Results 1 - 10 of 1876
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[en] Owing to growing interest in the study of emitted antineutrinos from nuclear reactors to test the Atomic Energy Agency safeguards, antineutrino flux was studied in the Tehran Research Reactor (TRR) using ORIGEN code. According to our prediction, antineutrino rate was obtained 2.6 x 1017 (ve/sec) in the core No. 57F of the TRR. Calculations indicated that evolution of antineutrino flux was very slow with time and the performed refueling had not an observable effect on antineutrino flux curve for a 5 MW reactor with the conventional refueling program. It is seen that for non-proliferation applications the measurement of the contribution of 239Pu to the fission using an antineutrino detector is not viable in the TRR.
[en] The nuclear reactor remote monitoring system of the state of Baden-Wuerttemberg (Kernreaktor-Fernueberwachung Baden-Wuerttemberg - KFUeBW) is implemented according to the recently renewed ''recommendations for remote monitoring of nuclear power plants''. In Baden-Wuerttemberg, the application area of the system covers both, the surveillance of internal procedures on one hand, and the handling of incidents or accidents on the other. The following paper shows the role of the KFUeregarding the determination and evaluation of the radiological situation in the range of off-site emergency response. Progress is reported on the measurement conception and the technical possibilities for the investigation of the radiological situation after the end of the deposition of radio nuclides (ground phase). (orig.)
[en] Gadolinium is mixed with nuclear fuel for extended burnup, increased reactor cycle Lengths, and in-out core refueling schemes. The purpose of this work is to investigate the effect of Gadolinium on neutronic parameters. A comprehensive analysis of different fuel assemblies bearing gadolinia with different concentration and different number of gadolinia rods was carried out. The EPR fuel assemblies were chosen in this study. The fuel assemblies are of seven different types, each assembly has unique design characteristics in terms of enrichment, number of gadolinia rods and gadolinium concentration. The calculations were achieved using MCNP6 code and with ENDF/B-VII library. A fine mesh tally was superimposed on the geometry to illustrate flux distribution in the whole assembly and its change with burnup. The variation of reactivity and isotopic composition for each region of the assembly with burnup and its influence on flux distribution was studied. The results showed that the presence of gadolinium greatly affects the power distribution. It causes some skewness in axial power shape towards the top of the assembly, the assembly which has largest number of gadolinia rods and the lowest enrichment has the largest skewness of power distribution at BOC. At EOC the flux and axial power have a double hump shape due to the buildup of gadolinium isotopes and the large decrease in reactivity with burnup.
[en] The Fukushima nuclear disaster in 2011 has raised widespread concern over the safety of nuclear power plants. This study employed knowledge management in conjunction with the Teoriya Resheniya Izobreatatelskih Zadatch (TRIZ) method in the formulation of a database to facilitate the evaluation of post-fire safe shutdown capability with the aim of safeguarding nuclear facilities in the event of fire. The proposed approach is meant to bring facilities in line with US Nuclear Regulatory Commission (NRC) standards. When implemented in a case study of an Asian nuclear power plant, our method proved highly effective in the detection of 22 cables that fell short of regulatory requirements, thereby reducing 850,000 paths to 0. This study could serve as reference for industry and academia in the development of systematic approaches to the upgrading of nuclear power plants.
[en] In this paper, at the same time, two separate objectives and two safety and operational constraints are chosen to optimize fuel reloading pattern of a Material Testing Reactor (MTR), independently and coherently. This is one of the most difficult type of engineering problems as a constrained, non-continuous, combinatorial, and fully multi-objective optimization problem. Decision space is a non-continuous multimodal space restricted by both of the combinatorial and safety constraints. A smart software application and a robust hybrid algorithm have been developed to get Pareto optimal set with respect to both of the economy of irradiating utilizations and nuclear safety based on the heuristic soft computing. The hybrid algorithm is composed of a fast and elitist Multi-Objective Genetic Algorithm (MOGA) and a fast fitness function evaluating system based on the semi-deep learning cascade feed forward Artificial Neural Networks (ANNs). The smart software is used to produce database automatically required for the ANN training and test data. It can be also used to revise data accurately, impose further irradiating benefits or Operating Limits and Conditions (OLCs), and to advise the reactor supervisor on the most desire pattern based on the smart searches and filtering. The results are highly promising. For more details, optimization results dominate conventional operating core parameters, significantly. Also chosen OLCs are protected. Furthermore, this is very good practice to reach a fully developed practical application of the complex soft computing for the nuclear fuel management problems.
[en] The dead of Alexander Litvinenko in London in the late 2006 was linked with the visit of Dimitri Kovtun. So an investigation was started by the Hamburg Police. As the presence of polonium-210 was uncertain, the action was supported by the Federal Defense against Nuclear Hazards (NGA) of the Federal Office for Radiation Protection (BfS). Radiation measurements in some flats in Hamburg confirmed the suspicion of polonium-210 contaminations. As incorporations by ingestion or inhalation could not generally be excluded, the Coordinating Office on Incorporation Monitoring of the BfS (Leitstelle Inkorporationsueberwachung des BfS) was requested to clarify this issue. The BfS office then coordinated the required bioassay analyses of urine samples carried out at four officially appointed in-vitro laboratories for incorporation monitoring. The group of people to be examined included the members of the family involved living in the contaminated flats, the emergency forces, as well as potentially exposed members of the public. The calculation of the internal dose was based on standard assumptions and also conducted by the BfS. The internal radiation doses proved to be within the range of radiation doses due to natural exposures. Retrospectively it should be stressed that the collaboration and cooperation of all institutions involved in the operation in Hamburg was extremely good despite their differing organisational structures. As a result of the incident in Hamburg various middle and long-term measures have been taken since then by the BfS Coordinating Office on Incorporation Monitoring. (orig.)
