Method for calculating probability of failure to operate on command of reactor protection system

Abstract

The invention belongs to the technical field of probabilistic safety analysis of nuclear power safety level control and instrumentation systems, and particularly relates to a method for calculating the probability of failure to operate on command of a reactor protection system. The method comprises the steps that the probability of failure to operate on command of a channel caused by non-diagnosedand non-common cause failures of the channel is analyzed; the probability of failure to operate on command caused by the non-diagnosed and non-common cause failures which simultaneously occur in three channels or four channels among four channels is calculated under the situation that periodic tests are alternately conducted on each channel of the reactor protection system; the probability of failure to operate on command caused by diagnosable and non-common cause failures of the channel is calculated through failure repair rates; the probability of failure to operate on command caused by thediagnosable and non-common cause failures which simultaneously occur in three channels or four channels is calculated; the probability of failure to operate on command caused by the non-diagnosed andcommon cause failures and the probability of failure to operate on command caused by the diagnosable and common cause failures of the occurrence of failure to operate of the channel are calculated byanalyzing non-diagnosed and non-common cause failure factors and diagnosable and non-common cause failure factors; the probability of failure to operate on command of each part are added to obtain the probability of failure to operate on command of the reactor protection system. The method improves calculation efficiency.

Description

technical field [0001] The invention belongs to the technical field of probabilistic safety analysis of nuclear power safety-level instrumentation and control systems, and in particular relates to a calculation method for the probability of refusal of a reactor protection system. Background technique [0002] The probability of refusal refers to the probability that the safety-level I&C system refuses to execute the safety function due to its own random failure when the on-site working conditions are abnormal and the protection system needs to be activated. The system refuses to move. The function of the reactor protection system is mainly to protect the integrity of the three major nuclear safety barriers, namely the fuel cladding, the primary circuit pressure boundary and the containment vessel. When the protection system refuses to operate, it will not be able to initiate an emergency shutdown, which may lead to serious accidents such as core damage and release of radioa...

AI Technical Summary

Problems solved by technology

[0004] (1) When considering the rejection caused by non-diagnosable faults, due to the limitation of the model, it is assumed that each of the four channels conducts periodic tests at the same time. However, in actual engineering applications, the four channels of the reactor protection system are alternately carried out periodic tests. The periodic test of one channel is carried out every T / 4, and the failure probability of the system in the case of alternating regular test time of each channel is lower than that of the system when each channel is periodically tested at the same time. Therefore, it is assumed that the model of 4 channels carrying out periodic tests at the same time is not accurate. cannot be guaranteed

[0005] (2) In the models of reliability block diagram and fault tree, there is a lack of consideration of common cause failure, which accounts for a relatively large proportion of the contribution of the system rejection probability, so the calculation results are not considered. accuracy cannot be guaranteed

[0006] (3) In addition, the calculation methods and modeling processes of the above-mentioned companies are relatively complicated, the calculation efficiency is low, and the engineering applicability is not strong

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