Search

The EPRI (1991) and the Clark et al. (2014) drift-flux correlations implemented in RELAP5/MOD3 code were benchmarked against the low-pressure void fraction data collected by Clark et al. (2014) at ...

Accurate prediction of interfacial drag in the downcomer annulus is crucial for the assessment of downcomer void fraction for the loss of coolant accident analysis. The downcomer annulus is...

The MAAP5.04 code uncertainty analysis was carried out for the Power Burst Facility Severe Fuel Damage Test 1-4. Comparisons between experimental data and analysis results were focused on hydrogen generation. The uncertainty propagation analysis was conducted through random variations of input uncertainty parameters of phenomenological models whose ranges were determined by the MAAP5 Zion parameter file. The time series clustering technique using the mean-shift algorithm was applied to the data set generated by the uncertainty propagation analysis. It was confirmed that the code predicted well the hydrogen mass generated and the uncertainty bounds of the analysis included the measured hydrogen generation history. The time series clustering technique demonstrated that the key model parameters could be identified for classifying the uncertainty analysis results using a decision tree classifier. Furthermore, the regression models were constructed which predict the uncertainty of the hydrogen generation from the model uncertainty parameters by using the support vector regressions. The hold-out method of cross validation was applied to the regression models of the hydrogen generation to investigate the training error and the test error for the uncertainty prediction of the hydrogen generation.

This research’s purpose is to examine the effect of conflict on diplomatic representation. First, new datasets are created, which include annual data and separate baseline changes and short-term changes. Second, ANOVA shows that the mean difference in short-term changes, but not in baseline changes, between conflict and no-conflict years is significant. Third, the 26 most impacted countries are selected for a case study. The results indicate that a shock to the legitimacy of a government or state leads to a downward change in diplomatic representation (the conflict effect). On the other hand, a celebratory event expands the size of diplomatic corps (the celebration effect). This observation follows our thesis even in a hard case with a long duration of conflict. Last, the author argues that decision-makers are required to ask themselves if they have the responsibility not to leave under given circumstances.

In view of the quality assurance of two-phase flow simulations, CSAU (Code Scalability, Applicability, and Uncertainty) methodology and code V & V (Verification and Validation) have been proposed. The estimation of simulation uncertainty is indispensable in using best-estimate computational codes. A key of successful two-phase flow simulations is to use the state-of-the-art constitutive equations to close the mathematical system used in two-phase flow analyses. The advanced constitutive equations should be developed based on “physics” behind phenomena and should consider scaling parameters which enable their application beyond test conditions used for a code validation. Two-phase flow simulations in a rod bundle is important in various industrial apparatuses such as heat exchangers and nuclear reactors. Constitutive equations for two-phase flows in a vertical rod bundles have been advanced in recent five years. In view of this, this paper provides a comprehensive review of most advanced constitutive equations for two-phase flow analyses in a vertical rod bundle. The constitutive equations of two-phase flow parameters reviewed in this paper are flow regime map, void fraction, void fraction covariance and relative velocity covariance, interfacial area concentration and wall friction. In addition, an exact formulation of one-dimensional momentum equation in two-fluid model considering void fraction distribution is discussed.

Application of the statistical safety evaluation method to the analysis for reflux cooling in the loss of residual heat removal system (RHR) event during mid-loop operation was conducted with RELAP...

We previously developed a one-dimensional (1-D) computation method with parameters adjusted from CCFL (countercurrent flow limitation) data in hot leg and pressurizer surge line models to generalize the prediction method for CCFL in nearly horizontal pipes. In the 1-D computation method, the constant value for the interfacial friction coefficient of fi = 0.03 was used. On the other hand, many correlations for the interfacial friction coefficient in horizontal and inclined pipes have been proposed. In this study, therefore, we carried out 1-D computations for CCFL in nearly horizontal pipes with the diameter of D = 0.03–0.75 m and the length to diameter ratio of L / D = 4.5–63 by using some selected correlations for the interfacial friction coefficient, which are a function of the gas or liquid Reynolds number. As a result, we confirmed that the correlation of the interfacial friction coefficient in terms of the Reynolds number cannot be used for large Reynolds numbers but fi = 0.03 can be used for the wide range of diameters. To improve the correlation with the gas or liquid Reynolds number, we proposed a modified correlation.

A hybrid plasma-enhanced chemical vapor deposition (PECVD)/sputtering system was developed to prepare iron (Fe)-nitrogen (N)-doped carbon catalysts for oxygen reduction reaction (ORR). This hybrid system combines PECVD effective for the synthesis of nanocarbons with sputtering technique for the doping of metals such as Fe where the amount of the doping can be independently controlled during synthesizing nanocarbons. By using this system, Fe-N-doped carbon catalysts are directly synthesized on carbon papers which have been widely used as a gas diffusion layer in fuel cells. The synthesized catalysts with carbon papers exhibit high ORR activity. This is attributed to Fe-N coordination bonds which are stably formed in the synthesized catalysts.

