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Snisar I.B.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2014

This paper analyzes a mathematical model of ionizing radiation fields generated near material surfaces by the sources distributed over them. It is shown that there is an objective limit of their spatial heterogeneity, and this limit does not depend on the distribution of sources on surfaces. Some possible applications of the obtained result in radiation protection and dosimetry have been identified.


Shevchenko I.A.,State Scientific and Technical Center for Nuclear and Radiation Safety | Vorobyov Y.Y.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2015

The thermal-hydraulic aspects of modeling the mixed core (several types of nuclear fuel) with TVSA, TVS-W and TVS-WR fuel are analyzed. The safety criteria for the maximal fuel cladding temperature are evaluated for representative events of design basis accident (DBA) analysis for WWER-1000 reactors using RELAP5/MOD3.2 computer code. It is shown that the maximal cladding temperature increases with introduction of new TVS-WR or TVS-W fuel as compared to TVSA. Preliminary analyses have shown that the maximal cladding temperature does not exceed its limit of 1200°C in the events involving seizure of the main coolant pump (MCP) and double-ended cold leg break of the main coolant piping. The results confirm the need for further thermal-hydraulic analysis of WWER-1000 mixed cores. DBA analysis has to be complemented with calculations for mixed cores.


Chumak D.,State Scientific and Technical Center for Nuclear and Radiation Safety | Klevtsov O.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2015

Active introduction of information technology, computer instrumentation and control systems (I & C systems) in the nuclear field leads to a greater efficiency and management of technological processes at nuclear facilities. However, this trend brings a number of challenges related to cyber-attacks on the above elements, which violates computer security as well as nuclear safety and security of a nuclear facility. This paper considers regulatory support to computer security at the nuclear facilities in Ukraine. The issue of computer and information security considered in the context of physical protection, because it is an integral component. The paper focuses on the computer security of I & C systems important to nuclear safety. These systems are potentially vulnerable to cyber threats and, in case of cyber-attacks, the potential negative impact on the normal operational processes can lead to a breach of the nuclear facility security. While ensuring nuclear security of I & C systems, it interacts with nuclear safety, therefore, the paper considers an example of an integrated approach to the requirements of nuclear safety and security.


Bilodid I.,State Scientific and Technical Center for Nuclear and Radiation Safety | Duspiva J.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2015

Interest in the analysis of beyond design basis accidents, involving a combination of several failures with fuel damage, has increased throughout the world after the Fukushima accident. Stress tests were performed at NPPs, and development of severe accident management guidelines was started. These activities necessitated calculations to analyze the probability of beyond design basis accidents and assess their initiating events and consequences. One of the aspects in analysis of beyond design basis accidents is to determine the potential for re-criticality during such accidents. The paper provides results of some criticality safety calculations for VVER reactors performed, in particular, by ÚJV Řež and SSTC NRS experts. It is shown how criticality can occur in different severe accident phases. © I. Bilodid, J. Duspiva, 2015.


Snisar I.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2015

The paper presents original procedures for zoning, survey optimization and verification of surface radiation fields dosimetry data. These procedures give an opportunity to find unambiguous solutions for the problems of zoning and survey routing of the above fields at any scope of input data, as well as an opportunity to verify field measurements data acquired at any measurement grid and using any methods.


Bilodid Y.,State Scientific and Technical Center for Nuclear and Radiation Safety | Kovbasenko Y.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2015

The paper presents parameters calculated with SCALE-4.4 code to assess impact of fabrication tolerances and uncertainty of input data on geometrical and material composition of VVER-1000 fuel assembly (FA) elements on results of nuclear fuel criticality analysis. The most conservative set of parameters within the process error has been identified in terms of effect on fuel multiplication properties. The dependence of multiplication properties on FA material temperature has been analyzed.


Vorobyov Y.,State Scientific and Technical Center for Nuclear and Radiation Safety | Zhabin O.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2015

Applicability of cladding deformation model in RELAP5/MOD3.2 code is analyzed for VVER-1000 fuel cladding from Zr+1%Nb alloy. Experimental data and calculation model of fuel assembly channel of the core are used for this purpose. The model applicability is tested for the cladding temperature range from 600 to 1200 °C and pressure range from 1 to 12 MPa. Evaluation results demonstrate limited applicability of built-in RELAP5/MOD3.2 cladding deformation model to the estimation of Zr+1%Nb cladding rupture conditions. The limitations found shall be considered in application of RELAP5/MOD3.2 cladding deformation model in the design-basis accident analysis of VVER reactors.


Dybach O.,State Scientific and Technical Center for Nuclear and Radiation Safety | Nosovsky A.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2015

The paper considers the general task on checking compliance of probabilistic safety indicators with regulatory criteria. It presents correlations to assess probable exceeding of safety criterion for different laws of distribution of the numerical results of the probabilistic safety analysis (PSA). The paper presents the scale for rationing probability of safety criteria exceeding.


Klevtsov A.,State Scientific and Technical Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2013

The approaches and methods accepted in Ukraine for reliability assessment of NPP instrumentation and control systems are presented in the paper. The software for reliability calculation which was developed by SSTC NRS and results of its verification are described as well.


Vorobyov Y.Y.,State Scientific and Technical Center for Nuclear and Radiation Safety | Perepelitsa M.L.,Taras Shevchenko National University | Sverdlov V.V.,Taras Shevchenko National University
Nuclear and Radiation Safety | Year: 2012

The spent fuel pool model for computer code MELCOR 1.8.5 is developed for WWER-1000 units. The initiating event involving loss of heat removal from the spent fuel pool is analyzed. Time frames of fuel damage, hydrogen generated mass and radiation consequences are estimated. Based on different spent fuel pool loads, the relationships characteristic of severe accidents are determined to allow scaling of the results to other spent fuel pool configurations.

Loading State Scientific and Technical Center for Nuclear and Radiation Safety collaborators
Loading State Scientific and Technical Center for Nuclear and Radiation Safety collaborators