Izbrani članki (selected papers)

2026

• P. Lesjak, L. Snoj et al., Simulation of water activation in the KATANA activation loop of the TRIGA reactor, Fusion Engineering and Design, Volume 227, June 2026, 115711

• J. Peric, L. Snoj et al., Validating a simplified water-activation transport model using time-resolved reactor-pulse neutron measurements at KATANA, Nuclear Engineering and Technology, Volume 58, Issue 4, April 2026, 104090

• J. Peric, L. Snoj et al., Cherenkov reactor power meter: Development of an innovative and cost-effective technique for reactor power monitoring, Nuclear Engineering and Technology, Volume 58, Issue 3, March 2026, 104042

• T. Goričanec, L. Snoj et al., Advanced Monte Carlo analysis of ex-vessel neutron dosimetry for cycle 25 of Krško nuclear power plant, Nuclear Engineering and Technology, Volume 58, Issue 1, January 2026, 103887

2025

• I. Švajger, L. Snoj et al., Zirconium hydride thermal scattering law, Nuclear Engineering and Technology, Volume 57, Issue 12, December 2025, 103834

• E. Masia, L. Snoj et al., Application of the radio species transport model to the JSI water activation loop, Fusion Engineering and Design, Volume 219, October 2025, 115264

• J. Peric, L. Snoj et al., Neutron emission from water activation: Experiments and modeling under fusion-relevant conditions at the KATANA facility, Fusion Engineering and Design, Volume 216, July 2025, 115052

• T. Goričanec, L. Snoj et al., A half-century of nuclear research, education and training: Story of the JSI TRIGA reactor, Annals of Nuclear Energy, Volume 214, May 2025, 111122

• A. Pungerčič, L. Snoj et al., European research reactor strategy derived in the scope of the towards optimized use of research reactors (TOURR) project, Annals of Nuclear Energy, Volume 211, February 2025, 110963

2024

• A. Prašnikar, L. Snoj et al., Catalytic methanol cracking to hydrogen and formaldehyde over heterogeneous catalysts by radiolysis: Sectoral industrial symbiosis by waste radiation utilisation, International Journal of Hydrogen Energy, Volume 92, 26 November 2024, Pages 560-568

• D. Kotnik, L. Snoj et al., KATANA - water activation facility at JSI TRIGA, Part I: Final design and activity calculations, Fusion Engineering and Design, Volume 57, Issue 3, March 2025, 103233

• D. Kotnik, L. Snoj et al., KATANA - water activation facility at JSI TRIGA, Part II: First experiments, Fusion Engineering and Design, Volume 57, Issue 4, April 2025, 103290

• J. Malec, L.Snoj, et al., Advancing Nuclear Research and Education in Slovenia and EU: From Operating the TRIGA Reactor to Building a New Generation Facility, Arabian Journal for Science and Engineering, 2024

• D. Čalić, L. Snoj, M. Kromar, Impact of fuel temperature on nuclear core design calculations, Nuclear Engineering and Technology, Volume 56, Issue 9, September 2024, Pages 3668-3685, 2024

• V. Mascolino, L. Snoj, et al., Experimental validation of the 3-D neutron kinetics algorithm of RAPID using the JSI TRIGA Mark-II reactor, Progress in Nuclear Energy, Volume 176, 105391, 2024

• G. Žerovnik, A.Levpušček, L. Snoj, Parametric study of the influence of 135Xe build-up on required excess reactivity for load-following operations, Nuclear Engineering and Design, Volume 424, 113297, 2024

• A. Žohar, L. Snoj, et al., Evaluation of cross sections for fast ion reactions with beryllium in helium and hydrogen fusion plasmas, Nuclear Fusion, Volume 64, Number 7, 2024

• A. Pungerčič, L. Snoj et al., JSI TRIGA fuel rod reactivity worth experiments for validation of Serpent-2 and RAPID fuel burnup calculations, Nuclear Engineering and Technology, Volume 56, Issue 8, August 2024, Pages 3405-3424

• I. Švajger, L. Snoj et al., Evaluation of reactor pulse experiments, Nuclear Engineering and Technology, Volume 56, Issue 4, April 2024, Pages 1165-1203

• V. Sola, L. Snoj, et al., Fluence profiling at JSI TRIGA reactor irradiation facility, Nuclear instruments and methods in physics research. Section A, 2024, vol. 1063, 169258

