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Andreas Pautz

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Publications associées (121)

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Development of a novel two-phase flow solver for nuclear reactor analysis: algorithms, verification and implementation in OpenFOAM

Andreas Pautz, Carlo Fiorina, Stefan Radman

A porous medium-based representation of nuclear reactors and complex engineering systems more in general can significantly reduce simulation and modelling costs, while preserving a reasonable degree of accuracy via regime map-based correlations for modelli ...

2021

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

Sub-critical gamma noise measurements in the CROCUS zero-power reactor

Andreas Pautz, Vincent Pierre Lamirand

Monitoring and verification o f t he n uclear f uel c ycle r equires t echnology a t e very s tep including power generation. Monitoring the count rate from a nuclear reactor core in neutron detectors is an effective way to confirm the power level as well ...

American Nuclear Society2024

The OFFBEAT multi-dimensional fuel behavior solver

Andreas Pautz, Alessandro Scolaro, Carlo Fiorina

The OpenFOAM Fuel BEhavior Analysis Tool, or OFFBEAT, is a multi-dimensional fuel performance code under collaborative development at the Laboratory for Reactor Physics and Systems Behaviour (LRS) of the EPFL and at the PSI. The code can be used both for s ...

ELSEVIER SCIENCE SA2020

Kilogram-Scale Crystallogenesis of Halide Perovskites for Gamma-Rays Dose Rate Measurements

László Forró, Andreas Pautz, Andrzej Sienkiewicz, Bálint Náfrádi, Endre Horvath, Vincent Pierre Lamirand, Pavel Frajtag, Márton Kollár, Pavao Roko Andricevic

Gamma-rays (gamma-rays), wherever present, e.g., in medicine, nuclear environment, or homeland security, due to their strong impact on biological matter, should be closely monitored. There is a need for simple, sensitive gamma-ray detectors at affordable p ...

2020

Unmoderated molten salt reactors design optimisation for power stability

Andreas Pautz, Axel Guy Marie Laureau

The critical region of unmoderated molten salt reactors consists in a cavity filled with a liquid fuel. The lack of internal structure implies a complex flow structure of the circulating fuel salt. A preliminary core shape optimization has been performed d ...

PERGAMON-ELSEVIER SCIENCE LTD2022

Statistical Burnup Distribution Of Moving Pebbles In Htr-Pm Reactor

Andreas Pautz, Fanny Vitullo, Horst-Michael Prasser

In the pebble-bed high temperature reactor under construction in China, called HTR-PM, the spherical fuel elements continuously flow downward in the cylindrical core. After the discharge, the burnup of each pebble is checked at the core outlet and, accordi ...

AMER SOC MECHANICAL ENGINEERS2018

Design of Separated Element Reflector Experiments in CROCUS: PETALE

Andreas Pautz, Mathieu Hursin, Vincent Pierre Lamirand, Pavel Frajtag, Daniel Jerôme Siefman

The present article describes the preliminary design studies for PETALE (Programme d'Etude en Transmission de l'Acier Lourd et ses Elements), an oncoming experimental program in the CROCUS reactor. Within the framework of the Venus-Eole-Proteus collaborati ...

ASTM INTERNATIONAL2018

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

A reduced order accelerator for time-dependent segregated neutronic solvers

Andreas Pautz, Alessandro Scolaro, Carlo Fiorina, Stefan Radman

The deterministic solution of the neutron transport problem entails the coupled solution of several partial differential equations, one for each energy group, direction and/or spherical harmonic. Several techniques have been devised for accelerating the so ...

PERGAMON-ELSEVIER SCIENCE LTD2018

On data assimilation with Monte-Carlo-calculated and statistically uncertain sensitivity coefficients

Andreas Pautz, Mathieu Hursin, Daniel Jerôme Siefman

Sensitivity coefficients from Monte Carlo neutron transport codes have uncertainties that can affect nuclear data adjustments with integral experiments. This paper presents an extended version of Generalized Linear Least Squares (GLLS), called xGLLS, that ...

PERGAMON-ELSEVIER SCIENCE LTD2020

Determination of the activity inventory and associated uncertainty quantification for the CROCUS zero power research reactor

Andreas Pautz, Vincent Pierre Lamirand, Mathieu Hursin, Pavel Frajtag

The paper describes the source term estimation of CROCUS, the zero power research reactor of EPFL, to be used for dispersion analysis under accidental conditions. To fulfil regulatory requirements, the source term of the CROCUS fuel is estimated through Mo ...

2019

Investigation on the effect of eccentricity for fuel disc irradiation tests

Andreas Pautz, Carlo Fiorina, Alessandro Scolaro

A varying degree of eccentricity always exists in the initial configuration of a nuclear fuel rod. Its impact on traditional LWR fuel is limited as the radial gap closes relatively early during irradiation. However, the effect of misalignment is expected t ...

2021

Convergence Analysis and Criterion for Data Assimilation with Sensitivities from Monte Carlo Neutron Transport Codes

Andreas Pautz, Mathieu Hursin, Daniel Jerôme Siefman

Sensitivity coefficients calculated with Monte Carlo neutron transport codes are subject to statistical fluctuations. The fluctuations affect parameters that are calculated with the sensitivity coefficients. The convergence study presented here describes t ...

ANS2018

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

Piecewise linear interface-capturing volume-of-fluid method in axisymmetric cylindrical coordinates

Andreas Pautz, Lubomír Bures

The paper describes a novel implementation of the piecewise linear interface-capturing volume-of-fluid method (PLIC-VOF) in axisymmetric cylindrical coordinates. The principal innovative feature involved in this work is that both the forward and inverse re ...

ACADEMIC PRESS INC ELSEVIER SCIENCE2021

Extension of the OFFBEAT fuel performance code to finite strains and validation against LOCA experiments

Andreas Pautz, Alessandro Scolaro, Carlo Fiorina, Edoardo Luciano Brunetto

The mechanical analysis of nuclear fuel behavior under base-irradiation conditions has traditionally been performed adopting the small-strain approximation. However, many cases of interest for fuel behavior involve the occurrence of large rod deformations ...

ELSEVIER SCIENCE SA2023

Computation of sensitivity coefficients in fixed source simulations with SERPENT2

Andreas Pautz, Mathieu Hursin

Within the scope of the implementation of a nuclear data pipeline aiming at producing the best possible evaluated nuclear data files, a major point is the production of relevant sensitivity coefficients when including integral benchmark information. Thanks ...

Elsevier Science Sa2024