05 Nuclear fuels (scientific, technical)

98lO3805 Study on concrete with low-heat portland cement replaced by slag and fly ash Takeuchi, M. et al. Semento. Konkurito Ronbunshu, 1997, 51, 340-345. (In Japanese) The paper examines the effect of replacing low-heat portland cement with blast-furnace slag or fly ash on the compressive strength development and adiabatic temperature increase. This was compared with the cases of replacing normal portland cement and moderate heat portland cement. When normal portland cement was replaced by blast-furnace slag, the compressive strength at early age decreased with increasing replacement ratio of blast-furnace slag. Long-term strength was higher than for the plain concrete. When low-heat portland cement was replaced by blast-furnace slag, the compressive strength at early age was improved when the fineness of the blast-furnace slag was high and compressive strength at the age of 91 days was about 80% compared to concrete without slag regardless of slag fineness. In the case of replacing low-heat portland cement with blast- furnace slag or fly ash, the rate of temperature increase was smaller than for concrete without blast-furnace slag or fly ash.

98lO3806 Study on properties to evaluate quality of fly ash Higaki, T. et al. Semento, Konhurito Ronbunshu, 1997, 51, 114-119. (In Japanese) There has been a growing availability of fly ash containing more than 5% carbon and below the Japanese Industrial Standards. The replacement of domestic coal with imported coal as fuel and a lowering of the burning temperature in power plants are factors responsible for this. From a resources recycling viewpoint, it is necessary to recycle sub-standard fly ash into concrete material. However, the carbon content of the sub-standard ash decreases the air content of concrete. A suitable method for estimating the air-entraining capacity of concrete containing sub-standard fly ash was investigated. It was difficult to estimate air content of mortar including fly ash from LOI, surface area measured by Blaine method and BET specific surface area of the fly ash. However, defining the effective specific surface area as the surface area in pores of >4 nm diameter, gives an index which relates to the so air entraining capacity and air content in mortar.

9ato3.807 A study pn the effect of heat treatment *on pTr;tronal groups of patch based actrvated carbon fiber usmg

Shin, S. et al. Carbon, 1998, 35, (12) 1739-1743. By introducing a very thin KBr layer on their surfaces, pitch based active carbon fibres (ACFs) were analysed by a FTIR micro-ATR technique. The ACFs were thermally treated at 600, 1100, and 1200°C to investigate the change in their surface functionalities. Increase in the heat treatment temperature reduced the amount of oxygen containing surface functional groups and caused the ACFs to become more hydrophobic. When the ACFs were thermally treated, the decrease of carboxylic acid groups occurred first and ketone or quinone groups subsequently disappeared at higher heat treatment temperatures. When treated at 1100 and 1200°C the degree of graphitization of the ACF was significantly increased, which was partially attributed to the release of the C=O groups in the conjugated ketone or quinone structures.

98103808 Swelling of pitch-based carbon fibres during acti- vation in carbon dioxide Gondy, D. and Ehrburger, P. Carbon, 1998, 35, (12), 1745-1751. Carbon dioxide and steam were used to activate isotropic pitch-based carbon fibres at 850-1000°C. A significant increase in micropore volume, as measured by the physical adsorption of Nz and COs, was discovered in both cases. Fibre diameter steadily decreases during gasification by steam. In contrast, an intermediate diameter increase is observed during activation by COs. The interval of burn-off corresponding to fibre swelling was found to depend on the gasification temperature. Swelling was not displayed by phenolic resin-based fibres, inferring that it is a phenomenon specific to pitch-based fibres activated by COz. During swelling, oxygen is taken up on the incompletely stabilized part of the isotropic pitch-based carbon fibres. In relation to fibre stabilization during activation, the origin of swelling and its effect on microporosity are discussed.

98103809 Treatment method of coal ash for recycling as admixtures for cement Arai, S. Jpn. Kokai Tokkyo Koho JP 10 45,444 [98 45,444] (Cl. C04B7/26), 17 Feb 1998. ADDI. 96/199.885. 30 Jul 1996, 4 PP. (In Japanese) The coal ash is heated with hot air in a cyclone to comb&t unburnt carbon and is then separated into coal ash and combustion gas. The coal ash is sieved into coarse fractions and fine fractions and the fine fractions are recovered as admixtures for fly ash cement. Sieving can also be carried out before the heat treatment, instead.

