Computational Analysis of the Shutdown of One MCP of VVER-1000 During Operation of the Reactor Facility at Nominal Power

The article considers results of the computational analysis of process with a disturbance in the operation of VVER-1000 reactor facility, caused by the de-energizing of a single Main Circulation Pump (MCP-195).Calculations of de-energizing of the MCP were made with the CORSAR/GP software package developed by Federal State Unitary Enterprise "Alexandrov RESE". This software package is a contour code which allows making calculations of emergency situations taking into account the operation of various systems, including safety systems. CORSAR/GP is certified and verified for facilities with water-cooled reactors including VVER-1000.Developed nodalization scheme (computational scheme) of the first circuit of VVER-1000 allows adding or excluding the operation of protective safety systems and can also be used for a computational analysis of other disturbances of normal operation.To perform the calculations parameters of the core were chosen to ensure conservative results for the parameters determining the current state of the reactor facility (fuel temperature, boiling point, etc.).The computational analysis showed that in case of de-energizing of a single MCP when the reactor is operated at nominal power criteria describing the safety of the facility are fulfilled, protective automatic actions of safety systems transfer the reactor facility to a controlled safe state

Standalone hydrogen generator based on chemical decomposition of water by aluminum

AbstractA standalone hydrogen generator (SHG) has been developed based on chemical decomposition of water in heterogeneous compositions containing finely dispersed aluminum powder and crystallohydrates of sodium metasilicate. The kinetics of hydrogen generation has been studied depending on constants of the aluminum activation and oxidation rate, and aluminum and oxygen concentrations. In the hydrogen accumulation kinetics, the length of the induction period is determined by the concentration of oxygen. The SHG design, hydrogen selection and capacity are discussed. The availability and low cost of domestically manufactured chemical agents make the SHG a promising choice as the source of hydrogen for various applications, including nuclear power plants (NPP)

Study of Hydrogen Generation of Aluminum-Containing Compositions with Boric Acid

The results of investigations of the kinetics of hydrogen generation compositions with aluminum, chemical activators (hydrated sodium metasilicate, oxide and calcium hydroxide) boric acid. Aluminium and its alloys used for the manufacture of protective sheaths of fuel elements and control rod protection system management, pipelines, tanks, and various support structures in the active zone of atomic reactors RBMK, research water-cooled reactors. The aluminum is protected from direct contact with water and steam surface layer of metal oxide having a high corrosion resistance at high temperatures in powerful radiation fields. However, after removal or when the discontinuity of the oxide layer of activated metal efficiently decompose water to hydrogen. It is established that the hydrogen aluminum-containing compositions is dependent on the concentration of boric acid. The discovery of the involvement of boric acid in these reactions expands the ideas about regularities of chemical processes of formation of hydrogen flowing in the water coolant of VVER reactors with the participation of the corrective additives and impurities

GABRIELA : a new detector array for gamma-ray and conversion electron spectroscopy of transfermium elements

With the aid of the Geant4 Monte Carlo simulation package a new detection system has been designed for the focal plane of the recoil separator VASSILISSA situated at the Flerov Laboratory of Nuclear Reactions, JINR, Dubna. GABRIELA (Gamma Alpha Beta Recoil Investigations with the Electromagnetic Analyser VASSILISSA) has been optimised to detect the arrival of reaction products and their subsequent radioactive decays involving the emission of alpha- and beta-particles, fission fragments, gamma- and X-rays, and conversion electrons. The new detector system is described and the results of the first commissioning experiments are presented.Comment: 24 pages, Submitted to NIM

Forecasting reliability of ShADR-32M coolant flow rate sensors

Complexity of technical systems, such as NPPs, implicates the necessity to undertake efforts for assessment of reliability of equipment, especially critical equipment influencing the reactor operation safety. Therefore, tasks associated with investigation of regularities of variations of parameters of equipment and the processes of their approaching to the conditions of equipment failures, and with the development of methodologies and algorithms for obtaining quantitative reliability indicator values with respect to progressive (parametric) failures become important. Such task is addressed in the present paper as applicable to ShAFDR-32M coolant flow rate sensors of RBMK-1000 reactor. Analysis of statistical data obtained during planned diagnostic measurements of two determining parameters of functionality of ShAFDR-32M coolant flow rate sensors (minimum values of negative half wave of the amplitude and standard deviation for the rotation period of the flow rate sensor ball) allowed developing the mathematical model of sensor parametric reliability. The process which is the superposition of elementary regeneration process and the stochastic process with independent increments will be understood as the mathematical model of coolant flow rate meter. Investigation of mathematical model of coolant flow rate sensor functioning reliability allowed obtaining in closed form the correlations between the average time of the flow rate meter operation before crossing of the preset boundary by each of the determining parameters and the probability of failure-free operation of the flow rate meter in asymptotic setting without introducing any assumptions with regard to the laws of distribution of random values. The results obtained can be easily generalized to embrace the case when the dimension of the vector of determining parameters is larger than two. Results of the investigation are applied in the calculations of quantitative indicators of parametric reliability of flow rate sensors