• H. Weisen, L. Snoj, et al., TCV Tokamak Neutron Shielding Upgrade for Dual NBI Operation, Fusion Science and Technology , Volume 80, 2024 - Issue 2

• T. Goričanec, L. Snoj et al., Analysis of fluctuations in ex-core neutron detector signal in Krško NPP during an earthquake, Nuclear Engineering and Technology, Volume 56, Issue 2, February 2024, Pages 575-600

• A. Bratkič, L. Snoj et al., The colonization of an irradiated environment: the case of microbial biofilm in a nuclear reactor, International Journal of Radiation Biology, Volume 100, 2024, Issue 1, Pages 108-121

2023

• A.G. Plant, L. Snoj, et al., Nuclear Cogeneration of Methanol and Acetaldehyde from Ethylene Glycol Using Ionizing Radiation, Ind. Eng. Chem. Res. , 2023, 62, 49, 21152–2116

• A. Sarkar, L. Snoj et al., Influence of neutron and gamma irradiation on the electrocaloric properties of Mn-doped 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 ceramics, Journal of Physics: Energy, Volume 5, Number 4, 045006

• S. Gerkšič, L. Snoj et al., A perspective of using nuclear power as a dispatchable power source for covering the daily fluctuations of solar power, Energy, Volume 284, 1 December 2023, 128531

• A. Pungerčič, L. Snoj et al., Verification of a novel fuel burnup algorithm in the RAPID code system based on Serpent-2 simulation of the TRIGA Mark II research reactor, Nuclear Engineering and Technology, Volume 55, Issue 10, October 2023, Pages 3732-3753

• M. Fortuna, L. Snoj et al., Evaluation of neutron dose rates at the TCV tokamak facility, Fusion Engineering and Design, Volume 191, June 2023, 113562

• D. Kotnik, L. Snoj et al., Design optimization of the closed-water activation loop at the JSI irradiation facility, Fusion Engineering and Design, Volume 193, August 2023, 113632

• T. Goričanec, L. Snoj, et al., Determination of neutron flux redistribution factors for a typical pressurized water reactor ex-core measurements using Monte Carlo technique, Frontiers in Energy Research - Section Nuclear Energy, Vol. 11, 2023

• Review paper: G. Žerovnik, L. Snoj, et al., An overview of power reactor kinetics and control in load-following operation modes, Frontiers in Energy Research - Section Nuclear Energy, Vol. 11, 2023

2022

• H. Uršič, L. Snoj et al.,High radiation tolerance of electrocaloric (1-x)Pb(Mg1/3Nb2/3)O3–xPbTiO3, Journal of the European Ceramic Society, Volume 42, Issue 13, Pages 5575-5583, October 2022

• D. Fourmentel, L. Snoj et al., Nuclear heating measurements for fusion and fission relevant materials in the JSI TRIGA reactor, Fusion Engineering and Design, Volume 179, June 2022, 113136

• A. Žohar, L. Snoj, et al., Validation of realistic Monte Carlo plasma gamma-ray source on JET discharges, Nuclear Fusion, Volume 62, Number 6, 2022

• M. Joyce, L.Snoj, et al., Wireless information transfer with fast neutrons, Nuclear Instruments and Methods in Physics Research Section A: , Volume 1021, 1 January 2022, 165946

• V. Mascolino, A. Haghighat & L. Snoj, Development and validation of new algorithms for control rods insertion modeling in the RAPID code system using the JSI TRIGA Mark-II reactor, Annals of Nuclear Energy, Vol. 166,108711, February 2022

2021

• Ž. Štancar, L. Snoj, et al., Experimental validation of an integrated modelling approach to neutron emission studies at JET, Nuclear Fusion, vol 61, number 12, 2021

• A.G. Plant, L. Snoj, et al., Nuclear-driven production of renewable fuel additives from waste organics, Nature Communications Chemistry, 4, 132, 2021

• T. Goričanec, L. Snoj, et al., Applicability of the Krško nuclear power plant core Monte Carlo model for the determination of the neutron source term, Nuclear Engineering and Technology, Vol. 53, Iss. 11, 2021

• V. Mascolino, A. Haghighat & L. Snoj, Verification and Validation of RAPID Formulations and Algorithms based on Dosimetry Measurements at the JSI TRIGA Mark-II Reactor, Nuclear Science and Engineering,Vol. 195, 2021

