1、 RECOMMENDED PRACTICE ISARP67.04.022010 Methodologies for the Determination of Setpoints for Nuclear Safety-Related Instrumentation Approved 10 December 2010 ISARP67.04.022010 2 Copyright 2010 ISA. All rights reserved. ISARP67.04.022010 Methodologies for the Determination of Setpoints for Nuclear Sa
2、fety-Related Instrumentation ISBN: 978-1-936007-74-5 Copyright 2010 by ISA The International Society of Automation. All rights reserved. Not for resale. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or
3、 by any means (electronic mechanical, photocopying, recording, or otherwise), without the prior written permission of the Publisher. ISA 67 Alexander Drive P.O. Box 12277 Research Triangle Park, North Carolina 27709 3 ISARP67.04.022010 Copyright 2010 ISA. All rights reserved. Preface This preface, a
4、s well as all footnotes and annexes, is included for informational purposes and is not part of ISARP67.04.022010. This recommended practice has been prepared as part of the service of ISA, The International Society of Automation, toward a goal of uniformity in the field of instrumentation. To be of
5、real value, this document should not be static but should be subject to periodic review. Toward this end, the Society welcomes all comments and criticisms and asks that they be addressed to the Secretary, Standards and Practices Board; ISA; 67 Alexander Drive; P. O. Box 12277; Research Triangle Park
6、, NC 27709; Telephone (919) 549-8411; Fax (919) 549-8288; E-mail: standardsisa.org. The ISA Standards and Practices Department is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrume
7、ntation standards, recommended practices, and technical reports. However, since this recommended practice does not provide constants or dimensional values for use in the manufacture or installation of equipment, English units are used in the examples provided. It is the policy of ISA to encourage an
8、d welcome the participation of all concerned individuals and interests in the development of ISA standards, recommended practices, and technical reports. Participation in the ISA standards-making process by an individual in no way constitutes endorsement by the employer of that individual, of ISA, o
9、r of any of the standards, recommended practices, and technical reports that ISA develops. CAUTION ISA DOES NOT TAKE ANY POSITION WITH RESPECT TO THE EXISTENCE OR VALIDITY OF ANY PATENT RIGHTS ASSERTED IN CONNECTION WITH THIS DOCUMENT, AND ISA DISCLAIMS LIABILITY FOR THE INFRINGEMENT OF ANY PATENT R
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15、IBLE APPLICATIONS OR ADDRESS ALL POSSIBLE SAFETY ISSUES ASSOCIATED WITH USE IN HAZARDOUS CONDITIONS. THE USER OF THIS DOCUMENT MUST EXERCISE SOUND ISARP67.04.022010 4 Copyright 2010 ISA. All rights reserved. PROFESSIONAL JUDGMENT CONCERNING ITS USE AND APPLICABILITY UNDER THE USERS PARTICULAR CIRCUM
16、STANCES. THE USER MUST ALSO CONSIDER THE APPLICABILITY OF ANY GOVERNMENTAL REGULATORY LIMITATIONS AND ESTABLISHED SAFETY AND HEALTH PRACTICES BEFORE IMPLEMENTING THIS DOCUMENT. THE USER OF THIS DOCUMENT SHOULD BE AWARE THAT THIS DOCUMENT MAY BE IMPACTED BY ELECTRONIC SECURITY ISSUES. THE COMMITTEE H
17、AS NOT YET ADDRESSED THE POTENTIAL ISSUES IN THIS VERSION. 5 ISARP67.04.022010 Copyright 2010 ISA. All rights reserved. The following people served as members of ISA Subcommittee ISA67.04, which approved the 2010 recommended practice: NAME COMPANY Jerry D. Voss, Chair Isys Consulting Co. Carl Sossma
18、n, Vice Chair CLS Tech-Reg Consultants Robert C. Webb, Managing Director ICS Secure LLC Reed Wiegle, Managing Director Stone however, the design control and documentation requirements of manual calculations or computer software are outside the scope of the recommended practice. This recommended prac
19、tice is intended for use primarily by the owners/operating companies of nuclear power plant facilities or their agents (NSSS suppliers, architects, engineers, etc.) in establishing setpoint methodology programs and preparing safety-related instrument setpoint calculations. This recommended practice
20、utilizes statistical nomenclature that is customary and familiar to personnel responsible for nuclear power plant setpoint calculations and instrument channel uncertainty evaluations. It should be noted that this nomenclature may have different definitions in other statistical applications and is no
