Through‐wall welding residual stress profiles for dissimilar metal nozzle butt welds in pressurized water reactors

This paper provides approximate expressions for through‐wall welding residual stresses in dissimilar metal nozzle butt welds of pressurized water reactors. An idealized shape of nozzle is proposed, based on which systematic elastic–plastic thermo‐mechanical finite element analyses are conducted by varying the thickness and radius of the nozzle and the length of the safe‐end. Based on the results, a through‐wall welding residual stress profile for dissimilar metal nozzle butt welds is proposed by modifying the existing welding residual stress profile for austenitic pipe butt welds in the R6 procedure.     

Decomposition of acetamide and formamide in pressurized hot water

Acetamide and formamide were individually decomposed in a pressurized hot water in a tubular flow reactor at temperatures from 573 to 693 K, and pressure of 23 MPa, residence times up to 500 s, and the initial concentrations of both amides from 0.005 to 0.5 mol/L. The major products were ammonia and acetic acid from decomposition of acetamide, and ammonia and formic acid from that of formamide. Formic acid was further decomposed readily into carbon dioxide. Although the decomposition reactions for both amides were represented acceptably by the first order reaction kinetics, the rate constants increased with increasing the initial sample concentrations due to the autocatalytic effect. Apparently the second order reaction kinetics with respect to the concentration of each amide remained more represented the global decomposition rates, and the rate constants decreased with increasing the initial concentrations. The effects of hydrogen peroxide added on the global decomposition rates and the product yields were not evident: the addition slightly lowered the rates, but the major products were almost the same as those in the absence of hydrogen peroxide at temperatures lower than 653 K. Above 653 K more CO₂ was produced.     

Failure mechanics of uPVC cyclically pressurized water pipelines

An extensive investigation has been directed towards explaining fatigue failure of pressurized water pipelines under service conditions, in terms of laboratory studies of the base material (unplasticized polyvinyl chloride, uPVC). It is established that many such failures are located in the regime to which linear elastic fracture mechanics can be applied, with encouraging predictive accuracy. Only failures at very low stress levels are not reliably explained by these methods, which nevertheless provide direction for further study.     

Optical modeling of nickel-base alloys oxidized in pressurized water reactor

The knowledge of the aging process involved in the primary water of pressurized water reactor entails investigating a mixed growth mechanism in the corrosion of nickel-base alloys. A mixed growth induces an anionic inner oxide and a cationic diffusion parallel to a dissolution-precipitation process forms the outer zone. The in situ monitoring of the oxidation kinetics requires the modeling of the oxide layer stratification with the full knowledge of the optical constants related to each component. Here, we report the dielectric constants of the alloys 600 and 690 measured by spectroscopic ellipsometry and fitted to a Drude-Lorentz model. A robust optical stratification model was determined using focused ion beam cross-section of thin foils examined by transmission electron microscopy. Dielectric constants of the inner oxide layer depleted in chromium were assimilated to those of the nickel thin film. The optical constants of both the spinels and extern layer were determined.     

Determination of water in pressurized pharmaceutical metered dose aerosol products

Abstract

An easy, rapid and reproducible method for the determination of a low level of water content in pressurized metered dose aerosol products is described. A Mitsubishi Moisture Meter Model CA-06 with Karl Fischer reagent was used for this study. The sample can be introduced into the reagent chamber through the septum plug using a syringe needle from the valve of sample canister. One determination takes 2～3 minutes and the results are accurate and reproducible (CV=2～6%) in the range of 10～30 ppm, H₂O. The linear correlation coefficient was 0.9994 in the range of 50-200 μg of H₂O.     

Determination of water in pressurized pharmaceutical metered dose aerosol products

An easy, rapid and reproducible method for the determination of a low level of water content in pressurized metered dose aerosol products is described. A Mitsubishi Moisture Meter Model CA-06 with Karl Fischer reagent was used for this study. The sample can be introduced into the reagent chamber through the septum plug using a syringe needle from the valve of sample canister. One determination takes 2~3 minutes and the results are accurate and reproducible (CV=2~6%) in the range of 10~30 ppm, H₂O. The linear correlation coefficient was 0.9994 in the range of 50-200 μg of H₂O.     

In-service inspections of the reactor cooling system of pressurized water Reactors

In order to guarantee constant safety of the components of the reactor cooling system, regular in-service inspections are carried out after commissioning of the nuclear power plant. This contribution is concerned with the components of the reactor cooling system, referring to the legal requirements, safety-related purposes and scope of the in-service inspections during the entire period of operation of a nuclear power plant. Reports are made with respect to type, examination intervals, examination technique, results and future development. The functional tests which are carried out within the scope of the inservice inspections are not part of this contribution.     

Rapid determination of low levels of water in pressurized pharmaceutical inhalation aerosol products

A simple, fast and rugged method for the determination of low levels of water in pressurized pharmaceutical inhalation aerosol products is described. The pressurized canister is pierced and the contents are directly transferred into a Karl Fischer unit. The water content is measured by coulometric titration. This method has been applied to two commercial products and two development formulations.     

Hyperspectral temperature and salt dependencies of absorption by water and heavy water in the 400-750 nm spectral range

The temperature and salt dependencies of absorption by liquid water (H2O) and heavy water (D2O) were determined using a hyperspectral absorption and attenuation meter (WET Labs, AC-S). Sodium chloride (NaCl) was used as a proxy for seawater salts. There was no significant temperature (PsiT) or salt (PsiS) dependency of absorption at wavelengths <550 nm. At wavelengths >550 nm, PsiT exhibited peaks at approximately 604, 662, and 740 nm. A small negative trough in PsiS occurred at approximately 590 nm, followed by a small positive peak approximately 620 nm, a larger negative trough at approximately 720 nm, and a strong positive peak at approximately 755 nm. The salt dependency of absorption by heavy water, Psis(H), exhibited a negative power-law shape with very low Psis(H), at wavelengths >550 nm. Our experiments with NaCl, clean open ocean seawater, and artificial seawater support the hypothesis that salts modify the absorption spectra of seawater by modifying the molecular matrix and vibrations of pure water.     