• A. West, L. Snoj, et al., Use of Gaussian process regression for radiation mapping of a nuclear reactor with a mobile robot , Nature Scientific reports, 11, 13975

• I. Lengar, L. Snoj, et al. Shutdown dose rate calculations with modified DEMO single sector model, Fusion Engineering and Design. vol. 171, art. 112569,

• D. Kotnik, L. Snoj, et al. Assessment of sky-shine in DEMO during breeding blanket maintenance, Fusion Engineering and Design, vol. 167

• V. Radulović, L.Snoj, et al. Preparation of a water activation experiment at JET to support ITER, Fusion Engineering and Design, vol. 169, 112410,

• A. Jazbec, L.Snoj, et al., Dose rate calculations at beam tube no. 5 of the JSI TRIGA mark II research reactor using Monte Carlo method. Applied Radiation and Isotopes, 2021, vol.168, art.109510,

• A. Žohar, L.Snoj, et al., Modelling of plasma gamma ray sources in large tokamaks. Fusion engineering and design, 2021, vol. 163, art. 112158,

• L. Pirker, L.Snoj, et al., Sterilization of polypropylene membranes of facepiece respirators by ionizing radiation. Journal of membrane science. 2021, vol. 619, art. 118756,

• I. Tsitsimpelis, L.Snoj, et al., Simultaneous, robot-compatible gamma -ray spectroscopy and imaging of an operating nuclear reactor, IEEE sensors journal, 2021, vol. 21, no. 4,

• R. Bernat, L.Snoj, et al., 4H-SiC Schottky Barrier Diodes for Efficient Thermal Neutron Detection, Materials, 14(17), 5105, 2021

2020

• A. Pungerčič, L.Snoj, et al. Computational burnup analysis of the TRIGA Mark II research reactor fuel. Progress in Nuclear Energy, 2020, vol. 130, art. 103536, .

• V. Radulović, L.Snoj, et al., Characterization of the neutron spectra in three irradiation channels of the JSI TRIGA reactor using the GRUPINT spectrum adjustment code. Nuclear data sheets, 2020, vol. 167, 67-75

• J. Malec, D. Toškan & L. Snoj, PC-based JSI research reactor simulator, Annals of Nuclear Energy, 2020, vol. 146, art. 107630,

• A. Žohar, I. Lengar & L. Snoj, Analysis of water activation in fusion and fission nuclear facilities . Fusion engineering and design, 2020, vol. 160, art. 111828, 17 str.,

• A. Žohar, L.Snoj, et al., Analysis of irradiation experiments with activated water radiation source at the JSI TRIGA Research Reactor, Fusion engineering and design, 2020, vol. 161, art. 111946

• D. Kotnik, L.Snoj, et al., Use of ADVANTG to analyse skyshine [gamma]-dose rates around a silo type LILW repository. Annals of Nuclear Energy, Volume 145, 15 September 2020, 107585

• V. Radulović, L.Snoj, et al., Silicon carbide neutron detector testing at the JSI TRIGA reactor for enhanced border and port security. Nuclear instruments and methods in physics research. Section A, 2020, vol. 972, no. 164122,

• A. Gruel , L.Snoj, et al., Gamma-heating and gamma flux measurements in the JSI TRIGA reactor, results and prospects. IEEE transactions on nuclear science, Volume: 67, Issue: 4, April 2020

• K. Ambrožič & L. Snoj JSIR2S code for delayed radiation simulations: Validation against measurements at the JSI TRIGA reactor . Progress in Nuclear Energy. vol. 129, art. 103498

• A. Jazbec, L.Snoj, et al.,Dose rate calculations at beam tube no. 5 of the JSI TRIGA mark II research reactor using Monte Carlo method, Applied Radiation and Isotopes, 2020, vol.168, 109510

2019

• D. Kotnik, L.Snoj, et al., Validation and evaluation of the ADVANTG code on the ICSBEP skyshine benchmark experiment , Annals of Nuclear Energy, Volume 125, March 2019, Pages 249-260

• Review paper: A. Žohar & L. Snoj, On the dose fields due to activated cooling water in nuclear facilities , Progress in Nuclear Energy, Volume 117, November 2019, 103042

