Multi-scale Microstructural Characterization and Precipitation Mechanism of Hydrides in Zr-2.5Nb Alloy Pressure Tube

Anisotropic behavior of delayed hydride cracking in Zr-2.5Nb pressure tube

The performance of Zr-2.5Nb alloy pressure tubes in nuclear reactors is critically dependent on the behavior of precipitated hydrides. In this study, a hydrogen-charged Zr-2.5Nb alloy pressure tube was subjected to in situ tensile testing combined with electron backscatter diffraction to elucidate microcrack evolution and microstructural adaptation. Initially, longitudinal hydride–hydride interface cracks nucleated at non-coherent interfaces of two types of hydrides due to the inherent brittleness. Subsequently, stress redistribution by a small proportion of hydride–hydride interface cracks resulted in the emergence of microcracks at the transverse hydride–matrix interfaces, accompanied by partial hydride phase transformation. Finally, under high strain conditions, increased dislocation movement in the matrix triggered a single slip system, leading to the formation of numerous low-angle grain boundaries. As strain further increased, multiple slip systems were activated, and longitudinal matrix–matrix interface cracks began to nucleate at certain grain boundary locations.

Abstract Zr-2.5 wt.% Nb pressure tube removed from KAPS-2 PHWR after 15.3 effective full power year of operation was subjected to detailed microstructural examination under a transmission electron microscope. Emphasis was given to examine and analyze the defects evolved in the microstructure due to neutron irradiation. For the purpose of comparison, samples from the unirradiated offcut of the same pressure tube were also examined. The unirradiated microstructure comprised laths of α-Zr phase, with β-Zr(Nb) phase distributed both in the form of continuous film as well as globular precipitates at the lath boundaries. The Nb-content of interlath β-precipitates was found to be higher in comparison of β-film. This microstructure, upon irradiation, did not exhibit any gross change in respect of matrix phase morphology, although spheroidization of β-Zr(Nb) film, thereby leading to film discontinuity and enhanced precipitation at lath boundaries, was noticed. The irradiated matrix phase showed presence of < a >—and < c > -type dislocation loops.

Effect of microstructure on the delayed hydride cracking behavior of Zr-2.5Nb alloy pressure tube

Abstract Recent years the development of pumped storage plant (PSP) has increased rapidly worldwide due to the quick penetration of the intermittent renewable energy sources (RES). Hydraulic transient analysis in the PSP, to obtain the control parameters such as extreme water hammer pressure, is vital to the safe design of water conveyance system. And the schemes comparison of water conveyance system is usually conducted and determined based on the results of hydraulic transient analysis during the design term. Empirically, it is considered that the longer diversion pipelines and shorter tailrace pipelines can induce larger spiral case pressure (SCP) and draft tube pressure (DTP) in the PSP. However, it is not completely true for the PSP when considering the successive load rejection (SLR). Based on the transient flow theory, the dynamic transient numerical model for load rejection of the PSP is developed by introducing the method of characteristics (MOC). Then the fluid transients of different length of main diversion and tailrace pipelines under load rejection are simulated to investigate the hydraulic behaviors. The results show that the maximum SCP is increased with the increasing length of main diversion pipes, which is consistent with the conventional knowledge. For the minimum DTP, however, it decreases firstly, then increases slightly, and finally decreases under successive load rejection. This phenomenon is ascribed to both the positive and negative effect of main tailrace pipes on the DTP. The length increase of tailrace main pipes, on the one hand, lengthens the total length of the tailrace pipe, resulting in the decrease of DTP. On the other hand, the tailrace main pipe has a certain regulation and storage effect on the tailrace branch pipe, which in turn leads to an increase in DTP. The achievements of the study can serve as a reference for the design of water conveyance system for PSP projects.

Measurement uncertainty prediction of pressure tube sag measurement tool using two stage Monte Carlo simulation

High concentrations of hydrogen isotopes have been observed at the ends of CANDU Zr-2.5Nb pressure tubes in the region associated with the rolled joints with 403 stainless steel end fittings. These concentrations are above current regulatory limits, causing concerns over how long pressure tubes should remain in service. This paper reviews two differing interpretations of the mechanisms for these high concentrations, leading to two conclusions. Ingress after about 30 y is attributed to pressure tube sag creating a crevice between the end fitting and the top of the tube that provides a window for hydrogen isotopes to enter from the annulus gas under reducing conditions. Small additions of oxygen should close this window. A new mechanism is suggested to explain deuteride precipitates past the rolled joint contact region after about 30 y. Surprisingly, the mechanism relies on deuterium and protium diffusing in solution at the same rate, i.e., no mass-dependent isotope effect.