RELAP5/MOD3.2 is a thermal-hydraulic system analysis code used to predict the response of nuclear reactor coolant systems in the event of certain accident scenarios. It is important that RELAP and other system analysis codes are able to accurately predict various two-phase flow phenomena, particularly the interfacial transfers between the liquid and gas phases. It is also important to understand how much uncertainty exists in these predictions due to uncertainties in the constitutive relations used to close the two-fluid model. In this paper, the uncertainty in the interfacial drag calculated by RELAP5/MOD3.2 due to errors in the drift-flux models used to close the model is evaluated and compared to the correlation developed by Goda et al. (2003). The case of downward flow is considered due to the importance of co-current and counter-current downward flow for predicting behavior in the downcomer of reactor systems during small-break Loss of Coolant Accidents (LOCAs) in nuclear reactor systems. The overall uncertainty in the interfacial force calculations due to error in the distribution parameter models were found to have a bias of +8.1% and error of 20.1% for the models used in RELAP5, and a bias of −30.8% and error of 23.1% for the correlation of Goda et al. (2003). However this analysis neglects the effects of compensating errors in the drift-flux parameters, as the drift velocity is assumed to be perfectly accurate. More physically meaningful results could be obtained if the distribution parameter and drift velocity were calculated directly from local phase concentration and velocity measurements, however no studies were available which included all of this information.

The Best Estimate Plus Uncertainty (BEPU) method is applied to analysis of the “intentional depressurization of steam generator secondary side” which is an accident management procedure in a small break loss-of-coolant accident with high pressure injection system failure. In the present study, scaling calculations from the LSTF small break LOCA tests were carried out for a conventional Westinghouse type four-loop PWR. The two test cases were selected with different break size and different depressurization conditions to ensure the reliability for the analyses for the accident scenario. The uncertainty propagation analyses were performed for the PWR. The dominating input uncertainty parameters, i.e. those few with the highest influence on the output uncertainty were identified. The analysis results were compared with those for the LSTF to address the scaling up capability and the similarity evaluation between the LSTF model and the PWR plant model. It was found that the PWR plant model results had overall agreements with the LSTF model, and the uncertainty of the predicted PCT included the measured PCT. Furthermore, the correlation coefficients between the input uncertainty parameters and the PCT for the PWR plant model had similarities with those for the LSTF model.

A new drift-flux correlation has been developed to predict void fraction over a wide range of two-phase flow conditions in rod bundle geometries. An experimental database that represents low liquid flow and low pressure conditions in a scaled 8 × 8 rod bundle test facility is emphasized for this work. At these conditions, recirculating flow patterns may affect two-phase flow characteristics. Such effects may not be appropriately considered in earlier rod bundle correlations for drift velocity and distribution parameter. In the current approach, an existing drift-flux correlation that accounts for the effect of recirculating flow as two-phase flow regimes transition from bubbly to cap-bubbly flow is incorporated to determine distribution parameter. A performance analysis demonstrates that the proposed correlation improves upon existing correlations with an average relative error of ±4.5% when predicting the database utilized for in this work. The new correlation is also demonstrated to scale appropriately to prototypic plant conditions.

The prediction of the peak cladding temperature is key for the evaluation of the safety characteristics of nuclear reactor designs. One of the most important parameters in determining the peak cladding temperature is the two-phase mixture level in the core, which in turn depends on the void fraction in the core. In the two-fluid model, which is used in best-estimate thermal-hydraulic analysis codes such as RELAP and TRACE, the void fraction is largely determined by the interfacial drag. In the codes, the interfacial drag is determined based on drift-flux type correlations for the distribution parameter and void-weighted area-averaged drift velocity. It is essential that the model for the prediction of void fraction in the reactor core be accurate to ensure safe shutdown of the reactor. In light of this, a thorough review of the Chexal–Lellouche drift-flux type correlation currently used in RELAP5/MOD3.2.2 has been initiated to evaluate the scalability and uncertainty of the correlation. Analysis of the physical dependencies indicates some serious concerns regarding the presence of compensating errors in the models for the distribution parameter and void-weighted area-average drift velocity.

