The core monitoring and surveillance system of Paks nuclear power plant has been replaced recently with a new version of the system VERONA utilizing virtualization technology and GPU accelerated numerical computations. In the new system, the process variables are monitored by the visual engine of a new simulation platform SIMTONIA (SIMulation TOols for Nuclear Industrial Application). In this paper the hardware and software architecture of the new system is presented in details enlighten the advantages of the application of stateof- art computational technologies.

Between 2003 and 2007 the Hungarian Paks NPP performed a large modernization project to upgrade its VERONA core monitoring system. The modernization work resulted in a state-of-the-art system that was able to support the reactor thermal power increase to 108% by more accurate and more frequent core analysis. Details of the new system are given in Végh et al. (2008), the most important improvements were as follows: complete replacement of the hardware and the local area network; application of a new operating system and porting a large fraction of the original application software to the new environment; implementation of a new human-system interface; and last but not least, introduction of new reactor physics calculations. Basic novelty of the modernized core analysis was the introduction of an on-line core-follow module based on the standard Paks NPP core design code HELIOS/C-PORCA. New calculations also provided much finer spatial resolution, both in terms of axial node numbers and within the fuel assemblies. The new system was able to calculate the fuel applied during the first phase of power increase accurately, but it was not tailored to determine the effects of burnable absorbers as gadolinium. However, in the second phase of the power increase process the application of fuel assemblies containing three fuel rods with gadolinium content was intended (in order to optimize fuel economy), therefore off-line and on-line VERONA reactor physics models had to be further modified, to be able to handle the new fuel according to the accuracy requirements. In the present paper first a brief overview of the system version (V6.0) commissioned after the first modernization step is outlined; then details of the modified off-line and on-line reactor physics calculations are described. Validation results for new modules are treated extensively, in order to illustrate the extent and complexity of the V&V procedure associated with the development and licensing of the new calculations running in version V6.22 of VERONA. Some details on the experience collected during the operation of the new reactor physics calculations are also discussed. Finally conceptual plans for the next system modification phase are outlined briefly; these changes are induced by the forthcoming introduction of 15 month long fuel cycles (instead of the present 12 month long cycles).

In 2002 the Hungarian Paks NPP started a large-scale reconstruction project to upgrade its core monitoring system called VVER On-Line Analysis (VERONA). The main reason for the reconstruction decision was the planned reactor thermal power increase from 1375 MW to 1485 MW (108%), in order to achieve 500 MW electric power output. Considering safety margins and operation limits the basic approach was to keep all previously valid limits at 108%, as well. However, increased core power and a new type of fuel required a more accurate and more frequent core analysis; therefore modernization of the VERONA system was necessary and unavoidable. At this moment Unit 3 and Unit 4 are served by the new system. The reconstruction project is planned to be fully completed in 2008, when all Paks units will have a modernized core analysis system, providing state-of-the art services and operator support.The paper first presents a brief overview of the reconstruction process, and then main design principles and functions of the new VERONA system are outlined. Details of the new system architecture, hardware devices and software tools are also given, and then elements of the new human-machine interface are described and illustrated. A special emphasis is devoted to the new core analysis software with a detailed description of the validation methods and results. The process of reaching 108% power at Unit 4 is discussed; core behavior is illustrated by real data taken during the power increase procedure. Finally experience related to the development and operation of the new system is discussed briefly. (C) 2007 Elsevier B.V. All rights reserved.

In 2004 the Hungarian Paks NPP completed a project for upgrading the reactivity measuring system applied during reactor startup experiments. Almost all components of the previous system were replaced, only ex-core ionisation chambers remained unaltered. New hardware and software components were introduced for neutron flux signal handling, for data acquisition, as well as for measurement evaluation and data presentation. High-precision picoamper meters were installed at each reactor unit, current signals are handled by a portable signal processing unit. The system applies an accurate on-line reactivity calculation algorithm based on the point-kinetic model with six delayed neutron groups. Detailed off-line evaluation and analysis of startup measurements can be performed on the portable unit, as well.The paper describes the architecture, data acquisition modules, services and man-machine interface of the new system. Functions and results are illustrated with measured data recorded during a startup of Unit 3. In 2003 and 2004 the RMR was installed and tested at all Paks NPP units successfully and now it is in regular use during unit startups.The second part of the paper illustrates an extension of the new system to perform reactivity measurements using the well-known Rossi-alpha and Feynman-alpha statistical methods. The modified system was needed to estimate the reactivity of a subcritical system formed by damaged fuel assemblies stored at the fuel service pit of Paks Unit 2. Theoretical background of the applied algorithms is outlined, then results of validation tests and on site measurements are treated. The measurements have shown that the subcriticality of the damaged fuel was sufficiently deep if the high boron concentration in the fuel service pit was maintained. (c) 2006 Elsevier B.V. All rights reserved.

