05 Nuclear fuels (scientific, technical)

The monitoring method of discharge cleaning which was based on microwave spectroscopy was developed in order to apply it to fusion devices and availability of this method was experimentally investigated. Water molecules are one of the major residual molecules in a vacuum vessel, and hence the partial pressure of water is a good index of progress in conditioning. Temporal changes in the partial pressure were measured by using this method during discharge cleaning consequently. Three subjects were studied with a Stark modulated microwave spectrometer, namely, proportionality between the spectrum intensity and the partial pressure, resolving power of the spectrometer for isotopic water molecules and applicability of this method to the measurement of radioactive water molecules. Rotational spectra of the light water H20 (22.235 GHz) and the hydrogen isotopic waters HDO (22.307 GHz) and HTO (16.563 GHz) were observed in several plasma devices for these purposes.

00101345 Neutron density fluctuations due to randomly distributed sources in finite media Williams, M. M. R. Annals of‘&fuc/. Bwg_v. 2000, 17, (3). 233-267. A theory which describes the effect on the neutron flux of sources in the form of lumps randomly distributed in a finite medium is formulated. One- speed diffusion theory is used, but the method can readily be extended to energy-dependent transport theory. The mean flux, the covariance and a new statistical indicator, the mean flux difference between regions, are calculated for an infinite and semi-infinite medium. Numerical results are obtained using Markov and Gaussian models for the random geometry of the lumps. It is concluded that the statistical anisotropy of the medium can play a significant role and that, even though what is ostensibly a one- dimensional problem in the x-direction is considered, it is necessary to incorporate the medium properties in the other two directions via the correlation lengths Xy and Xz. It is also noted that there can be marked differences in the average fluxes in the various source regions which can deviate considerably from the conventional average flux. These results may have practical implications in the design of radioactive waste drums in which sources of neutrons (or gamma rays) are encased randomly in a background matrix. Conventional averaging may lead to a significant underestimate of the surface flux and current. The theory neglects the associated random material properties but should be a good approximation if the volume fraction of the source material is small.

00101346 Neutronic evaluation of two proposed fuel lattice pitches for ET-RR-1 reactor Ashoub, N. and Saleh, H. G. Awds ofNuc/~~r Energy. 2000, 27. (6), 553- 561. The present fuel element of the ET-RR1 research reactor has a 1.75 cm lattice pitch. The neutronic studies were proved that, this lattice pitch is over moderated and not the suitable one from the fuel economic point of view. Two fuel lattice pitches are proposed, one has 1.4 cm lattice pitch with 10% Uz3’ enrichment and the other has 1.75 cm lattice pitch with 15% Uz3s enrichment. The comparative neutronic study was done between these two proposed fuel lattice pitches against the present one in two cases, one for the complete core configuration of the ET-RR-l which includes 52 fuel elements and the other for one of the actual core configuration load contains 47 fuel elements. This study is included the calculations of different neutronic parameters as the infinite and effective multiplication factor, the multi-group neutron flux along the reactor core, and the power peaking factor. The above factors were calculated by using the WIMSD4 code for lattice cell calculation, and the DIXY2 code for diffusion calculations. The results are represented in some tables and figures.

00/01347 On-line stability monitoring of BWR’s using artificial neural networks Tambouratzis, T. and Antonofoulos-Domis, M. Annuls of Nucl. Energy, 1999, 26. (14), 1287-1302. The problem of uncovering stability parameters of boiling water reactors (BWRs) from short neutron noise records for on-line monitoring is investigated. The aim is to use the smallest possible number of points of the auto-correlation function (ACE) at the shortest possible time lags as input to a number of back-propagation artificial neural networks (BP ANNs), which are trained to approximate the relationship that exists between the ACE of the neutron noise signals and the stability parameters of interest (e.g. the decay ratio (DR)). Tests on novel ACFs illustrate the potential of the proposed approach for on-line stability monitoring.

OOlO1346 Research on the incineration of plutonium in a modular HTR uslng thorium-based fuel Riitten, H. J. and Haas, K. A. Nucl. Eng. crud Design. 2000, 195, (3). 353- 360. Large stockpiles of plutonium have accumulated globally. In order to avoid the production of second-generation .plutonium during the reuse of this nuclear fuel, it can be incinerated in combination with the fertile material thorium instead of uranium. The coated-particle fuel of high-temperature reactors (HTR) allows a very high heavy metal burnup and thus it can achieve a very high incineration fraction of the initially loaded-generation plutonium (86%) already during the first reuse in a modular pebble-bed HTR. Only a negligible amount of second-generation plutonium is bred from the small quantity of highly enriched uranium, which is used as make- up fissile material. An optimization of the fractions of Pu, U and Th

contained in the fuel elements has been done on condition that a negative temperature coefficient of the reactivity has to be achieved over the whole range of operating temperature.