A numerical study is presented to examine the effects on countercurrent flow limitation (CCFL) of shape and size of hot leg models with a rectangular cross section. The CCFL was described in terms of Wallis parameters using the channel height H as the characteristic length. Numerical simulations, using the CFD software code FLUENT 6.3.26, were done for the air-water CCFL experiments carried out previously at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in the 1/3 scale hot leg model with a rectangular channel (HxW = 0.25x0.05 m2), and the results were compared with the air-water CCFL data obtained at Kobe University in the 1/5 scale hot leg model with rectangular cross section (HxW = 0.15x0.01 m2) and the results of simulations. It was found that both the height-to-width ratio and the size of the cross section affected the CCFL characteristics in the Wallis diagram. Comparison of CCFL characteristics in rectangular channels with those in circular channels showed that the hydraulic diameter, Dh, was a major cross section geometry term influencing the CCFL characteristics. CCFL constants of the Wallis correlation were about 0.61 on average for the range of 0.05 m < Dh < 0.75 m but became small for Dh < 0.0254 m, and these tendencies were well reproduced by the numerical simulations.

An experiment has been performed to measure void fraction at stagnant to low liquid flow conditions in a rod bundle. An 8 × 8 rod bundle test facility scaled from a boiling water reactor design was utilized at atmospheric pressure with air and water as working fluids. Superficial liquid velocity ranged from 0 to 1.0 m/s and superficial gas velocity ranged from 0.03 to 10.0 m/s. Area-averaged measurements of superficial liquid velocity, superficial gas velocity, and void fraction are used to calculate distribution parameter from a kinematic constitutive equation of the drift-flux model. Results indicate a significant increase in distribution parameter when mixture volumetric flux is relatively low. This observation may be attributed to recirculating flow patterns. An investigation is conducted for existing rod bundle drift-flux correlations because they may not appropriately consider these mechanisms at low liquid flow and low pressure conditions. Results suggest that improvements may be made if the effects of recirculating flow are taken into consideration.

Currently Appendix K of 10 CFR 50 is used in the United States to evaluate models for the emergency cooling systems of light-water reactors. To assure that these models are accurate enough to ensure that the cooling systems are satisfactory, code scalability, applicability and uncertainty methodologies are used to evaluate the uncertainty in system analysis code predictions due to the various models. One cornerstone of this methodology is the development of the Phenomenon Identification and Ranking Table (PIRT), which summarizes the thermal-hydraulic phenomenon associate with a particular accident scenario and ranks their importance in determining the effectiveness of core cooling and the parts of the accident for which the phenomenon may be important. In this paper the PIRT developed by the Institute for Nuclear Safety Systems for a small-break LOCA with loss of high-pressure emergency coolant injection is analyzed in detail and several modifications are proposed based on a mechanistic understanding of the phenomenon involved. The resulting PIRT should provide a more accurate guide for model evaluation and development in advanced thermal-hydraulic system analysis codes.

The main therapeutic strategy against human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) characterized by lower extremity motor dysfunction is immunomodulatory treatment, with drugs such as corticosteroid hormone and interferon-α, at present. However, there are many issues in long-term treatment with these drugs, such as insufficient effects and various side effects. We now urgently need to develop other therapeutic strategies. The heparinoid, pentosan polysulfate sodium (PPS), has been safely used in Europe for the past 50 years as a thrombosis prophylaxis and for the treatment of phlebitis. We conducted a clinical trial to test the effect of subcutaneous administration of PPS in 12 patients with HAM/TSP in an open-labeled design. There was a marked improvement in lower extremity motor function, based on reduced spasticity, such as a reduced time required for walking 10 m and descending a flight of stairs. There were no significant changes in HTLV-I proviral copy numbers in peripheral blood contrary to the inhibitory effect of PPS in vitro for intercellular spread of HTLV-I. However, serum soluble vascular cell adhesion molecule (sVCAM)-1 was significantly increased without significant changes of serum level of chemokines (CXCL10 and CCL2). There was a positive correlation between increased sVCAM-1and reduced time required for walking 10 m. PPS might induce neurological improvement by inhibition of chronic inflammation in the spinal cord, through blocking the adhesion cascade by increasing serum sVCAM-1, in addition to rheological improvement of the microcirculation. PPS has the potential to be a new therapeutic tool for HAM/TSP.

A 54-year-old female was admitted to our hospital because of the Raynaud phenomenon and muscle weakness of the upper limbs. The neurological findings showed somatic and proximal limb weakness. Laboratory studies showed a high serum creatine kinase level. Computerized tomography (CT) revealed enlargement of the thymus. A muscle biopsy showed a small number of degenerating and regenerating fibers but no inflammatory infiltrations. At first, she was initially treated with a three-day course of intravenous methylprednisolone (1 g/day). However, the weakness progressed and the serum creatine kinase level remained high. She was subsequently treated with a combination of tacrolimus (3 mg/day) and prednisolone, but showed no any improvement of the muscle weakness. Following additional treatment with intravenous immunoglobulin, she showed improvement in her muscle weakness. Further, anti-signal recognition particle antibodies were identified after treatment. There have been no previous reports of myopathy with antibodies against the signal recognition particle and enlargement of the thymus, so we herein report the details of this unique case.

