Document: NUREG-0800
Document ID: 1da20040-18d5-4c75-9863-5f578a9d73a5
Document Type: srp
Title: Revision 5 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550078.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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Content:
ion intervals for each instrument type. • Instrument loop diagrams showing all hardware elements of the instrument loop(s). • Instrument and tubing layout drawings and installation details showing locations and elevations of instruments and tubing relative to a reference datum, as well as the points where the instrument interfaces with the monitored process. • For digital instrumentation, the configuration database for the instrumentation functions, and identification of digital elements (hardware and software) where error could be introduced into the measurement-for example, errors that could result from analog-to-digital or digital-to-analog conversion or from numerical methods used in the software (e.g., curve fitting). The description of assumptions in accordance with ISA-S67.04-1994, Part I, should include the environmental allowances (temperature, pressure, humidity, radiation, vibration, seismic, and electrical) for the instruments. Analysis Supporting Establishment of Setpoints and Instrumentation Tolerances The applicant/licensee should document the bases and the calculations of measurement uncertainties. The methods by which setpoints are calculated should conform to the guidance of Regulatory Guide 1.105, Revision 3. Statistical Guidelines for Instrument Uncertainty In the review of uncertainties in determining a trip setpoint and its allowable values, the NRC staff typically uses 95/95 tolerance limits as an acceptable criterion, i.e., a 95 percent probability that the constructed limits contain 95 percent of the population of interest for the surveillance interval selected. BTP 7-12-7 Revision 5 - March 2007 Guidelines for Graded Approach ISA-S67.04-1994, Part I, Section 4 states that the safety significance of various types of setpoints important to safety may differ, and thus a less rigorous setpoint determination method for certain functional units and limiting conditions of operation may be applied. The use of a graded approach allows a less