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1、BRITISH STANDARD BS IEC 61226:2005 Incorporating corrigendum no. 1 Nuclear power plants Instrumentation and control systems important to safety Classification of instrumentation and control functions ICS 27.120.20 ? Licensed Copy: London South Bank University, London South Bank University, Fri Nov 1
2、6 07:32:29 GMT+00:00 2007, Uncontrolled Copy, (c) BSI BS IEC 61226:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 August 2007 BSI 2007 ISBN 978 0 580 60524 6 National foreword This British Standard is the UK implementation of IEC 612
3、26:2005. The UK participation in its preparation was entrusted to Technical Committee NCE/8, Reactor instrumentation. A list of organizations represented on this committee can be obtained on request to its secretary. In the opinion of the UK committee, specific clauses of IEC 61226 Edition 2.0 imply
4、 requirements that are contrary to the custom, practice, and regulatory expectations as set down by the United Kingdom Health and Safety Executives Nuclear Installations Inspectorate and the understanding in the United Kingdom of the IAEA safety guides. Users of this standard are therefore advised t
5、hat, in the United Kingdom, this standard should be read in conjunction with the attached National annex NA (informative) that explains how the requirements of this standard could be used for plant that is subject to regulatory licensing. The specific parts of this standard that are the subject of t
6、he National annex NA are: clause 5.3 (description of categories) and clause 5.4 (assignment criteria); clause 7.4.1 (basic equipment requirements), and Annex A (examples of categories). This publication does not purport to include all the necessary provisions of a contract. Users are responsible for
7、 its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments issued since publication Amd. No. DateComments 17452 Corrigendum No. 1 30 November 2007 Correction to national foreword Licensed Copy: London South Bank University, London South Ban
8、k University, Fri Nov 16 07:32:29 GMT+00:00 2007, Uncontrolled Copy, (c) BSI blank Licensed Copy: London South Bank University, London South Bank University, Fri Nov 16 07:32:29 GMT+00:00 2007, Uncontrolled Copy, (c) BSI BS IEC 61226:2005 BSI 389 Chiswick High Road London W4 4AL BSI British Standard
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19、assign specification and design requirements to I b) the consequences of failure to perform the function; c) the probability that it (the I d) the time following a PIE at which, or the period throughout which it (the I the time for which alternative actions can be taken; the timeliness by which hidd
20、en faults can be detected and remedied. This standard extends the classification strategy presented in IAEA Safety Guide NS-G-1.3, and establishes the criteria and methods to be used to assign the I b) functions, the failure or spurious actuation of which would lead to unacceptable consequences, and
21、 for which no other category A mitigation function exists; 13 BS IEC 61226:2005 Licensed Copy: London South Bank University, London South Bank University, Fri Nov 16 07:32:29 GMT+00:00 2007, Uncontrolled Copy, (c) BSI c) functions required to provide information and control capabilities that allow s
22、pecified manual actions necessary to reach the controlled state. 5.4.2 Category B An I b) functions required to provide information or control capabilities that allow specified manual actions necessary after the controlled state has been reached to prevent a DBE from leading to unacceptable conseque
23、nces, or mitigate the consequences; c) functions, the failure of which during normal operation, would require the operation of a category A function to prevent an accident whose study is required; d) functions to reduce considerably the frequency of a DBE as claimed in the safety analysis; e) plant
24、process control functions operating so that main process variables are maintained within the limits assumed in the safety analysis and whose failure could lead directly to operation of a category A function. 5.4.3 Category C An I b) functions used to prevent or mitigate a minor radioactive release,
25、or minor degradation of fuel, within the NPP design basis; c) functions which alert control room staff to failures in, or monitor continuously the availability of, systems that perform category A or B functions; d) functions necessary to reach the safety probabilistic goals including those to reduce
26、 the expected frequency of a DBE; e) functions to reduce the demands on a category A function, as claimed in the safety analysis; f) functions which perform tests to ensure the reliability of systems, which perform category A and B functions and recording the status of these systems (fit for operati
27、on, operating, failed or inoperative), especially those whose malfunction could cause a PIE; g) functions to monitor and take mitigating action following internal hazards within the NPP design basis (e.g. fire, flood); h) functions to warn personnel or to ensure personnel safety during or following
28、events that involve or result in release of radioactivity in the NPP, or risk of radiation exposure; i) functions to monitor and take mitigating action following natural events (e.g. seismic disturbance, extreme wind); 14 BS IEC 61226:2005 Licensed Copy: London South Bank University, London South Ba
29、nk University, Fri Nov 16 07:32:29 GMT+00:00 2007, Uncontrolled Copy, (c) BSI j) functions provided for the benefit of accident management strategy to reach and maintain safe state for beyond design accidents; k) functions provided to minimise the consequences of severe accidents; l) functions which
30、 provide access control for the NPP. 6 Classification procedure An outline of the procedure is shown in Figure 1. 6.1 Identification of design basis A main input to the classification process of functions is the nature of the NPP and the reactor type (e.g. PWR (pressurized water reactor), BWR (boili