• Ž. Štancar et. al. Multiphysics approach to plasma neutron source modelling at the JET tokamak, Nuclear Fusion, Volume 59, Number 9

• A.A. Astronomo, L.Snoj, et al., Computational design and characterization of a subcritical reactor assembly with TRIGA fuel . Nuclear Engineering and Technology, 2019, vol. 51, issue 2, p. 337-344,

• T. Goričanec, L.Snoj, et al., Evaluation of the criticality and reaction rate benchmark experiments utilizing UO2F2 aqueous solution of intermediate enrichment in spherical geometry at ORNL, Progress in Nuclear Energy, Volume 111, March 2019, Pages 97-108

2018

• K. Ambrožič, L.Snoj, et al., Delayed gamma determination at the JSI TRIGA reactor by synchronous measurements with fission and ionization chambers, Nuclear instruments and methods in physics research. Section A, 2018, vol. 911, p. 94-103

• I. Lengar, L.Snoj, et al., Activation material selection for multiple foil activation detectors in JET TT campaign. Fusion engineering and design, 2018, vol. 136, p. 988-992

• Ž. Štancar, L.Snoj, et al., Generation of a plasma neutron source for Monte Carlo neutron transport calculations in the tokamak JET, Fusion engineering and design, Volume 136, Part B, November 2018, Pages 1047-1051

• A. Čufar, L.Snoj, et al., Modelling of the neutron production in a mixed beam DT neutron generator . Fusion engineering and design, 2018, part B, vol. 136, p. 1089-1093

• A. Čufar, L.Snoj, et al., Calculations to support In situ neutron yield calibrations at the joint European torus, Fusion science and technology, 2018, iss. 4, vol. 74, p. 370-386

• P. Batistoni, L.Snoj, et al., 14 MeV calibration of JET neutron detectors-phase 2 : in-vessel calibration. Nuclear fusion, 2018, iss. 10, vol. 58

• R. Henry, I. Tiselj & L. Snoj, Transient CFD/Monte-Carlo neutron transport coupling scheme for simulation of a control rod extraction in TRIGA reactor. Nuclear Engineering and Design , 2018, vol. 331, p. 302-312

• I. Capan, L.Snoj, et al. Double negatively charged carbon vacancy at the h- and k-sites in 4H-SiC : combined Laplace-DLTS and DFT study, Journal of applied physics, 2018, vol. 123, no. 16, p. 161597-1-161597-6

• Ž. Štancar, L.Snoj, et al., Computational validation of the fission rate distribution experimental benchmark at the JSI TRIGA Mark II research reactor using the Monte Carlo method, Annals of Nuclear Energy, Volume 112, February 2018, Pages 94-108

• T. Goričanec, L.Snoj, et al., Evaluation of neutron flux and fission rate distributions inside the JSI TRIGA Mark II reactor using multiple in-core fission chambers, Annals of Nuclear Energy, Volume 111, January 2018, Pages 407-440

• G. Gorine, L.Snoj, et al., Ultrahigh Fluence Radiation Monitoring Technology for the Future Circular Collider at CERN, IEEE Transactions on Nuclear Science, Volume: 65, Issue: 8, Aug. 2018

• I. Capan, L.Snoj, et al., Double negatively charged carbon vacancy at the h- and k-sites in 4H-SiC: Combined Laplace-DLTS and DFT study, Journal of Applied Physics, 123, 161597, 2018

• V. Radulović, L.Snoj, et al., Qualification of heavy water based irradiation device in the JSI TRIGA reactor for irradiations of FT-TIMS samples for nuclear safeguards, Nuclear instruments and methods in physics research. Section A, Volume 885, Pages 139-144

2017

• A. Čufar, L.Snoj, et al., The analysis of the external neutron monitor responses in a simplified JET-Like Tokamak using ADVANTG. Fusion science and technology, Volume 71, 2017 - Issue 2, Pages 162-176

• J. Lukan, K. Ambrožič, G. Žerovnik & L. Snoj, Analytical measures of homogeneity of the photon radiation field and possible applications. Nuclear instruments and methods in physics research. Section A. Volume 864, 21 August 2017, Pages 50-60

• A. Peršič & L. Snoj et al., TRIGLAV : A program package for TRIGA reactor calculations., Nuclear Engineering and Design, Volume 318, July 2017, Pages 24-34

