Publications by Oskari Ville Pakari

Related publications (34)

Experimental and numerical study of stochastic branching noise in nuclear reactors

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

Measurement of the Prompt Neutron Decay Constant in a Zero-Power Reactor Using a Novel 3D Detector System

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

Analyzing neutron noise in zero-power reactors provides information about integral parameters, such as the prompt decay constant

\alpha

alpha. This information can be used to validate codes that predict said parameters, or time-dependent behavior, part ...

TAYLOR & FRANCIS INC2025

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

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

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

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

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

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

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

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

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

Kinetic Parameter Measurements in the CROCUS Reactor Using Current Mode Instrumentation

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

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

Neutron-Gamma Noise Measurements in a Zero-Power Reactor Using Organic Scintillators

Andreas Pautz, Vincent Pierre Lamirand, Oskari Ville Pakari

Noise measurements in light water reactor systems aid in generating validation data for integral point kinetic parameter predictions and generating monitoring parameters for reactor safety and safeguards. The CROCUS zero-power reactor has been used to supp ...

Ieee-Inst Electrical Electronics Engineers Inc2024

Measurement of the Prompt Decay Constant in a Zero Power Reactor Using a Novel 3D Detector System

Andreas Pautz, Vincent Pierre Lamirand, Oskari Ville Pakari, Michel Saliba

Analyzing neutron noise in zero power reactors is a valuable tool for gaining insights into integral parameters, such as the prompt decay constant α. This information can be used to validate codes that predict said parameters, or time-dependent behavior, p ...

American Nuclear Society2024

Design and Simulation of Gamma Spectrometry Experiments in the CROCUS Reactor

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

Towards the Validation of Noise Experiments in the CROCUS Reactor Using the TRIPOLI-4 Monte Carlo Code in Analog Mode

Andreas Pautz, Vincent Pierre Lamirand, Oskari Ville Pakari

Intrinsic neutron noise experiments offer a non-invasive manner to measure the prompt decay constant or reactivity of fissile systems. Using the fluctuations in the density of fission chains, one can infer the kinetics parameters via correlation analysis s ...

2021

High accuracy measurement of the prompt neutron decay constant in CROCUS using Gamma Noise and bootstrapped uncertainties

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

We experimentally demonstrate the advantages of gamma detection for noise measurements to deter-mine the prompt neutron decay constant a of a nuclear reactor using the power spectral density (PSD) method, coupled to a new uncertainty estimation scheme base ...

PERGAMON-ELSEVIER SCIENCE LTD2022

Intra-pin Reaction Rate Measurements in the CROCUS Experimental Reactor

Andreas Pautz, Vincent Pierre Lamirand, Mathieu Hursin, Oskari Ville Pakari, Thomas Jean-François Ligonnet, Tom Mager

In response to the need for validating high-fidelity deterministic neutronics solvers capable of providing pin-resolved neutron flux distributions, intra-pin reaction rates measurements were performed in the CROCUS experimental reactor. A specially designe ...

2024

Future experimental programmes in the CROCUS reactor

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

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

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

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

First in-core gamma spectroscopy experiments in a zero power reactor

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

Gamma rays in nuclear reactors, arising either from nuclear reactions 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 neutr ...

E D P SCIENCES2021

Power calibration methodology at the CROCUS reactor

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

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

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

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

Fast simulation of neutron noise using the Transient Fission Matrix approach and validation on the CROCUS reactor

Vincent Pierre Lamirand, Oskari Ville Pakari

This article presents the development of a neutron noise calculation technique with a reduced calculation time based on the TFM (Transient Fission Matrix) approach. The latter contains different information such as the system transfer function (fission and ...

EDP Sciences2024

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

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

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