A prototype of a new concept noise diagnostics data acquisition system has been developed recently to renew the aged present system. This new system is capable of collecting the whole available noise signal set simultaneously. Signal plugging and data acquisition are performed by autonomous systems (installed at each reactor unit) that are controlled through the standard plant network from a central computer installed at a suitable location. Experts can use this central unit to process and archive data series downloaded from the reactor units. This central unit also provides selected noise diagnostics information for other departments. The paper describes the hardware and software architecture of the new system in detail, emphasising the potential benefits of the new approach.

In capillary electrochromatography (CEC) the flow of the mobile phase is generated by electrosmotic means in high electric field. This work compares band spreading measured experimentally in several packed capillaries with electrosmotic flow (EOF) and viscous flow under otherwise identical conditions. The data were fitted to the simplified van Deemter equation for the theoretical plate height, H = A + B/u + Cu, in order to evaluate parameters A and C in each mode of flow in the different columns. The ratio of these two parameters obtained with the same column in microscale HPLC (mu-HPLC) and CEC was used to quantify the attenuation of their contribution to band spreading upon changing from viscous flow (in mu-HPLC) to electrosmotic flow (in CEC). The capillary columns used in this study were packed with stationary phases of different pore sizes as well as retentive properties and measurements were carried out under different mobile phase conditions to examine the effects of the retention factor and buffer concentration. In the CEC mode, the value of both column parameters A and C was invariably by a factor of two to four lower than in the mu-HPLC mode. This effect may be attributed to the peculiarities of the EOF flow profile in the interstitial space and to the generation of intraparticle EOF inside the porous particles of the column packing. Thus, band spreading due to flow maldistribution and mass transfer resistances is significantly lower when the mobile phase flow is driven by voltage as in CEC, rather than by pressure as in mu-HPLC.

Functionally intact 1,4-dihydropyridine receptors have been isolated from digitonin-solubilized skeletal muscle membranes with the combined use of Wheat-germ Lectin-Sepharose affinity chromatography and ion-exchange HPLC. Lectin affinity chromatography was used for the purification of glycoproteins containing N-acetyl-glucosamines residues. Separation of functionally intact 1,4-dihydropyridine receptor/calcium channel complex from Mg2+ -ATPase, one of the most abundant glycoproteins in skeletal muscle T-tubular membranes, was successfully performed by HPLC on a TSKgel DEAE-5PW column.

Short columns packed with micropellicular stationary phases consisting of 2-μm fused silica microspheres with covalently bound iminodiacetate (IDA) functions at the surface were used for rapid HPLC analysis of proteins by metal-interaction chromatography (MIC). In contrast to conventional porous stationary phases which elicit relatively long analysis times, the columns packed with sorbents having micropellicular configuration and Ni2+ or Co2+ chelated by the IDA functions yielded separation of model proteins in a few minutes with good resolution. A Fe3+/IDA column was used for separation of phosphorylated and non-phosphorylated peptides derived from enzymatically digested erythrocyte membrane proteins. Stability of the Fe3+/IDA column was quite satisfactory as determined by monitoring the iron content of the column effluent and by measuring the amount of iron present in the stationary phase.

The nuclear track technique (NTT) is used to enhance the porosity of silica micro-particles. The enhanced porosity is a result of the formation of surface and interior pores or tracks in the silica by the action of external and internal fission fragments. The fission tracks produced at the surface and within the interior of the micro-particles are a result of coating the particles with trace quantitities of uranium, instead of having trace quantities of uranium incorporated within the silica matrix.

Summary  β-Lactoglobulins A and B were separated by high performance displacement chromatography on an anion-exchanger column with chondroitin sulfate as the displacer. A sample of 100 mg containing a mixture of the two β-lactoglublins was separated on a column of 75×7.5 mm in a single chromatographic run. The separation process followed the rules of the classical displacement development: the two proteins formed contiguous rectangular bands and their concentrations were dependent on the displacer concentration. The results demonstrate that high performance displacement chromatography is a useful technique for the separation of proteins in preparative amounts with columns and instrumentation typically used in analytical HPLC. Furthermore, it has the potential to become the method of choice in large scale separation of proteins.

