Preliminar analysis in support to the experimental activities on the mixing process in the pressurizer of a small modular reactor integrated primary system

Nowadays, there is a renewed interest in the development of advanced/innovative small and medium sized modular reactors (SMRs). The SMRs are variants of the Generation IV systems and usually have attractive characteristics of simplicity, enhanced safety and require limited financial resources. The concept of the integrated primary system reactor (IPSR) is characterized by the inclusion of the entire primary system within a single pressure vessel, including the steam generator and pressurizer. The pressurizer is located within the reactor vessel top, this configuration involves changes on the techniques and is necessary investigate the boron mixing. The present work represents a contribution to the design of an experimental facility planned to provide data relevant for the mixing phenomena in the pressurizer of a compact modular reactor. In particular, in order to evaluate the boron concentration in the surge orifices to simulate the in-surge and out-surge in a facility, scaled 1:200, respect to the ¼ of the pressurizer. The facility behavior studied from one inlet and one outlet of the test section with represent one in-surge e one out-surge the pressurizer of a small modular reactor integrated primary system

Evaluation of the mobility of 123CS in soil profiles of the pantanal region

Radioactive pollutants can cause impact on the environmental quality of soils and represent a risk to human health. Radioecological studies have shown that soils with low pH, low organic matter content and low fertility are more vulnerable to contamination by 137Cs, since the transfer to plants is high. In this study, some surface horizons of soils from Jaraguari, situated at Brazilian Pantanal were assessed in order to map their vulnerability to contamination by 137Cs. It was also proposed some mitigation measures adapted to the regional scenario in order to optimize radiological protection for rural areas. A conceptual model established to detect the vulnerability of radioactively contaminated soils was applied for soils located in the municipality of Jaraguari (Mato Grosso do Sul). This conceptual model was established based on the relationship between reference values of the soil-to-plant transfer factor (TF) for 137Cs and critical pedological parameters for each radiovulnerability category (pH, CTC and exchangeable K). The application of this conceptual model to a soil databank using Geographic Information System (GIS) tools generated vulnerability soils maps. This result identified that most of Pantanal soils presented very low radiovulnerability, but it was possible to detect some small areas presenting extreme radiovulnerability. It was possible to conclude that these small areas is not indicated for activities that presents a potential risk for 137Cs contamination and also it must receive priority actions for remediation in the case of accident, since a superficial contamination with 137Cs in these areas can lead to a contamination of subsoil and to a significant spread of contamination via groundwater

An experimental low-pressure facility to study boron transients in the pressurizer of an a integral modular nuclear reactor

Small and medium size modular reactors offer many advantages when compared with typical nuclear plants in various circumstances, such as offering greater simplicity of design, economy of mass production, and reducing siting costs. The integral configuration is characterized by having most of its components inside the pressure vessel, eliminating the probability of accidents. However, for this configuration there is no spray system for boron homogenization, which may cause power transients. Thus, it is necessary to investigate boron mixing. The Federal University of Pernambuco (UFPE), in a partnership with the Regional Center of Nuclear Sciences of Northeast (CRCN-NE) and the Nuclear Engineering Institute (IEN/CNEN-RJ), is developing a project that aims to analyze transients in a compact modular integral reactor. This analysis will be made by using the data obtained from one experimental bench that is mounted at CRCN-NE. A study accomplished in 2012 using a simplified bench (built in reduced scale with a test section manufactured with transparent acrylic) showed that it was possible to obtain preliminary experimental results for the boron homogenizing process

Insights of probabilistic risk analysis on the development of severe accident management guidance: a case study for a plant similar to Angra I

Probabilistic Risk Analysis (PRA) surges as a way to evaluate the risk of Nuclear Power Plants (NPPs) and to quantify it. Its objective was to track sequences of accidents and define mitigate actions to prevent core damage. But when the core is damaged the question is how to avoid releases of radionuclides to the environment. PRA evaluates this scenario too and is input to the Severe Accident Management Guidance (SAMG). This paper aims in the interaction between PRA and SAMG, both under development for the Brazilian NPPs, focusing in one specific Plant Damage State (PDS). The objective is to develop an Accident Progression Event Tree (APET) proposing the mitigate actions for the event, helping to understand the phenomena

One-dimensional termohidraulic model of the nucleus and lower and upper pool regions of the reactor RMB

The computer codes used in construction of nuclear reactors projects, specifically with regard to the thermo-hydraulics concepts part of your core, whose main goal reproduce actual operating conditions in order to predict quantitatively the limiting conditions of operation so that the safety limit is not exceeded. Computational methods for studies of fluid flow are developed around the world, including Brazil. With the evolution of computers application of numerical methods greatly reduced response time results, and tends to further decrease the extent that the computers and processors develop, making it feasible to use programming accident simulations of heat transfer reactors. The software developed in this paper presents a method for analyzing the thermo-hydraulic behavior of the Brazilian Multipurpose Reactor (RMB) after its shutdown. The software solves the conservations equations applied to the core and also the lower and upper regions of the RMB. The thermo-hydraulics characteristics studied are: the temperatures of the core, cladding and refrigerant, the mass flow and the heat transfer. The numerical resolution was performed using the Matlab language and the outputs are presented in graphs and tables forms

Modeling of the dispersion of tritium from postulated accidental releases from nuclear power plants

