Assessment of Irradiation Performance in the Jules Horowitz Reactor (JHR) using the CARMEN Measuring Device

The development of the JHR experimental devices rely on the operational feedback from previous French material testing reactors (i.e. SILOE and OSIRIS). The experimental devices used for the irradiation of structural material were already facing technological limitations, in particular regarding the control of irradiation temperature and of the thermal gradients in the experimental samples, which is essential to ensure the quality of the experiments. Obtaining satisfactory thermal fields (in compliance with the setpoint and the homogeneity) is all the more difficult as the level of nuclear heating is higher in the JHR. This paper attempts to characterize the irradiation conditions in different experimental positions of the JHR and to compare them with the conditions and the empirical criteria of maximum acceptable temperature measured in OSIRIS. The study shows that the irradiation conditions obtained inside the experimental devices can sometimes be significantly different from the measured conditions using instrumentation devices. The interpretation of the experimental results and their transposition to other situations will always require a calculation versus measurement adjustment and the intensive use of computer simulation. However, despite all simulation and transposition efforts, the control of temperature conditions is not yet fully demonstrated and nothing will ultimately replace experimental validation.

Coordinated Control Scheme Design of a Nuclear Heating Reactor Cogeneration Plant for Balancing Renewables

To balance the intermittent renewable energy (IRE), it is necessary for nuclear power plants (NPPs) to operate flexibly. The flexibility can be given by cogeneration, where the main steam flow are used to drive several thermal loads such as the turbine and seawater desalination process. The electric power of a nuclear cogeneration plant (NCP) can be regulated through adjusting the excess steam flow to the cogeneration processes. Due to the fluctuation of IRE generation, the distribution of main steam to different thermal loads in a NCP varies with net demand frequently, which in turn results in a floating feedwater temperature, and further forms a disturbance to the operation of nuclear reactor. To mitigate the fluctuation of process variables caused by balancing IRE generation, it is necessary to study the coordinated control of flexible nuclear cogeneration plants. In this paper, the scheme of a NCP form by a 200MWth nuclear heating reactor NHR-200II based nuclear steam supply system (NSSS) driving a turbine and a seawater desalination process is first introduced. To balance the IRE generation, a plant coordinated control strategy is newly proposed. The feasibility of this control is verified through numerical simulation, which shows that this NCP can be adopted for balancing IRE.

Proportional-Integral Disturbance Observer of Nuclear Reactors

A proportional-integral disturbance observer (PI-DO) for monitoring nuclear reactors is newly proposed, which is driven by the measurements of neutron flux and coolant temperature at reactor inlet as well as their integrations. This PI-DO provides a globally asymptotic estimation with a bounded steady-state error for the reactor key process variables as well as the total disturbances in channels of the neutron kinetics and primary coolant thermal-hydraulics. Moreover, the PI-DO is applied to reconstruct the unmeasurable state variables and total disturbances of a nuclear heating reactor (NHR). Numerical simulation results not only verify the theoretic analysis but also show both the satisfactory performance and the influence of observer parameters.

Computational support on the development of nuclear heating calorimeter detector design

Heating due to energy deposition of intense ionizing radiation in samples and structural materials of nuclear reactors poses severe limitations in terms of cooling requirements for safe reactor operation, especially in high neutron and gamma flux environments of material testing fission reactors (MTRs) and novel fusion devices. A bilateral CEA-JSI research project was launched in 2018 with the objective to measure the gamma heating rates in standard reactor-related materials (graphite, aluminium, stainless steel and tungsten) as well as fusionrelevant materials (low-activation steel Eurofer-97 and Nb3Sn superconductor) in the JSI TRIGA reactor my means of gamma calorimeters. The calorimeter design will be based on the the CALMOS-2 calorimeter developed at the CEA and used to perform gamma heating measurements in the OSIRIS MTR in Saclay. In order to optimize the detector response inside the JSI TRIGA reactor field and not to perturb the measurement field, a detailed computational analysis was performed in terms of energy deposition assessment and measurement field perturbation using the MCNP v6.1 code, and in terms of heat transfer using the COMSOL Multiphysics code. The abovementioned activities enabled us to finalize the detector design with the experimental campaign planned for the end of year 2019.