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[en] The environment and the population of the planet today are subject to various environmental risks. The risk of radioactive contamination of the environment requires increased attention, since the consequences of radiation disasters are especially damaging to the environment. The main sources of the threat of radioactive contamination are objects of the atomic industry, as well as nuclear weapons and terrorism. The use of radiation portal monitor systems at various potentially dangerous facilities is the main preventive measure to suppress the illicit trafficking of radioactive materials and allows for the radiation safety of the population. (authors)
[en] The main aim of this work is to provide an overview on the nuclear propulsion technologies for space exploration under research and development through a literature review in order to clarify the misunderstandings and unfamiliarity related to such subject. Firstly, they are introduced some of the potential advantages of nuclear propulsion over the traditional concept based on the combustion between hydrogen and oxygen. After that, the basic physical principles, some possible approaches (nuclear fission propulsion, nuclear thermal propulsion and nuclear electric propulsion) and projects of nuclear propulsion technologies are described. Finally, the challenges related to this research field are also discussed. All these features, allied with its challenges, will help the Department of Nuclear Engineering at Federal University of Minas Gerais (UFMG) to define a research line about nuclear propulsion, what justifies the development of this paper.(author)
[en] Control and accounting of fissionable nuclear materials is based on the following documents: “IAEA safeguards. Guidelines for State Systems for Control and Accounting of Nuclear Materials” and “Regulations on the Structure of the State System for Control and Accounting of Nuclear Materials”, adopted by the Resolution of the Board of the Regulating Authority of the Republic of Uzbekistan. Control and accounting of fissionable nuclear materials provides for reliable and timely information about quantity and distribution of nuclear materials, timely detection of losses, non-authorized use or theft of fissionable nuclear materials. Control and accounting of nuclear materials at the WWR-SM reactor INP AS RU are carried out constantly from the moment of the first receipt of nuclear fuel. Until 1991, quarterly control and accounting of nuclear materials was carried out in collaboration with the Ministry of Atomic Energy and Industry of the former USSR. Since 1994, all documents containing information about the accounting of nuclear materials are submitted to the Republic of Uzbekistan’s State Inspectorate, “SANOATGEOKONTEXNA-ZORAT”, and further communicated by official channels to the IAEA. The main tasks for the control and accounting of nuclear materials in the Republic of Uzbekistan are to improve the regulatory legal framework of the Republic of Uzbekistan for countering the illegal circulation of nuclear materials and radioactive substances. Questions on control and accounting of nuclear materials outside facilities have been resolved, with all the owners of nuclear materials identified, with measurements on nuclear materials carried out to more accurately determine the mass and other characteristics. It is planned to discuss the possibility of a training course on the ORIGEN and TRITON software to provide practical research information to the specialists of the research reactor on the implementation of IAEA safeguards, particularly methods for calculating the burnup of 235U and plutonium recovery. Training in the various methods for calculating the burnup of 235U and the production of plutonium will be used at WWR-SM to provide more accurate record-keeping of nuclear materials. (author)
[en] Highlights: • No study has been performed for mixed D2O-H2O coolant with soluble-boron-free SMR. • Neutron spectrum variation over burnup is observed for mixed D2O-H2O coolant. • Wetter-than-normal or dryer-than-normal lattice are better for higher burnup. • D2O-H2O and H2O are effective for the drier and wetter lattices, respectively. • Duplex fuel offers higher discharge burnup potential for all moderation regimes. - Abstract: Civilian marine reactors face a unique set of design challenges in addition to the usual irradiation and thermal-hydraulic limits affecting all reactors. These include requirements for a small core size, long core lifetime, a 20% cap on fissile loading, and limitations on the use of soluble boron. One way to achieve higher burnup/longer core life is to alter the neutron spectrum by changing the hydrogen-to-heavy-metal ratio, thus increasing the conversion of fertile isotopes in the fuel. In this reactor physics study, we optimize the two-dimensional lattice geometry of a 333 MWth soluble-boron-free marine PWR for 18% 235U enriched micro-heterogeneous ThO2-UO2 duplex fuel and 15% 235U enriched homogeneously mixed all-UO2 fuel. We consider two types of coolant: H2O and mixed 80% D2O + 20% H2O. We aim to observe in which spectrum discharge burnup is maximized in order to improve uranium utilization, while satisfying the constraint on moderator temperature coefficient. It is observed that higher discharge burnup for the candidate fuels is achievable by using either a wetter lattice or a much drier lattice than normal, while epithermal lattices are distinctly inferior performers. The thorium-rich duplex fuel exhibits higher discharge burnup potential than the all-UO2 fuel for all moderation regimes for both coolants. The candidate fuels exhibit higher initial reactivity and discharge burnup with the mixed D2O-H2O coolant than with the H2O coolant in the under-moderated regime, whereas these values are lower for the D2O-H2O coolant in the over-moderated regime.