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- ItemAssessing the Phebus FPT-1 experiment: Insights from MELCOR 2.2 and ASYST codes(Korean Nuclear Society, 2024-07-14) Mičian, Peter; Černý, Tomáš; Petrosyan, Taron; Foral, Štěpán; Katovský, Karel; Ptáček, MichalPhebus is an experimental facility that represents a scaled-down version of the French 900 MWe pressurized water reactor (PWR) with a ratio of 1/5000. In order to study phenomena occurring during severe accidents in light water reactors, five experiments (FPT-0 to FPT-4) were performed under different fuel and cooling conditions. This paper provides a comprehensive description of the Phebus FPT-1 experiment, MELCOR and ASYST computer codes, discusses the modelling approaches employed and compares the calculated results with the experimental data. To quantitatively assess the results, the Figure of Merits of selected parameters were calculated for both computer codes using ACAP software.
- ItemTransient Current Density in a Pair of Long Parallel Conductors(MDPI, 2021-07-27) Coufal, OldřichTwo infinitely long parallel conductors of arbitrary cross section connected to a voltage source form a loop. If the source voltage depends on time, then due to induction there is no constant current density in the loop conductors. It is only recently that a method has been published for accurately calculating current density in a group of long parallel conductors. The method has thus far been applied to the calculation of steady-state current density in a loop connected to a sinusoidal voltage source. In the present article, the method is used for an accurate calculation of transient current using transient current density. The transient current is analysed when connecting and short-circuiting the sources of sinusoidal, constant and sawtooth voltages. For circular cross section conductors, the dependences of maximum current density, maximum current and the time of achieving steady state on the source frequency, the distance of the conductors and their resistivity when connecting the source of sinusoidal voltage are examined.
- ItemAstrophysical S factor and reaction rate of 92,94Mo(p,) relevant to the p-process(EDP Sciences, 2023-06-01) Hingu, Akash; Prajapati, P M; Mukherjee, Surjit; Pizzone, R.G.; Katovský, KarelLow energy proton capture cross sections on heavy isotopes are necessary for a better understanding of the astrophysical p-process. There are around 35 proton-rich stable isotopes between 74Se and 196Hg which are bypassed by the s-and r-processes. These are commonly referred as p-nuclei whose origin is still not completely understood. In the present study, proton capture reactions are studied on Mo isotopes at astrophysically relevant energies using nuclear modular code TALYS. Astrophysical S factor and reaction rates are also calculated inside a core-collapse supernova. The obtained results are compared with the literature data taken from EXFOR data library. In addition, the effect of different combinations of the nuclear input parameters entering the stellar reaction rate have been investigated.
- ItemInvestigation of critical heat flux on abraded inconel 625 tube(Czech Technical University in Prague, 2020-12-01) Suk, Ladislav; Števanka, Kamil; Petrosyan, Taron; Vlček, DanielAim of this work was to study flow boiling in an annular channel at low pressure and lowflow on a tube with modified surface roughness. The tube with the outer diameter of 9.14 mm and theheated length of 380 mm was made of Inconel 625 and was manually modified using 150 grit sandpaper.The tube was placed in a glass tube with an inner diameter of 14.8 mm. Outlet pressure was set to 120,200 and 300 kPa with varying mass flow from 400 to 600 kg/(m2·s). A high speed camera was used torecord several experiments to fully understand ongoing phenomena. Surface roughness was analysedusing a confocal laser microscope and the effects of different mass flux and pressure on the CHF valuewere observed. Above all, the optimization of the flow parameters was done from the collected dataand from the observed behaviour of the experimental loop
- ItemDistribution of neutrons and protons in elongated targets(EDP Sciences, 2020-10-03) Zeman, Miroslav; Adam, Jindřich; Baldin, Anton Alexandrovich; Brunčiaková, Miriama; Gustov, S.A.; Katovský, Karel; Khushvaktov, Jurabek; Král, Dušan; Solnyshkin, Alexander A.; Svoboda, Josef; Šťastný, Ondřej; Tichý, Pavel; Tyutyunnikov, S.; Vrzalová, Jitka; Wagner, Vladimír; Závorka, LukášAnalysis of neutron distribution was carried out for two elongated targets. The targets have cylindrical shape and are made of lead and carbon, respectively. The dimensions are approximately one meter in length and 19 cm in diameter. The targets were irradiated with 660 MeV proton beam at Phasotron accelerator at the Joint Institute for Nuclear Research. The total number of protons was 2.35(18)E15 for the experiment with carbon target and the total number of particles at the second experiment was 2.32(19)E15. The produced neutron field was monitored by cobalt threshold activation detectors at various positions. The activation detectors were measured by means of gamma spectroscopy using HPGe detectors. Reaction rates of different radionuclides produced in the activation detectors were determined and the results from both experiments were compared. The ratios were calculated for 7 reactions produced in cobalt detectors. The ratio of the reaction rates shows that the number of residual nuclei with higher threshold energies is higher for experiment with carbon target than for the experiment with the lead target.