Molecular surface areas accessible to a 4 Å diameter spherical probe were calculated from crystallographic data for five proteins: α-chymotrypsinogen A, lysozyme, trypsinogen, ribonuclease A and ribonuclease S. The retention factors of various proteins were measured on stationary phases having polyether- and phenylligates and with aqueous eluents containing (NH4)2SO4, Na2SO4 or NaCl at pH 7.0. The logarithmic retention factors were plotted against the salt molality and the hydrophobic interaction parameters evaluated from the limiting slopes of the plots at high salt concentrations for the proteins in the chromatographic systems investigated. The hydrophobic interaction parameters thus obtained were linear in both the molecular surface areas of the proteins and the molal surface tension increments of the salts. The experimental results obtained with these relatively simple proteins of known molecular structure, which were available in high purity, support earlier theoretical predictions for the dependence of the hydrophobic interaction parameter on the surface area of the protein and the surface tension raising effect of the salt.

Retention factors for alkylbenzenes, polyaromatic hydrocarbons, steroids, amino acids, peptides, nucleotides, nucleosides were measured with phenylsilica, benzylsilica, phenethylsilica and octylsilica stationary phases using hydro-organic eluents containing methanol, acetonitrile or tetrahydrofuran. The retention behavior of the three arylsilicas was similar but distinctly different from that of octylsilica. The difference is attributed to the chemical properties of the organic ligates, i.e., of the alkyl- and aryl functions. The slight variations of retention behavior observed with arylsilicas on the other hand are believed to arise from differences in the pertiment phase ratios. The method used for interpretation of data is based on the analysis of the pertinent retention moduli, relative column retentivities and relative phase ratios. In addition, relationships between eluite structure and retention were examined. The results give insight into various phenomena underlying the retention process in reversed-phase chromatography.

Silica-bonded stationary phases were developed for the separation of nucleic acid constituents and their properties investigated with homologous oligoriboadenylic acids in electrostatic interaction chromatography and with alkylbenzenes in reversed-phase chromatography. Analysis of retention data confirmed the stratified molecular structure of the surface which consist of a layer of propyl chains anchoredvia siloxane bridges to the silica surface proper and of polar moieties attached to the hydrocarbonaceous functions. The polar top layer contains weak cationic and/or hydrophobic binding sites, is strongly hydrated in contact with aqueous eluents and bars the access by large biopolymers to the hydrocarbonaceous sublayer. In reversed-phase chromatography of small non polar molecules with hydro-organic eluents, however, this layer is accessible and engenders a retentive behavior typical for weak hydro-carbonaceous bonded phases. As a result the stationary phases, depending on the nature of the sample and the mobile phase, exhibit the properties of "soft" phases for the chromatography of biopolymers under mild elution conditions and those of "hard" phases for the separation of small non-polar molecules under conditions generally employed in reversed-phase chromatography. The retention of nucleic acid constituents on most of the stationary phases investigated subject to a dual mechanism as a result of the interplay of electrostatic and hydrophobic interactions between the eluites and the binding sites on the stationary phase surface. Siliceous stationary phases having surface morphology described above are suitable for the separation of nucleic acid constituents having widely ranging molecular weights up to 3 × 106 Daltons provided the support has appropriate pore dimensions. This is demonstrated by the separation of mixtures arising from digesting t-RNApha or polyadenylic acids as well as those of ribosomal RNA’s and different forms of the plasmid pBR322 DNA.

Retention behavior in hydrophobic-interaction chromatography was examined within the framework of the solvophobic theory. The principal parameters which determine the effect of salt on the retention are salt molality and the molal surface tension increment of the salt. According to the theory, in the absence of special binding effects, increase in salt molality in the mobile phase or change of salt to one of greater molal surface tension increment will result in increased retention of proteins in hydrophobic chromatography. The theory is expanded to treat retention in gradient elution with linear decrease in salt concentration that is equivalent to linear increase in eluent strength. The results of the simple model lead to an expression with two parameters: the adjusted isocratic retention volume of the eluite with the gradient former and the slope of plot of logarithmic adjusted elution volume against salt molality, lambda. The latter parameter is linearly dependent on molal surface tension increment if no specific interactions between the eluite and the stationary phase and/or salt are present. In practice, deviations are to be expected from the predicted behavior due to such effects. The results of calculations are consistent with experimental results obtained with several proteins as the eluites and various salts in the eluent. Although unique values of the critical parameter lambda could not be obtained from the data, the trends showed that lambda is strongly correlated with the value of the molal surface tension increment. The prediction that increase in salt concentration in the initial eluent leads to increase in retention volume was found to be generally true, even when the isocratic retention volumes obtained with use of eluent having low salt concentration were small. Use of NaClO4 in the starting eluent led in some cases to decrease in retention volume with increase in the salt concentration at the beginning of the gradient elution. This effect may be due to specific binding effects.

