Publications de Oskari Ville Pakari

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

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

Andreas Pautz, Oskari Ville Pakari

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

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, Nicolas Weiss, Thomas Jean-François Ligonnet, Axel Guy Marie Laureau, Adolfo Rais, Fanny Vitullo

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

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

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

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

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

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

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

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

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

Oskari Ville Pakari, Alessandro Scolaro

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

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