00101349 Stochastic neutron transport equations for rod and plane geometries Sharp, W. D. and Allen, E. J. A/m& o/‘Nucl. Dfer~y,r. 2000, 27. (2). 99-l 16. In the derivation of the neutron transport equation, it is assumed that neutron populations are large enough so that fluctuations in the neutron population due to random neutron interactions can be ignored. This assumption is removed in this investigation. The result is a system of stochastic differential equations that models the random behaviour of neutron transport. Rod and plane geometries are considered in the present investigation. Isotropic scattering is assumed. Numerical procedures are developed and tested for solving these systems. The results are compared with Monte-Carlo calculations, which confirm the accuracy of these stochastic neutron transport equations.

00101350 The Pen measurement results on FCA-XIX cores Doulin, V. A. CI al. Progrrs.~ in Ntrcl. Energy, 1999. 35, (2), 163-168. This paper is devoted to the results of /&r measurements on FCA-XTX rores. Two independent experimental techniques were used. Basic relationships and measurement results are presented.

00101351 The effect of random geometry on the criticality of a multiplying system II: extension to resonance absorption Williams, M. M. R. Anncr/.s of Nw/ctrr Enu,q~~. 2000. 27. (6). 5 I7 -552 In an earlier paper, a method was developed for calculating the probability distribution of the multiplication factor in a reactor in which the fuel elements are randomly distributed across the core. In this paper, the method is extended to include resonance absorption and also to the case where the fuel elements have random values of enrichment. As before, the Feinberg-Galanin-Horning source-sink method is used. The probability distribution P(k,,,) is calculated for a bare reactor containing from one to ten fuel plates. It has been observed that li,,, lies in the range (X,,,, ,,,!“. k s,,,m.,x) and it is also noted that as the number of fuel plates increases, the form of P(k,,,) becomes Gaussian-ltke, but can never be exactly Gaussian because of the finite limits on li,.,,. Discoveries have also been made that the general rule put forward by previous workers in this field. namely that (h,,,) for the spatially random medium is always greater than the corresponding deterministic value. no longer holds in general. Further calculations with “‘U and Al plates suggests that the presence of resonance absorption may be the cause of this discrepancy. There IS also the fact that In this work a realistic slowing down model is used whereas previous workers used one- speed theory. Some new results for basic source-sink theory are also reported.

00101352 Variational processing of stochastic simulation in neutron transport: the three-dimensional system Allagi, M. 0. and Lewins, J. D. Anrds of Nurlrur Enrrg~. 2000. 27. (6). 483-503. The variational processing of Monte Carlo results in a two-group infinite homogeneous multiplying system, one-dimensional scattering and neutron deep penetration problems improved the accuracy and reduced the variance of the analogue Monte Carlo estimates, especially when virtual sampling was utilized. In this paper, the use of virtual sampling in variational processing of Monte Carlo solutions to a more realistic three-dimensional problem is addressed. The results of this study are in agreement with the results of previous papers. The analytical solutions of this model are obtained by Neumann iterative method for different values of scattering ratios and for different cell widths. The important functions used in the variational processing are first obtained by fictitious sampling and then by the virtual sampling technique. Both show a significant reduction in variance and in percentage difference from the exact results. The overall performance, however, favours the use of virtual sampling. As in previous cases, correlation effects were found to be advantageous for the cases considered. The convergence of the variationally processed Mo?te Carlo is found to obey approximately the Lewins conjecture: a IiN- behavlour rather than the l/N for the analogue Monte Carlo.

