In-vessel fluid flow measurements using thermocouples cross-correlation.

Fluid flow rate in high temperature and pressure vessels can be difficult to measure due to the associated harsh environment, inaccessible locations and pressure boundary integrity concerns. However, by using quick response miniature thermocouples to measure the naturally occurring temperature variations within the flow, the fluid velocity can be inferred from the transit time analysis. This flow measurement technique has other advantages such as the flow profile is not significantly disturbed, no additional flow restrictions introduced and the system fiction factor is not increased. Furthermore, since the measured flow rate is generally unaffected by the global system dynamics, such as heat increases or losses, as well as changes in the flow regimes, the location of the thermocouple pairs is extremely flexible. Due to the mentioned advantages, the thermocouple cross-correlation flow measurement method has been developed for use at the Purdue University Multi-Dimensional Integral Test Assembly (PUMA). Currently, thermocouple cross-correlation technique is used to measure the Reactor Pressure Vessel downcomer fluid velocity and the suppression pool in-vessel natural circulation velocity

A theoretical and numerical investigation of turbulent steam jets in BWR steam blowdown.

The preliminary results of PHOENICS and RELAP5 show that the current numerical models are adequate in predicting steam flow and stratification patterns in the upper Drywell of a BWR containment subsequent to a blow-down event. However, additional modeling is required in order to study detailed local phenomena such as condensation with non-condensables, natural convection, and stratification effects. Analytically, the intermittence modified similarity solutions show great promise. Once {gamma} is accounted for, the jet's turbulent shear stress can be determined with excellent accuracy

BWR drywell behavior under steam blowdown.

Historically, thermal hydraulics analyses on Large Break Loss of Coolant Accidents (LOCA) have been focused on the transients within the reactor or steam generator. Few have studied the effects of steam blowdown on the containment building. This paper discusses some theoretical issues as well as presenting numerical and experimental results of the blowdown tests performed at the Purdue University Multi-Dimensional Integrated Test Assembly (PUMA)

Turbulent steam jets in enclosed structures: An application to nuclear reactor accident analysis

The primary objective of this thesis is to characterize the behavior of steam jets within an enclosed structures. To satisfy the above objective, the following areas were studied and addressed: (1) study the analytical models of round turbulent jets, (2) to model the turbulent jets using commercially available CFD codes, (3) measure steam convection and stratification pattern within the PUMA Drywell and compare against numerical models. The analytical approach is limited because the solutions for complex geometry and boundary conditions are not readily available. However, the analytical studies provided the necessary understanding of the physical processes involved in turbulent steam jet discharge and convection. From this analytical study, a new mechanistic model of turbulence eddy viscosity model is introduced to replace the ad hoc model recently proposed. Numerical modeling of the current problem allows greater flexibility. Even though the present state of numerical modeling of turbulent flows is still far from complete, the slightly modified k-&egr; models of turbulent round jets match that of experimental data extremely well. Based on the basic models of axisymmetric turbulent round jets, PUMA DW geometry and boundary conditions specific were developed. The results of these numerical models compared favorably against the PUMA MSLB tests. The 3-D simulations show that the PUMA DW environment was highly stratified and that the temperature and velocity distributions were extremely complicated. Experimentally, it was found that even though the discharged steam was stably stratified in the upper drywell, the PCCS operation was largely unaffected. Additionally, it was determined that DW wall condensation is not a significant factor in containment cooling. Additionally, it was found that homogeneous condensation within the upper drywell was not possible because steam entering the upper drywell was superheated

Three dimensional analysis of turbulent steam jets in enclosed structures : a CFD approach.

