6.2 requirements for i&c function dependability i&c功能可靠性要求
6.2.1 general 概述
appropriate dependability is of prime importance so that the I&C does not jeopardise the safety and availability goals assigned to the power plant. Dependability encompasses availability and credibility, which are themselves broken down into two sub-items: 适当的可信赖性是最重要的，这样I&C就不会损害指定给电站的安全和可用性目标。可信赖性包括可用性和可信性，它们自身由可细分为两个子项：
? reliability and maintainability for the first one, and前者可分为可靠性和可维护性，
? integrity and safety for the second one.后者可分为完善性和安全性。
The definitions of ‘dependability’ and of its subsidiary items are those given in IEC 61069 – PART 5. IEC 61069 —— 第5部分提供了 “可依赖性”及其附属子项的定义。
Dependability assessment is carried out through the assessment of each sub-items. It is based on analyses of test or study results and also on evidence that specific requirements applicable to I&C design during the various phases of its lifecycle are met. Specific requirements are further developed in the following sections. 可依赖性评定是通过对所有子项的评定来进行的。它依据于对测试或研究结果的分析，还依据于能够证明在其生命周期的各个阶段适用于I&C设计的特定要求都得到满足的证据。上述特定要求会在以下章节中进一步得到阐述。
The Designer shall identify the requirements which can either directly or indirectly affect I&C dependability and shall develop them into detailed requirements applicable to the I&C architecture and system design. The whole I&C life cycle shall be considered. 设计师应确定对I&C可依赖性具有直接或间接影响的要求，并应将其扩展为适用于I&C结构与系统设计的详细要求。I&C的整个生命周期都应予以考虑。
In order to ensure that all the dependability requirements have been taken into account and implemented correctly, the Designer shall establish and implement a dependability programme. 为了确保所有的可依赖性要求都得到考虑和良好的执行，设计师应建立和实施可依赖性计划。
IEC 60300 can assist the Designer in establishing this programme and selecting the tasks relevant to I&C. This programme may be included in the quality assurance programme if the requirements are well identified. IEC 60300可协助设计师建立上述计划并选择与I&C相关的任务。若要求都能很好地得到确认，可以将该计划包括在质量保证计划中。
Beijing Chinese Subtitling Translation Service Agency has translated many technical documents about requirements for i&c function dependability.
华译网上海翻译公司曾经翻译过大量有关i&c功能可靠性要求资料文件。
6.2.2 Availability 可用性
6.2.2.1 Reliability 可靠性
The reliability of the I&C functions will result from the implementation of the deterministic design requirements and the intrinsic reliability that can be claimed for the I&C systems and equipment which perform these functions. I&C功能的可靠性来源于对确定性的设计要求的执行，以及履行这些功能的I&C系统和设备所所声称具有的固有可靠性。
The reliability that can be claimed for the I&C system and equipment may be based on the following approach: I&C系统和设备所声称具有的可靠性可依据以下方法：
? the contribution of hardware to the reliability of the function may be estimated in a quantitative way based, for instance, on the failure rate of the I&C components and a failure mode analysis;硬件在功能可靠性方面的作用可采用定量方式来评估，比如，可依据I&C构件的故障率以及故障模式分析。
? the software contribution, where appropriate, may be estimated on a qualitative way based on evaluation of the complexity of design, the quality of development and relevant experience feedback, etc.软件的作用可采用定性方式进行评估，依据对设计复杂性、开发质量及相关经验反馈的评定。
The reliability values eventually decided upon for the I&C functions and used in the PSA to assess the implementation of the Safety Functions shall be justified by a reliability assessment making use of reliability and availability data from relevant sources, analyzed in such a way that they can be verified.依据I&C功能最终确定的、用于PSA对安全功能执行进行评估的可靠性数值，应由采用出自相关来源的可靠性和可用性数据的可靠性评定来进行证明，并采用可进行核查的方式实施分析。
The Designer shall demonstrate that the anticipated probability of failure of safety I&C system and equipment to perform their design function (full processing, sensors included, actuators excluded) is less than related technical features of IAEA 50-SG-D3,D8. 设计师应证明安全I&C系统和设备执行其设计功能（满处理，包含传感器，不包含致动器）所预期发生故障的概率，小于IAEA 50-SG-D3,D8的相关技术指标。
Functions, which may influence plant operation, shall have an appropriate degree of reliability. 可能影响电站运行的功能，应具有适当的可靠性程度。
Due to availability concern the probability of failure of each of the functions of the safety-related/non-safety I&C systems and equipment should be less than related technical features of IAEA 50-SG-D3,D8. 出于可用性的考虑，安全相关/非安全I&C系统与设备的所有功能发生故障的概率应小于IAEA 50-SG-D3,D8的相关技术指标。
6.2.2.2 Maintainability 可维护性
Safe loading and consistency of software and parameters in the different processing units of the equipment shall be ensured. 应确保设备不同处理单元中的软件和参数的安全载荷与一致性。
Taking into account the considerable amount of data and parameters required to define the different processing, it is very important that the adequacy and the consistency of these data are assured.考虑到设定不同处理过程所需数据和参数的可观数量，确保这些数据的充分性和一致性是十分重要的。
The introduction of modifications to the application software shall be possible without disturbing the operating staff and without impairing the safety and the availability of the plant. 在不打扰操作人员和不妨害电站设备的安全性与可用性的前提下，应可以对应用软件做出修改。
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