A 60-year-old woman suffered from high fever (38°C) and abnormal behavior, was admitted to our hospital on the seventh day of the fever. At admission, she was stuporous, and a cerebrospinal fluid (CSF) analysis revealed pleocytosis (55/μl, monocytes). Fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) images showed high-intensity signals in the medial temporal lobe, inferior surface of the frontal cortex, right cerebellar vermis, and left thalamus. We diagnosed herpes simplex encephalitis, based on the finding of an elevated titer of herpes simplex virus antibody in the CSF (2.90). She was started on treatment with acyclovir and steroid pulse therapy, which was followed by rapid clinical improvement. After recovering from the stupor, the patient exhibited the symptoms of hypersomnia with low orexin level in the CSF. Thus, we should bear in mind that other than consciousness disturbance, patients with herpes simplex encephalitis can also present with rare complications due to the extent of the lesions.

A novel retarding type electron energy analyzer implementing an electrostatic lens system to achieve a high energy resolution sufficient to measure thermodynamic temperature has been investigated b...

A 29-year-old man diagnosed as having pulmonary sarcoidosis in 2008, and hypothyroidism secondary to thyroidectomy for Basedow's disease was admitted to our hospital with pustular psoriasis in November 2010. He experienced high fever (38°C) and headache in late October 2010. Gadolinium-enhanced T1-weighted image showed multiple micronodular lesions with leptomeningeal enhancement, mainly in the brainstem. Cerebrospinal fluid (CSF) analysis revealed pleocytosis, raised protein level and hypoglycorrhachia (7 mg/dl). The patient was also found to have osteonecrosis of the left femoral head. Antituberculous treatment and steroid pulse therapy were started, but produced no improvement of either the symptoms or the laboratory data. Finally, the patient was diagnosed as having meningeal disseminated sarcoidosis by meningeal biopsy in late March 2011. He was started on treatment with 60 mg prednisolone per day, which resulted in marked clinical improvement. It should be borne in mind that marked hypoglycorrhachia in the CSF can also be seen in meningeal disseminated sarcoidosis.

The Best Estimate Plus Uncertainty (BEPU) method has been applied by the authors to analysis of the “intentional depressurization of steam generator secondary side” which is an accident management procedure in a small break loss-of-coolant accident with high pressure injection system failure. In the present study, experimental analyses using the RELAP5/MOD3.2 code were carried out for the ROSA/Large Scale Test Facility (LSTF) secondary-side depressurization tests. The two test cases were selected with different break sizes and different depressurization conditions to ensure the reliability for the accident scenario analyses. The uncertainty propagation analyses were performed through the random variations of input parameters whose uncertainty ranges and distributions were determined previously by the PIRT and the separate effects tests. One thousand random calculations were conducted to get the 95% upper limit values of the peak cladding temperature (PCT) by the Monte Carlo method. Furthermore, the 95%/95% tolerance limits for the PCT were obtained according to Wilks formula. It was confirmed that the code predicted well the major event progressions such as rod surface temperature and the 95% uncertainty bands included the measured values. Furthermore, the 95% upper limit values of the PCT are below the 95%/95% tolerance limit values. However, the statistical fluctuation of the tolerance limit values by Wilks first order formula is as large as the uncertainty value itself. The statistical fluctuation decreases with increasing order of Wilk formula. It is desirable to increase the order of Wilks formula to more than the second order to get the reliable safety margin.Copyright © 2016 by ASME

The Best Estimate Plus Uncertainty (BEPU) method is applied to analysis of the “intentional depressurization of steam generator secondary side” which is an accident management procedure in a small break loss-of-coolant accident with high pressure injection system failure. In the present study, experimental analyses using the RELAP5/MOD3.2 code were carried out for the ROSA/Large Scale Test Facility (LSTF) secondary-side depressurization tests. The two test cases were selected with different break sizes and different depressurization conditions to ensure the reliability for the accident scenario analyses. The input parameter uncertainty propagation analyses were performed to get 95%/95% tolerance limit values of the output parameters. It was confirmed that the code predicted well the major event progressions of the accident for both test cases and the 95%/95% uncertainty bounds of the peak cladding temperatures included the measured values. On the other hand, the same ranges of some input uncertainty parameters could lead to different influences on the output uncertainties between the test cases. The dominating input uncertainty parameters could be different depending on the break sizes and depressurization conditions of the accident scenario.