The physico-chemical framework is examined by comparing the predictions of three models for the combined effects of the composition of the hydroorganic mobile phase and the column temperature on the retention ofn-alkylbenzenes on hydrocarbonaceous bonded stationary phases. The “well-mixed” model leads to expressions for the dependence of retention on three factors which are equivalent to those derived previously from linear extrathermodynamic relationships. The “diachoric” model stems from the assumption that the mobile phase is microscopically heterogeneous and the “displacement” model is identical to the retention model most widely used in chromatography with polar sorbents and less polar solvents. Over limited ranges of mobile phase composition and temperature, each model does describe retention behavior. However, only the wellmixed model describes retention well over the entire range of mobile phase composition and temperature studied here. The success of the well-mixed model, and its limits, give insight into the role of the organic solvent in determining the magnitude of chromatographic retention on non-polar stationary phases with hydro-organic eluents.

The retention volume of a peak that is neither retained nor excluded from the mobile phase space in the column is required for determination of retention (capacity) factor and related thermodynamic quantities. In liquid chromatography with multi-component eluents, however, the mobile phase space is theoretically indeterminate owing to interaction between the individual components and the stationary phase and therefore definition and measurement of the mobile phase necessitates that an appropriate convention be found. Here the following four conventions are examined: (i) “all mobile phase components are present in the solvation layer”; (ii) “no solvation layer exists”; (iii) “one given eluent component is not present in the solvation layer”; and (iv) “the most weakly bound solvent component is not present in the solvation layer”. Whereas all conventions appear to be acceptable for a thermodynamic description of the interaction between mobile phase components and the stationary phase in most cases, they yield different values of retention factors and associated thermodynamic properties for eluites. Furthermore, the use of some conventions can give rise to practical problems, e.g., experimental determination of void volume by use of the first convention is ill-defined in general and the second and third conventions can lead to negative values for the mobile phase space. The present work suggests that the fourth convention is free of these problems and provides retention factor values which are more appropriate for use in liquid chromatography than those obtained by the other conventions.

Anisotropic polysulfone membranes were prepared with carboxypeptidase G1 embedded in the polymer structure. The enzymatically active flat and hollow-fiber membranes were obtained by precipitating the polymer from solution in an organic mixture in which an aqueous solution of the enzyme had been dispersed. The process has been found to be particularly suitable for the immobilization of enzymes in anisotropic hollow fibers that exhibited no detectable enzyme leakage upon perfusion. The pH profiles measured with the enzyme in free solution and in the embedded form were similar. Kinetic parameters of multitubular enzyme reactors were investigated by measuring the rate of hydrolysis of glutamate from folic acid or methotrexate at different flow rates and substrate concentrations. The relatively slow mass transfer in such reactors was found to affect strongly the observed kinetics. The results of in vitro experiments with 5000 fiber reactors suggest that hollow fiber cartridges prepared with such membranes have clinical potential for the extracorporeal removal of methotrexate from blood.

Zwitterionic detergents such as n-decylbetaine and alkyl-sultaines, which contain quaternay ammonium functions, were found to be useful cationic hetaerons in ion-pair chromatography with alkyl-silica bonded stationary phases and acidic eluents. Retention moduli with zwitterion-pairing agents are generally lower than those obtained under comparable conditions with n-alkyltrimethylammonium salts having the same alkyl chain length. This behaviour is attributed to the presence of the negatively charged acid group in zwitterionic hetaerons. The effect is particularly pronounced with eluites having more than one acidic group. Zwitterionic detergents make possible ion pair chromatography with hydroorganic eluents having much lower concentration of organic solvent than those employed conventionally. Moreover they may offer significantly higher selectivity than the commonly used cationic hetaerons. With decylbetaine, the pH of acidic mobile phase strongly effects retention even if the negative charge on the eluite remain the same in the pH range investigated, because dissociation of the carboxylic group (pKa=1.83) drastically reduces retention moduli.

Linear free-energy relationships are manifest in the linear dependence of the logarithmic retention factor on the carbon number for homologous series in reversedphase chromatography and allow the comparison of the free-energy increments of substituents for retention of a given elute by different stationary phases. Three methods were used for such comparison. In the first two, methylene group selectivities obtained from retention data obtained with homologous series on different hydrocarbonanceous bonded phases were compared by using different approaches. In the third method the energetics of retention of the end groups such as phenyl-, bromo- and disulfide-moieties of homologous series were examined. The results show that at fixed mobile phase composition and temperature the free energy increments due to methylene groups upon retention by alkyl-silica stationary phases are identical. Only hydrocarbonaceous bonded phases with short (C1–C2) alkyl chains or functional groups of unusual shape show consistent differences from octyl- or octadecyl-silicas. The results broaden the theoretical basis for the development of quantitative structure-retention relationships to be used for the prediction or interpretation of retention data in reversed-phase chromatography.