06 Electrical power supply and utilization (scientific, technical)

04•01847 Stochastic techniques for the control and surveillance of a modular pebble bed reactor Kemeny, L. G. Progress in Nuclear Energy, 2003, 43, (1-4), 445 452. This paper represents the first of a series of publications describing work in progress on the research, design and testing of a control and surveillance system for a Modular Pebble Bed Reactor. The scope of the project involves the design of a simple state of the art control system for the reactor and a surveillance system based on smart instrumentation and expert system logic. It is noted that there are some physical and experimental problems unique to the MPBR family. These problems are connected with long neutron lifetimes, the need for a new evaluation of kinetic parameters and reactivity effects, and the need for very high sensitivity counting channels.

04/01848 Water level in boiling water reactors - measurement, modelling, diagnostic Hampel, R. et al. Progress in Nuclear Energy, 2003, 43, (1 4), 121-128. The paper deals with the hydrostatic water level measurement in connection with the application of knowledge-based and model-based methods of signal processing using Fuzzy Set Theory, and under utilization of internal gamma radiation as well as application of Artificial Neural Networks (ANN). The utilization of Fuzzy-Set Theory and ANN's is explained. The principle of different measuring methods are described and placed underneath with applications, like Hybrid Observers and diverse measuring system for boiling water reactors.

Economics, policy, supplies, forecasts

04/01849 A comparative physics study of alternative long- term strategies for closure of the nuclear fuel cycle Cometto, M. et al. Annals of Nuclear Energy, 2004, 31, (4), 413-429. The appropriate management of radioactive waste arising from the nuclear fuel cycle is considered to be a key issue in the development of future, more sustainable nuclear energy systems. In this context, the partitioning and transmutation of actinides could play an important role through the achievement of very significant reductions in the actinide content and radiotoxicity of the high-level waste requiring geological disposal. The current paper reports on the results of a detailed physics study carried out to compare the pros and cons of alternative strategies for closure of the nuclear fuel cycle. Different long-term 'steady-state' scenarios have been considered, involving the deployment, to varying degrees, of light water reactors (LWRs) and advanced fast-spectrum systems. The same nuclear data and calculation methods have been used throughout, so that a consistent and reliable comparison of the relative performance of the three basic fuel cycle options (once-through, plutonium recycle, and recycling of all actinides) has been made possible. In addition, with transmutation having been considered employing both critical and accelerator-driven fast-spectrum systems, the study has provided an evaluation of the advantages and disadvantages of these two different advanced system types.

04/01850 Fuzzy inference system for evaluating and improving nuclear power plant operating performance C6sar, A. F. et al. Annals of Nuclear Energy, 2004, 31, (3), 311-322. This paper presents a fuzzy inference system (FIS) as an approach to estimate Nuclear Power Plant (NPP) performance indicators. The performance indicators for this study are the energy availability factor (EAF) and the planned (PUF) and unplanned unavailability factor (UUF). These indicators are obtained from a non-analytical combi- nation among the same operational parameters. Such parameters are, for example, environment impacts, industrial safety, radiological protection, safety indicators, scram rate, thermal efficiency, and fuel reliability. This approach uses the concept of a pure fuzzy logic system where the fuzzy rule base consists of a collection of fuzzy IF-THEN rules. The fuzzy inference engine uses these fuzzy IF-THEN rules to determine a mapping from fuzzy sets in the input universe of discourse to fuzzy sets in the output universe of discourse based on fuzzy logic principles. The results demonstrated the potential of the fuzzy inference to generate a knowledge base that correlate operations occurrences and NPP performance. The inference system became possible the development of the sensitivity studies, future operational condition previsions and may support the eventual corrections on operation of the plant.

04/01851 Testing the dynamics of shutdown systems instrumentation in reactor trip measurements Gl6ckler, O. Progress in Nuclear Energy, 2003, 43, (1-4), 91 96. Periodic testing of the dynamics of the shutdown systems and their instrumentation is performed in the CANDU nuclear power plants of Ontario Power Generation (OPG) and Bruce Power. Measurements of

in-core flux detector (ICFD) and ion chamber (I/C) signals responding to the insertion of shut-off rods (shutdown system No. 1, SDS1), or to the injection of neutron absorbing poison (shutdown system No.2, SDS2) are regularly carried out at the beginning of planned outages. A reactor trip is manually initiated at high power and the trip response signals of ICFDs and I/Cs are recorded by multi-channel high-speed high-resolution data acquisition systems set up temporarily at various locations in the station. The sampling of the seaprate data acquisition systems are synchronized through the headset communication systems of the station. A total of 120 station signals can be sampled simultaneously up to 2500 samples per second. The effective prompt fractions of the ICFDs are estimated from the measured trip response. Effectiveness and the timeline of the trip mechanism are assessed in the measurement as well. The measurement can identify ICFDs with abnormally slow response (under-prompt) or overshooting response (over-prompt) at the beginning of the outage. The time required for the signals to drop to predefined fractions of their pre-trip values (level crossing time) is plotted as a function of detector position and compared against safety requirements. The propagating effect of shut- off rod insertion or poison injection on the flux is monitored by the level crossing times of ICFDs and ion chambers.

06 ELECTRICAL POWER SUPPLY A N D UTILIZATION

Scientific, technical

04•01852 A genetic algorithm approach to generator unit commitment Swamp, K. S. and Yamashiro, S. International Journal of Electrical Power & Energy Systems, 2003, 25, (9), 679-687. The application of genetic algorithms for the solution of unit commitment with detailed problem formulation, solution methodology and representation is described in this paper. A New Encoding and Representation strategy is proposed that can handle large systems with an improvement in solution and faster convergence. The unit commitment problem is formulated as the minimization of the performance index, which is the sum of objectives (fuel cost, start-up cost) and constraints (minimum up time (MUT), minimum down time (MDT), spinning reserve). Solution methodology and Simulation Results are provided for a 10-generator unit commitment problem for 24 h duration.

04/01853 A minimum-time based fuzzy logic dynamic braking resistor control for sub-synchronous resonance Rahim, A. H. M. A. International Journal of Electrical Power & Energy Systems, 2004, 26, (3), 191-198. Dynamically switched resistor banks connected to the generator transformer bus are known to improve transient stability of the power system. In this article, a braking resistor control strategy designed through fuzzy logic control theory has been proposed to damp the slowly growing sub-synchronous resonant (SSR) frequency oscillations of a power system. The proposed control has been tested on the IEEE second benchmark model for SSR studies. A fuzzy logic controller designed through a classical minimum-time strategy was compared with a general fuzzy strategy employing generator speed variation and acceleration as input to the controller. It was observed that the proposed minimum~time based fuzzy controller provides better damping control; and it is computationally very efficient.

04/01854 A process for generating power from the oxidation of coal in supercritical water Bermejo, M. D. et al. Fuel, 2004, 83, (2), 195-204. A theoretical study of power generation from oxidation of coal by supercritical water oxidation (SCWO) is presented. Two versions of SCWO power plant are compared to two of the most efficient conventional power plant processes: pulverised coal power plants and pressurised fluidised bed power plant. The effects of steam pressure and temperature on produced (Wp), consumed (Wo) and net work (WN) are calculated in order to compare the efficiency of these power plants for the same steam conditions. Enthalpies have been calculated using residual enthalpies by Peng-Robinson equation of state. Calculated results show that net work in SCWO power plant is 5% higher than in other power plants, due to the fact that no air surplus is

258 Fuel and Energy Abstracts July 2004