[en] Applied non-parametric methods for calculation of point and interval estimations for the basic nomenclature of reliability factors for the RBMK fuel assemblies and elements are described. As the fuel assembly and element reliability factors, the average lifetime is considered at a preset operating time up to unloading due to fuel burnout as well as the average lifetime at the reactor transient operation and at the steady-state fuel reloading mode of reactor operation. The formulae obtained are included into the special standardized engineering documentation

[en] To calculate the reliability indices of a nuclear reactor and to make a quantitative probability analysis of the safety of a reactor it is necessary to know the failure flux ω(t) and the coefficient of readiness K_r(t) of the equipment (in what follows, elements) of the nuclear reactor in the general case in the form of functions of the operating time of an element plus the unplanned (accidental) downtime for renovation or replacement after failure. The index ω(t) is the average number of failures of the element in a short unit interval Δt of operating time around the moment t. The readiness coefficient K_r(t) is the probability that at the time t of operation the element is in an operable state. The author notes that the parameter ω(t) takes into account the finite renovation (replacement) time for the element after failure, unlike the usual failure-flux parameter ω₀(t), referred to the pure operating time of the element. The paper uses fuel assemblies in the active zone of a reactor to illustrate a system of equations for readiness determination

[en] Reliability analysis of pipelines and pressure vessels at NPP is given. The main causes and failure mechanisms of these elements, the ways of reliability improvement and preventing of great damages are considered. The reliability estimation methods both according to the statistical operation data and under the conditions of absence of failure statistics are given. The main characteristics and actual reliability factors of pipelines and pressure vessels of three home NPP: the first in the world NPP, VK-50 and Beloyarsk NPP, are presented. From the start-up there were practically no failures of the pipelines and pressure vessels at the VK-50 pilot installation. The analysis of the operation experience of the first and second blocks of the Beloyarsk NPP, as well as the first in the world NPP, shows that the most part of failures of the pipelines and pressure vessels of these energy blocks with the channel reactors is connected with the coolant leakage at minority pipelines of a small diameter. The most part of failures at individual pipelines of the first and second blocks of the Beloyarsk NPP are connected with the leakages of stuffing boxes of switching off devices. It is noted that serious failures of large pipelines and pressure vessels at all home NPP under operation have not been observed

[en] Methods for evaluating reliability of NPP components operating in a complex regime under which functioning periods interchange with expectation periods are proposed. Such operating modes are typical for NPP control systems. The methods allow one to express probabilities of reliable operation of components under a complex regime in the form of time function and to bring them to the unified form with the reliability indices of a system as a whole

[en] The role of NPP auxiliaries (valves, heat-exchange equipment, water treatment equipment) in the provision of reliable and safe operation of NPPs with WWER-1000 and RBMK-1000 type reactors is evaluated. Basic indices of the auxiliary equipment safety are considered. A conclusion is drawn, that the auxiliary equipment is of sufficient (if not the leading) value in the provision of the NPP radiation safety being the main element of water treatment and NPP safety systems, which requires a high quality of its designing, production and operation directed to achieving the assigned reliability indices

[en] One of the most important questions in designing the equipment for a nuclear power plant is to guarantee its reliability taking into account operational peculiarities. This concerns primarily the equipment operating in a complex regime, in which periods of functioning alternate with periods of expectation, since such operation is characteristic for equipment in the shielding and safety systems of the power plant. In the expectation regime the technical state of the equipment is affected by different factors - pressure, temperature, water chemistry, irradiation, etc. - in spite of the fact that it is not functionally loaded. Mathematical models of the reliability of different systems operating in a complex regime, for example, safety systems, often ignore the peculiarities of this regime, and the regime is regarded as a simple one. This approach substantially affects the accuracy and reliability of the results of the investigation. To calculate the reliability of a technical system that operates in a complex regime, a stochastic model taking into account the peculiarities of the regime is proposed. The authors study a real situation when the operating time is short compared with the expectation time, assuming in so doing that during periods of expectation the operability of the system is not checked, so that failure of the system can be established only at the moment that the system must be actuated. The operating time of the equipment to failure in this complex regime is a random quantity that depends on two parameters - the total expectation interval and the number of actuations up to failure

[en] Formulas for determining reliability indices of unrecoverable NPP components (for example, fuel assmeblies) on their achieving some certain assigned resource prior to a possible failure or on their reaching the critical state after which their further operation is stopped are derived. Formulas for determining failure flux parameter, the parameter of element decommissioning flux and serviceability factor are obtained

[en] In 1978 the first specialized technical manual ''Technique of Calculating the Structural Reliability of an Atomic Power Plant and Its Systems in the Design Stage'' was developed. The present article contains information about the main characteristics and capabilities of the manual. The manual gives recommendations concerning the calculations of the reliability of such specific systems as the reactor control and safety system, the system of instrumentation and automatic control, and safety systems. 2 refs

[en] Reviewed are the main statements peculiarities and possibilities of the first branch guiding technical material (GTM) ''The methods of calculation of structural reliability of NPP and its systems at the stage of projecting''. It is stated, that in GTM presented are recomendations on the calculation of reliability of such specific systems, as the system of the reactor control and protection the system of measuring instruments and automatics and safe systems. GTM are based on analytical methods of modern theory of realibility with the Use of metodology of minimal cross sections of complex systems. It is stressed, that the calculations on the proposed methods permit to calculate a wide complex of reliability parameters, reflecting separately or together prorerties of NPP dependability and maintainability. For NPP, operating by a variable schedule of leading, aditionally considered are parameters, characterizing reliability with account of the proposed regime of power change, i.e. taking into account failures, caused by decrease of the obtained power lower, than the reguired or increase of the required power higher, than the obtained

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