21、t universal, nor is it intended to be. Furthermore, in keeping with the conservative philosophy employed in power plant calculations, the combination of uncertainty methodology for both dependent and independent uncertainty components is intended to be bounding. That is, the resultant uncertainty sh
22、ould be correct or overly conservative to ensure safe operation. In cases where precise estimation of measurement uncertainty is required, more sophisticated techniques should be employed. ISA Standard Committee ISA67.04 operates as a Subcommittee under ISA67, the ISA Nuclear Power Plant Standards C
23、ommittee, with Robert Queenan as Chairman.ISARP67.04.022010 14 Copyright 2010 ISA. All rights reserved. This page intentionally left blank. 15 ISARP67.04.022010 Copyright 2010 ISA. All rights reserved. 1 Scope This recommended practice provides guidance for the implementation of ANSI/ISA-67.04.01-20
24、06 in the following areas: a) Methodologies, including sample equations to calculate total channel uncertainty; b) Common assumptions and practices in instrument uncertainty calculations; c) Equations for estimating uncertainties for commonly used analog and digital modules; d) Methods to determine
25、the impact of commonly encountered effects on instrument uncertainty; e) Application of instrument channel uncertainty in setpoint determination; f) Sources and interpretation of data for uncertainty calculations; g) Discussion of the interface between setpoint determination and plant operating proc
26、edures, calibration procedures, and accident analysis; h) Documentation requirements. 2 Purpose The purpose of this recommended practice is to present guidelines and examples of methods for the implementation of ANSI/ISA-67.04.01-2006 in order to facilitate the performance of instrument uncertainty
27、calculations and setpoint determination for safety-related instrument setpoints in nuclear power plants. 3 Definitions 3.1 analytical limit (AL): limit of a measured or calculated variable established by the safety analysis to ensure that a safety limit is not exceeded. 3.2 abnormally distributed un
28、certainty: a term used in this recommended practice to denote uncertainties that do not have a normal distribution. See 6.2.1.2.2 for further information. 3.3 as-found value: the condition in which a channel, or portion of a channel, is found after a period of operation and before recalibration (if
29、necessary). 3.4 as-left value: the condition in which a channel, or portion of a channel, is left after calibration or final setpoint device setpoint verification. 3.5 bias: an uncertainty component that consistently has the same arithmetic sign and is expressed as an estimated limit of error. ISARP
30、67.04.022010 16 Copyright 2010 ISA. All rights reserved. 3.6 dependent uncertainty: uncertainty components are dependent on each other if they possess a significant correlation, for whatever cause, known or unknown. Typically, dependencies form when effects share a common cause. 3.7 design basis: th
31、e design basis for protection systems is as defined in Part 4, Safety System Design Basis, of IEEE Standard 603-1998. (See IEEE Std. 603.) 3.8 drift: a variation in sensor or instrument channel output that may occur between calibrations that cannot be related to changes in the process variable or en
32、vironmental conditions. (ANSI/ISA-67.04.01-2006) 3.9 effect: a change in output produced by some outside phenomena, such as elevated temperature, pressure, humidity, or radiation. 3.10 error: the arithmetic difference between the indication or measured value and the ideal value of the measured signa
33、l. 3.11 final setpoint device: a component or assembly of components, that provides input to the process voting logic for actuated equipment. NOTE Examples of final setpoint devices are bistables, relays, pressure switches, and level switches. 3.12 independent uncertainty: uncertainty components are
34、 independent of each other if their magnitudes or arithmetic signs are not significantly correlated. 3.13 instrument channel: an arrangement of components and modules as required to generate a single protective action signal when required by a plant condition. A channel loses its identity where sing
35、le protective action signals are combined. (See IEEE Standard 603.) 3.14 instrument span: the region between the limits within which a quantity is measured, received, or transmitted, expressed by stating the lower- and upper-range values. 3.15 limiting safety system setting (LSSS): limiting safety s