98iO3810 Treatment of fly ash from coal fired power plants for recycling and artlflclal soil Fukunaga, M. Jpn. Kokai Tokkyo Koho JP 10 29,848 [98 298481 (Cl. C04B28/02), 3 Feb 1998, Appl. 96/187,685, 17 Jul 1996, 12 pp. (In Japanese) Artificial soil is produced from a mixture of fly ash, solid clays (from mud), stabilizers and pH controlling agents. In the mixing process, engine exhaust gases may be introduced into the mixtures. The artificial soil may contain mud or soil and sand and optionally micro-organisms.

98/03811 Triboelectrostatic separation of unburned carbon from fly ash for ash recycling Lee, J.-K. Chawon Risaikring, 1997, 6, (3), 15-21. (In Korean) In 1996, 3 million tons of fly ash was generated from a coal-fired power plant, causing a serious environmental problem due to disposal in an ash pond. Fly ash is an accepted additive in concrete where it adds strength, sulfate resistance and reduced cost, provided acceptable levels of unburned carbon are maintained. The technical feasibility of a dry triboelectrostatic process to separate unburned carbon from fly ash into economically valuable products is investigated here. Particles of unburned carbon and fly ash can be imparted positive and negative surface charges, respectively, with a copper tribological charger, due to differences in the work function values of the particles and the tribological charger and can be separated by passing them through an external electric field. A laboratory-scale separation system consists of a screw feeder for ash supply, a tribological charger, vertical collecting copper plates, power supplies, a flow meter, and a fan. Fly ash recovery was strongly dependent on the tribological charger geometry, electric field strength, fly ash size and ash feeding rate. Optimal separation conditions were fly ash size less than 125 ,Irn and electric field strength 200 kV/m. Over 80% of the fly ash with 7% loss on ignition was recovered at carbon contents less than 3%.

98103812 Use of wastes from coal beneficiation processes for production of electric and thermal power Adamczyk, R. and Zygmanski, W. Karbo-Energochemical-Ekol., 1996, 41, (8), 295-297. (In Polish) Based on data for the Janina mine, Poland, the feasibility of utilization of coal flotation tailings as fuel for a power station is analysed.

98103813 Utilization of power station waste products in hydraulically hardening immobilization systems Krug, M. et al. VCR Kraftwerkstech., 1998, 78, (3), 115-123. (In German) The paper studies the utilization of lignite fly ash and waste incinerator filter dust for producing the title immobilization systems. Following a detailed chemical, mineralogical, and physical characterization of the raw materials, the production of -50 binder and immobilization systems is reported. After 28 days of hydration, a mixture of 535% water/lignite fly ash, 50% water/incineration filter dust, and 15% water/additives met the requirements of a class II dump. Excellent water permeability, high compressive strength and water resistance were exhibited by the immobi- lization systems. Due to their good constructional properties and processibility, the binder systems produced from the waste products of power stations may be used in construction materials.

05 NUCLEAR FUELS

Scientific, Technical

98103814 Feasibility study of U-235, Pu-239 and Pu-240 content determination in an irradiated fuel by neutron transmis- sion analysis Naguib, K. et al. Ann. Nucl. Energy, 1998, 25, (ll), 893-901. The paper describes a non-destructive method and its feasibility for determining U-235, Pu-239 and Pu-240 contents in an irradiated fuel. The use of shape fit analysis of the Time-Of-Flight (TOF) neutron transmission data of the irradiated fuel for neutron energies below 3 eV forms the basis for the model. one of the TOF spectrometers installed at ET-RR-l reactor was used for the neutron transmission experiment of the irradiated fuel. Taking into account the known parameters of resonance of certain fissile and fission product nuclei to provide the fit analysis, the computer code SHAPE has been adapted. The content of the gross-fissile and fission product isotopes were determined from the burn-up calculations of the fuel assembly of the ET-RR-l reactor with defined history. The effect of both uncertainties in resonance parameters on the deduced contents of fissile nuclei and statistical accuracy of the TOF measurements are estimated.