This paper compares the three-dimensional numerical simulation with the experimental data of a steam blowdown event in a light water reactor containment building. The temperature and pressure data of a steam blowdown event was measured at the Purdue University Multi-Dimensional Integrated Test Assembly (PUMA), a scaled model of the General Electric simplified Boiling Water Reactor. A three step approach was used to analyze the steam jet behavior. First, a 1-Dimensional, system level RELAP5/Mod3.2 model of the steam blowdown event was created and the results used to set the initial conditions for the PUMA blowdown experiments. Second, 2-Dimensional CFD models of the discharged steam jets were computed using PHOENICS, a commercially available CFD package. Finally, 3-Dimensional model of the PUMA drywell was created with the boundary conditions based on experimental measurements. The results of the 1-D and 2-D models were reported in the previous meeting. This paper discusses in detail the formulation and the results of the 3-Dimensional PHOENICS model of the PUMA drywell. It is found that the 3-D CFD solutions compared extremely well with the measured data

In vivo characterization of B-2 receptors mediating hypotension in anesthetized rabbits and guinea pigs

With the discovery of suitable pharmacologic tools for B 2 receptor characterization, it has been demonstrated in vitro that the pharmacological spectrum of this receptor type obtained in various organs (e.g. intestine, vessels, urogenital tract) remains the same within the species but may show marked differences among species (e.g. the rabbit, the guinea pig) (Regoli et al., 1993; Regoli et al., 1994). Thus, orders of potency of agonists in rabbit and guinea pig tissues are opposite in that [Hyp3]BK is approximately 50- 100 times more potent than [AibT]BK in the rabbit and inversely, the latter compound is 2-10 times more active than [Hyp3]BK in the guinea pig. Furthermore, competitive antagonists, such as DArg[Hyp3,d-PheV,LeuS]BK and WIN 64338 (a nonpeptide compound), have also shown differences in their ability to block bradykinin responses in these two species while HOE 140, a non-competitive and long-acting antagonist, shows equipotent activities on both. Based on these results, we have suggested that B 2 receptors may be pharmacologically subject to interspecies variability. The present study was designed to find out if results obtained in vitro can be reproduced in vivo by measuring pharmacological parameters (namely EDs0 for agonists and ICso for antagonists) on kinin-induced blood pressure changes in the rabbit and the guinea pig

Kinin receptors in the diabetic mouse

It has been proposed that kinins are important inflammatory mediators involved in the pathogenesis of several diseases. In the present study, we attempted to determine the effects of kinins in a type I diabetic mouse model, using in vitro assays. Injection of streptozotocin (STZ) to the C57BL/Ks mdb mice causes an insulitis (inflammation of Langerhans islets) that leads to the diabetic condition. Ten days following the STZ treatment, the mice showed increased glycemia. We examined the effect of kinins and other agents (substance P, neurokinin A, acetylcholine) on the stomach fundus and urinary bladder of control and diabetic mice. Our results show that the sensitivity of the stomach fundus to bradykinin (BK) and desArg9BK (DBK), but not to other contractile agents, was substantially increased in the tissues of diabetic mice. The maximal contractions induced by BK and DBK were increased 1.5- to 2-fold in the stomachs from diabetic mice compared with those from normal mice. BK induced similar maximal contractions of urinary bladder strips from normal or STZ-treated mice, while DBK did not show any effect on this preparation. Interestingly, the apparent affinities of all agonists are similar in the two groups, normal and diabetic. These results suggest that B, and B, receptors are overexpressed in the stomach fundus but not in the urinary bladder of diabetic mice

Using surface envelopes to constrain molecular modeling

Molecular density information (as measured by electron microscopic reconstructions or crystallographic density maps) can be a powerful source of information for molecular modeling. Molecular density constrains models by specifying where atoms should and should not be. Low-resolution density information can often be obtained relatively quickly, and there is a need for methods that use it effectively. We have previously described a method for scoring molecular models with surface envelopes to discriminate between plausible and implausible fits. We showed that we could successfully filter out models with the wrong shape based on this discrimination power. Ideally, however, surface information should be used during the modeling process to constrain the conformations that are sampled. In this paper, we describe an extension of our method for using shape information during computational modeling. We use the envelope scoring metric as part of an objective function in a global optimization that also optimizes distances and angles while avoiding collisions. We systematically tested surface representations of proteins (using all nonhydrogen heavy atoms) with different abundance of distance information and showed that the root mean square deviation (RMSD) of models built with envelope information is consistently improved, particularly in data sets with relatively small sets of short-range distances