36、ystem settings for nuclear reactors are settings for automatic protective devices related to those variables having significant safety functions. Where a limiting safety system setting is specified for a variable on which a safety limit has been placed, the setting must be so chosen that automatic p
37、rotective action will correct the abnormal situation before a safety limit is exceeded. (See Title 10 Part 50 Paragraphs 50.36c1iA and 50.36c1iiA). 3.16 margin: in setpoint determination, an allowance added to the instrument channel uncertainty. Margin moves the setpoint farther away from the analyt
38、ical limit. 17 ISARP67.04.022010 Copyright 2010 ISA. All rights reserved. 3.17 module: any assembly of interconnected components that constitutes an identifiable device, instrument, or piece of equipment. A module can be removed as a unit and replaced with a spare. It has definable performance chara
39、cteristics that permit it to be tested as a unit. A module can be a card, a drawout circuit breaker, or other subassembly of a larger device, provided it meets the requirements of this definition. (See IEEE Standard 603.)3.18 nuclear safety-related instrumentation: that which is essential to provide
40、 emergency reactor shutdown; provide containment isolation; provide reactor core cooling; provide for containment or reactor heat removal; prevent or mitigate a significant release of radioactive material to the environment; or is otherwise essential to provide reasonable assurance that a nuclear po
41、wer plant or nuclear reactor facility can be operated without undue risk to the health and safety of the public. 3.19 performance test: a test that evaluates the performance of equipment against predefined acceptance criteria. 3.20 primary element: the system element that quantitatively converts the
42、 measured variable energy into a form suitable for measurement (e.g., Venturi, orifice plate). 3.21 process measurement instrumentation: an instrument, or group of instruments, that converts a physical process parameter, such as temperature, pressure, etc., to a usable, measurable parameter, such as
43、 current, voltage, etc. 3.22 random:1describing a variable whose value at a particular future instant cannot be predicted exactly but can only be estimated by a probability distribution function. (See ANSI C85.1.) 3.23 reference accuracy (also known as “accuracy rating“ as defined in ISA-51.1): a nu
44、mber or quantity that defines a limit that errors will not exceed when a device is used under specified operating conditions. 3.24 safety limit: a limit on an important process variable that is necessary to reasonably protect the integrity of physical barriers that guard against uncontrolled release
45、 of radioactivity. (See 10 CFR 50.36 c1iA.) _ 1In the context of this document, “random“ is an abbreviation for “random, independent, and approximately normally distributed.” The arithmetic sign of a random uncertainty is equally likely to be positive or negative with respect to some median value. T
46、hus, random uncertainties are eligible for the square-root-sum-of-squares combination propagated from the process measurement module through the signal conditioning module of the instrument channel to the module that initiates the actuation. ISARP67.04.022010 18 Copyright 2010 ISA. All rights reserv
47、ed. 3.25 sensor: the portion of an instrument channel that responds to changes in a process variable and converts the measured process variable into an instrument signal; e.g., electric or pneumatic. (See IEEE Standard 603.) 3.26 setpoint: a predetermined process value for actuation of a final trip
48、device, control device or indicated action point. Typically associated with trip bistables; reactor vessel pressure control; verification of technical specifications minimum condensate water storage tank level; and operator actions associated with emergency response procedure setpoint. 3.27 signal c
49、onditioning: one or more modules that perform signal conversion, buffering, isolation, or mathematical operations on the signal as needed. 3.28 signal interface: the physical means (cable, connectors, etc.) by which the process signal is propagated from the process measurement module through the signal conditioning module of the instrument channel to the module that initiates the actuation. 3.29 test interval: the elapsed time between the initiation (or successful completion) of