98/03ai 5 Modelling of core protection and monitoring sys- tem for PWR nuclear power plant simulator Lee, J. K. and Han, B. S. Ann. Nucl. Energy, 1998, 25, (7), 409420. Developed for Younggwang units 3 and 4 nuclear power plant (YGN Nos 3 and 4) in Korea, a nuclear power plant simulator has been in operation since November 1996. The core protection calculator (CPC) and the core operating limit supervisory system (COLSS) for the simulator were also developed. As a digital computer-based core protection system, the CPC performs on-line calculation of departure from nucleate boiling ratio (DNBR) and local power density (LPD). It initiates reactor trip when the core conditions exceed designated DNBR or LPD limitations. By implementing the limiting conditions for operations in the technical specifications, the COLSS is designed to assist operators. With these systems, it is possible to increase capacity factor and safety of nuclear power plants, because the COLSS data can show accurate operation margin to

356 Fuel and Energy Abstracts September 1998

06 Electrical power supply and utilization (scientific, technical)

plant operators and the CPC can protect reactor core. The function of CPU COLSS is analysed in detail and a simulation model for CPUCOLSS is then presented, based on the function. The model results are reasonable when compared with the YGN Nos 3 and 4 plant operation data and CEDIPS/ COLSS FORTRAN code test results.

96lO3616 Standardization of oxidation induction time testing used in life assessment of polymeric electric cables Mason, L. R. and Reynolds, A. B. J. Appl. Polym. Sci., 1997,66, (9), 1691- 1702. In assessing the extent of degradation in the polymer insulation of electric cable in nuclear power plants, oxidation induction time (OIT) has been proven to be a useful diagnostic tool. OIT is influenced by test temperature, sample preparation, sample geometry, sample mass, particle size, thermo- gram interpretation and shelf life. The effects of these parameters were investigated for ethylene propylene diene monomer (EPDM) and cross- linked polyethylene (XLPE) polymer cable insulations, which were aged in radiation and thermal environments. Standards for an OIT methodology suited for practical use in the nuclear power industry were determined on the basis of these results. Development work was also carried out on techniques to estimate error in thermogram interpretation and reproduci- bility.

98i03af 7 Thermochemical prediction of chemical form dis- tributions of fission products in LWR oxide fuels irradiated to high burnup Morivama, K. and Furuva, H. 1. Nucl. Sci. Technol., 1997,34, (9), 900-908. The radial distribution of chemical forms of fission products (FPs) in LWR fuel pins was theoretically predicted by a thermochemical computer code SOLGASMIX-PV, based on the result of micro-gamma scanning of a fuel pin irradiated to high burnup in a commercial PWR. The absolute amounts of fission products generated in the fuel was calculated by ORIGEN-2 code, and the radial distributions of temperature and oxygen potential were calculated by taking the depression and oxygen redistribution in the fuel into account. A fuel pellet was radially divided into 51 sections and chemical forms of FPs were calculated in each section. The effects of linear heat rating (LHR) and average oxygen/uranium ratio on the radial distribution of the chemical form were evaluated.

98103818 Thermodynamics of zinc chemistry in PWRs: effects and alternatives to zinc Korb, J. and Stellwag, B. Nucl. Energy, 1997, 36, (5), 377-383. In terms of the properties of spinels the favourable effect of zinc on radiation field control in PWRs is evaluated. The identification of an alternative element to zinc is described. Chromites were revealed to have a higher stability than ferrites and zinc has a high affinity for the relevant spinels. Therefore, cobalt and other elements should be displaced from existing oxide layers. In the identification of an alternative element to zinc, the following selection criteria were used: activation behaviour, valency and ion radius of candidate elements; affinity for spine1 formation and occupational health and safety aspects. Based of these criteria, magnesium was identified as a possible alternative to zinc.

95lO3819 Three dimensional evaluation of two-phase flow in BWR fuel bundles based on compressible two fluid-one pressure and k-e turbulence models Hotta, A. er al. Ann. Nucl. Energy, 1998, 25, (7), 437-463. Developed to simulate a comprehensive two-phase flow field in fuel bundles of boiling water reactors, the three dimensional fluid dynamic code system is based on the compressible two fluid-one pressure (six equations) model. It is designed for application to both detailed fully three-dimensional geometries and porous medium sub-channel type geometries. In the detailed modelling, the turbulence effect is considered by the additional four conservation equations of the k--E turbulence model and the convective terms are formulated by the modified skewed upwind scheme. The sub- channel type modelling, in contrast, is built from coarser meshes. The empirical void drift and turbulence mixing models are introduced to replace the k-e turbulence model and other additional constitutive models such as the local loss are added to facilitate efficient sub-channel-type calculations. General problems were investigated regarding numerical methodologies in discretizing a vapour-liquid two-phase flow field based on the two fluid-one pressure model. The performances of several pressure iteration schemes were compared in combination with the outer Newton-Raphson iteration loop. Among them, the MILUCR scheme is found to be most stable and efficient. Two sample calculations, one numerical and the other experi- mental verification, were performed to prove the performance of the code system. The void distribution was compared with the measurement by the X-ray CT scanner and it was indicated that not only the axial pressure loss, but also the transverse pressure loss, has a significant effect on the planar void distribution in the wake of the spacers.