An application of the Best Estimate Plus Uncertainty (BEPU) method is made to an analysis of the “Intentional depressurizaion of steam generator secondary side” which is an accident management procedure in a small-break loss-of-coolant accident (SBLOCA) with high pressure injection (HPI) system failure. RELAP5/MOD3.2 is used as the system analysis code. Interfacial friction in the core affects the two-phase mixture level and the distribution of the dispersed gas phase. This phenomenon is very important in terms of the influence its uncertainty has on the peak cladding temperature. The RELAP5/MOD3.2 code uses drift-velocity to describe the interfacial friction coefficients in vertical dispersed flow. The Chexal-Lellouche drift-flux correlation is used for the rod bundle geometry. In the present study, the RELAP5 model uncertainty was quantified regarding the interfacial friction coefficients in the rod bundle geometry by conducting numerical analyses of separate effect tests. As the separate effect tests, two-phase mixture level swell tests in the Thermal Hydraulic Test Facility (THTF) of the Oak Ridge National Laboratory (ORNL) were used. After considering applicability to the SBLOCA, tests were selected for which conditions of pressures and rod powers were similar to PWR plant conditions. A total of 55 data were used. The model uncertainty parameter was defined as a multiplier for the interfacial friction coefficient. Numerical analyses were performed by adjusting the multiplier so that the predicted void fractions agreed with the experimental measured data. The resultant distribution of the multipliers represented the model uncertainty. The mean, standard deviation, minimum and maximum values of this uncertainty distribution were 0.88, 0.55, 0.13 and 3.0, respectively.Copyright © 2014 by ASME

In order to evaluate flow patterns and CCFL (countercurrent flow limitation) characteristics in a PWR hot leg under reflux condensation, numerical simulations have been done using a two-fluid model and a VOF (volume of fluid) method implemented in the CFD software, FLUENT6.3.26. The two-fluid model gave good agreement with CCFL data under low pressure conditions but did not give good results under high pressure steam-water conditions. On the other hand, the VOF method gave good agreement with CCFL data for tests with a rectangular channel but did not give good results for calculations in a circular channel. Therefore, in this paper, the computational grid and schemes were improved in the VOF method, numerical simulations were done for steam-water flows at 1.5 MPa under PWR full-scale conditions with the diameter of 0.75 m, and the calculated results were compared with the UPTF data at 1.5 MPa. As a result, the calculated flow pattern was found to be similar to the flow pattern observed in small-scale air-water tests, and the calculated CCFL characteristics agreed well with the UPTF data at 1.5 MPa except in the region of a large steam volumetric flux.

In reflux condensation, steam generated in the reactor core and water condensed in a steam generator (SG) form countercurrent flow in a hot leg, which consists of a horizontal pipe, an elbow and an inclined pipe. Both countercurrent air–water and steam–water tests were previously carried out at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) using the 1/3 scale rectangular channel simulating a PWR hot leg installed in the pressure chamber of the TOPFLOW facility. In this paper, in order to evaluate the effects of fluid properties, the steam–water CCFL (countercurrent flow limitation) tests at HZDR were simulated using the CFD software, FLUENT 6.3.26. The computational domain included the reactor vessel simulator, hot leg and SG inlet chamber in order to avoid uncertainties of boundary conditions at both ends of the hot leg. The VOF (volume of fluid) method and two-fluid (2F) model were used. In the 2F model, the combination of three correlations on the interfacial friction coefficients, which had been validated for the 1/15 and 1/5 scale tests at Kobe University, was used as a function of local void fractions. The CCFL characteristics predicted by the 2F and VOF agreed relatively well with the steam–water CCFL data at HZDR but overestimated the effects of fluid properties on CCFL. The VOF simulations were better able to reproduce the fluid properties than the 2F simulations.

Numerical simulations have been done to evaluate CCFL (countercurrent flow limitation) in a PWR hot leg under reflux condensation by using a VOF (volume of fluid) method implemented in the CFD software, FLUENT6.3.26. The calculated CCFL characteristics have been verified and agreed well with known values including the UPTF data at 1.5 MPa. Therefore, in this paper, parameter calculations using the VOF method were done for system pressures up to 8 MPa under PWR full-scale conditions with the diameter of 750 mm. As a result, calculated CCFL characteristics in the Wallis diagram were slightly mitigated from 0.1 MPa to 1.5 MPa with increasing system pressure, but they did not change from 1.5 MPa to 8 MPa. The CCFL database calculated in this study and values measured under air-water and steam-water conditions were used to derive a CCFL correlation and its uncertainty, where the CCFL constant was . Most of the CCFL data and the current correlation predictions were within the uncertainty of +-0.03.

