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Alpeev A.S.,Scientific and Engineering Center for Nuclear and Radiation Safety
Nuclear and Radiation Safety | Year: 2014

The paper discuses safety classification of process equipment and automation devices of nuclear power plants. It is indicated that safety classes are incorrectly transferred from safety functions to process equipment and automation devices that perform these functions. Three functional groups are proposed for equipment classification, which are the most crucial for NPP safety assurance and are the basis for developing any control system since no other control system component is characterized by such complete and unique requirements on quality indicators. A control system is just an aggregate of functional groups and their characteristics. Source


Lankin M.,Scientific and Engineering Center for Nuclear and Radiation Safety
11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012, PSAM11 ESREL 2012 | Year: 2012

Russian national regulatory documents require an analysis of beyond design basis accidents to be carried out for NPPs for the scope of working out control strategies for such accidents, as well as strategies of sufficiency evaluation of the NPP's technical equipment, used in mitigating the consequences of such accidents. Since sheer quantity of possible beyond design basis accidents is limitless, we face a necessity of working out selection criteria for choosing scenarios of such accidents to be taken into consideration in developing technical equipment for accident-protection, mitigation and accident control at the new NPPs, as well as in evaluation of sufficiency of such equipment at the already operational NPPs. The article presents a regulatory body's experience in developing guidelines for defining a list of beyond design basis accidents that are to be taken into account at an NPP. Developing such a list is to include examination of the following criteria: 1) representativity (from the point of view of organizing emergency response operations) of phenomenology of the processes of the scenario under analysis with reference to protection of each of the physical barriers and critical safety functions. For severe accidents, in addition to all of the above, with reference to each of the aims of accident management; 2) evaluated occurrence possibility for the scenario under analysis, taking into account uncertainty of such evaluation; 3) necessity to take into account current national and international practices of selecting scenarios of beyond design basis accidents. On their approbation the developed methods are planned to be implemented as a Regulatory Safety Guideline. Source


Lankin M.,Scientific and Engineering Center for Nuclear and Radiation Safety
11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012, PSAM11 ESREL 2012 | Year: 2012

The article sets forth algorithms, created in the process of developing Russian Risk-Informed Decision Making (RIDM) Guideline for NPPs: 1) algorithm of assessment of risk acceptability in conjunction with making a decision; 2) algorithm of assessment of decision acceptability from the point of view of its influence on the defence-indepth. he first algorithm takes into account such risk metrics as Base Severe Accident Frequency (SAF) and increase of SAF as a result of making a decision, instantaneous value of SAF, as well as Large Release Frequency (LRF) and its increase as a result of making a decision. Based on the combination of values of the abovementioned metrics and according to the developed algorithm, risk falls into one of the zones: acceptable risk (green zone), unacceptable risk (red zone) or zone of conditionally acceptable risk (yellow zone). This article describes and explains those criteria, on the basis of which borderlines between the aforementioned zones are being established. A nomenclature of threats to the defence-in-depth and of possible implementation mechanisms of the indicated threats have been proposed within the framework of the second algorithm. For the decision under analysis it is necessary to evaluate for each of the nomenclature implementation mechanisms of threats to the DiD whether the decision has influence on DiD according to the mechanism under consideration. The article presents rules of assessment of level of changes in DiD vulnerability, caused by the decision under analysis, contained in the described algorithm. Source


Glushko A.I.,Russian Academy of Sciences | Neshcheretov I.I.,Scientific and Engineering Center for Nuclear and Radiation Safety
Quarterly Journal of Mechanics and Applied Mathematics | Year: 2012

The article deals with nonlinear elastic media deformed differently under tension and compression that can accumulate microdefects. State of the medium is assumed to be uniquely determined by strain tensor, damage tensor and temperature. The strains are assumed to be small. The damage tensor is a second-rank symmetric positive definite tensor. With the damage tensor being equal to zero, the free energy is supposed to be represented as a homogeneous function of degree 2 that is twice differentiable with respect to the strain tensor for any non-zero values of the strain tensor. We propose an approach to approximate the free energy and the rate of damage tensor that enable to obtain the well-posed mathematical model. In addition, we give the constraints on the model parameters that guarantee, under the condition that temperature is constant, the system of differential equations of the model to be hyperbolic, with any solution of that satisfying the Clausius-Duhem inequality. © 2012 The Author. Published by Oxford University Press; all rights reserved. Source


Lankin M.,Scientific and Engineering Center for Nuclear and Radiation Safety
11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012, PSAM11 ESREL 2012 | Year: 2012

Russian regulatory body, Rostechnadzor, exercises supervision of a considerable number of different nuclear facilities: NPPs of different capacities, generations and types, research reactors, various fuel cycle facilities, radioactive sources, nuclear-powered fleet etc. This article presents a developed algorithm of ranking different nuclear facilities according to the potential hazard level they represent, for the scope of optimizing controlling and supervising practices of Rostechnadzor. Four criteria are used for ranking. The first criterion is the scale of a hypothetical accident in a situation of total inefficiency of safety barriers. Depending on whether maximum hypothetical accident leads to off-site consequences and what these consequences are, as well as depending on the A/D ratio, four categories have been identified, the third of which has been further divided into four subcategories. The second and the third criteria, used for ranking, are estimated values of probabilities that operational occurrences could take place at the facility and corresponding conditional probabilities that the said occurrences would not develop into an accident of a specific level of severity. And, finally, the fourth criterion is efficiency of defence-in-depth of the facility. This article sets forth a detailed algorithm of assessment of the said efficiency. It also contains a nomenclature of threats to DiD and algorithm of evaluation of DiD vulnerability of the facility in respect of each of the threats and to the mechanisms of their implementation. Based on the assessment results for DiD efficiency, the facility under consideration is ranked as belonging to one of the four categories. According to the rules, described in the article, after the facility under consideration has been rated according to all of the four criteria (or only according to some of them if evaluation according to the others is not possible), it is being assigned a final resulting rating of potential hazard. Source

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