This study explores the possibility of the direct reuse of spent fuel from the NuScale small modular reactor (SMR) 160-MW(thermal) in CANDU6 reactors via the DUPIC (Direct Use of spent PWR fuel in CANDU reactors) cycle, employing the Oxidation and Reduction of Oxide (OREOX) process to mitigate nuclear proliferation risks and improve spent fuel management. The analysis begins with the isotopic inventory of SMR spent fuel after a fuel burnup of 60 GWd/tonne heavy metals (HM) followed by 5 years of cooling. Neutronics and thermal-hydraulic simulations were performed on two OREOX fuel configurations, both utilizing D2O as the moderator, with the difference in the coolant materials being D2O in the first configuration and H2O in the second. The neutronics analysis was carried out using a full-core model. Based on the resulting power and flux profiles, the thermal-hydraulic analysis was then focused on the hottest pressure tube. The neutronics results showed that OREOX fuel increases the inventory of 238Pu, hindering the reprocessing of spent fuel for weapons-grade plutonium. Additionally, the OREOX process significantly depletes transuranic elements such as 239Pu, 241Pu, 241Am, and 243Am, further reducing proliferation risks. The configuration with D2O as both coolant and moderator demonstrated the longest fuel cycle (300 effective full-power days (EFPDs)) with a burnup of 7.26 GWd/tonne HM, along with an improved power distribution in comparison to both standard UO2 fuel and the second OREOX configuration. The thermal-hydraulic results further confirmed the safe operation of the hottest pressure tube in this configuration, showing higher safety margins than the alternative, while considering the substantial decrease in the thermophysical properties of the OREOX fuel resulting from burnup in SMRs.

Fluid therapy is essential for maintaining circulatory homeostasis and ensuring adequate oxygen delivery to tissues during surgery and certain traumatic conditions. According to Poiseuille’s Law, flow rate is influenced by pressure gradient, tubing radius, tubing length, and fluid viscosity; however, clinical situations often necessitate the use of smaller gauge catheters (for example, 20-gauge) due to poor vein quality or limited access, which significantly reduces flow. The main goal of this study was to develop a means of improving rates of fluid resuscitation in such situations. Conventional strategies, such as high-pressure infusion devices, can increase flow but also carry risks including venous rupture and air embolism. In this laboratory-based study, we investigated whether connecting multiple IV systems to a single catheter could improve flow rates in scenarios where catheter gauge size is limited. We hypothesized that adding IV systems would improve flow rates in accordance with Poiseuille’s law. Using 16-gauge, 18-gauge, and 20-gauge catheters (internal diameter 16G (gauge) ≈1.7 mm; 18G, ≈1.3 mm; 20G, ≈1.0 mm) at three different heights (110 cm, 140 cm, 170 cm), we compared flow achieved with one, two, or three IV systems to that produced by a pressure bag set at 250 mm of mercury (millimeters of mercury (mmHg)). Our findings demonstrated that multiple IV systems significantly increased flow rates; for example, with a 20-gauge catheter at 110 cm, the flow rate increased from 38.87 mL per minute (mL/min) with a single pressured system to 45.25 mL/min using three gravity-fed systems—an improvement of approximately 16.4%. Similar enhancements were observed across other catheter sizes and heights. These results suggest that using multiple IV systems can provide a practical, lower-risk alternative to pressurized infusion for situations requiring rapid resuscitation, especially in patients with difficult access or fragile veins. Further clinical trials are warranted to validate these findings and assess their applicability in real-world settings.