A one-dimensional drift-flux model was developed and benchmarked with existing models in the present study. Different from existing empirical correlations, this newly developed 1-D drift-flux model started from the variations of two-phase flow distribution parameter C0 for non-dimensional superficial gas velocity 〈 j g + 〉 from low to high, which represents the variation of phase distribution patterns. Due to a combination of small-scale sub-channel effect and large-scale casing effect in a rod bundle, the Hibiki–Ishii’s drift velocity V gj + was introduced to describe the relative motion between two phases. A clear boundary of distribution parameter, C0, can be found when the non-dimensional superficial gas velocity 〈 j g + 〉 is closed to 0.5. A linearly increasing trend and an exponentially decreasing trend of C0 were found in the lower and higher gas sides divided by this boundary, respectively. Through the present model, one dimensional area-averaged gas velocity and void fraction can be determined for rod bundles in pool conditions. The prediction results were compared with several existing models and experimental data. The present model shows a good agreement with the existing experimental data and can be applied to both boiling and adiabatic air–water two-phase flows. In order to explain the peak values of C0 in low superficial gas velocity conditions, several possible superficial velocity and void fraction profiles were examined by considering the recirculation flow/void distributions.

In order to establish a reliable rod bundle database under pool conditions and to benchmark the existing models, a well-scaled 8 × 8 rod bundle test loop was designed based on the scaling criteria and a series of experiments was carried out with adiabatic air–water two-phase flow. Experiments for pool conditions covered the area-averaged void fraction 〈α〉 range of 0.12–0.93. Existing models and experimental data including boiling and air–water two-phase flow were compared and analyzed. Experimental results show that differences exist between large and small casing rod bundles as the flow structure changes with the casing scale. In addition, traditional drift-flux models for pipes may reflect the casing scale effect, but cannot be directly applied to the rod bundle geometry in pool conditions. Among the existing models for rod bundles, the Murase et al., 1986 , Kamei et al., 2008 , Ishizuka et al., 1995 give relatively better predictions in most regions. All benchmark results of existing models are tabulated in terms of void fraction prediction error for the present database.

In order to improve the countercurrent flow model of a transient analysis code, countercurrent air–water tests were previously conducted using a 1/15 scale model of the PWR hot leg and numerical simulations of the tests were carried out using the two-fluid model implemented in the CFD software FLUENT 6.3.26. The predicted flow patterns and CCFL characteristics agreed well with the experimental data. However, the validation of the interfacial drag correlation used in the two-fluid model was still insufficient, especially regarding the applicability to actual PWR conditions. In this study, we measured water levels and wave heights in the 1/15 scale setup to understand the characteristics of the interfacial drag, and we considered a relationship between the wave height and the interfacial drag coefficient. Numerical simulations to examine the effects of cell size and interfacial drag correlations on numerical predictions were conducted under PWR plant conditions. Wave heights strongly related with the water level and interfacial drag coefficient, which indicates that the interfacial drag force mainly consists of form drag. The cell size affected the gas velocity at the onset of flooding in the process of increasing gas flow rate. The gas volumetric fluxes at CCFL predicted using fine cells were higher than those using normal cells. On the other hand, the cell size did not have a significant influence on the process of decreasing gas flow rate. The predictions for the PWR condition using a reference set of interfacial drag correlations agreed well with the Upper Plenum Test Facility data of the PWR scale experiment in the region of medium gas volumetric fluxes. The reference interfacial drag correlations employed in this study can be applied to the PWR conditions.

A 68-year-old woman was admitted to our hospital because of sudden onset of involuntary movements, similar to those associated with chorea, of the right side of the body and for further evaluation of thrombocythemia. She had no family history of chorea. Neurological findings did not show any abnormality except for chorea of the right side. Laboratory studies showed increased number of white blood cells (14,000/microl) and platelets (188.3 x 10(4)/ microl). Lupus anticoagulant, anti-cardiolipin antibody, and ceruloplasmin levels were within the normal range. Her NAP score was 240, and result for bcr-abl gene expression was negative. Bone marrow puncture showed hypercellularity and increased number of megakaryocytes (550/microl), but there was no atypism. On the basis of these laboratory findings, she was diagnosed with essential thrombocythemia T1-weighted magnetic resonance imaging (MRI) showed a hyperintense lesion extending from the region around the left globus pallidum to putamen. The MRI findings of our study were similar to those related to diabetic hemichorea; however, the results of some tests did not indicate diabetes mellitus. An MRI scan showing high T1 signal intensity in the basal ganglia might not be specific for diabetic hemichorea. In this case, MRI revealed the cause of hemichorea to be micocirculatory failure or small cerebral hemorrhages.

