Abstract. For safety reasons, reactor coolant system (RCS) flows in nuclear power plants have to be maintained between a high and a low limit. The current measurement uncertainty is impacted by the heterogeneity of the RCS fluid. The objective of the present study is to use the existing plant elbow taps to measure accurately and absolutely the RCS flow continuously and independently of the temperature measurement. CFD simulations are used to find out a calibration coefficient for the method. An uncertainty calculation is performed. This innovative method was tested on actual data issued from French nuclear power plants.Résumé. Pour des raisons de sûreté, le débit primaire des centrales nucléaires doit rester entre une limite haute et une limite basse. L'incertitude de la mesure actuelle est impactée par l'hétérogénéité de température du fluide primaire.L'objectif de cette étude est d'utiliser les mesures de delta de pression existantes dans certains coudes de centrales nucléaires pour mesurer en absolu et précisément le débit primaire sans que des mesures de température du fluide primaire ne soient nécessaires. La simulation CFD est utilisée pour déterminer un coefficient d'étalonnage de la méthode. Un calcul d'incertitude est alors réalisé. Cette méthode innovante de mesure de débit primaire a été testée sur des données anciennes de centrales nucléaires françaises.
The RCS flow measurement in PWRs is currently performed with a heat balance between primary and secondary systems: thus temperature heterogeneity impacts this measurement. In case of RCS flow shutdown (incident situation), a relative measurement of the RCS flow is monitored using an existing elbow tap. The goal of the present study is to assess the feasibility of using the existing plant elbow taps to accurately measure an absolute value of the RCS flow continuously and independently of the RCS temperature measurements. RCS flow is basically proportional to the square root of the differential pressure in the pipe elbow taps. Experiments on a scale model and sensitivity analyses with CFD simulations have been carried out and show that only few parameters have an influence on the proportionality coefficient. CFD is seen as able to predict this coefficient with an adequate accuracy. Potential applications of this method are RCS flow monitoring from start to full load after the change of primary coolant pumps or of steam generators.
Many industries require heat or cold in their production plants. To meet these needs, companies usually equip their generation sites with combined heat and power plants. The goal of the present study is to build an accurate 1D-physical model of a cogeneration plant and to use it to optimize the plant from design phase to operation phase. The study shows that using the Modelica language and a library of plant components such as ThermoSysPro are adequate for building a modular 1D-physical model. Once the model built, optimization tools were used for optimizing both design (component specification for allowing maximized profit and minimized investment) and operation (loads of turbines and engines for maximized profit). Physical models may therefore be used for an optimization purpose. Moreover the developed tools may prove useful for engineers operating combined heat and power plants for monitoring and optimizing purposes.
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