The Horizon2020 European project CORTEX aims at developing an innovative core monitoring technique that allows detecting anomalies in nuclear reactors, such as excessive vibrations of core internals, flow blockage, or coolant inlet perturbations. The technique will be mainly based on using the fluctuations in neutron flux recorded by in-core and ex-core instrumentation, from which the anomalies will be differentiated depending on their type, location and characteristics. The project will result in a deepened understanding of the physical processes involved, allowing utilities to detect operational problems at a very early stage. In this framework, neutron noise computational methods and models are developed. In parallel, mechanical noise experimental campaigns are carried out in two zero-power reactors: AKR-2 and CROCUS. The aim is to produce high quality neutron noise-specific experimental data for the validation of the models. In CROCUS, the COLIBRI experimental program was developed to investigate experimentally the radiation noise induced by fuel rods vibrations. In this way, the 2018 first CORTEX campaign in CROCUS consisted in experiments with a perturbation induced by a fuel rods oscillator. Eighteen fuel rods located at the periphery of the core fuel lattice were oscillated between ±0.5 mm and ±2.0 mm around their central position at a frequency ranging from 0.1 Hz to 2 Hz. Signals from 11 neutron detectors which were set at positions in-core and ex-core in the water reflector, were recorded. The present article documents the results in noise level of the experimental campaign. Neutron noise levels are compared for several oscillation frequencies and amplitudes, and at the various detector locations concluding to the observation of a spatial dependency of the noise in amplitude.

Electromagnetic vibratory sources used iuboreholes to develop a vibrational action on the walls of a casing string can also be employed for intensifying the influx of oll and gas, clearing filters in water holes, cementing the casing column, extracting the drilling tools that get caught in the hole, etc.The broad range of applications determines the wide variety of therms/ conditions under which vibratory sources operate. The thermal exchange between the winding of the vibration source and the environment takes place under vibtation which distinguishes it from processes in transformers and rotational electric motors [i, 2]. Studies of the systmns for cooling electromagnetic machines of a reciprocating motion that take into consideration the vibration of the machine's body are mainly concerned with systems of air cooling [3, 4]. In [5], the thermal exchange between two parallel metal walls was studied, which was accomplished by free convection of liquid fllling the space between the walls in the presence of vibration. However, in electromagnetic vibration sources in boreholes, two-contact cooling of the winding is done: by liquid convection inside the vibrator's body, and the convection of the liquid surrounding the vibration source inside the hole.Convectional thermal exchange, of course, depends on the shape of the surface being cooled [6]. The surfaces of the toll and the body of the vibrator that take part in the thermal exchange through convection of liquid filling the body are not parallel. These are cylindrical surfaces with perpendicular axes, and the results of [5] cannot be transferred to the system of coollng of electromagnetic sources in boreholes.

At EPFL, the CROCUS reactor has been used to carry out experiments with vibrating fuel rods. The paper presents a first attempt to employ the measured data to validate CORE SIM+, a neutron noise solver developed at Chalmers University of Technology. For this purpose, the original experimental data are processed in order to extract the necessary information. In particular, detector recordings are scrutinized and detrended, and used to estimate CPSDs of detector pairs. These values are then compared with the ones derived from the CORE SIM+ simulations of the experiments. The main trend of the experimental data along with the values for some detectors are successfully reproduced by CORE SIM+. Further work is necessary on both the experimental and computational sides in order to improve the validation process.

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