In reflux cooling, the steam generated in the reactor core and the water condensed in a steam generator form a countercurrent flow in a hot leg. In order to investigate flow patterns in the hot leg under countercurrent flow conditions, countercurrent air-water tests were previously conducted using a 1/15th scale model of a PWR hot leg. Numerical simulation results for the tests using a three-dimensional twofluid model in FLUENT6.3.26, implemented with an appropriate set of correlations for the gas-liquid interfacial friction, were in good agreement with the measured data. In the present study, further numerical simulations were carried out for a full-scale hot leg under PWR plant conditions to investigate the effects of pipe diameter and fluid properties. The predicted countercurrent flow limitation characteristics were well correlated with the Wallis parameters and agreed well with the measured data from the 1/15th scale air-water tests as well as the full-scale steam-water UPTF tests. The results indica...

To examine the effects of fluid properties on countercurrent flow limitation (CCFL) in a hot leg of a pressurized water reactor (PWR), experiments are conducted using glycerol-water solutions and a 1/5 scale hot leg model with a rectangular channel. Numerical simulations are also carried out using a VOF (volume of fluid) method implemented in the CFD software, FLUENT 6.3.26. The increase in the liquid viscosity does not change the intercept coefficient C in the Wallis-type CCFL correlation but increases the proportional coefficient m, which indicates that the liquid viscosity does not affect the interfacial drag but influences the wall friction. CCFL predicted for steam-water flow at 5 MPa, corresponding to a high gas density and low liquid viscosity condition, is greatly mitigated, which indicates that the gas density has a significant effect on the interfacial drag.

Electronic structure of carbon nanowalls (CNW) was measured by ultraviolet photoelectron spectroscopy (UPS) in comparison with highly oriented pyrolitic graphite (HOPG). While the interlayer band of CNWs was observed at same energy of that in HOPG, the σ and π bands were observed as are in carbon nanotubes. Electronic effects by deuterium adsorption were investigated by combination of UPS and temperature programmed desorption (TPD) measurements. Deuterium adsorption preferably occurred in the boundary regions between crystallites in CNWs and enhanced the density of states associated with them.

One-dimensional (1D) sensitivity computations were carried out for air–water countercurrent flows in a 1/15-scale model of the hot leg and a 1/10-scale model of the pressurizer surge line in a pressurized water reactor (PWR) to generalize the prediction method for countercurrent flow limitation (CCFL) characteristics in slightly inclined pipes with elbows. In the 1D model, the wall friction coefficient fwG of single-phase gas flows was used. The interfacial drag coefficient of fi=0.03, an appropriate adjustment factor of NwL=6 for the wall friction coefficient fwL of single-phase liquid flows (NwG=1 for fwG of single-phase gas flows), and an appropriate adjustment factor of Nde=6 for the pressure loss coefficient ζe of elbows in single-phase flows were determined to give good agreement between the computed and measured CCFL characteristics. The adjusted factors were used to compute and then discuss effects of the inclination angle and diameter on CCFL characteristics.

Alternate conjugated copolymers consisting of phenylene or biphenylylene unit and linear carbons unit such as cumulene and polyyne were synthesized. The optical property of these polymers was investigated by UV–Vis and fluorescence spectroscopies. Among cumulene-type polymers, the polymer having allene moiety showed a unique hypsochromic shift and intense blue fluorescence in solution, while poly(phenylenebutadiynylene)s, typical of polyyne-type linear conjugated polymers, showed fluorescence in the region from blue-green to green in high efficiency besides thermotropic liquid crystalline property. Substituent effects of the polymers on optical property as well as the band structure were evaluated on the basis of Hammet parameters, which was utilized for designing of the polymers. The poly(arylenebutadiynylenes)s were applied in polymer LED. The devices consisting of ITO/PEDOT-PSS/emitting polymer/Ca/Al realized EL emissions in the region covering RGB colors.

We devised a new method of determining the temperatures of materials with their electron-energy distributions. The Fermi–Dirac distribution convoluted with a linear combination of Gaussian and Lorentzian distributions was fitted to the photoelectron spectrum measured for the Au(110) single-crystal surface at liquid N2-cooled temperature. The fitting successfully determined the surface-local thermodynamic temperature and the energy resolution simultaneously from the photoelectron spectrum, without any preliminary results of other measurements. The determined thermodynamic temperature was 99 ± 2.1 K, which was in good agreement with the reference temperature of 98.5 ± 0.5 K measured using a silicon diode sensor attached to the sample holder.