• Ž. Štancar & L. Snoj, An improved thermal power calibration method at the TRIGA Mark II research reactor, Nuclear Engineering and Design, Volume 325,Pages 78-89, December 2017

• J. Beričič & L. Snoj, On the calculation of angular neutron flux in MCNP. Annals of Nuclear Energy, Volume 100, Part 2, February 2017, Pages 128-149

• G. Žerovnik, J. Beričič & L.Snoj, On the equivalence of neutron source and flux spectra. Annals of Nuclear Energy, Volume 99, January 2017, Pages 54-57

• R.Henry,Tiselj & L.Snoj, CFD/Monte-Carlo neutron transport coupling scheme, application to TRIGA reactor. Annals of Nuclear Energy, Volume 110, December 2017, Pages 36-47

• K.Ambrožič, G.Žerovnik & L.Snoj, Computational analysis of the dose rates at JSI TRIGA reactor irradiation facilities. Applied Radiation and Isotopes, Volume 130, December 2017, Pages 140-152

• H. Weisen, L. Snoj, et al., The "neutron deficit" in the JET tokamak. Nuclear fusion, Volume 57, Number 7

2016

• M.K. Jaradat, L.Snoj et al., Verification of MCNP6 model of the Jordan Research and Training Reactor (JRTR) for calculations of neutronic parameters , Annals of Nuclear Energy, 2016, vol. 96, p. 96-103.

• D. Čalič, G. Žerovnik, A. Trkov & L. Snoj, Validation of the Serpent 2 code on TRIGA Mark II benchmark experiments, Applied Radiation and Isotopes, 2016, vol. 107, str. 165-170

• L. Snoj et al., Neutronic analysis of JET external neutron monitor response. Fusion engineering and design, 2016, vol. 109, p. 99-103

• A. Čufar, L. Snoj et al.,Comparison of DT neutron production codes MCUNED, ENEA-JSI source subroutine and DDT. Fusion engineering and design, 2016, vol. 109, p. 164-168

• D. Fourmentel, L. Snoj et al.,Delayed Gamma Measurements in Different Nuclear Research Reactors Bringing Out the Importance of Their Contribution in Gamma Flux Calculations, IEEE Transactions on Nuclear Science, Volume: 63, Issue: 6, Dec. 2016

2015

• P. Filiatre, L. Snoj et al., Experimental assessment of the kinetic parameters of the JSI TRIGA reactor. Annals of Nuclear Energy, Volume 83, September 2015, Pages 236-245

• G. Žerovnik,L. Snoj et al., Validation of the neutron and gamma fields in the JSI TRIGA reactor using in-core fission and ionization chambers, Applied Radiation and Isotopes, Volume 96, February 2015, Pages 27-35

• R. Henry, I. Tiselj, L. Snoj, Analysis of JSI TRIGA MARK II reactor physical parameters calculated with TRIPOLI and MCNP. Applied Radiation and Isotopes, Volume 97, March 2015, Pages 140-148

• S. Manojlovič. A. Trkov, G. Žerovnik & L.Snoj, Capture cross section measurement analysis in the Californium-252 spectrum with the Monte Carlo method, Applied Radiation and Isotopes, Volume 101, July 2015, Pages 101-106

• T. Goričanec,L. Snoj et. al., Validation of neutron flux redistribution factors in JSI TRIGA reactor due to control rod movements, Applied Radiation and IsotopesVolume 104, October 2015, Pages 34-42

• A. Kolšek, V. Radulovič, A. Trkov & L.Snoj, Using TRIGA Mark II research reactor for irradiation with thermal neutrons, Nuclear Engineering and Design , Volume 283, March 2015, Pages 155-161

2014

• G. Žerovnik,L. Snoj et. al., Measurements of Thermal Power at the TRIGA Mark II Reactor in Ljubljana Using Multiple Detectors, IEEE Transactions on Nuclear Science, Volume: 61, Issue: 5, Oct. 2014

• L. Snoj, I.A. Kodeli, I. Remec Evaluation of the KRITZ-2 criticality and reaction rate benchmark experiments, Nuclear science and engineering, Volume 178, 2014 - Issue 4, p. 496-508

• J.D. Bess, L.M. Montierth, O. Koberl & L.Snoj, Benchmark evaluation of HTR-PROTEUS pebble bed experimental program, Nuclear science and engineering, Volume 178, 2014 - Issue 3, Pages 387-400

