Helium implanted FeCr alloys studied by positron annihilation lifetime technique

The influence of chromium on the radiation damage resistance of iron based alloys has been studied using conventional positron lifetime technique and a pulsed low energy positron beam. To simulate high neutron flux, the helium implantation has been used. Different levels of helium doses (6.24·10¹⁷–3.12·10¹⁸ cm⁻²) corresponding to a local damage of up to 90 dpa were accumulated in a thin 1 nm) and small vacancy clusters together with the initial dislocations and small point defects.Досліджувався вплив хрому на стійкість до радіаційного пошкодження сплавів на основі заліза за допомогою загальновизнаного методу вимірювання часу життя позитронів та імпульсного пучка позитронів низької енергії. Різні рівні доз гелію (6,24·10¹⁷– 3,12·101¹⁸см⁻²), що відповідають локальному пошкодженню до 90 зсувів/атом, накопичувались в області товщиною не менш 1 мкм. У даній роботі використовувались чотири бінарних сплави Fe-Cr (2,6; 4,6; 8,4; 11,6 ваг.% Cr). Отримані результати показують, що хром має значний вплив на розмір та розподіл створених дефектів. Характер цих дефектів визначався у вигляді великих пор (>1 нм) і малих вакансійних кластерів поряд з початковими дислокаціями і малими точковими дефектамиИсследовалось влияние хрома на стойкость к радиационному повреждению сплавов на основе железа с помощью общепринятого метода измерения времени жизни позитронов и импульсного пучка позитронов низкой энергии. Различные уровни доз гелия (6,24·10¹⁷– 3,12·101¹⁸см⁻²), соответствующие локальному повреждению до 90 смещ./атом, накапливались в области толщиной менее 1 мкм. В настоящей работе использовались четыре бинарных сплава Fe-Cr (2,6; 4,6; 8,4; 11,6 вес. % Cr ). Полученные результаты показывают, что хром оказывает значительное влияние на размер и распределение созданных дефектов. Характер этих дефектов определялся в виде больших пор (>1 нм) и малых вакансионных кластеров наряду с начальными дислокациями и малыми точечными дефектами

Criticality Safety Analysis of Spent Fuel Storage Pool for NPP Mochovce using MCNP5 Code

The paper presents results of nuclear criticality safety analysis of spent fuel storage and handling for the 1st and 2nd unit of NPP Mochovce. Spent fuel storage pool (compact and reserve grid) and T-12 transport cask were modeled using the Monte Carlo code MCNP5. Conservative approach was applied and calculation of max eff k values was performed for normal and various postulated emergency conditions in order to evaluate the final maximal max eff k values. The requirement of current safety regulations to ensure 5% subcriticality was met except some especially conservative cases

Komparácia európskeho a islamského poisťovníctva

The diploma thesis is focused on a comparison of European and Islamic insurance. The theoretical part describes the main principles of European and Islamic insurance. The thesis compares development of insurance premiums and takaful contributions. The thesis provides an analysis of insurance markets of Saudi Arabia, Malaysia and the United Kingdom, including their comparison. The thesis describes development of amount of Muslim population. Based on the results, recommendations for implementation of insurance products for European insurance companies on takaful basis have been suggested

Analysis of Personal Investments

V práci analyzujem možnosti dlhodobého investovania pre bežných ľudí. Mojou hypotézou bolo, že pri investičnom cieli priemerného ročného výnosu 5% v období 40 rokov nie je nutné vybrať jeden konkrétny investičný produkt (akcie, zlato, nehnuteľnosti, dlhopisy, kryptomeny a ďalšie) a tým zvýšiť riziko volatility, ale je možné nájsť investičný mix, pozostávajúci z viacerých štandardných investičných produktov, ktorý takýto výsledok dosiahne. Moja hypotéza bola potvrdená.In diploma thesis I analyse the possibilities of long-term investment for ordinary people. My hypothesis is that for the investment goal of an average annual revenue of 5% over a period of 40 years, it is not necessary to select one specific investment product (stocks, gold, real estates, bonds, cryptocurrencies and others) and by thus increase volatility risk, but it is possible to find an investment mix, consisting of several standard investment products, which will achieve such a result. My hypothesis was confirmed

