French Power Plants Research Articles

Ensemble Learning for Nuclear Power Generation Forecasting Based on Deep Neural Networks and Support Vector Regression

Forecasting nuclear energy production is essential for market operations such as security, economic efficiency, resource optimization, grid stability, and the integration of renewable energy sources. Forecasting approaches allow nuclear power plants to operate consistently, contributing to the overall reliability and long-term viability of the energy system. It is noted that energy systems researchers are increasingly interested in machine learning models used to face the challenge of time series forecasting. This study evaluates a hybrid ensemble learning of three time series forecasting models including least-squares support vector regression, gated recurrent unit, and long short-term memory models applied to nuclear power time series forecasting on the dataset of French power plants from 2009 to 2020. Furthermore, this research evaluates forecasting results in which approaches are directed towards the optimized RreliefF (Robust relief Feature) selection algorithm using a hyperparameter optimization based on tree-structured Parzen estimator and following an ensemble learning approach, showing promising results in terms of performance metrics. The suggested ensemble learning model, which combines deep learning and the RreliefF algorithm using a hold-out, outperforms the other nine forecasting models in this study according to performance criteria such as 75% for the coefficient of determination, a root squared error average of 0.108, and an average absolute error of 0.080.

Composite repair system extends service life of pipework at French power plant

Power-generating company Électricité de France SA (EDF) decided to repair, rather than replace, leaking pipework at its nuclear power plant in Bugey, France. This article explains why this has proved hugely beneficial, both practically and financially. It also looks at how this was done using a composite repair system from Henkel Adhesive Technologies which not only avoided the high cost of pipe replacement, but also the expense and time involved in installing a temporary bypass.

Influence of Crushing Conditions on Recycled Concrete Aggregates (RCA) Leaching Behaviour

The French construction industry generates almost 250 million tons of mineral waste per year. This waste can be used, after preparation, to replace natural materials used for construction work. This can preserve natural resources by contributing to a circular economy. A better understanding is necessary with regards to the deconstruction waste behaviour when used in redevelopment project or construction work, as backfill or embankments. This article intends to better understand how crushing influences recycled concrete aggregates leaching behaviour. Four concrete samples were studied from French power plant deconstructions. The leaching behaviour, of different grain size classifications, was tested with standard (i.e. with size reduction < 4 mm) and non-standard leaching tests (i.e. without size reduction). The samples were crushed with different industrial tools. The results showed that the final products maximum grain-size (Dmax) for crushing operation seems to have an influence on fine grain production. The role of the crushing technique used still remains uncertain. The analytical results from the leaching tests showed that the major elements leached are calcium, sulphates, carbonates, potassium, aluminium and silica. The trace elements were usually found in the smallest grain-size classification (0–6 mm). For the standard leaching tests, the total dissolved solids rose for the larger grain size classifications, whereas for non-standard leaching tests (performed without size reduction) the opposite occurred. All samples followed the environmental acceptability requirements. It seems essential to control the crushing parameters to sustain and strengthen continued concrete waste recovery to help improve French and European waste recovery objectives.

Is there a trend in extremely high river temperature for the next decades? A case study for France

Abstract. After 2003's summer heat wave, Electricité de France created a global plan called "heat wave-dryness". In this context, the present study tries to estimate high river temperatures for the next decades, taking into account climatic and anthropogenic evolutions. To do it, a specific methodology based on Extreme Value Theory (EVT) is applied. In particular, a trend analysis of water temperature data is done and included in EVT used. The studied river temperatures consist of mean daily temperatures for 27 years measured near the French power plants (between 1977 and 2003), with four series for the Rhône river, four for the Loire river and a few for other rivers. There are also three series of mean daily temperatures computed by a numerical model. For each series, we have applied statistical extreme value modelling. Because of thermal inertia, the Generalized Extreme Value (GEV) distribution is corrected by the medium cluster length, which represents thermal inertia of water during extremely hot events. The μ and σ parameters of the GEV distributions are taken as polynomial or continuous piecewise linear functions of time. The best functions for μ and σ parameters are chosen using Akaike criterion based on likelihood and some physical checking. For all series, the trend is positive for μ and not significant for σ, over the last 27 years. However, we cannot assign this evolution only to the climatic change for the Rhône river because the river temperature is the resultant of several causes: hydraulic or atmospheric, natural or related to the human activity. For the other rivers, the trend for μ could be assigned to the climatic change more clearly. Furthermore, the sample is too short to provide reliable return levels estimations for return periods exceeding thirty years. Still, quantitative return levels could be compared with physical models for example.

