A new Material Testing Reactor, called the Jules Horowitz Reactor (JHR), is being constructed in southern France on the premises of the Cadarache research centre, belonging to the French Alternative Energies and Atomic Energy Commission (CEA). The start of the JHR operation is planned in 2015. The primary goal of the JHR is to investigate the effect of material degradation and aging in existing commercial nuclear power plants. This is of particular importance since such plants were originally designed for a 40-year lifetime. In many countries, extension to 60-year and even 80-year lifetimes are being considered. In order to reproduce the conditions of accelerated degradation and aging, the JHR was designed so that the behavior of materials and fuels in extreme conditions of radiation, temperature, and pressure could be studied.
The optimization of the design of the facility was performed by state-of-the-art computational algorithms and models, primarily meant at modeling the facility with a high level of accuracy and fidelity. Such tools have the disadvantage of requiring prohibitively-long computing times. Due to the high neutron flux in the JHR, the composition of the nuclear fuel assemblies will change more drastically than for commercial reactors. In addition, many measurements campaigns are planned, and the corresponding operational schedule of the reactor will also vary significantly with time. In such conditions, the computational methods used for the design of the facility are inadequate for following such rapid changes, due to the excessive computing time such methods require. Consequently, other fast running methods and models need to be developed so that any change in the fuel composition and in the operating conditions of the reactor could be more easily accounted for. In addition, such fast running models would allow testing different operating alternatives, predicting the effect of fuel depletion, and thus optimizing the reactor operation. Furthermore, they would also allow modeling rapid changes of the reactor conditions in case of incidental/accidental situations. The investigations of such situations are essential for verifying that the facility fulfills its safety design criteria during all foreseeable conditions.
Such other computational methods and models, to be used for the optimization of the reactor operation and for safety analyses, have to provide results with a sufficient level of accuracy, while at the same time being fast running. In order to decrease the computational time, these methods usually rely on solving a large set of equations describing the different physical phenomena occurring in a reactor with some level of simplification. These methods are usually referred to as deterministic methods.
The present project, named DEMO-JHR (for DEterministic MOdeling of the Jules Horowitz Reactor), aims at developing such deterministic methods. This project is carried out by the Division of Nuclear Engineering, Chalmers University of Technology, and the Division of Nuclear Reactor Technology, the Royal Institute of Technology. These divisions have a long tradition in the development and use of deterministic methods for the simulation of nuclear reactors.
More specifically, the project investigates how to speed-up the necessary computing time by coupling solution strategies at different scales, with a coarse mesh solution guaranteeing the modeling of large scales phenomena that can influence several parts of the reactor core or facility, and with a fine mesh solution in mostly the reactor core, where detailed information about local conditions are necessary. In addition, the project also considers the effect of uncertainties in basic physical data, in engineering design data, as well as in the underlying models themselves, onto the computed results. Due to the extreme operating conditions of the JHR, assessing the effect of such uncertainties is crucial for guaranteeing reliable predictions of the behavior of the facility.
Although such methods are tuned and specific to a given reactor, they can be applied in a more generic fashion to all types of light water reactors. Furthermore, the present project contributes to a safer operation of the JHR. This, in turn, will contribute to a better understanding of material degradation and aging in current commercial nuclear reactors, and will thus lead to a safer fleet of operating reactors.