Speaker
Description
Crucial nuclear facilities, such as Material Testing Reactors (MTRs), support existing nuclear power plants and future generations of reactors thanks to studies on material and fuels under representative and extreme conditions, including accelerated aging and accidental conditions. Due to the aging of the Material Testing Reactor (MTR) park, the Jules Horowitz Reactor (JHR), a new research reactor with unequaled performance in Europe, is currently under construction at the CEA Cadarache center in the south of France. With a thermal power of 100 MWth and an expected nuclear heating rate of 20 W.g-1 in aluminum, this reactor impulse new research programs between AMU and CEA since 2009, thanks to the LIMMEX joint laboratory. These research programs aim to improve on-line measurements of critical nuclear quantities, such as the nuclear heating rate, which is essential to size, control and interpret experiments conducted in experimental channels of the JHR. Non-adiabatic differential calorimeters (such as CALMOS, CARMEN, or CALORRE type) and/or single-cell calorimeters (such as gamma thermometers or KAROLINA-type calorimeters) are used to measure the nuclear heating rate.
In the state of the art, differential calorimeters are composed of one calorimetric cell containing a sample, in which the nuclear heating rate is quantified, and one reference cell used to subtract the energy deposition associated with the structure. Each calorimetric cell integrates a heating element used for the calibration (in steady state) or to apply different measurement methods under real conditions. However, these different measurement methods, combined with the large size of the calorimetric cells, require several displacements and thus significant measurement times to measure local nuclear heating rates. In comparison, single-cell calorimeters are composed of one single cell containing a sample, and in most cases do not incorporate heating elements. In this case, the simplified geometries and reduced size allow shorter measurement times and better integration or coupling with other sensors or detectors. Nevertheless, the calibration must be carried out under a transient regime and only one measurement method is applicable under real conditions. More recently, the axial dimension of the CALORRE type differential calorimeter was reduced and the geometry was optimized in the framework of the CALOR-I program for the irradiation in MITR but limits were shown in terms of mechanical design and manufacturing techniques. As a result, a new approach, with technological breakthroughs, was adopted to design and study a single-cell calorimeter prototype integrating a thin-film heating element (patented in 2020 by AMU and the CEA).
The presented work focuses on the specifications and experimental characterization (chemical, electrical, and thermal) of the new thin-film heating element. The performance of a Mono-CALO calorimeter prototype integrating this heating element will be presented, detailing ist metrological characteristics (reproducibility, response time, linearity, and sensitivity) and comparing them with classical calorimeters. Then, the new heating element was integrated into a single-cell CALORRE type calorimeter for an irradiation campaign at the JSI reactor (Slovenia), and its properties before and after irradiation was analyzed to validate ist behavior under irradiation. This validation allows the quantification of very low nuclear heating rates using two measurement methods (including one using the new validated heating element). Finally, new challenges associated with the calorimeter miniaturization will be presented.