• G. Žerovnik, M. Podvratnik & L. Snoj , On normalization of fluxes and reaction rates in MCNP criticality calculations, Annals of Nuclear Energy, Volume 63, January 2014, Pages 126-128

• V. Radulović, Ž.Štancar, L.Snoj & A.Trkov , Validation of absolute axial neutron flux distribution calculations with MCNP with 197Au(n,γ)198Au reaction rate distribution measurements at the JSI TRIGA Mark II reactor, Applied Radiation and Isotopes, Volume 84, 2014, Pages 57-65

2013

• L.Snoj et al., Calculations to support JET neutron yield calibration : Modelling of the JET remote handling system, Nuclear Engineering and Design, Volume 261, August 2013, Pages 244-250

• I. Lengar & L.Snoj, Benchmark evaluation of interacting aluminum cylinders containing uranyl fluoride solution, Nuclear Engineering and Design, Volume 261, August 2013, Pages 232-237

2012

• L. Snoj, A. Trkov, M. Ravnik, G. ŽerovnikTesting of cross section libraries on zirconium benchmarks, Annals of Nuclear Energy, Volume 42, April 2012, Pages 71-79

• L. Snoj, G. Žerovnik, A. Trkov, Computational analysis of irradiation facilities at the JSI TRIGA reactor, Applied Radiation and Isotopes, Volume 70, Issue 3, March 2012, Pages 483-488

• I.A. Kodeli, L. Snoj, Evaluation and uncertainty analysis of the KRITZ-2 critical benchmark experiments, Nuclear science and engineering, Volume 171, 2012 - Issue 3, Pages 231-238

• D.B. Syme, L.Snoj et al., Fusion yield measurements on JET and their calibration,Nuclear Engineering and Design, Volume 246, May 2012, Pages 185-190

• L. Snoj et al., Calculations to support JET neutron yield calibration : Contributions to the external neutron monitor responses, Nuclear Engineering and Design, Volume 246, May 2012, Pages 191-197

• L. Snoj et al., Calculations to support JET neutron yield calibration: Neutron scattering in source holder,Fusion Engineering and Design, Volume 87, 2012, p. 1846-1852

2011

• L. Snoj et al., Analysis of neutron flux distribution for the validation of the computational methods for the optimization of research reactor utilization. Applied Radiation and Isotopes, 2011, vol. 69, issue 1, p. 136-141

• L. Snoj, M. Kromar, G. Žerovnik & M.Ravnik Advanced methods in teaching reactor physics, Nuclear Engineering and Design, Volume 241, Issue 4, April 2011, Pages 1008-1012

2010

• L. Snoj et al., Calculation of kinetic parameters for mixed TRIGA cores with Monte Carlo. Annals of Nuclear Energy, 2010, iss. 2, vol. 37, p. 223-229.

• L. Snoj et al.,Advanced methods in teaching reactor physics. Nuclear engineering and design, 2011, vol. 241, issue 4, . 1008-1012.

2009

• A. Trkov, G. Žerovnik, L. Snoj & M. Ravnik, On the self-shielding factors in neutron activation analysis, Nuclear instruments and methods in physics research. Section A, 2009, issue 2, vol. 610, p., 553-565,

• G. Žerovnik, L. Snoj & M. Ravnik, Optimization of spent nuclear fuel filling in canisters for deep repository, Nuclear science and engineering, 2009, vol. 163, p. 183-190.

2008

• L. Snoj & M. Ravnik, Power peakings in mixed TRIGA cores, Nuclear Engineering and Design, Volume 238, Issue 9, 2008, P 2473-2479

• I.. Lengar, L. Snoj, P. Rogan & M .Ravnik, Re-evaluation of the criticality experiments of the "Otto Hahn Nuclear Ship" reactor, Kerntechnik, 2007, vol. 73, p. 5-6

2007

• L. Snoj & M. Ravnik, Effect of fuel particles' size and position variations of multiplication factor in pebble-bed nuclear reactors, Kerntechnik, 2007, vol. 72, p. 251-254

2006

• L. Snoj & M. Ravnik, Effect of packing fraction variations on the multiplication factor in pebble-bed nuclear reactors, Kerntechnik, 2006, vol. 71, p. 208-213.