304L stainless steel is used in nuclear applications, such as pressurized water reactors, instrumentation tubing, and storage tanks, due to its corrosion resistance, durability, and strength. The objective of this paper is to study the thermal-elastoplastic analysis using finite element modelling of a 304 L steel plate welded using A-TIG welding processes. For heat source analysis, a bead-on-plate experiment was conducted for both TIG and A-TIG welding. Two different heat source models were used: a double ellipsoidal model and a combined conical and double ellipsoidal model. The bead-on-plate result showed a narrow heat distribution with a deep depth of penetration in A-TIG welding due to localized high heat intensity. Based on a bead-on-plate trial square butt joint plate was at the same heat input. Finite element analysis of the A-TIG square butt joint plate was carried out using the above combined model. Predicted thermal cycles, residual stress and distortion measured in the A-TIG square butt joint plate were validated with experimentally measured values. K-type thermocouples were used to measure transient welding temperatures in multiple locations of the welded zone. Residual stresses were measured using the ultrasonic testing method. The predicted peak tensile residual stress at the weld line is 291 MPa, which is closer to the experimental value of 274 MPa. The distortion analysis was carried out considering two different theories: large and small displacement. Further, both predicted distortions were validated with experimental values. The comparison of distortion showed that the predicted distortion using the large distortion theory is more accurate, with a 17% error, than the small distortion theory, which has a 72% error.

Introduction: Prone positioning is essential for various surgical procedures, including spinal surgeries, posterior cranial fossa procedures and urological interventions, as it provides optimal access to posterior anatomical structures. However, this positioning significantly alters respiratory mechanics and cardiovascular physiology, potentially affecting patient safety during general anaesthesia. Peak Airway Pressure (PAP) and Endotracheal Tube (ETT) cuff pressure are critical parameters that require careful monitoring during prone positioning to prevent complications such as barotrauma and tracheal injury. Aim: To evaluate simultaneous changes in PAP and ETT cuff pressure during prone positioning under general anaesthesia and to assess associated haemodynamic alterations. Materials and Methods: This prospective observational study was conducted at Department of Anaesthesiology and Critical Care, Adesh Institute of Medical Sciences and Research, Adesh University, Bathinda, Punjab, India. The study enrolled 105 consecutive American Society of Anaesthesiologists (ASA) I-II patients scheduled for elective procedures requiring prone positioning. Standardised protocols were used to document PAP, ETT cuff pressure and haemodynamic variables at multiple time points: baseline in the supine position, immediately after prone positioning and at 15-minute intervals throughout the procedure. Statistical analysis employed paired comparisons, with a significance threshold of p-value <0.05. Results: A total of 105 patients completed the study (mean age 45.36±10.26 years; 62.9% female; mean Body Mass Index (BMI) 21.41±2.56 kg/m²). Transitioning from supine to prone position produced significant respiratory mechanical alterations. Baseline supine PAP (19.03±3.35 cm H2 O) progressively increased to a maximum of 34.36±2.59 cm H2 O during prone maintenance (p-value <0.001), representing an 80.6% elevation. Similarly, ETT cuff pressure increased from baseline (24.64±2.99 cm H2 O) to 43.65±4.49 cm H2 O at maximum prone measurement (p-value <0.001). Cardiovascular parameters demonstrated significant alterations during the initial 15 minutes post-positioning before stabilising during the maintenance phase. Conclusion: In patients under general anaesthesia, the prone position significantly increases PAP and ETT cuff pressure. This finding underscores the importance of regular monitoring and timely interventions to limit the risks associated with elevated pressures.

An innovative approach to organizing the monitoring of gas wells is considered, which involves the creation of an automated system with an emergency shutdown function for damaged loops. The main objective of the study is to improve the safety and reliability of gas production and underground gas storage facilities by promptly detecting malfunctions in well equipment and responding to potential emergencies in a timely manner. One option for implementing this method is to use a pneumometric approach. Pressure tubes act as sensitive elements, registering the dynamic pressure that arises as a result of gas flow around the tube. The measuring system determines the flow rate based on the difference between the total and static pressure, which allows the gas flow rate to be obtained. The results of modelling the dynamics of wells under various accident scenarios (when the trail breaks) have been analyzed, confirming the effectiveness of the proposed method. The system allows not only to respond quickly to the occurrence of defects, but also to prevent the development of emergency situations, which has a positive effect on the level of industrial safety and the environmental situation in the production area. The application of this approach may be relevant both for new buildings and for the modernization of existing facilities. The proposed monitoring method, thanks to a computer node that collects, processes and analyses data received from peripheral sensors in real time with the ability to automatically disconnect damaged loops , is an effective means of increasing the technological reliability of gas storage and gas production systems, significantly reducing the risks associated with gas leaks and emergencies. The system is designed with a modular structure, which makes it easy to adapt to different numbers of wells, change the topology or integrate with existing technological equipment without the need for complete reconstruction. The system is based on a combination of modern parameter control devices (pressure, temperature, gas flow) and signal logic processing modules that generate commands to shut down individual infrastructure elements in the event of abnormal situations.

