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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - CORTEX (Core monitoring techniques and experimental validation and demonstration)

Teaser

Summary

Being able to monitor the state of reactors while they are running at nominal conditions is extremely advantageous. The early detection of anomalies gives the possibility for the utilities to take proper actions before such problems lead to safety concerns or impact plant availability. The analysis of measured fluctuations of process parameters (primarily the neutron flux) around their mean values has the potential to provide non-intrusive on-line core monitoring capabilities. These fluctuations, often referred to as noise, primarily arise either from the turbulent character of the flow in the core, from coolant boiling (in the case of two-phase systems), or from mechanical vibrations of reactor internals. Because such fluctuations carry valuable information concerning the dynamics of the reactor core, one can infer some information about the system state under certain conditions and detect possible anomalous behaviour of the system. The main goal of the project is to develop a monitoring technique, based on pre-computed reactor responses, allowing backtracking the nature and spatial distribution of possible anomalies, which give rise to the neutron flux fluctuations recorded by the in-core and ex-core instrumentation of the reactor. The project will also contribute to a lowering of the CO2 footprint to the environment and to a higher availability of cheap base-load electricity to the consumers.

Work performed

Detailed models for fluid-induced vibrations of reactor components were generated and a reduced order model is investigated. Capabilities were built and tested to simulate reactor neutron noise arising from fuel assembly vibrations with the codes SIMULATE-3, SIMULATE-3K, PARCS, KMACS, FEMFFUSION and CORE SIM. Neutron noise solvers using higher order approximations in energy, space and angle, have been developed. A statistical methodology for uncertainty and sensitivity analysis has been created.
The first measurement campaigns at AKR-2 and CROCUS were carried out successfully in 2018, demonstrating the availability of vibrating absorber and absorber of variable strength experimental setups. The deliverable describing the experimental campaigns and the qualifications of the data acquisition systems was released on time. Code validation activities are on-going. The next measurement campaigns will be designed to resolve the issues raised by the first experimental data set. A large number of simulated data, in frequency and time domains, in related scenarios, were generated in WP3.1. Advanced signal processing methods, based on wavelet and frequency transformations were developed for trend & noise removal and visualization purposes in WP3.2. Novel machine and deep learning methods were successfully applied to the data for predicting perturbation type/location, in WP3.3. Very promising results were obtained and published. Extensions to real data are now examined. Four measurement campaigns for additional neutron noise data were prepared and executed at GÃ¶sgen NPP. A collection of already available data of KWU, US PWR and VVER reactors was prepared and distributed within the project. Also, core data for steady state calculations were distributed. Four short courses/workshops were arranged on the following topics: signal processing and noise analysis, fundamentals of reactor kinetics and theory of small space-time dependent fluctuations, reactor dynamics, advanced signal processing methods. The publication records are as follows: journal papers: 1 (+2 under review), conference papers: 8 (+10 under review), presentations: 7. The following communications channels were developed and are regularly updated: website, LinkedIn page, leaflet.

The ethics issues about the CORTEX project raised by the European Commission concerning third countries ethics, environmental protection and safety ethics, and dual use ethics, were properly addressed.

Final results

WP1: development of high-fidelity simulation tools specifically targeted at the modelling of the neutron noise
WP2: establishement of first-of-a-kind noise specific measurements in research reactors for validating the simulation tools
WP3: applications of machine learning-based techniques for retrieving anomalies in nuclear reactors, using simulations as training data sets
WP4: demonstration of the technique on actual plant data and identification of anomalies (expected progress beyond state-of-the-art)

Economic impact
As the fleet of nuclear reactors in Europe is becoming older, operational problems will become more frequent. Concerning the availability of new units, lower plant availability is also expected in the starting phase of the renewal of the units. In addition, new plant technologies are being introduced whereas operational experience is limited for such technologies. This will also impact the availability of the units. As a consequence, the impact of core monitoring on plant availability and on the profitability of the plants as proposed in CORTEX will be significant. The capabilities to automatize and correctly diagnose reactor internal anomalies in nuclear power plants will play a role in supporting the extension of the operating licenses for the existing reactors and when building and operating new reactors. Moreover, this will justify the use of nuclear power as a safe and efficient baseload power source. The proposed technology will also create new business opportunities for companies servicing the nuclear industry.

Societal impact
The increased availability of the reactor units resulting from the proposed technique will allow maintaining an as large as possible fraction of electricity coming from nuclear power. With its low levelised cost compared to the other forms of electricity generation in Europe, the new method will thus contribute to a lowering of the cost of electricity to the European consumers. Moreover, by making the plants more available, the technique will further reduce CO2 emissions in the atmosphere. The project will moreover contribute to make the exploitation of nuclear reactors safer, thus leading to a better acceptance of nuclear power throughout Europe.