The application of the Best Estimate Plus Uncertainty (BEPU) method is made to analysis of the “Intentional depressurization of steam generator secondary side” which is an accident management procedure in a small-break loss-of-coolant accident (SBLOCA) with high pressure injection (HPI) system failure. RELAP5/MOD3.2 is used as the analysis code. By applying the BEPU method, the uncertainties of the analysis results can be estimated quantitatively. However, the accuracy of the analysis results depends primarily on the base case result predicted by the best estimate code. In this study, in order to investigate the appropriate base case model, simulation analyses using the RELAP5/MOD3.2 were carried out for the ROSA Large Scale Test Facility (ROSA/LSTF) secondary-side depressurization tests. It was found that the code predicted well the major event progressions such as pressure responses, core liquid level responses, and rod surface temperatures, as well as important phenomena such as formation and clearing of loop seals, accumulation of water from condensation, and countercurrent flow limitation (CCFL) at the inlet of the U-tubes, which are characteristic features of this accident scenario.Copyright © 2014 by ASME

Poly(m-phenylenebutadiynylene)s having a side chain with p-(4-pentylcyclohexyl)phenyl and cyanobiphenylyl mesogenic core were synthesized from corresponding m-diethynylbenzene by oxidative polycond...

A conjugated polymer with a butatriene segment in the main chain, poly(biphenyl-4,4'-diyl-1,4 bis(4-dodecyloxyphenyl)buta-1,2,3-triene-1,4-diyl), was synthesized from 1,4-bis(4-bromophenyl)-1,4-bis(4-dodecyloxyphenyl)buta-1,2,3-triene by dehalogenative poly-condensation using Ni(cod) 2 . The polymer was well soluble in usual organic solvents such as CHCl 3 and THF. Structural analyses and characterizations were carried out by IR, NMR, UV-Vis, PL, and Raman spectroscopy, as well as electrical conductivity. It is suggested that π-conjugation is extended to some degree through biphenylyl ene and butatrienylene linkages.

The Raman and UV–Vis spectra of poly(2,5-dialkoxy-1,4-phenylene- alt -oligoethynylene)s bearing ethynylene, 1,3-butadiynylene, or 1,3,5,7-octatetraynylene segment and corresponding oligoethynylene models, diphenylacetylene, diphenylbutadiyne, and diphenyloctatetrayne, have been studied. The Raman frequencies ( ν ) around 2100–2200 cm −1 due to symmetric CC stretching mode in the oligoethynylene segments of the models as well as the polymers shifted to lower wavenumbers with increasing number of ethynylene units. The ν values were correlated with an inverse of the carbon numbers ( N ) in the oligoethynylene segment. The absorption maxima ( λ max ) of the polymers in the longest UV–Vis absorption were all shifted to longer wavelengths than the corresponding models. The UV–Vis absorption bands of the polymers were also correlated with a relationship, λ 2 vs. number of carbon–carbon triple bonds in the oligoethynylene segment as has been well established for various polyenes and oligoynes.

We investigated whether matrix metalloproteinase-2 (MMP-2) is induced in peripheral blood T cells after their contact with tumor necrosis factor-alpha (TNF-alpha)-stimulated glioblastoma cell line (T98G), expressing vascular cell adhesion molecule-1 (VCAM-1), in patients with HTLV-I-associated myelopathy (HAM) compared to control patients with other neurological disorders (OND). Gelatin zymography revealed that the incremental ratio of gelatinolytic activity of MMP-2 in culture supernatants derived from T cells cocultured with TNF-alpha-stimulated T98G to that of supernatants derived from cultures of T cells alone was significantly higher in HAM patients than in control patients with OND. Immunoblot analysis of immunoprecipitates of culture supernatant showed that increased gelatinolytic activity of MMP-2 was due to increased production of MMP-2 protein in T cells. Increased gelatinolytic activity of MMP-2 in T cells of HAM patients was blocked by pretreatment of TNF-alpha-stimulated T98G with anti-VCAM-1 antibody before coculture with T cells, indicating that MMP-2 induction was VCAM-1-mediated. Although no significant differences were noted in the percentage of VLA-4-positive cells in cultured T cells between HAM patients and control patients with OND, our results indicate that VCAM-1-mediated MMP-2 induction is up-regulated in T cells of HAM patients.

Syntheses of novel π-conjugated polymers with a cumulene unit such as allene and butatriene in the main chain were attempted in order to investigate properties of cumulene moiety in the conjugated polymer chain. Electroreductive polycondensation of tetraiodoallene afforded an ill-characterized transparent dark filmy product. Polymerization of 1,4-bis(4-bromophenyl)-1,4-diphenylbutatriene by dehydrohalogenative polymerization with Ni(cod) 2 gave a soluble red polymer having a semiconducting property was obtained without decomposition of the cumulenic bond, which was characterized by IR, Raman, and UV-Vis spectroscopy. Oxidative polycondensation of 1,4-bis(4-ethynylphenyl)-1,4-diphenylbutatriene with a Cu-TMEDA catalyst gave a conjugated polymer with butatriene and butadiyne segments.