00/01353 Waste analysis generated by alternative reprocessing fuels from pressurised water reactors Pereira, C. Ann& of Nucl. Enrrgy. 2000, 27, (5). 449-464. The final disposal of the spent fuel implies an associated environmental impact. This depends on the composition of the fuel and on the irradiation conditions. Previously, the insertion in PWR of fuels coming from alternative reprocessing techniques has been proposed and many studies have been developed to evaluate their neutronic viability. This article tries to analyse the waste generated by these fuels, when submitted to the same irradiation conditions. To reprocess the fuels, alternative techniques were used. Coprocessing and AIROX Multirecycles will be simulated and the effects of the insertion of Thorium in the composition of these reprocessed fuels will be studied. In comparison, the standard fuel used, UOz, was also simulated. The goal of this study is to verify the radiological risk associated with the simulated fuels, relating the fuel inventory to its radiotoxicity.

00/01354 Xenon transient analysis for direct use of spent pressurized water reactor fuel in CANDU reactors (DUPIC) Jeong, C. J. and Choi, H. Annals of Nucl. &erg)‘, 2000. 17, (3). 269-278.

152 Fuel and Energy Abstracts May 2000

The xenon transient in a CANDU-6 reactor loaded with DUPIC fuel has been studied. This study utilized WIMS-AECL to generate xenon proper- ties for the RFSP code to calculate the xenon load. The xenon property generation method by WIMS-AECL was validated for a natural uranium CANDU-6 core. The validation calculation has shown that the xenon load predicted by WIMS-AECL and RFSP is within 2% of the reference value obtained by the design codes POWDERPUFS-V and RFSP. The xenon load of the DUPIC fuel core was calculated for various reactor conditions such as shutdown, start-up and power level change; and the results were compared with those of a natural uranium core. This study has shown that the xenon load of CANDU-6 reactor loaded with DUPIC fuel is much lower than that of the natural uranium core: however, the xenon transients are stabilized in both cores.

Economics, policy, supply, forecasts

00101355 Heat removal characteristics of vault storage system with cross flow for spent fuel Sakamoto, K. Nrrcl. Eag. and Design, 2000. 195, (I), 57-68. Since the amount of spent fuel to be stored is expected to steadily increase in Japan, a use of large-scale dry storage facilities is considered to be a promising method in practice at reasonable economic cost. The present study is concerned with the heat removal experiment of vault storage system adopting cross flow with passive cooling, using a l/5 scale model. The results show that the flow pattern of air in the storage module strongly depends on the ratio of the buoyancy to the inertia force. A simple method to estimate air-flow patterns in the storage module was proposed, where the Ri(Richardson) number was considered as the most representative parameter. Then the heat transfer rate from a storage tube to cooling air was estimated, which could apply to the design of a full-scale vault storage system with cross flow, in which dozens of storage tubes were placed. The acquired information was also used to optimize heat removal design of the vault storage system in the present study.

06 ELECTRICAL POWER r AND GENERATIO&

UTILIZATION

Scientific, technical

00101356 A global dynamic error driven control scheme for static VAR compensators Sharaf, A. M. Elccrric Poner S~~srems R~~crrch. 1999. 51, (2). 131-93. The paper presents a novel static VAR compensator SVC control scheme. The new SVC control strategy is validated on a single machine infinite bus power system with a dynamic non-linear load.

00/01357 A hybrid neural network model for fast voltage contingency screening and ranking Srivastava, L. PI al. Electrical Power & Energy Sysietns, 2000, 22, (I), 35-42. In this paper, a hybrid neural network based approach is proposed for fast voltage contingency screening and ranking. The developed hybrid neural network is a combination of a filter module and ranking modular neural network. All the selected contingency cases are applied to the filter module, which is trained to classify them either in critical contingency class or in non-critical contingency class using a modified BP algorithm. The screened critical contingencies are passed to the ranking modular neural network for their further ranking. The ranking modular neural network reduces a K- class problem to a set of K two-class problems with a separately trained network for each of the simpler problems. Total load demand, real and reactive pre-contingency line-flows and terminal voltages in the contingent element, along with a topology number corresponding to the contingent element, are selected as input features for the neural networks. The continuous values of voltage performance index are classified into four classes (levels) according to their severity, and the modular neural network is trained for this multi-class classification problem. The effectiveness of the proposed method is demonstrated by applying it for contingency screening and ranking at different loading conditions for IEEE 30-bus system and a practical 75bus Indian system. Once trained, the hybrid neural network gives fast and accurate screening and ranking for unknown patterns and is found to be suitable for on-line applications at Energy Management Systems.