This study has the aim to assess the impact of accidental release of tritium postulate from a nuclear power reactor through environmental modeling of aquatic resources. In order to do that it was used computational models of hydrodynamics and transport for the simulation of tritium dispersion caused by an accident in a CANDU reactor located in the ongoing Angra 3 site. It was postulated, then, the LOCA – Loss of coolant accident –, accident in the emergency cooling system of the nucleus ( without fusion), where was lost 66m³ of soda almost instantaneously. This inventory contained 35 PBq and was released a load of 9.7 TBq/s in liquid form near the Itaorna beach, Angra dos Reis –Rj. The models mentioned above were applied in two scenarios ( plant stopped or operating) and showed a tritium plume with specific activities larger than the reference level for seawater (1.1MBq/m³), during the first 14 days after the accident. The main difference between the scenario without and with seawater recirculation (pumping and discharge) is based on the enhancement of dilution of the highest concentrations in the last one. This dilution enhancement resulting in decreasing concentrations was observed only during the first two weeks, when they ranged from 1x109 to 5x105 Bq/m³ close to the Itaorna beach spreading just to Sandri Island. After 180 days, the plume could not be detected anymore in the bay, because their activities would be lower than the minimum detectable value (<11 kBq/m³)

Reactivity variation's analysis in nuclear propulsion considering the operational real conditions requirements

The work presented in this paper highlights the need for the study to determine the reactivy variation ramps needed and possible to meet the real operational condicitions required by a nuclear submarine in this several operating fases. In accordance with the operational needs and necessary maneuvers in certain tactical situations, large power variations in the propulsion are demanded. As these sudden and severe changes in propulsion come from the thermal power of nuclear origin, the operation of the nuclear island has to know what kind of answers and criticality variations are necessary to meet each demand speed required. It should be noted that these criticality inserts are conditioned, not only by the propulsion needs, but fundamentally by the imperative need to ensure the core integrity and the chain reaction sustainability considering the phenomenons and complex effects, nonlinear and retro-fed involved. It has to be determined what is the past and required time for each criticality insertion is perceived as motor power. Considering the highlighted aspects, this article concludes and indicates to its end, the need to establish a base operating transitional agenda, according to the naval combat doctrine, to be tested and analyzed under the aspects and peculiarities of kinetic reactors, with the purpose of being generated the appropriate criticality curves for each real need and their respective times of anticipated action

THEWASP Library Thermodynamic Water & Steam Properties Library in GPU.

In this paper we present a new library for thermodynamic evaluation of water properties, THEWASP. This library consists of a C++ and CUDA [13] based programs used to accelerate a function evaluation using GPU and GPU clusters. Global optimization problems need thousands of evaluations of the objective functions to find the global optimum implying in several days of expensive processing. This problem motivates us to seek a way to speed up our code, as well as to use MPI on Beowulf clusters [5] [17], which however increases the cost in terms of electricity, air conditioning and others. The GPU based programming can accelerate the implementation up to 100 times[7] and help increase the number of evaluations in global optimization problems using, for example, the PSO[8] or DE[15] Algorithms. THEWASP is based on Water-Steam formulations publish by the International Association for the properties of water and steam, Lucerne - Switzerland[2] [16], and provides several temperature and pressure function evaluations, such as specific heat, specific enthalpy, specific entropy and also some inverse maps. In this study we evaluated the gain in speed and performance and compared it a CPU based processing library

ANALYTICAL REPRESENTATION OF THE SOLUTION OF THE SPACE KINETIC DIFFUSION EQUATION IN A ONE-DIMENSIONAL AND HOMOGENEOUS DOMAIN

In this work we solve the space kinetic diffusion equation in a one-dimensional geometry considering a homogeneous domain, for two energy groups and six groups of delayed neutron precursors. The proposed methodology makes use of a Taylor expansion in the space variable of the scalar neutron ux (fast and thermal) and the concentration of delayed neutron precursors, allocating the time dependence to the coefficients. Upon truncating the Taylor series at quadratic order, one obtains a set of recursive systems of ordinary differential equations, where a modi ed decomposition method is applied. The coefficient matrix is split into two, one constant diagonal matrix and the second one with the remaining time dependent and off-diagonal terms. Moreover, the equation system is reorganized such that the terms containing the latter matrix are treated as source terms. Note, that the homogeneous equation system has a well known solution, since the matrix is diagonal and constant. This solution plays the role of the recursion initialization of the decomposition method. The recursion scheme is set up in a fashion where the solutions of the previous recursion steps determine the source terms of the subsequent steps. A second feature of the method is the choice of the initial and boundary conditions, which are satis ed by the recursion initialization, while from the rst recursion step onward the initial and boundary conditions are homogeneous. The recursion depth is then governed by a prescribed accuracy for the solution

The nuclear energy, public opinion and the awareness of work of nuclear institutions

With Brazil facing a prospect of expanding its nuclear-energy sources and the development of new nuclear techniques there is a need for imminent integration in the nuclear industry with the tool information. In this paper we propose the creation of a program aimed at the servers of the institutions that make up the Brazilian Nuclear Sector, with a view to preparing these to become multipliers in the dissemination of activities developed by the institution so that they can, with strong arguments, defending the work of industry criticism of this form of energy. The goal is to create an important process of change of mentality and attitude among people who relate to the servers in the industry, expanding the debate on the subject, so that society, clearly and free of prejudices can understand the benefits the use of nuclear energy