[en] Highlights: • Transit time of steam void fraction is used for local surveillance in fuel channels. • A modified reduced March-Leuba model is proposed using a rational approximation and Prony’s method. • First minimum frequency method is used for comparison purposes. • Both models are used to characterize Laguna Verde Power Plant LPRM signals producing comparable results. • An alternative method for local surveillance in BWR channels is obtained. - Abstract: A new method to perform “local surveillance” of fuel channels is proposed, it is based on the reduced model of March-Leuba for BWR dynamics along with the measurements of the characteristic frequency of the neutronic signal in steady state. The steam voids are one of the main characteristics in BWR reactors and their speed is a good indicator to verify that there is not an abnormal restriction blocking the coolant flow through the fuel channel. Previous analysis using the March-Leuba reduced model have been performed by using the transit time of steam voids through the fuel assemblies, in those analysis the whole length of the fuel assembly was considered. In this study, a “local surveillance” of the coolant flow is proposed by assessing the measurements of different monitors allocated at different levels of the fuel assemblies. As a new characteristic for the proposed “local surveillance”, the Prony’s method is applied to obtain the frequency from the more unstable pole, which is used to obtain the transit time of steam voids. In addition, a rational approximation is used because the original Padé (2,2) approximation considered in the March-Leuba original reduced model does not follow the asymptotic behavior of the exponential in the range of local monitors. To verify the proposed method LPRM signals are analyzed from an actual power plant and the results are compared against the results obtained by using the method of first minimum of the transfer function between two detectors of neutronic flux, which are placed at different levels. Results show agreement between the first minimum of the transfer function and the proposed local surveillance method (using the rational approximation). However, the proposed local surveillance method shows transit time differences smaller than 5% for different APRMs inasmuch the method of the first minimum of the transfer function shows transit time differences up to 22% for different LPRMs. It is here proposed to use both methods for the reactor characterization and to verify if there is or is not an abnormal restriction blocking the coolant flow through the fuel channel.

[en] We have created a new mixed-oxide (MOX) fuel assembly design for standard pressurized water reactors (PWRs). Design goals were to maximize the plutonium throughput while introducing the lowest perturbation possible to the control and safety systems of the reactor. Our assembly design, which we call MIX-33, offers some advantages for the disposition of weapons-grade plutonium; it increases the disposition rate by 8% while increasing the worth of control material, compared to a previous Westinghouse design. The MIX-33 design is based upon two ideas: the use of both uranium and plutonium fuel pins in the same assembly, and the addition of water holes in the assembly. The main result of this paper is that both of these ideas are effective at increasing Pu throughput and increasing the worth of control material. With this new design, according to our analyses, we can transition smoothly from a full low-enriched-uranium (LEU) core to a full MIX-33 core while meeting the operational and safety requirements of a standard PWR. Given an interruption of the MOX supply, we can transition smoothly back to full LEU while meeting safety margins and using standard LEU assemblies with uniform pinwise enrichment distribution. If the MOX supply is interrupted for only one cycle, the transition back to a full MIX-33 core is not as smooth; high peaking could cause power to be derated by a few percent for a few weeks at the beginning of one transition cycle

[en] A method for nonlinear analysis of instabilities in boiling water reactors (BWRs) is presented. Both the Dominant Lyapunov Exponent method and the Slope of the Correlation Integral (SOCI) method are used to analyze the average power reactor monitor (APRM) signals from a BWR. The main advantage of using the two methods in a complementary manner is that doing so results in an enhancement of the capability to analyze noisy systems, such as the APRM signals in a BWR. Previously, such nonlinear analysis had been performed using independently either the Dominant Lyapunov Exponent Method or the SOCI method. These two methods are sensitive to noise in a signal and normally require large amounts of data for a reliable analysis.This proposed system for nonlinear analysis is composed first of a home-developed computer program called 'SLOPE', which is based on the SOCI method. Then, the signal analysis is also performed by the 'LENNS' code, which is used to obtain the dominant Lyapunov exponent. Since only the dominant Lyapunov exponent is computed, there is no need to acquire large amounts of data; thus, computational processing time is greatly reduced, even in the case of noisy data.The system was used to analyze BWR signals containing stationary and nonstationary limit cycles. It was found that this method satisfactorily calculates the limit cycles, extracting useful information from noisy signals

[en] Some of the new nuclear reactor technologies (Generation III+) are claiming the production of process heat as an additional value to electricity generation. These technologies are still under development and none of them has shown how this can be possible and what will be the penalty in electricity generation to have this additional product. The current study assess the likeliness of generate process heat from a Pebble Bed Modular Reactor to be used for a refinery showing different plant balance and alternatives to produce and use that process heat. An actual practical example is presented to demonstrate the cogeneration viability using the fact that the PBMR is a modular small reactor and also the challenges that this option has. (author)

[en] The complexity of the processes involved in water erosion of soils has led to widespread use of models with high level of empiricism. However, there are few applications based on models with a considerable physical basis in this field. The purpose of this work is to evaluate the potential of a model of physical basis for estimating soil loss by erosion basin-scale and analyze the behavior of the variables in this model response. The study area was located in the Sub-basin V anniversary, which belongs to the basin of the Cuyaguateje, in the province of Pinar de Rio. You were a database of physical properties of main soils of the basin, the series-temporales of solid spending and runoff measured at River, and rain recorded by a network of rain gauges across the basin. The equation of physical basis used was the sediment transport model (STM), according to Biesemans (2000). As input variables of the model were obtained the following maps: the digital elevation model, accumulative area of drainage, drainage, land use, surface water retention capacity, retention of moisture and hydraulic conductivity of saturation curve. Soil loss was obtained per pixel, and these were correlated with each time series. The results show that the process can be extended to other sub-basins without the need to validate all the variables involved

