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Accelerator driven nuclear reactor neutron field parameters determination
Zemčíková, Kristína ; Šťastný, Ondřej (referee) ; Katovský, Karel (advisor)
The master thesis deals with calculation of neutron field parameters in systems controlled by an accelerator called the Accelerator Driven System (ADS). Firstly physical principle is described, along with its parts as well as the history and present of ADS projects worldwide. Subsequently, neutron activation analysis and gamma spectrometry are described in more detail. The experiment on AmBe neutron source and on Microtron MT25 is presented in the experimental part. Lastly, the reaction rates are calculated.
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Accelerator driven nuclear reactor neutron field parameters determination
Zemčíková, Kristína ; Šťastný, Ondřej (referee) ; Katovský, Karel (advisor)
The master thesis deals with calculation of neutron field parameters in systems controlled by an accelerator called the Accelerator Driven System (ADS). Firstly physical principle is described, along with its parts as well as the history and present of ADS projects worldwide. Subsequently, neutron activation analysis and gamma spectrometry are described in more detail. The experiment on AmBe neutron source and on Microtron MT25 is presented in the experimental part. Lastly, the reaction rates are calculated.
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Study of reaction cross-sections important for advanced nuclear systems
Chudoba, Petr ; Wagner, Vladimír (advisor) ; Krása, Antonín (referee) ; Krtička, Milan (referee)
The doctoral thesis is focused on measurements of neutron cross-sections mainly cross-sections of (n,xn) threshold reactions. With the dawn of advanced nuclear systems such as fast reactors of GenIV, accelerator driven system or even fusion reactors, monitoring of fast neutron fields will gain on importance. The activation detectors are one of the viable options how to monitor these neutron fields and (n,xn) reactions would be one of the best options how to do such monitoring. There is one condition though. We need to have good cross- section data in high neutron energy region. Unfortunately, the current situation is rather bad. There is only a small amount of reliable data for neutron energies above 20 MeV and with increasing energy, the situation gets only worse. For this reason, we measure the cross-sections of (n,xn) reactions on perspective materials such as yttrium, gold and tantalum with neutron energies from 17.4 up to 94 MeV. In this thesis, the measurements together with motivation and methodology are described. Obtained results are in agreement with existing data. Severe discrepancies were observed between the predictions and experimental data for high order (n,xn) reactions. This problem is discussed and solved. The results in this region are in form of cross-section values and also...
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Study of reaction cross-sections important for advanced nuclear systems
Chudoba, Petr ; Wagner, Vladimír (advisor) ; Krása, Antonín (referee) ; Krtička, Milan (referee)
The doctoral thesis is focused on measurements of neutron cross-sections mainly cross-sections of (n,xn) threshold reactions. With the dawn of advanced nuclear systems such as fast reactors of GenIV, accelerator driven system or even fusion reactors, monitoring of fast neutron fields will gain on importance. The activation detectors are one of the viable options how to monitor these neutron fields and (n,xn) reactions would be one of the best options how to do such monitoring. There is one condition though. We need to have good cross- section data in high neutron energy region. Unfortunately, the current situation is rather bad. There is only a small amount of reliable data for neutron energies above 20 MeV and with increasing energy, the situation gets only worse. For this reason, we measure the cross-sections of (n,xn) reactions on perspective materials such as yttrium, gold and tantalum with neutron energies from 17.4 up to 94 MeV. In this thesis, the measurements together with motivation and methodology are described. Obtained results are in agreement with existing data. Severe discrepancies were observed between the predictions and experimental data for high order (n,xn) reactions. This problem is discussed and solved. The results in this region are in form of cross-section values and also...
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Geological and geophysical exploration of the Kokonín fault for building constructions (Jablonec n. Nisou, Czech Republic)
Tumurkhuu, Gereltsetseg ; Goliáš, Viktor (advisor) ; Thinová, Lenka (referee)
Radioactivity is an important part of the environment. In the years 2014 - 2015 a survey on medicinal radioactive springs was carried out in the Tanvald granite body. During extensive radiohydrogeochemical exploration in the surrounding area of Schindler spring, the outcrop of U - mineralization has been found at a new construction site in the Kokonín fault. It is possible to find "hot" pieces of uranium ore fragments in the quaternary cover in this place. The occurrence of the hydrothermal (vein) type of uranium in the Krkonoše - Jizera is new as it hasn't been mentioned in literatures before. After an agreement with the owners, detailed radiometric survey proceeded in the surrounding area of two affected houses by using gamma spectrometry and emanometry at the dense net. There is a wider area between two houses with activities of 222 Rn over 1 MBq/m3 and on the ore outcrop was measured 3.3 MBq/m3 . A quaternary solifluction flow with an increased radioactivity creeps down under the House 1. The highest uranium contents reached up to 291 ppm eU (= 3 595 Bq/kg 226 Ra) on the uranium ore lens outcrop. The average of gamma dose rate is 85,6 nGy/h with maximem 261 nGy/h on the outcrop. A further radiometric survey through the entire Kokonín fault line was carried out in an area of roughly 0.25 x 1 km2...
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Comparison of the measured specific activities of cesium 137 in different species of bryophytes.
TRNKOVÁ, Michaela
This bachelor thesis focuses on measuring specific activities of Cs-137 in different species of moss in areas affected by radiation fallout and compares the species different tendencies to absorb radionuclides. The research question is: Do different species of moss in areas affected by radiation fallout contain different amounts of Cs-137? The theoretical part of the thesis introduces the radiobiological problematics, including basic terms and units, and its contemporary situation. This part also focuses on radionuclide Cs-137 and its sources and kinetics in nature. The practical part describes used methodology and consequently focuses on the results of measuring chosen moss samples, including their subsoils. Specialised literature describes mosses as significant bioindicators of radionuclides. This thesis tries to distinguish different species and establish whether those different species have different tendencies to absorb radionuclides. The locations for sampling were chosen according to previous studies which located areas with high concentration of Cs-137 caused by radiation fallout in 1986. The total amount of moss and subsoil samples is 20 samples each. One of the locations was Russian island Valaam in Ladoga Lake where four samples were collected. Specific activity was measured using semiconductor gamma spectometry. Beside Cs-137, the focus was on concentration of natural radionuclide K-40. Measured spectra were evaluated by GAMWIN software. Measuring specific activity of Cs-137 in moss and subsoil samples and calculation of transfer ratio proved that different species of moss in areas affected by radiation fallout contain different amount of Cs-137.
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Application of semiconductor gamma spectrometry in experimental reactor physics
KUČERA, Jan
In the present bachelor thesis, a database for efficiency calibration of a gamma-spectrometry device with cascade summing correction was built using software developed by the company Canberra. The formation of the database consists in the construction of a model for a shielding of semiconductor detector and of models for measured radioactive samples with various geometries. The designed model was tested on measured spectra of gamma radiation and a selected calibration curve was compared with the results obtained by Research Center Rez using the MCNP method. Moreover, several theoretical results were obtained in the course of this work, including the technical parameters and usage of experimental reactors at Research Center Rez and the principles of gamma radiation spectrometry in the LR-0 reactor.
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