Effects of impurities on heat transfer in lead coolants

A feature of the heavy liquid metal coolant technology has been investigated, namely the effect of impurities on the heat transfer in the wall-adjacent area. An analysis of the accumulated theoretical base for the problem under consideration has showed that earlier studies did not take into account the presence of impurities in heavy coolants. Recent experimental data used to update the calculated dependencies of heat transfer has turned out to be rather controversial. However, an explanation has been proposed for one of the observed effects that influenced the experimental data (for the coolant heating conditions). The dependencies in question are generalized in this paper. Using the obtained dependency, the effects of impurities on heat transfer have been estimated for various Peclet numbers as compared to “pure” conditions

Study of reactor plant disturbed cooling condition modes caused by the VVER reactor secondary circuit

Based on the equations of energy, mass and momentum conservation for the three-dimensional unsteady flow of the two-phase mixture, simulations were made of reactor plant disturbed cooling condition modes caused by the VVER secondary circuit using computer thermohydraulic codes. The use of computer codes to investigate these modes makes it possible to analyze transient and some emergency processes, without involving the industrial testing method; this helps create a basis for solving the problems of reliability, operational safety, and efficiency of nuclear power plants. A modern nuclear reactor is a complex system which cannot be investigated or calculated by using only simple theoretical models. Thermohydraulic calculations are an essential part of most of the design and technological developments in the nuclear power industry. Since the NPP conditions exclude the traditional technical way to check and specify the results and conclusions of an aprioristic analysis based on industrial testing, in some instances, it is possible to examine and predict the parameters of thermohydraulic processes in the reactor circulation circuit involving computer simulations. The primary objective of this work is to calculate and investigate reactor disturbed plant cooling condition modes caused by the VVER secondary circuit in order to determine whether the calculated parameters conform to the acceptance criteria established in the regulatory documents. Based on the RELAP-5, TRAC, and TRACE software codes, reactor plant cooling condition malfunction modes caused by the VVER-1000 secondary circuit were simulated and investigated. Experimental data on the mode with the turbine-generator stop valve closing are presented. The obtained dependences made it possible to determine the maximum values of pressure and temperature in the circulation circuit as well as estimate the Minimum Critical Heat Flux Ratio (MCHFR). It has been found that, if any of the initial events occurs, safety systems are activated according to the set points; transient processes are stabilized in time; and the Critical Heat Flux (CHF) limit is provided. Therefore, in the event of emergency associated with the considered modes, the reactor plant safety will be ensured

Hydrozirconium reaction in heterogeneous compositions

The research results presented in this article show the behavior of a hydrozirconium reaction for hydrogen generation at temperatures below 100°C in heterogeneous compositions containing zirconium and chemical activators (e.g., hydrated sodium metasilicate, sodium water glass, or quicklime). The hydrogen yield increases with a temperature increase up to 95°C and is about 0.1–0.2l per 1g of zirconium. Zirconium processing with γ-radiation as well as exposure to acidic and neutral aqueous media increases the hydrogen yield by about 1.2 times. A hydrozirconium reaction is caused by the chemical activators removing the passivating protective zirconium oxide ZrO2 layer from the metal surface. The possibility of a hydrozirconium reaction occurrence should be considered in the organization of technical measures to ensure hydrogen explosion protection at NPPs

Тhe transformation of the oxide coatings of aluminum by imitation factors of nuclear power plants

The authors present the results of a study on kinetics of hydrogen generation by heterogeneous compositions with aluminum exposed to γ-irradiation in air, in different aqueous solutions at room temperature and high temperature annealing. It has been found that hydrogen generation kinetics depends on the γ-irradiation dose, temperature and aqueous medium chemistry. Changes in hydrogen generation kinetics are due to transformations of aluminum oxide coatings influenced by factors simulating the NPP conditions. The effect of metal oxide coating transformations should be considered in predicting the corrosion resistance of NPP structural materials