[en] The mysterious death of the former secret service agent Alexander Litvinenko on 23 November 2006 suddenly attracted the attention of the public to the rather unknown radionuclide (210)Po. In this respect, this paper presents some general background information about this radionuclide as well as some details about its biokinetic behaviour and internal dosimetry. The results are discussed in the context of the Litvinenko case with regard to possible health effects on people from Germany being potentially contaminated. However, no evidence for contamination with (210)Po could, be found for any people tested at the GSF-National Research Center for Environment and Health (since 01.01.2008 Helmholtz Zentrum Muenchen). (orig.)
[en] The mission of the Comprehensive Nuclear-Test-Ban Treaty International Data Centre (IDC) is to: (a) acquire data over a Global Communications Infrastructure from a global network of 337 facilities of the International Monitoring Systems (IMS), (b) to process and analyze these data, and (c) to provide the IMS data, IDC products and services to Member States. In effect, the IDC symbolizes a new brand of arms control for the information age, leveraging Internet communications, knowledge-based data fusion, graphical decision support systems and Web-based user interfaces to achieve its mission. During 2000, the IDC was disseminating products based on data from about 90 seismic, hydroacoustic, infrasound and radionuclide stations of the future network. The number of events in the reviewed seismo-acoustic bulletins ranged from 40 to 360 each day. On average, some 200 radionuclide spectra were processed and analysed each month. Users from 45 Member States received an average of close to 18,000 data and product deliveries per month from the IDC. As the IDC continues to prepare for entry-into-force of the CTBT, it will continue to integrate the state-of-the-art in science and technology in order to meet the demands of the increasing volume of new types of IMS data, expanded IDC services, and a growing base of users. (orig.)
[de]Die Aufgaben des Internationalen Datenzentrums (IDC) fuer das Umfassende Verbot fuer Nuklearversuche (UVNV) sind die folgenden : (a) Sammeln der Daten vom globalen Netzwerk mit 337 Einrichtungen des Internationalen Ueberwachungssystems (IMS) ueber eine globale Kommunikationsinfrastruktur, (b) Verarbeitung und Analyse dieser Daten, und (c) Versorgung der Mitgliedsstaaten mit diesen IMS Daten sowie mit IDC Produkten und Diensten. Das IDC symbolisiert damit eine neuen Typ der Ruestungskontrolle im Informationszeitalter und stuetzt sich dabei auf Internet Kommunikation, wissensbasierte Datenfusion, graphische Systeme zur Entscheidungshilfe sowie Web-gestuetzte Schnittstellen um diese Aufgabe zu erfuellen. Im Laufe des Jahres 2000 verbreitete das IDC Produkte, die auf Daten von etwa 90 bereits existierenden seismischen, hydroakustischen, Infraschall- und Radionukliddetektoren des zukuenftigen Netzwerkes basieren. Die Anzahl der Ereignisse in den analysierten seismoakustischen Bulletins reichte von 40 bis 360 pro Tag. Im Durchschnitt wurden rund 200 Radionuklidspektren pro Monat verarbeitet und analysiert. Nutzer aus 45 Mitgliedsstaaten haben im Durchschnitt nahezu 18,000 Daten- und Produktauslieferungen pro Monat vom IDC erhalten. Im Zuge seiner fortlaufenden Vorbereitungen auf das Inkrafttreten des UVNV wird das IDC seine Methoden weiterhin dem Stand von Wissenschaft und Technik anpassen, um den Anforderungen des wachsenden Umfangs von neuen Arten der IMS Daten, erweiterten IDC Diensten und einer wachsenden Nutzerschaft gerecht zu werden. (orig.)
[en] Unauthorized dilution of boric acid in the reactor coolant due to improper operation of the chemical and volume control system (KBA) is a project mode with the violation of normal operation. The operator is obliged to identify unauthorized dilution within half an hour and stop feeding with pure condensate. The power unit has automation, which stops feeding on EP (emergency protection) and ATWS (Anticipated transient without scram) signals. The situation without the intervention of the operator and the failure of automation to stop dilution can be considered as a beyond design basis accident. The article presents an analysis of unauthorized boric acid dilution process in the primary circuit coolant of the NPP-2006 power unit up to the controlled state, either considering the operator's intervention after a 30-minute period of process, i. e. with a forced cessation of dilution, or without the operator's intervention until the tanks with pure condensate are completely emptied.
[en] Turbulent mixing rate between adjacent subchannels in a two-phase flow has been known to be strongly dependent on the flow pattern. The most important aspect of turbulent motion is that the velocity and pressure at a fixed point do not remain constant with time even in steady state but go through very irregular high frequency fluctuations. These fluctuations influence the diffusion of scalar and vector quantities. The Advanced Heavy Water Reactor (AHWR) is a vertical pressure tube type, heavy water moderated and boiling light water cooled natural circulation based reactor. The fuel bundle of AHWR contains 54 fuel rods set in three concentric rings of 12, 18 and 24 fuel rods. This fuel bundle is divided into number of imaginary interacting flow channel called subchannels. Alteration from single phase to two phase flow situation occurs in reactor rod bundle with raise in power. The two phase flow regimes like bubbly, slug-churn, and annular flow are generally encountered in reactor rod bundle. Prediction of thermal margin of the reactor has necessitated the investigation of turbulent mixing rate of coolant between these subchannels under these flow regimes. Thus, it is fundamental to estimate the effect of spacer grids on turbulent mixing between subchannels of AHWR rod bundle.