Results 1 - 10 of 361
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[en] Transients resulting from the accidental withdrawal of a control rod pair from the Fort St. Vrain reactor core from 100% power conditions have been analyzed with the ORTAP nuclear steam supply system simulation. This analysis was done as part of an ongoing effort to obtain an independent assessment of the HTGR system response to several postulated accidents. Results are presented and discussed
[en] A simple prescription to account for spatial feedback weighting effects in RDA (rod drop accident) point-kinetics analyses has been derived and tested. The point-kinetics feedback model is linear in the core peaking factor, F/sub Q/, and in the core average void fraction and fuel temperature. Comparison with detailed spatial kinetics analyses indicates that the improved point-kinetics model provides an accurate description of the BWR RDA
[en] The techniques and models used in the analysis of the control rod drop accident (CRDA) in a BWR have ranged from approximate conservative methods with a simple feedback model to detailed representations of the thermal-hydraulic and neutronic mechanisms. In a recent paper Cheng and Diamond presented a detailed evaluation of the CRDA and the effects of varying a number of important accident parameters. Their calculations performed with the BNL-TWIGL core dynamics code, have shown that the effect of inlet subcooling and rod drop speed play an important role in determining the severity of the rod drop accident. The purpose of the work summarized in this paper has been to determine in detail the dependence of the rod drop accident parameters on the (1) inlet subcooling; and (2) rod drop speed
[en] An account of the 1952 NRX accident is taken from the official report by W.B. Lewis and a 1955 paper by G.W. Hatfield. The accident was caused by a combination of human error and sticking shut-off rods. Some fuel melted, and about 4·108 MBq of fission products were released into water which was contained in the basement. With the exception of the aluminum calandria and one steel shield, all the equipment was reused after being decontaminated when the reactor was rebuilt. This accident is the most serious in the history of the Canadian nuclear program
[en] The 9m free drop accident presented in 10CFR 71 is considered as the most critical scenario of hypothetical accident conditions during transport. In this paper, the 9m free drop for OASIS-32D using the LS-DYNA program was evaluated. The results of the analyses confirm that the structural integrity of OASIS-32D is maintained. The 9m free drop analyses of OASIS-32D were carried out for typical conditions. The results of the analyses show that the structural integrity of OASIS- 32D is maintained for the 9 m free drop analyses of horizontal and vertical drop conditions.
[en] BWR off-center RDA calculations have been performed for selected rod worths and drop speeds. While in all cases the peak fuel enthalpy was well below the 280 cal/g fuel criterion, a substantial sensitivity to control rod worth and rod drop speed was observed
[en] Highlights: • Ensemble learning methods are proposed to improve performance of abnormal detectability. • Methods of PEM, TPS, WCM and ANN are used as base learners. • Boosting and bagging reduce errors for unstable learners; otherwise may increase them. • Stacking performs much better than bagging and boosting. - Abstract: Several ensemble learning methodologies have been presented to improve the performance of the core power distribution reconstruction, such as boosting technology, bagging technology and stacking technology. Four commonly used core power reconstruction methods, including PEM, TPS, WCM and ANN are adopted as base learners or meta-learners. The power distribution of the control rod drop accident and quadrant power tilt accident, which combine with detectors measurement noise, is reconstructed. The numerical simulation shows that the results of the stacking methodology can be better than any single one of these base learners under large sample spatial variation of power distribution and large measurement uncertainty. Otherwise results that close to the best one of these base learner results could be generated in stacking methods. In bagging and boosting methodologies, for the unstable learner such as TPS and ANN methods with large measurement uncertainty, both methodologies will help to reduce the reconstruction errors. The boosting methodology could even get better results than bagging. While for the stable learner (such as PEM learner, WCM learner) or unstable learner (e.g. the TPS or ANN method) but under small spatial variation (or small measurement uncertainty) that is not sensitive to the change of sample data, the bagging or boosting method even will reduce the reconstruction performance. Generally, ensemble learning methodologies have capability to improve the core abnormal detectability in most operation scene. Usually stacking methodology performs much better than bagging and boosting methodologies.
[en] The document describes the calculation results of the rod drop transient that occurred at the Bohunice NPP Unit 3 on 6 January 1999. The static calculations were performed with the 3D reactor dynamic code DYN3D (version DYN3D2000/M1). The transient calculations were made with externally coupled codes ATHLET Mod. 1.2 Cycle A and DYN3D (version DYN3D2000/M1). The calculations are compared with experimental results. (author)