Assessment of the constitutive law by inverse methodology: Small punch test and hardness

The relevance of small-punch tests and indentation (hardness) tests are compared with regard to the determination of a constitutive law in the case of non active ferrite–bainite steel taken from a French power plant. Firstly, small-punch tests were performed on material samples and the load deflection curves were compared with finite element calculations using the FORGE2 Standard code. As a result the strength coefficient and the strain hardening exponent of Hollomon’s constitutive law were determined by an inverse method (Simplex method). Besides, it was shown that a three-parameter constitutive law such as Ludwik Hollomon’s leads to an indetermination since its parameters are correlated with each other. Secondly indentation tests were performed with a ball indenter and the parameters of the constitutive law were determined from the analysis of the load–indentation depth curves. Both methods give results in good agreement with the true stress–true strain curve obtained by classical tensile testing, thus proving their applicability to nuclear materials.

Combustion of an electrical cable insulation: thermal study and modelling at EDF

The association of two test benches, the PITCAIRN oven and the EDF/CNRS Calorimeter is used to determine the evolution of the net heat of combustion (NHC) of samples of electric cables. The NHC is determined by three different methods: the thermal balance, the quantity of oxygen consumed and the quantity of carbon dioxide produced during combustion. The tests performed on several types of fire-resistant cables commonly used in the French power plants show a substantial variation of this parameter during the combustion, affected by the composition and the structure of the cables. The paper summarizes the modeling work in progress.

Decentralized Fiber Optic Acquisition System

The paper describes a decentralized data acquisition system installed for a long term on-site test at a French power plant. Two local autonomous stations acquire the information from 24 channels ; the data are continuously transmitted to a concentrator through two 600 m long optical cables at a rate of 0.96 Mbits/sec.. An error ratio lower than 10” on transmission, made possible through the use of optical fiber, allows testing to be performed in an industrial environment using only very simple error detection technique. The optical cables which follow interchangeable paths inside and outside the station, and operate in a temperature range of between -20°C and +60°C, are operational transmission media, which, during testing on large sites, eliminate the constraints related to the location of central computer facilities.

Occupational Radiation Exposure at French Power Plants: Measurement and Prediction

Electricite de France and the Commissariat a l’Energie Atomique have developed experimental and theoretical approaches to obtain a better understanding and to provide accurate predictions in the fi...

Les contraintes de réalisation des pompes utilisées dans les centrales thermiques et nucléaires d'Electricité de France

Power station water circuits include a large number of pumps which vary considerably as regards size, design, use, water properties (temperature, purity, corrosion, etc.) and the material of which they are made. Even pumps designed for heaviest-duty operation often give trouble, owing to the complex operation of their fixed and moving components (guide and thrust bearings, shaft seals, static seals, hydraulic balancing components, etc.), satisfactory behaviour of which may be impaired by vibration, corrosion, erosion, cavitation and other factors difficult to keep under control. Pump manufacturers have accumulated a wealth of experience since the turn of the century and, in the face of severe competition, are endeavouring to standardise their products with a view to ensuring satisfactory service at minimum cost. Standardisation so far has been confined to widely-used small pumps and specific components, i.e. guide and thrust bearings and shaft seals. On the other hand, technical development has resulted in increasingly higher equipment performance and design sophistication, as in the case of power station pumps for example, the outputs of which have risen sharply during the last thirty years or so. Here, standardisation possibilities for specific pump types are limited to individual technical stages, with the result that increasingly complex, diversified design studies are required for such purposes as definition of operating conditions, solution of metallurgy problems, determination of maintenance requirements, etc. In addition to availability, the effect of conditions appliable to construction of nuclear power plant in France has been requiring increasingly closer attention during the past tow years. These conditions are as follows : a) Wider standardisation possibilities associated with the scope of French power plant construction policy. b) Operating security specifications, for which highly reliable equipment designs are essential. c) Specifications for the protection of power plant service personnel against radiation, which imply minimal maintenance requirements and dismantling and assembly times. These factors all affect the hitherto conventional quality / cost ratio for pumps and justify the issuing by users of such equipment of from equipment meeting various security, reliability, investment cost and maintenance requirements. Such specifications are included among the mutual commitments of users and manufacturers to one another. To meet these various requirements, Electricite de France has concentrated action on the following points in relation to pumps for nuclear power plant : a) Choice of manufacturers according to their design and production facilities. b) Closer attention to detail in design studies by use of series effect. c) Definition of conditions under which equipment is to operate and relating to the service to be provided. d) Drawing-up of special design and manufacturing specifications. e) Choice and inspection of materials. f) Systematic checking and testing of prototype and industrial equipment.