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Oskari Ville Pakari

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Related publications (34)

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Analysis of the first COLIBRI fuel rods oscillation campaign in the CROCUS reactor for the European project CORTEX

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

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 techn ...

2021

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

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

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

Comparison of high-fidelity transport code predictions against the NECTAR intra-pin reaction rate measurements

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

The advancement of high-fidelity nuclear reactor simulation methods is essential for reducing conservatism in safety margins and optimizing reactor design and operation. This work evaluates the predictive capabilities of the deterministic solvers GeN-Foam ...

2025

Validation of axial void profile measured by neutron noise techniques in CROCUS

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

Recently a joint project has been carried out between the Paul Scherrer Institut, the Ecole Polytechnique Federale de Lausanne and swissnuclear, an industrial partner, in order to determine the axial void distribution in a channel installed in the reflecto ...

2021

Development of an Event Tracking Feature in OpenMC for Neutron Spectroscopy and Scatter Camera Systems

Andreas Pautz, Oskari Ville Pakari, Michel Saliba

This paper presents the development and application of an event tracking feature within the OpenMC Monte Carlo code, designed for advanced neutron spectroscopy and scatter camera system simulations. The newly implemented feature enables the tracking of ind ...

American Nuclear Society2025

Generative AI tools in the nuclear engineering community: A survey-based evaluation of the current adoption and impacts

Alessandro Scolaro, Oskari Ville Pakari

Generative AI tools (often abbreviated genAI or GAI), such as chatGPT, have arguably great potential to induce a paradigm shift in knowledge work.Herein, we present the results of a survey conducted within the nuclear engineering professional community to ...

American Nuclear Society2024

Gamma-ray Spectroscopy in Low-Power Nuclear Research Reactors

Andreas Pautz, Vincent Pierre Lamirand, Oskari Ville Pakari

Gamma-ray spectroscopy is an effective technique for radioactive material characterization, routine inventory verification, nuclear safeguards, health physics, and source search scenarios. Gamma-ray spectrometers typically cannot be operated in the immedia ...

MDPI2024

Welch Method and Bootstrapping Applied to Subcritical Gamma Noise

Andreas Pautz, Vincent Pierre Lamirand, Oskari Ville Pakari

We measured the prompt neutron decay constant

\alpha

alpha of the CROCUS zero-power reactor at the Swiss Federal Institute of Technology Lausanne using cross-power spectral density (CPSD) analysis of gamma-gamma correlations from two trans-stilbene org ...

TAYLOR & FRANCIS INC2025

CORE SIM+ simulations of COLIBRI fuel rods oscillation experiments and comparison with measurements

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

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 th ...

2021

Intercomparison of neutron noise measurement systems in the CROCUS reactor

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

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

CORTEX experiments – Part I: Modulation campaigns in AKR-2 & CROCUS for the validation of neutron noise codes

Andreas Pautz, Vincent Pierre Lamirand, Mathieu Hursin, Oskari Ville Pakari, Pavel Frajtag, Axel Guy Marie Laureau, Fanny Vitullo, Adolfo Rais, Thomas Jean-François Ligonnet, Nicolas Weiss, Daniel Godat, Klemen Ambrozic

We present the experimental campaigns – namely, three per facility – carried out between 2018 and 2021 in the AKR–2 and CROCUS zero power reactors within the framework of the Horizon 2020 European project CORTEX. Their purpose was to produce high-quality a ...

2025

Gamma noise to non-invasively monitor nuclear research reactors

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

Autonomous nuclear reactor monitoring is a key aspect of the International Atomic Energy Agency’s strategy to ensure nonproliferation treaty compliance. From the rise of small modular reactor technology, decentralized nuclear reactor fleets may strain the ...

Nature Research2024

Millimetric fuel rod displacements: an experimental study of the impact on local thermal neutron flux in the CROCUS reactor

Andreas Pautz, Vincent Pierre Lamirand, Oskari Ville Pakari, Pavel Frajtag, Fanny Vitullo, Thomas Jean-François Ligonnet, Daniel Godat

The impact on the thermal neutron flux due to a few mm displacement of a single fuel rod in the periphery lattice of the CROCUS zero-power reactor was measured. These high-resolution experiments were carried out using a miniature neutron detector positione ...

American Nuclear Society2022

CORTEX experiments, Part II: Postprocessing of neutron noise time series to determine reliable mean and uncertainties

Andreas Pautz, Vincent Pierre Lamirand, Mathieu Hursin, Oskari Ville Pakari, Axel Guy Marie Laureau, Adolfo Rais, Klemen Ambrozic

In this paper we present the methodology developed to analyze the detector response of neutron noise experiments performed at EPFL CROCUS and TUD AKR-2 reactors in the framework of the H2020 CORTEX project. The noise, or modulation, is induced by controlle ...

2024