Figure - available via license: Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Content may be subject to copyright.
Source publication
In this paper a probabilistic Leak-Before-Break analysis for WWER-1000 unit was performed based on the Failure Assessment Diagram (FAD), treating strength and crack morphology parameters as stochastic values. In order to perform probabilistic calculations Critical temperature of brittleness and Yield (Ultimate) Stress, were fitted by normal distrib...
Contexts in source publication
Context 1
... for LBB concept Henry-Fauske flow model is used with modified parameters accounting for crack morphology Rundlan et al. (2002). A flow model is an important part of analysis, since different crack types have a great differences in friction (µL, µG), bend and protrusion (nL), flow length (KG, KGL) parameters (see Table 3). Influence of half crack length on COA and pressure loss parameters is shown in Fig. 4. From Fig. 4(right) we can see that pressure loss due to bends and protrusions has the most significant impact, thus a special attention should be paid on IGSCC crack types (see Table 3). ...Context 2
... flow model is an important part of analysis, since different crack types have a great differences in friction (µL, µG), bend and protrusion (nL), flow length (KG, KGL) parameters (see Table 3). Influence of half crack length on COA and pressure loss parameters is shown in Fig. 4. From Fig. 4(right) we can see that pressure loss due to bends and protrusions has the most significant impact, thus a special attention should be paid on IGSCC crack types (see Table 3). ...Context 3
... using Eq. (4), COA as well as COD were calculated, followed by leak rate estimations, according to modified Henry-Fauske model for different crack types (see Table 3.). Some results of these calculations are presented in Fig. 5-7. ...Context 4
... we can see from Fig. 5, accounting for crack morphology strongly affects the results scatter, and it is more significant then mechanical properties scatter (see Fig. 6 and Fig. 7). Among the crack morphology characteristics nL(number of bends and protrusions per mm of flow length) is the most significant parameter, that's why IGSCC crack type (see Table 3) is the most representative in failure analysis. It can be seen from Fig 6 that Fracture toughness has bigger influence rather than Ultimate (Yield) strength, which corresponds to Stefanini & Bloom (2018) results. ...Similar publications
This paper gives the results of the safety analysis of the nuclear power plant structures in Slovakia in case of the extreme climatic loads. The linear and nonlinear analysis of NPP structures with the reactor VVER 440/213 in the case of the extreme external even is presented. On the base of the meteorological monitoring of the locality the extreme...
Citations
... In Figure 8, the ultimate yield strength has less influence when compared with fracture toughness, which is in line with Dubyk's results. 78 This failure probability can be considered the acquisition of critical cracks in piping, and the leak rate would be undetectable. The outcomes of the analysis can be seen in Table 4. ...
... The critical crack length is aligned with a typical normal distribution; however, the Weibull distribution is more suitable for leak rates. 78 A leakage rate model should be developed in future work, as the Henry-Fauske model has a drawback for two-phase physics, since leakage rate characteristics should be treated precisely for nuclear safety. ...
... Probabilistic analysis of fracture toughness (KIC) sul space for intergranular SCC cracks.78 ...
The effective operation of water management systems is contingent upon leak localization and detection – a common problem that is more acute in large networks. This paper reviews the salient literature in this context and demonstrates the effectiveness of leakage location methods (LLMs) and leakage detection methods (LDMs). Although there is a significant amount of literature that discusses leakage localization and detection technologies, an academic lacuna still exists concerning the linkage between degradation mechanisms and LDMs and do not cover or connect past efforts from the start of a degradation mechanism that leads to changes in the mechanical strength (such as a reduction in fracture toughness) of pipes and results in crack propagation and leakage. This review focuses on these issues in the context of degradation mechanisms and common detection methods.
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.
