[en] Submitted materials of the conference (May 9-22, 2015), conducted by OKB “GIDROPRESS”. 9 International scientific-technical conference “Safety Assurance of NPP with WWER” was aimed at the exchange of information and discussion of topics related to the safe operation of nuclear power plants with WWER reactors. The issues of reliability and safety of NPP, the calculation and theoretical and experimental justification of the RU with WWER, verification of computer programs for safety reasons were discussed. The problems of upgrading the RU for improving security are considered. The rationale for the safety of extending the life of NPP and the innovative fourth-generation reactors cooled by supercritical water were discussed at the conference

[en] The experience of the Federal Budget Institution of the Scientific and Technical Center for Nuclear and Radiation Safety in the field of expertise of the safety rationales for nuclear power plants with WWER-type reactors of new projects is disclosed. In determining the priority, in addition to the necessary time and financial resources, it also took into account the extent to which these activities significantly affect the completeness of the implementation of levels of defense in depth related to the management of beyond-design-basis accidents, including severe ones. And also, what impact does this or that measure have on reducing the likelihood of the onset of severe radiation effects. When examining the safety justification for new design solutions (including for nuclear power plants with a reactor type WWER), it is advisable to adhere to the following approach: during the examination it is necessary to study the experience in the country and the world related to the proposed new design solutions; It is preferable to take advantage of the differential approach to assessing various aspects related to nuclear and radiation safety. The result of the examination of the justification for new design solutions may be recommendations on the development of existing regulatory documents or development of the Regulatory Authority

[en] The main requirements for nuclear fuel today are ensuring security, reliability, economic efficiency and competitiveness. Achieving these goals requires the constant development of existing fuel assembly designs for various power reactors. Guaranteeing the geometric stability of the WWER-1000 fuel assemblies, increasing the fuel assembly's operational life, increasing the operational reliability of fuel assemblies, creating collapsible (repairable fuel assemblies), and implementing safe and cost-effective fuel cycles provides the solution of the main tasks. Much attention is paid to “TVEL” devotes new fuel compositions and works on improving zirconium materials

[en] The conclusions are drawn on the results of operation of nuclear power plants in Russia in 2014, where it is shown that the existing Russian nuclear power plants comply with Russian requirements for ensuring the safety of nuclear power plants and international recommendations for ensuring nuclear and radiation safety, measures have been developed and implemented to increase the stability of existing nuclear power plants to extreme external influences, and the objects of the new NPPs being built correspond to “post-Fukushima” the safety requirements are increased, reliability and resistance to extreme external influences of natural and technogenic nature. Ensuring the safe, reliable and cost-effective operation of all operating power units of the NPP with WWER, increasing the capacity of pilot unit 4 of the Balakovo NPP, putting into operation of the 3rd unit of Rostov NPP, bringing physical and power start-up to the 6th unit of Novovoronezh NPP, Balakovo NPP are the main tasks of OJSC “Concern Rosenergoatom”

[en] The tools of thermal-mechanical (strain measurement) inspection consisting of startup and adjustment measurement system (SAMS) are intended for determination of temperature and stress-strain state of the primary equipment and also thermal movements of equipment components due to RP self-compensation. Comparative tests of various strain gauges (traditional wire strain gages NMT-450, IMASH / “GIDROPRESS”, semiconductor strain transducers of the TPF deformations of 21 Moscow firms “SENSOR”, as well as high-tech strain gauges of the LZN series of the American company Vishay Micro-Measurements) are carried out. A comparison is made between the metrological and technological characteristics and properties declared by the manufacturer. The choice of the optimal design of the measuring points for static and dynamic strain gauging in the structure of SAMS has been worked out

[en] A new approach on on-line multiparameter monitoring of operational damageability of WJ №111 during the whole fuel campaign is proposed and checked in practice. The approach is based on mutual monitoring of actual thermo-mechanical loads, monitoring of formation and growth of operational defects covering the whole WJ perimeter, as well as numerical computation of accumulated metal damage in the inspected zone using the array of experimental data collected during monitoring. With the purpose of collection of reliable experimental data the system of on-line monitoring of the WJ №111 was installed on power unit №5 of Novovoronezh NPP. The system implements collection and processing of data regarding the operational loading factors using the records of temperatures, deformations and displacements in checkpoints, as well as data of on-line monitoring of metal integrity by acoustic and ultrasonic methods

[en] The method of atomistic simulations was used to study the structure of the quasi-equilibrium tetragonal phase U-Mo, formed during crystallization of the melt. Radial distribution function and bond-angle distribution function were calculated for the analysis of uranium and molybdenum structures in the alloy. The lattice constants of the uranium-molybdenum alloy were obtained for different concentrations of molybdenum. Results of calculations are in good agreement with experimental data and confirm the anisotropy of the lattice at low molybdenum concentrations. Temperature of the transition from anisotropic tetragonal phase to a body-centered cubic phase was calculated for different concentrations of molybdenum. It was found that the anisotropy is a consequence of the local arrangement of uranium atoms in the U-Mo alloy structure. It is shown that the anisotropy disappears with increase of molybdenum concentration not due to changes in the uranium atoms arrangement. It disappears because the number of molybdenum atoms – “stabilization centers of isotropy” increases. Also dependence of the enthalpy of mixing for uranium-molybdenum alloy on molybdenum concentration was calculated. It is shown that anomalous enthalpy of mixing - molybdenum concentration dependence, known from the experiments, can be obtained only when the atomic structure of the alloy is taking into account.

[en] The nuclear reactor safety technology (NRST) is considered, involving nuclear fission reactor and water-water reactors. A two-level idea is discussed. On the one hand, an independent mandatory safety analysis is required, planned and implemented in accordance with the latest scientific and technological developments. On the other hand - feedback analysis with the project, construction and operation of the nuclear power plant based on the design of systems and management. For this purpose, the parameters are determined and continuous monitoring of the extended safety stocks is carried out. The role of the safety analysis as a key component of the nuclear reactor safety technology is considered first. The concept of continuously monitored extended safety stocks is described

[en] The list of beyond design basis accidents (BDBA) is based on the probabilistic safety analysis (PSA) of the first and second levels for various categories of information systems (IS) and a complete set of operational states. The analysis of scenarios of accidents that do not lead to damage to the core, when operating at power, for nuclear reactor standby mode caused by external IS of natural and man-made nature caused by seismic interactions, in-site fires and floods during power operation, and for severe accidents is analyzed. Based on the analysis, a preliminary list of candidates of the BDBA was proposed. For full-scale PSA (PSA-1 and PS-2), taking into account all kinds of effects, the methodology allows selecting the most complete representative list of BDBA

[en] The results of the work on the verification of the SERPENT software for the calculation of K_e_f_f of various systems containing nuclear fissile materials are presented. Comparison of results of calculations K_e_f_f with use of software means SERPENT with experimentally measured values or results of calculations on the generally recognized precision (reference) programs is made. Verification calculations of K_e_f_f using SERPENT were carried out for various types of systems containing nuclear fissile materials, such as: uranium-water systems with nuclear fuel of WWER-type reactors, uranium-water-graphite and uranium-water systems with nuclear fuel of RBMK type reactors, and A number of systems containing solutions of uranium and plutonium. The results of the calculations show that the values of K_e_f_f of various critical and subcritical systems obtained using SERPENT are in good agreement with experimentally measured values, as well as values obtained using such widely used software tools as MCNP, MCU and SCALE