Economics, Policy, Supplies, Forecasts

9alO3820 Final report about operation of the AVR experi- mental nuclear power station Ziermann, E. and Ivens, G. Eer. Forschungszenr. Juelich, 1997, (Juel- 3448) 1-531. (In German) Operation of the 15 MW experimental nuclear power station with a helium- cooled high-temperature reactor and spherical fuel elements commenced in 1969. Full-power and experimental operation was extended until the end of 1988, during which time, approximately 1670 GWh of electric power was generated. The experiment’s objective was to test the concept and the components, especially the fuel elements, which were continuously developed and perfected during the operation period. The present report lists in detail all the shutdowns and power decreases, their causes, as well as major malfunctions. All malfunctions were completely eliminated without impairing further operation. The behaviour of all essential components and the water-steam circuit are described. The reactor physics, control of the coolant gas impurities, the final experimental programme and radiation protection are all addressed. The report shows that the helium-cooled high- temperature reactor with spherical fuel elements can be successfully built and operated, based on 21 years of experience. The system has excellent safety features and is not only suitable for electricity generation, but also for the production of process heat at a high temperature and as a heat source for helium turbine power plants.

9a/o3a21 Fusion breeder with enhanced safeguarding #capabilities against nuclear weapon proliferation Sahin, S. ef al. Energy Comers. Mgmt, 1998, 39, (9), 899-909. As a prospective alternative in addition to existing methods of nuclear fuel enrichment, such as gas diffusion and gas centrifuge plants, the breeding capability of a fusion reactor for z39Pu has been analysed to provide fissile fuel for LWRs. The analysis is conducted for the catalysed-(D,D) and (D,T) fusion reactors. Two different coolants (helium gas and Flibe ‘Li,BeF4’) are selected for the nuclear heat transfer out of the fissile breeding zone fuelled with natural uranium. Depending on the type of fusion driver and coolant in the fission zone, power plant operation periods between 12 and 36 months are evaluated to achieve a fissile fuel enrichment quality between 3 and 4% under a first-wall fusion neutron energy load of 5 MW/m’ and a plant factor of 75%. For unit fusion neutron energy flux on the first-wall, a catalysed (D,D) fusion reactor can breed faster than a (D,T) reactor because the former is richer in neutrons than the latter. The Flibe coolant is superior to helium coolant with regard to fissite fuel breeding. During a plant operation over four years, enrichment grades between 4.4% and 8.9% are calculated. The denaturation of the plutonium fuel requires about 2 years of irradiation with fusion neutrons for all investigated cases. During this period, it is possible to breed a high quality, but denatured plutonium for light water reactors. This is an important factor with regard to international safe- guarding.

06 ELECTRICAL POWER SUPPLY AND UTILIZATION

Scientific, Technical

98lO3822 Air-lithium secondary batteries with carbonaceous anodes Takami, N. and Osaki, T. Jpn. Kokai Tokkyo Koho JP 10 83,836 [98 83,836] (Cl. HOlM10/40), 31 Mar 1998, Appl. 96/239,156, 10 Sep 1996,s pp. (In Japanese) Anodes containing lithium-intercalating carbonaceous materials and solid electrolytes are used in the batteries, which display high capacity and long cycle life.

9alQ3823 lation of AIFuhaid, -1z *1?

Application of nonuniform-line theory to the simu- electromagnetic transients in power systems A. S. et al. Electrical Power & Energy Systems, 1998, 20, (3)

This article aims to illustrate the applicability of the non-uniform transmission line as a modelling tool in electromagnetic transient studies of power systems. The s-domain method, previously developed by the authors for lossless single-phase non-uniform transmission lines, was first generalized to include lossy untransposed three-phase lines with frequency- dependent parameters. The new generalized version was then used to obtain the transients on an actual transition segment between an overhead

Fuel and Energy Abstracts September 1999 357