Optimal operation strategy of LWR based on the PCI online prognosis model

Abstract The pellet-cladding interaction (PCI) is one of the major issues in fuel rod during the power change operation in light water reactors (LWR). The frequent power transient will lead to the PCI failure, which results in the radioactive leakage. Unfortunately, the failure cannot be detected on time during operation. For solving this problem, the PCI results is calculated and predicted before the power transient, and the results is used for optimizing the operation strategy. As everyone knows, the calculation of the fuel is a cumbersome work, which is not fit for online evaluation. At first, we present a PCI online prognosis model in this paper by the method of radial basis function neural network (RBFNN). Based on this online model, an optimal operation strategy is present then. The PCI evaluation results is treated as the feedback of the strategy, which will go to the power control system to decide to carry out the power plan or to modify it. The presented operation strategy used the fast online prognosis model to predict the PCI status, which is used as a feedback signal to the power control system. The optimal operation strategy is tested by the experimental data from the references, and the results demonstrate its effectiveness.

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Development and Validation of SAS4A Code and Its Application to Analyses on Severe Flow Blockage Accidents in a Sodium-Cooled Fast Reactor

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4040649 ◽

2019 ◽

Vol 5 (1) ◽

Cited By ~ 1

Author(s):

Yoshitaka Fukano

Keyword(s):

Control System ◽

Power Control ◽

Safety Evaluation ◽

Past Study ◽

The Past ◽

Power Control System ◽

Water Reactors ◽

Fuel Elements ◽

Reactor Protection System ◽

Flow Blockage

Local subassembly faults (LFs) have been considered to be of greater importance in safety evaluation in sodium-cooled fast reactors (SFRs) because fuel elements were generally densely arranged in the subassemblies (SAs) in this type of reactors, and because power densities were higher compared with those in light water reactors. A hypothetical total instantaneous flow blockage (HTIB) at the coolant inlet of an SA gives most severe consequences among a variety of LFs. Although an evaluation on the consequences of HTIB using SAS4A code was performed in the past study, SAS4A code was further developed by implementing analytical model of power control system in this study. An evaluation on the consequences of HTIB in an SFR by this developed SAS4A code was also performed in this study. It was clarified by the analyses considering power control system that the reactor would be safely shut down by the reactor protection system triggered by either of 116% over power or delayed neutron detector (DND) trip signals. Therefore, the conclusion in the past study that the consequences of HTIB would be much less severe than that of unprotected-loss-of-flow (ULOF) was strongly supported by this study. Furthermore, SAS4A code was newly validated using four in-pile experiments which simulated HTIB events. The validity of SAS4A application to safety evaluation on the consequence of HTIB was further enhanced in this study. Thus, the methodology of HTIB evaluation was established in this study together with the past study and is applicable to HTIB evaluations in other SFRs.

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