The probability of the existence of defects that lead to the destruction of the pressure vessel without leak

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Abstract


Relevance. To ensure the safety of a nuclear power plant on the basis of the requirements of norms and rules in the field of the use of atomic energy for pipelines of the primary circuit of a nuclear reactor, the design should apply the leak before break concept. The main idea of the concept is to prevent a sudden rupture of the pipelines of the reactor coolant loop, and consists in substantiating the fact that the rupture is preceded by the formation of a stable through crack, which is detected by the provided leak control means. When substantiating the concept, it is assumed that “break without leak” is an impossible event. This article provides a method for determining the probability of a failure event without a leak. Purpose - estimate the probability of the existence of a defect that can lead to the destruction of the vessel or pressure pipeline without leakage, as well as the probability of failure without leakage for a known number of loading cycles. Methods. To systematize the data obtained by different methods of non-destructive testing, conservative assumptions were used to determine the area of detected defects. On the basis of the obtained defect sizes, the defect size regions were determined, which can determine the scenarios of crack growth. Using the methods of mathematical statistics, the probability of the existence of a defect, which can lead to failure without leakage, was determined. Based on the methods of the theory of reliability, a comparison of the obtained probability of destruction with the admissible value is carried out. Results. A method for processing non-destructive testing data based on an assessment of the area of detected defects has been developed to systematize the data obtained by different non-destructive testing methods. The criterion for the development of cracks according to the scheme “leak before destruction” is determined. A method has been developed for determining the probability of a defect that can lead to failure without leakage. An example of calculation based on feed water pipelines is considered.


About the authors

Dmitry A. Kuzmin

All-Russian Research Institute for Nuclear Power Plants Operation

Author for correspondence.
Email: rodionova_m@bk.ru
SPIN-code: 3207-3489
25 Ferganskaya St, Moscow, 109507, Russian Federation

Head of Strength Reliability Division of NPP, Ph.D.

Marina V. Vertashenok

All-Russian Research Institute for Nuclear Power Plants Operation

Email: rodionova_m@bk.ru
SPIN-code: 4576-0036
25 Ferganskaya St, Moscow, 109507, Russian Federation

chief specialist of Strength Reliability Division of NPP

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