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发表于 2008-12-5 23:11
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来自： 中国上海
最正宗的原文解释
Description of the Single Failure
(1) The single failure is a failure which is additionally postulated in the safety features in the case of initiation under consideration, irrespective of the initiating event, but which does not occur as a result of the case of initiation during specified normal operation or incidents and which is not known prior to the occurrence of the case of initiation. The single failure also includes the consequential failures resulting from the postulated single failure.
It is considered a single failure if a component1) of the safety features does not fulfill its function when required. An operationally possible operator error which results in a malfunction in the safety features has to be equated with a single failure.
In general, reasons for the postulated single failure need to be stated.
Scope of Application of the Single Failure Criterion
(2) In the following Safety Criteria for Nuclear Power Plants, the postulation of a single failure in the associated safety features is required at the design stage:
4.2: Residual Heat Removal during Specified Normal Operation
4.3: Residual Heat Removal after Loss of Coolant
6.1: Reactor Protection System
7.1: Emergency Power Supply
8.5: Heat Removal from the Containment.
A single failure shall also be postulated in the design of
- the safety features for the shutdown of the reactor,
- the safety features for the residual heat removal if the main heat sink is not available,
- active features of the containment.2)
As a matter of principle, single failure are postulated with respect to both active and passive components.
Purposes of the Single Failure Criterion
(3) The postulation of a single failure (single failure concept) is a deterministic concept for the design of the safety features in nuclear power plants. Like other procedures and measures, such as the probabilistic analysis (reliability analysis) and quality assurance, it serves as a safety precaution.
In the design of safety features, the postulation of the single failure serves to ensure that a sufficient degree of redundancy and avoidance of interlacing is provided (cf. Sec. (5)).
If a safety feature is designed in accordance with the single failure concept it can be assumed with a sufficient degree of certainty that its operability will not depend on
1) The term “component” is defined to include all parts of a functional unit as such, as well as all parts of the supply, actuating and auxiliary equipment necessary for its correct functioning in terms of safety, even if such equipment is undant.
rd2) The redundancy requirements for the isolations of pipe penetrations through the containment vessel have been laid down in Safety Criterion 8.4 as a conclusion derived from a single failure consideration.
the accidental failure of any single component.
The reliable function of the safety features specified in the Scope of Application must also be assured if a single failure occurs and, to the extent required in Sec. (7), maintenance work is carried out at the same time. Beyond this, an additional single failure need not be postulated to tighten the boundary conditions in the incident analysis if it is demonstrated that the incident planning limits in Sec. 28, para. (3) of the Radiological Protection Ordinance3) are not exceeded. |
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