Poistné podvody v Českej republike

Bachelor thesis deals with topic of insurance frauds in Czech Republic. Literature review is focused on characteristics of insurance market, division of insurance market, classification of insurance, definition of insurance fraud. The thesis itself contains the description of insurance claim report process. Comparison of demonstrated insurance fraud cases in the years 2014 and 2015 by Czech Association of Insurance companies and four selected commercial insurance companies. The thesis discusses insurance fraud cases registered by the Police of Czech Republic and the amount of consequences of insurance fraud for assurers, assured, and offenders. Furthermore, concrete insurance fraud cases revealed from the years 2014 and 2015, and own illustration of organized crime in insurance fraud were introduced. The insurance fraud cases in Czech Republic and United Kingdom were compared. Final part brings personal recommendations which may help reduce insurance fraud committing

Optimization of Positron-Lifetime Measurement Geometry Based on Geant4 Simulation

Proper choice of measuring geometry and experimental setup of nuclear instrumentation modules and photomultipliers is a key element which affects substantial positron lifetime measurement properties: count rate and time resolution. An adequate compromise must be found, when it comes to geometry of measurement. The optimal geometry using three detector layout is inspected in this paper. During our work, we concentrated on the simulation of XP2020Q photomultipliers and the BaF₂ scintillator material. The Geant4 simulation allows to estimate an influence of the measuring geometry on detection efficiency and to choose the most appropriate crystals dimensions and positions. As mentioned in paper of Bečvaŕ et al., slight changes in geometry result in distortion or improvement of measured results. Experimental results already showed, changes of start crystals dimensions can result in significant increase in count rate of three-detector measurement

Positron Study of Radiation Embrittlement of Steels Used in Water Cooled, Water Moderated Energy Reactors

Positron annihilation spectroscopy (PAS) and Moessbauer spectroscopy (MS) were applied in the evaluation of the microstructure parameters and degratdation processes of nuclear reactor pressure vessel (RPV) steel surveillance specimens. Study was oriented to the material investigation of Russian WWER-1000 steels (15Kh2MNFAA and 12Kh2N2MAA) with highter Ni content (1,26 wt.% in base metal and 1,7 wt.% in weld). For comparison, the WWER-440 weld metal (Sv10KhMFT) without Ni wasw measured, too. Specimens were studied in as received stage, after irradiation in LVR-15 experimental reactor to the neutron fluence F(E>0.5 MeV)=4x10 23m-2s-1 and after annealing in vaccuum at 475 oC/2h. Changes due to different chemical composition and due to irradiation were registered using MS. Post-irradiation thermal treatment and annealing of defects was well detected by different PAS techniques. It was observed that the sensitivity of PAS and MS parameters to defined irradiation treatment decreases with Ni-content increase. Results confirm the hypothesis that Ni affects size (decrease) and distribution (more homogeneous) of the Cu- and P-rich clusters and MxCx carbides.JRC.F.4-Nuclear design safet

Microstructural Study of High Irradiated Reactor Steels

Positron Annihilation Spectroscopy (PAS) techniques in combination with other techniques were effectively used in the testing and selection process of optimal reactor steels for use in Generation III and IV reactors or thermonuclear fusion facilities. Conventional PAS lifetime technique and pulsed low energy positron system were applied on wide spectrum of reactor steels together with other techniques viz., Transmission Electron Microscopy and Mossbauer Spectroscopy focused on the role of Nickel in the steel microstructure. Experimental experiences in this area collected over the last twenty years were very useful in the actual study by avoiding many mistakes in handling with specimens or in careful interpretation of the results.JRC.F.4-Nuclear Reactor Integrity Assessment and Knowledge Managemen

Optimization of Positron-Lifetime Measurement Geometry Based on Geant4 Simulation

Proper choice of measuring geometry and experimental setup of nuclear instrumentation modules and photomultipliers is a key element which affects substantial positron lifetime measurement properties: count rate and time resolution. An adequate compromise must be found, when it comes to geometry of measurement. The optimal geometry using three detector layout is inspected in this paper. During our work, we concentrated on the simulation of XP2020Q photomultipliers and the BaF₂ scintillator material. The Geant4 simulation allows to estimate an influence of the measuring geometry on detection efficiency and to choose the most appropriate crystals dimensions and positions. As mentioned in paper of Bečvaŕ et al., slight changes in geometry result in distortion or improvement of measured results. Experimental results already showed, changes of start crystals dimensions can result in significant increase in count rate of three-detector measurement