31、ng water reactor) or other reactor type), the associated PIEs, and the major design criteria on redundancy of mechanical and electrical systems and equipment. Another main input is the identification of the major mitigation functions, and their supporting functions, for each PIE. The assessment of t
32、he frequency and consequences of PIEs leads to the identification of DBEs representing the design base of the plant. When considering the design features of the plant the specified ranges of operational states and accident conditions and the defined radiological limits have to be reflected. Individu
33、al safety principles that together make up an “integrated overall safety approach” ensure the safety of an NPP. These principles are used in the design by considering the identified DBEs and successive physical barriers to keep radioactive exposure within permitted limits. The DBEs and the major des
34、ign criteria (redundancy, separation, etc) of the plant as well as the identification of the prevention and mitigation functions, and their supporting functions are the main input to the classification process. The importance to safety of each I the role of the function in preventing or mitigating p
35、ostulated initiating events; the role of the function during all operating modes (e.g. start-up, normal operation, refuelling, etc); the role of the function following PIEs such as natural events (e.g. seismic disturbance, flood, extreme wind, lightning) and internal hazards (e.g. fire, internal flo
36、od, missiles, radioactive release from adjacent unit or chemical releases from other plants or industries); the consequences of failure of the I 15 BS IEC 61226:2005 Licensed Copy: London South Bank University, London South Bank University, Fri Nov 16 07:32:29 GMT+00:00 2007, Uncontrolled Copy, (c)
37、BSI the effects of spurious actuation of the I the probability that it will be required to perform a function important to safety; the time following a DBE at which, or during which it will be required to operate; the maintenance, repair and testing strategy. It will not be possible to identify in d
38、etail all the functions at an early stage in the design process, as the characteristics of the NPP will not then have been defined fully. The process of identification and classification of the functions must therefore continue iteratively throughout the design phase. Where an initial assignment of
39、a function to a category is uncertain, then an explanatory note should be added to the categorisation. Since individual functions may be involved in the implementation of several aspects of the requirements specification, such functions may be assigned to several categories. In that case, the highes
40、t category assigned shall be applied. As the redundancy, diversity and other technical requirements of the functions are determined more exactly, for example after the safety analysis progresses and the operating procedures are developed, the classification list shall be refined and revised, to deri
41、ve a final list. This list shall be documented and maintained under configuration control since it will be required by plant/I plant operating modes; list of PIEs and their likely frequency of occurrence; list of preventing and mitigating functions. 2. Initial list of functions including functional
42、requirements 3. Assignment of category A, B, C or non-classified 4. Development of detailed systems requirements 5. Identification of detailed I requirements that apply to the design of I requirements concerning the equipment features for the assurance of seismic and environmental durability and ele
43、ctro-magnetic compatibility; requirements that are associated with the quality assurance, verification and maintenance which apply to functions, systems and equipment. In most cases, these requirements are already detailed in appropriate codes and standards. The codes, guides and standards listed in
44、 Clause 2 of this standard are normative references and therefore provide the explicit requirements related to the I b) isolation of containment; c) provision of information for essential operator action. A.1.2 Typical I b) safety actuation system and safety system support features; c) key instrumen
45、tation and displays to permit pre-planned operator actions that are defined in the NPP operating instructions, and that are required to ensure NPP safety in the short term. A.2 Category B A.2.1 Typical functions The I b) main cooling system isolation; c) post accident monitoring system; d) automatic
46、 control of the NPP primary and secondary circuit conditions, keeping variables in the limits assumed in the safety analysis, and prevention of events from escalating to accidents; e) monitoring/controlling the handling of fuel where failure could cause a minor radioactive release. A.2.2 Typical I b
47、) part of the decay heat transport to ultimate heat sink not necessary in the short term; c) safety circuits and interlocks of fuel handling systems used when the reactor is shut down; d) instrumentation needed to apply operating procedures for DBE. 27 BS IEC 61226:2005 Licensed Copy: London South B
48、ank University, London South Bank University, Fri Nov 16 07:32:29 GMT+00:00 2007, Uncontrolled Copy, (c) BSI A.3 Category C A.3.1 Typical functions The I b) limiting the consequences of internal hazards; c) those for which operating mistakes could cause minor radioactive releases, or lead to radioac
49、tive hazard to the NPP operating staff; d) those necessary to warn of internal or external hazard (fire, flood, explosions, seismic events, etc.); e) access control systems. Communication systems to warn of significant on- or off-site releases for the purposes of implementing the NPPs emergency plan. A.3.2 Typical I b) radwaste stream monitoring and interlocks, area radiation mo