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Oskari Ville Pakari

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Publications associées (34)

Local and high distance neutron and gamma measurements of fuel rods oscillation experiments

Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Fanny Vitullo

We report in the present article on the successful observation using noise analysis of the lateral oscillation of one fuel rod by +/- 2.5 mm around nominal at 0.1 Hz frequency, using an mm(3) miniature neutron scintillator at the rod level, and a BGO gamma ...

E D P SCIENCES2021

Delayed gamma fraction determination in the zero power reactor CROCUS

Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Tom Mager

Gamma rays are an inextricable part of a nuclear reactor's radiation field, and as such require characterization for dose rate estimations required for the radiation protection of personnel, material choices, and the design of nuclear facilities. Most comm ...

EDP SCIENCES S A2021

Design and Simulation of Gamma Spectrometry Experiments in the CROCUS Reactor

Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Mathieu Hursin, Fanny Vitullo

Gamma rays in nuclear reactors, arising either from fission or decay processes, significantly contribute to the heating and dose of the reactor components. Zero power research reactors offer the possibility to measure gamma rays in a purely neutronic envir ...

E D P SCIENCES2020

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

Daniel Godat, Pavel Frajtag, Andreas Pautz, Adolfo Rais, Oskari Ville Pakari, Vincent Pierre Lamirand, Mathieu Hursin, Carlo Fiorina, Axel Guy Marie Laureau

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 motiva ...

2020

Power calibration methodology at the CROCUS reactor

Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Axel Guy Marie Laureau

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 ...

E D P SCIENCES2020

Neutron noise experiments in the AKR-2 and CROCUS reactors for the European project CORTEX

Daniel Godat, Pavel Frajtag, Andreas Pautz, Adolfo Rais, Oskari Ville Pakari, Vincent Pierre Lamirand, Mathieu Hursin, Carlo Fiorina, Axel Guy Marie Laureau

The present article gives an overview of the first experimental campaigns carried out in the AKR-2 and CROCUS reactors within the framework of the Horizon 2020 European project CORTEX. CORTEX aims at developing innovative core monitoring techniques that al ...

E D P SCIENCES2020

Measurement of the Gas Velocity in a Water-Air Mixture in CROCUS Using Neutron Noise Techniques

Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Mathieu Hursin

The possibility of measuring the gas-phase velocity in a two-phase mixture through the use of neutron noise techniques is demonstrated in the zero-power reactor CROCUS of the Ecole Polytechnique Federale de Lausanne. It is the first step toward the experim ...

TAYLOR & FRANCIS INC2020

Experimental and numerical study of stochastic branching noise in nuclear reactors

Oskari Ville Pakari

Noise analysis applied to nuclear reactor physics is a powerful tool to investigate a reactor's kinetic parameters, and more generally underlying physical processes determining core behavior. The kinetic parameters are the coefficients of simplified time-d ...

EPFL2020

A mm(3) Fiber-Coupled Scintillator for In-Core Thermal Neutron Detection in CROCUS

Jean-Baptiste Mosset, Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Fanny Vitullo

This article presents the development, full-characterization, and in-core testing of a miniature neutron detector for the investigation of highly localized in-core neutronics effects in the zero-power reactor CROCUS, operated at the Ecole Polytechnique fed ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2020

Developing and testing a miniature fiber-coupled scintillator for in-core neutron counting in CROCUS

Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Fanny Vitullo

An advanced neutron detection system for highly localized measurements in nuclear reactor cores was developed and tested in the Laboratory for Reactor Physics and System Behaviour (LRS) at the Ecole polytechnique federale de Lausanne (EPFL), Switzerland, i ...

E D P SCIENCES2020

Intercomparison of neutron noise measurement systems in the CROCUS reactor

Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Mathieu Hursin

In the framework of an international collaboration, the critical decay constant (α0 = β/Λ), and delayed neutron fraction (β) of the CROCUS reactor were measured by teams of EPFL/PSI, CEA and SCK•CEN research institutes using the Rossi-α and Power Spectral ...

American Nuclear Society2018

Kinetic Parameter Measurements in the CROCUS Reactor Using Current Mode Instrumentation

Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand

This paper is an overview of developments and results regarding neutron noise measurements in current mode at the CROCUS zero power facility. Neutron noise measurements offer a noninvasive method to determine kinetic reactor parameters such as the prompt d ...

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC2018

Investigation of spatial effects on neutron noise measurements in the zero power reactor CROCUS

Daniel Godat, Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Mathieu Hursin

This article presents the results of an experimental campaign in the CROCUS zero power reactor aimed at investigating the spatial effects of neutron noise measurements. Neutron noise measurements offer a non-invasive method to determine kinetic reactor par ...

American Nuclear Society2018

Future experimental programmes in the CROCUS reactor

Pavel Frajtag, Andreas Pautz, Oskari Ville Pakari, Vincent Pierre Lamirand, Mathieu Hursin

CROCUS is a teaching and research zero-power reactor operated by the Laboratory for Reactor Physics and Systems Behaviour (LRS) at the Swiss Federal Institute of Technology (EPFL). Three new experimental programmes are scheduled for the forthcoming years. ...

2016

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