06 Electrical power generation and utilization (scientific, technical)

00/01358 A novel approach to conventional power system stabilizer design using tabu search Abido, M. A. Electricd Power & Emv,g SI.,~ICI~T. 1999. 2 I. (6). Mm4S4. A tabu search (TS) based power system stabilizer (PSS) is presented in this article. The proposed approach uses the TS algorithm to search for the optimal settings of conventional lead-lag power system stabilizer (CPSS) parameters. Incorporation of the TS algorithm in the PSS design significantly reduces the time consumed in the design process. One of the main advantages of the proposed approach is the fact that the TS algorithm leads to the optimal solution regardless of the initial guess. The performance of the proposed PSS under different disturbances and loading conditions is investigated for single machine infinite bus and multi-machine power systems. The eigenvalue analysis and simulation results show the effectiveness of the proposed PSSs to damp out the local and the inter-area modes of oscillations and work effectively over a wide range of loading conditions and system parameter variations,

00101359 A study of the effects of compression on the performance of the positive active mass in lead-acid cells using absorptive glass mat separators CalAbek, M. er al. J. Power Sources, 1999, 78, (I-2). 94-98. A new electrochemical cell was designed and constructed to enable in situ measurements of the performance and internal resistances of lead-acid test electrodes in a vertical position during cycling at well-defined degrees of compression. The AGM separators used were combined with microporous paper separators to prevent short-circuiting by conducting bridges of lead dioxide. The test cells were subjected to pressures in the range O-g N/cm’; the compression decreased the positive active mass resistance and increased its cycle life.

00/01360 An experimental investigation of self-excitation in capacitor excited induction generators Levi, E. and Liao, Y. W. Ekwfric, Powr SI..TICI~ Rc.wcrrc~h, 2000. 53. (I), 59- 65. Self-excitation process in induction generators is a complex physical phenomenon that has been studied extensively in the past. In-depth coverage of methods of steady-state analysis and models for simulation of transients is provided in the existing literature. Reports regarding experimental investigation of dynamics are however much less detailed. Usually, their only purpose is to prove the theoretical concepts. This paper attempts to fill in this gap by providing a purely experimental treatment of the self-excitation process in induction generators. The emphasis is placed on situations that lead to voltage collapse and total demagnetization of the machine, and on variable speed operation of the induction generator with a fixed capacitor bank. Operation with capacitors connected in star and delta under no-load conditions, connection of the purely resistive load, and connection of the resistive load with short-shunt compensation is elaborated. It is shown that some of the commonly quoted features of a self-excited generator operation do not necessarily hold true, while others are confirmed.

00101361 Analysis of overvoltages in overhead ground wires of extra high volta

8 e (EHV) power transmission line under single-

phase-to-groun faults Dudurych, I. and Rosolowski, E. Ekectric Powr S~~srctns Rcseurch, 2000. 53. (2), 105-I 1 I. Overhead ground wires (GW) of extra high voltage (EHV) power transmission lines, apart from lightning-induced overvoltage protection are frequently used for carrier-current communication. In this case the ground wires are suspended on insulators. the dielectric strength of which should be sufficient for the line operational conditions. The insulation level is defined from the condition of the single-line-to-ground (SLG) fault, thus insulator protecting spark gaps should not be flashed-over during such conditions - in order to maintain continuity of the communication channel along the line. Overvoltages during such faults depend on many parameters such as fault place, fault angle, pre-fault load, etc. Therefore, designers should investigate the problem for determination of the worst-case scenario. In this paper, dependence of the overvoltages on 750 kV power transmission line ground wires upon the SLG fault place and pre-fault load of the line in transient and steady states is investigated. The analysis was performed by using dynamic arc model incorporated into the EMTP program. The provided simulations show that adequately introduced primary and secondary arc models are decisive factors for an accurate simulation of the electromagnetic phenomena in the EHV transmission lines during an arc crossing-over (here the primary arc plays an important role) and during so called dead-time, when the secondary arc takes place. This paper gives some recommendations for the insulator strings co- ordination in the 750 kV earth wires on the basis of computer simulation results.

00101362 Apparatus for testing of fuel ceils Dudnik, A. N. Ikotckhnol. Rcsrrr.soshcrr~het~~e, 1998, 3. 62-67. (In Russian) institut Gaza NAN Ukrainy. The main components and mechanisms of a fuel cell testing process are described. The main work parameters of the apparatus and the test results for obtaining synthesis gas are provided. The diagram of a start-up unit for testing molten carbonate fuel cells is also shown.

Fuel and Energy Abstracts May 2000 153