forwards Addl Info Re 870128 Application for Amend to License NPF-47,revising Tech Specs Re Scram Discharge Vol Instrumentation Setpoints
| author name = Booker J
| author affiliation = GULF STATES UTILITIES CO.
| addressee name = 
| addressee affiliation = NRC OFFICE OF ADMINISTRATION &amp; RESOURCES MANAGEMENT (ARM)
| docket = 05000458
| license number = 
| contact person = 
| document report number = RBG-25714, NUDOCS 8704280041
| document type = CORRESPONDENCE-LETTERS, INCOMING CORRESPONDENCE, UTILITY TO NRC
| page count = 4
| project = 
| stage = Request
}}

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GULF STATES                             UTILITIES COMPANY j                               RIVER BEPeD STATION     POST OFFICE BOX 220    ST FR ANOSVILLE. LOUlstANA 70775 2
AREA CODE 504     635-6094     346-8651 i
April 16, 1987 RBG- 25714 File No. G9.5 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Gentlemen:
i i                                                      River Bend Station - Unit 1 Docket No. 50-458 l                  Gulf States Utilities (GSU) hereby files supplemental information to
;                  support its application for an amendment to the River Bend Station -                                                  i Unit 1 Technical Specifications, Appendix A to Facility Operating License NPF-47, pursuant to 10CFR50.90. The original application was filed on January 28, 1987'(RBG-25277) regarding scram discharge volume instrumentation setpoints.
:                  If additional information is required, please contact Mr.                                          R. King at (504) 635-6995.
Sincerely, j                                                                                  J. E. Booker l'
n                         Manager-River Bend Oversight River Bend Nuclear Group JEB/ ERG /        je i
: i.                                                                                                                                       .
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8704280041 DR               870416 ADOCK 05000458                                                                                              5 l                                     PDR
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cc: Mr. Robert D. Martin, Regional Administrator U.S. Nuclear Regulatory Ccanission Region IV 611 Ryan Plaza Drive, Suite 1000 Arlington, TX 76011 NBC Senior Besident Inspector Mr. William II. Spell, Administrator Nuclear Energy Division Iadciana Department of Environmental Quality P. O. Box 14690                                                                                                   :
Baton Fouge, IA 70898

ATTACHMENT Per discussions with the staff the following additional information is provided as clarification to GSU's cubmittal of January 28, 1987.
       .ae margin of safety in River Bend design is the assurance the process safety limit, see the attached figure, will not be exceeded. This assurance is provided by the specific accounting of all inaccuracies between         the process . safety limit and the allowable value.                 The
      " additional margin" identified between the Process Safety Limit and the Allowable Value and the " additional allowance / installation tolerance" between the Allowable Value and the setpoint are not considered in                  the safety analysis.          The additional margin between the process limit           and the allowable value for float switches A&B is 1.12 and 8 inches                     for LSN013 C&D.          The inaccuracy maximum value is 1.0 inches. Since              the difference between the allowable value and the setpoint, in the proposed change, is greater than 1 inch, the new setpoint will not decrease the margin of safety.          As discussed below, this proposed change will maintain the nominal trip setpoint at or below the allowable alue thus assuring the margin of safety.
The attached figure illustrates the relationship between each setpoint and summarizes the input to each. As noted in the figure, each term contains margin in addition            to     identified          instrument   setpoint considerations.         For this application the differences between the allowable value and the setpoint are drift, installation tolerance, and margin.         The installation tolerance is included to account for the difference between the as-designed and as-built configurations.                    Once construction         is complete, the remaining tolerance is ' treated as additional margin. The drift is included to specifically account for instrument setpoint changes between Technical Specification surveillance required calibrations. Once the instrument is installed, any change to the setpoint is due to drift.
Drift allowance, between the setpoint and the allowable value, is maintained to ensure the instrument will support the analysis.                      The subject float switch drift is less than the drift allowance between the setpoint and the allowable value. Therefore, the requested change is bounded by the existing safety analysis.

Figure SETPOINT SAFE 1Y LIMIT PIOCESS SAFE 1Y LIMIT (Analytical Value)
Sum of inaccuracies Switch gravity Switch calibration Switch actuation Transient Lag Plus additional available margin LIMITING SAFETY SYSTEM SEITING (Allowable Value)
Drift Installation Tolerance Additional Allowance SerPOINT (Trip Setpoint)
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