[en] One of the main constraints to adopt a nuclear program is the public acceptance. In Mexico, at least, it lacks of an adequate promotion of its benefits and challenges. A big stigma for nuclear electricity production is the association with nuclear weapons, along with myths and misconceptions and bad information about nuclear energy. Mexico has adopted an energy policy to diversify the electricity sources and nuclear energy is among the alternatives to achieve this goal because current studies show that is a safe and a competitive option from an economical point of view. Public opinion plays a very important role in the policy decision making to adopt the deployment of new reactor units; therefore it is necessary to define communication strategies to promote nuclear energy. The current study is an investigation to learn what is the perception and positioning about nuclear energy as a starting point to define the way to improve public acceptance. The national assessment carry on here is divided in two parts, the first one is a qualitative study to know knowledge level, associations and nuclear perception, identifying controversy items and expectations about advantages and disadvantages to define the adequate question to be used in the second part, which is a quantitative study that shows the acceptance of nuclear energy at national level and in particular in two sites that are suitable to deploy new nuclear reactors. From the results of this study some communication and persuasion strategies to improve public perception are defined and they could be used as part of a nuclear program. (author)

[en] Mexico is an OECD member but is an emergent economy as can be seen from its electrical sector. Its electrical installed capacity has been growing during the last 10 years with a 4.5 % annual pace and it is planed to grow for the next 10 years with a 5.2 % annual pace. In 2004 the annual electrical consumption per inhabitant was of 2237 kWh, which is around the world average but almost one quarter of the industrial countries average consumption. The current document shows the prospective for the Mexican Electricity sector for the 2005-2014 time frames. It also shows the technologies that will be used to cover the requirements of electricity by region. (author)

[en] To assess the economical benefits of plutonium recycling we perform an analysis of recycling as a function of the reactor operation cycle. Three different cycle lengths were analyzed, 12, 18 and 24 months. These cycles differ in the average assembly enrichment, the number of fuel assemblies used and the discharge burnup. Thus to have a comparison basis we took the associated cost to produce 1000 kg of UO₂ for each enrichment considered. In each operation cycle two options are considered, direct disposal and recycling of the depleted fuel. The reactor analyzed is a BWR with a thermal power of 1931 MWe, an efficiency of 34% and a capacity factor of 85%. The analysis shows that the 18-month cycle has the lowest cost of the three scenarios considered because this one has the highest discharge burnup. Furthermore, the cost of the 18-month fuel cycle considering recycling is 5.26 Mills $/KWh, which is only 11% more expensive than the direct disposal. (author)

[en] One point on the government electricity policy in Mexico is to have a better mix sources including nuclear energy, currently there are two BWR units with a capacity of 1375 MW of nuclear power that provides around 4.5% of the electricity generation in Mexico and it represents 2.7 of the whole installed capacity. There is some planning to include the constructions of new nuclear units and they are comprised on three scenarios. The current paper deals with Mexican Uranium resources and how they can be used to support a Nuclear Program in Mexico. Currently, there are around 14000 tons of uranium in a category of probed reserves, however just a little has been done to search and quantify for new reserves in the last 25 years. Based on that quantity an study is carry out to learn the fuel assemblies supply that these resources could provide under a Nuclear Mexican Program. The scenarios considered assumed the ABWR as the reactor choice to be implemented with a single capacity of 1356 MW and the time frame is 2015-2030. The low scenario comprises the construction of two units starting in 2015 and the second one 5 years later; in the medium scenario 4 new units will be built starting in 2015 and every four years a new one and the high scenario assumes that 6 new unit will be added and each one of them will start construction with a three years of difference starting at 2015. Under these scenarios the availability of indigenous uranium resources is tested and an economical analysis is provided. (authors)

[en] In this paper an analysis will be performed to assess the economical competitiveness of Nuclear Power against other base load technologies. There are several plans to build more nuclear power plants in western countries; these plans are result among other things of the fossil fuel high prices and the concern for the global warming. France started the construction of one EPR at Flamanville in 2007 and at the end of 2008 there were 17 applications before NRC for construction and operation licenses (COL) to build as much as 26 new reactor units in USA, among the designs selected are the US-EPR, APWR, ESBWR, ABWR and AP1000. Currently, there is a lot of uncertainty about what is the overnight cost for a new generation III nuclear power plant and the vendors are not providing too much information. However, it is expected that under the new economy conditions the overnight cost will be between 2500 and 3500 USD/kW, the output electricity power of the units mentioned above are between 1100 and 1600 MW, construction time, from first concrete to commercial operation, is about five years as it has been demonstrated in the latest reactors built in Asia (e.g. Japan and China), also Flamanville is under schedule and budget. In the current paper we perform a levelized electricity cost analysis using the conditions given above, to compare the generation cost of electricity using nuclear reactors against using natural gas in combined cycle plants and also coal plants. The levelized cost analysis developed here assumes overnight cost in the range of 2500 to 3500 USD/kW to assess the levelized cost impact. Also a sensitivity analysis for construction time delays and different capacity factors in the range of 80% to 90% is offered along with a uranium fuel cost sensitivity analysis. The investment scenarios considered here comprise three different discount rates, 5%, 8% and 10%. Results obtained are presented in several graphs that show under which circumstance nuclear energy is a competitive option against other base-load electricity options. (authors)