In-core dosimetry for the validation of neutron spectra in the CROCUS reactor

Jiang, Yifeng; Laureau, Axel; Lamirand, Vincent; Frajtag, Pavel; Pautz, Andreas

doi:10.1051/epjconf/202022504021

Cited by 4 publications

(1 citation statement)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In preparation for the transmission experiments, a large effort was devoted to developing tools for reactor dosimetry, including a new gamma spectrometry platform, CERVIN, and in-house analysis scripts for full propagation of all uncertainties [44], [45]. Uncertainties with covariance include reactor power history, HPGe calibration, and dosimetry nuclear data using the specialized library IRDFF [46], [47].…”

Section: ) Uncertainty Propagation and Experimental Designmentioning

confidence: 99%

Ten springs of experiments in CROCUS

Lamirand

2023

EPJ Web Conf.

View full text Add to dashboard Cite

Around a decade ago, a new team rebuilt experimental research at EPFL’s nuclear facilities, and in particular in the CROCUS nuclear reactor. After a broad investigation and open discussions with colleagues from the nuclear community, a number of experiments and research directions were selected. They range from reactor physics to nuclear data, with a focus on instrumentation. We present here the variety of experiments carried out and how instrumentation has been instrumental in these perspectives. Developments on branching or intrinsic reactor noise were made possible thanks to extensive theoretical investigation coupled with the developments of pulse and current modes neutron detection systems, as well as the LEAF gamma detection array. With regard to modulation or perturbation reactor noise, a study of fuel rods vibration was carried out thanks to the unique COLIBRI in-core fuel rods oscillation device; in the VOID experiments, a method was tested to measure the void coefficient with neutron modulation; in the APRHODITE project, the PISTIL rotating absorber, or absorber of variable strength, was used to determine the zero power reactor transfer function, in order to obtain feedback on kinetics nuclear data, particularly delayed neutrons. On the topic of nuclear data, the PETALE programme consisted on criticality and transmission experiments for the study of stainless steel, using instrumented metal reflectors. New dosimetry methodologies were developed for consistent and complete propagation of uncertainties, which also enabled experiments to be optimized. It will be continued in the HARVEST-X project, and its pile-oscillation program, BLOOM. Last but not least, developments in dosimetry as well as for a novel miniature neutron scintillation technology (MiMi detectors) allowed for interand intrapin (NECTAR) neutron measurements. 160 MiMi detectors have recently been distributed throughout the CROCUS core in a unique 3D detector array called SAFFRON, paving the way for novel high-resolution neutronics.

show abstract

Section: ) Uncertainty Propagation and Experimental Designmentioning

confidence: 99%

Ten springs of experiments in CROCUS

Lamirand

2023

EPJ Web Conf.

View full text Add to dashboard Cite

show abstract

The COLIBRI experimental program in the CROCUS reactor: characterization of the fuel rods oscillator

et al. 2020

View full text Add to dashboard Cite

The present article presents the mechanical characterization of the fuel rods oscillator developed for the purposes of the COLIBRI experimental program in CROCUS. COLIBRI aims at investigating the radiation noise related to fuel vibrations. The main motivation is the increased amplitudes in the neutron noise distributions recorded in ex- and in-core detectors that have been observed in recent years in Siemens pre-Konvoi type of pressurized water reactors. Several potential explanations have been put forward, but no definitive conclusions could yet be drawn. Among others, changes in fuel assembly or pin vibration patterns, due to recent modifications of assembly structural designs, were pointed out as a possible cause. Computational dynamic tools are currently developed within the Horizon 2020 European project CORTEX, to help with understanding the additional noise amplitude. The COLIBRI program is used for their validation. An in-core device was designed, tested, and licensed between 2015 and 2019 for fuel rods oscillation in CROCUS, in successive steps from out-of-pile tests with dummy fuel rods to critical in-core tests. The characterization of its mechanical behavior is presented, in air and in water, and as a function of the load, for safety and experimental purposes. The device allows simultaneously oscillating up to 18 fuel rods. The maximum oscillation amplitude is 5 mm, while the maximum allowed frequency is 2 Hz, i.e. in the frequency range in which the induced neutron flux fluctuations are most pronounced in nuclear power plants.

show abstract

Power calibration methodology at the CROCUS reactor

et al. 2020

View full text Add to dashboard Cite

In the present article, we detail the method used to experimentally determine the power of the CROCUS zero-power reactor, and to subsequently calibrate its ex-core monitor fission chambers. Knowledge of the reactor power is a mandatory quantity for a safe operation. Furthermore, most experimental research programs rely on absolute fission rates in design and interpretation – for instance, tally normalization of reaction rate studies in dosimetry, or normalization of power spectral density in neutron noise measurements. The minimization of associated uncertainties is only achieved by an accurate power determination method. The main experiment consists in the irradiation, and therefore, the activation of several axially distributed Au-197 foils in the central axis of the core, which activities are measured with a High-Purity Germanium (HPGe) gamma spectrometer. The effective cross sections are determined by MCNP and Serpent Monte Carlo simulations. We quantify the reaction rate of each gold foil, and derive the corresponding fission rate in the reactor. The variance weighted average over the distributed foils then provides a calibration factor for the count rates measured in the fission chambers during the irradiation. We detail the calibration process with minimization of respective uncertainties arising from each sub-step, from power control after reactivity insertion, to the calibration of the HPGe gamma spectrometer. Biases arising from different nuclear data choices are also discussed.

show abstract

In-core dosimetry for the validation of neutron spectra in the CROCUS reactor

Cited by 4 publications

References 10 publications

Ten springs of experiments in CROCUS

Ten springs of experiments in CROCUS

The COLIBRI experimental program in the CROCUS reactor: characterization of the fuel rods oscillator

Power calibration methodology at the CROCUS reactor

Contact Info

Product

Resources

About