Interest in evaluation of reactor response and off-site consequences following beyond design basis accidents has significantly increased after Fukushima. MELCOR is an advanced computational aid that has been widely us...
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A parallel triangular tube bundle with a single flexible tube is taken as the object, and the most dangerous mechanism of flow induced vibration in the tube bundle structure, fluidelastic instability (FEI) is studied ...
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DS evidence theory is a widely used uncertainty inference algorithm for decision fusion that can fuse this complementary and redundant information to reduce the uncertainty of the system. Evidence conflict is the most...
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Based on the full reference to the existing engineering practice and safety review experience, and considering the actual design characteristics of the small modular reactor ACP100, a set of source term analysis metho...
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MAAP5 is capable of simulating the whole response of a PWR nuclear power plant under severe accident conditions. An analysis of the severe accident scenarios in a PWR by MAAP5 were carried out. It was assumed that the...
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reactorsystem modeling is the premise of reactor control systemdesign. The common commercial thermal and hydraulic analysis programs like RELAP5, RETRAN have complex structure and slow operational speed, which are n...
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system Availability, Rejection rate and Malfunction rate are vital technical indicators for safety class DCS when evaluating the reliability of the control system to meet technical requirements. This trend has attract...
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Compared to knowledge-based diagnostic systems, data-based methods tend to perform better in terms of speed and accuracy in diagnosing reactor accidents, and have significant advantages in terms of scalability of mode...
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ISBN:
(纸本)9789811987793
Compared to knowledge-based diagnostic systems, data-based methods tend to perform better in terms of speed and accuracy in diagnosing reactor accidents, and have significant advantages in terms of scalability of models. With the increasing use of high-precision system analysis programs in nuclear engineering, the number of high-fidelity computational data for accident simulation is exploding. Therefore, an algorithm that can achieve both automatic extraction of low-dimensional features from the data and guarantee the validity of the features is needed to improve the performance and confidence of the accident diagnosis system. This study proposes an autoencoder-based autonomous learning framework, namely Padded Auto-Encoder (PAE), which is able to automatically encode accident monitoring data that has been noise-added and with partially missing data into low-dimensional feature vectors via a Vision Transformer-based encoder, and to decode the feature vectors into noise-free and complete reconstructed monitoring data. Thus, the encoder part of the framework is able to automatically infer valid representations from partially missing and noisy monitoring data that reflect the complete and noise-free original data, and the representation vectors can be used for downstream tasks for accident diagnosis or else. In this paper, LOCA of HPR1000 was used as the study object, and the PAE was trained by an unsupervised method using cases with different break locations and sizes as the dataset. The encoder part of the pre-trained PAE was subsequently used as the feature extractor for the monitoring data, and several basic statistical learning algorithms for predicting the break locations and sizes. The results of the study show that the pre-trained diagnostic model with two stages has a better performance in break location and size diagnostic capability with an improvement of 41.62% and 80.86% in the metrics respectively, compared to the diagnostic model with end-to-end model st
Hydrogen security is an important problem of the severe accident analysis in NPP, and the security of hydrogen detonation is more important. The hydrogen risk mainly focused on the risk of flame acceleration (FA) and ...
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During the course of a hypothetical severe accident in a light water reactor, spray systems could be used in the containment in order to prevent overpressure in case of a steam line break and to enhance the gas mixing...
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ISBN:
(纸本)9784890471676
During the course of a hypothetical severe accident in a light water reactor, spray systems could be used in the containment in order to prevent overpressure in case of a steam line break and to enhance the gas mixing in case of the presence of hydrogen. Thus these two effects induced by spray might compete with each other having an influence on the hydrogen risk. Focusing on the dynamic effect of spray, the impact of spray on the breakup of a light gas layer in a closed vessel is simulated and the experimental test evaluated here is TOSQAN 113 test that belongs to the dynamic part of SARNET FP6 benchmarks. ANSYS FLUENT 14.5 is chosen for the simulation tool and spray droplets are tracked with using the Euler-Lagrange approach-Discrete Phase Model (DPM). The code validation and several sensitivity studies are done to sum up the basic method of numerical simulation of spray with CFD code and assess the influence of calculation settings and parameters, such as turbulence model and spray boundary condition. The code validation shows that the results of calculations acceptably agree with the experimental data and the sensitivity studies reveal that spray boundary condition is a rather important factor for the accuracy of simulation. Conclusion gained in from the present work can provide some reference of the numerical analysis of containment.
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