Is hydrogen preferentially picked- up in IPHWR's pressure tubes over deuterium?

Abstract Background: We suggest that nasal obstruction has a definite relationship with middle ear pressure (MEP) and Eustachian tube (ET) function. Does the surgery for nasal septal deviation have a favorable effect on the MEP and ET function? Objective: Assessment of MEP before and after septoplasty. Materials and Methods: This single-group clinical trial was conducted in the Department of Otolaryngology—Head and Neck Surgery during the period from January 2019 to December 2019 at Al-Sadr Medical City in Najaf. A total of 42 patients (30 males and 12 females), whose ages ranged from 17 to 48 years, were included in this study. All of them complained of nasal obstruction with or without aural fullness. Tympanometry was done for all patients preoperatively to assess MEP. Postoperatively, patients were followed up with an evaluation of MEP and aural fullness sensation at 10-day, 1-month, and 3-month intervals. Results: This prospective single-group clinical trial includes 42 patients complaining of nasal obstruction due to nasal septal deviation. There was a statistically significant improvement in MEP and aural fullness sensation—after a 3-month period of septoplasty ( P < 0.05). Conclusion: Nasal septal deviation has an impact on middle ear ventilation, which is more significant on the side of deviation, and septoplasty can improve middle ear ventilation after 3 months (12 weeks) of surgery.

Validation of a positive pressure tube ventilation system for heat abatement of outdoor preweaning dairy heifers.

Some observations on the habit plane of hydride plates precipitated in Zr-2.5Nb pressure tubes

Novel use of three-point bend test for determining the threshold stress for hydride reorientation in Zr-2.5%Nb pressure tube material

Complex non-Newtonian glues are widely used in electrical vehicle (EV) manufacturing plants. In this paper, we focus on initial transient and compressibility issues which are closely associated with high pressure, boundary conditions, and flexible tubes, as well as their respective fluid–structure interaction effects. Both thixotropic and power law non-Newtonian nearly compressible fluid models have been employed to couple with flexible tubes with two different sets of material properties, namely, Young’s modulus and density. In addition to thick-wall cylindrical pressure vessel solutions, different pressure and velocity boundary conditions have also been studied with the consideration of initial transient and steady solutions for acoustic models. Moreover, the radial direction displacement distributions through the tube wall thickness and axial directions compare well within 4 to 9 percentage points with theoretical solutions of thick-wall cylinders under internal and external pressures. Finally, inverse optimization methods have been employed for the calibration of key parameters in comparison with experimental and computational results.

In aerodynamic modeling, wind-tunnel and flight tests are usually assumed to be the ground truth for validating and calibrating physical or data-driven models. However, the measurements, such as pressure data, can contain several outliers, which can deteriorate the calibrated models. So far, outliers have been identified by visually inspecting the data, which can be time-consuming. Hence, it is desirable to automatically detect outliers during testing to exclude them from live monitoring, identify leakages in the pressure tubing, and obtain reliable data sets for calibration involving minimal manual interaction. This work introduces two methods for this task, with semisupervised anomaly detection approaches using simulation data for learning the normal behavior. The first method is based on a proper orthogonal decomposition of the training data, whereas the second relies on a variational autoencoder. These methods are applied to wind-tunnel tests of a two-dimensional airfoil and the NASA common research model. Both methods successfully detect outliers, whereas the proper-orthogonal-decomposition- based method better classifies them. However, the methods misclassify measurement points where Reynolds-averaged Navier–Stokes features systematic errors, thus illustrating the necessity of accurate simulations for outlier detection.