Fracture behavior of thin-walled Zircaloy fuel clad tubes of Indian pressurized heavy water reactor

For structural integrity analysis of thin walled tubular components such as fuel claddings used in nuclear reactors, knowledge of valid fracture mechanics parameters are required. As axially-cracked thin tubes possess a non-standard geometry from the point of view of specimen fabrication, there is no direct straight forward way to derive their fracture mechanics parameters with known functions as can be done for standard test methods. In the present work, the J–R curve for an axially cracked fuel pin from Indian 220 MWe pressurized heavy water reactor is derived after experimental and analytical derivation of the required parameters and the results are compared with earlier published data for similar material.     

Some practical considerations in treating dependencies in PRAs

This paper reviews the integrated framework for doing common cause failure analysis developed by the US Nuclear Regulatory Commission (USNRC) and the Electric Power Research Institute (EPRI). The important insights that have been gained from this concentrated effort are highlighted. They include a balance between the qualitative and quantitative analysis, the importance of having plant-specific data, and the explicit delineation of the assumptions underlying the various models. The paper also provides some insights into quantifying common cause failures and some approximations that can be used in the quantification process. Data collection needs for common cause failure events are briefly discussed.     

Bioremediation of endosulfan contaminated soil and water -- optimization of operating conditions in laboratory scale reactors

A mixed bacterial culture consisted of Staphylococcus sp., Bacillus circulans-I and -II has been enriched from contaminated soil collected from the vicinity of an endosulfan processing industry. The degradation of endosulfan by mixed bacterial culture was studied in aerobic and facultative anaerobic conditions via batch experiments with an initial endosulfan concentration of 50mg/L. After 3 weeks of incubation, mixed bacterial culture was able to degrade 71.58+/-0.2% and 75.88+/-0.2% of endosulfan in aerobic and facultative anaerobic conditions, respectively. The addition of external carbon (dextrose) increased the endosulfan degradation in both the conditions. The optimal dextrose concentration and inoculum size was estimated as 1g/L and 75mg/L, respectively. The pH of the system has significant effect on endosulfan degradation. The degradation of alpha endosulfan was more compared to beta endosulfan in all the experiments. Endosulfan biodegradation in soil was evaluated by miniature and bench scale soil reactors. The soils used for the biodegradation experiments were identified as clayey soil (CL, lean clay with sand), red soil (GM, silty gravel with sand), sandy soil (SM, silty sand with gravel) and composted soil (PT, peat) as per ASTM (American society for testing and materials) standards. Endosulfan degradation efficiency in miniature soil reactors were in the order of sandy soil followed by red soil, composted soil and clayey soil in both aerobic and anaerobic conditions. In bench scale soil reactors, endosulfan degradation was observed more in the bottom layers. After 4 weeks, maximum endosulfan degradation efficiency of 95.48+/-0.17% was observed in red soil reactor where as in composted soil-I (moisture 38+/-1%) and composted soil-II (moisture 45+/-1%) it was 96.03+/-0.23% and 94.84+/-0.19%, respectively. The high moisture content in compost soil reactor-II increased the endosulfan concentration in the leachate. Known intermediate metabolites of endosulfan were absent in all the above degradation studies.     

A case study of environmental assisted cracking in a low alloy steel under simulated environment of pressurized water reactor

The electromechanical behavior of a pressure vessel grade steel A516 has been investigated using potentiodynamic polarization curves and slow strain rate test (SSRT) in simulated environment of pressurized water reactor. The anodic polarization behavior shows that the steel remains active in the solution till localized attack (pitting) starts. The cracks initiated at the surface propagate in a trans-granular mode. These cracks are initiated at the inclusion (MnS) sites and at the interfaces between local anode (ferrite) and local cathode (pearlite). It seems that the ultimate fracture occurs when the propagating surface cracks join the subsurface hydrogen induced cracks. The addition of oxygen in the testing chamber to supersaturation levels shifts the corrosion potential to anodic side and significantly lowers the strength and ductility. Compared to the room temperature properties, the UTS and tensile elongation in various simulated conditions are reduced by 10–25% and 25–75%, respectively.     

Evolution of aerosols in large pressurized spaces

Results of experiments in pressurized spaces of 100 to 3200 m³, including a manned space station, carried out to study the evolution of aerosols and ions in the course of their spontaneous decay and removal by an electric field or mechanical means are considered. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 4, pp. 844–850, July–August, 2000.     

Fracture of pressurized cylindrical shells

Pipeline fracture is analyzed via Lagrangean mechanics. The bursting pipeline is a system with two degrees of freedom. The two equations of motion for the crack are derived and solved for a simplified case. The fluid mechanics of a pressurized pipe during fracture is discussed and the different behavior of liquids and gases is indicated.     

An axial crack in a pressurized cylindrical shell

Following an earlier analysis of a line crack in a spherical cap, the stresses in a cylindrical shell containing an axial crack are presented. The inverse square root singular behavior of the stresses peculiar to crack problems is obtained in both the extensional and bending components. This singularity may be related to that found in an initially flat plate by

$$\frac{{{}^\sigma {\text{shell}}}}{{{}^\sigma {\text{plate}}}} \approx 1 + ({\text{a + b}}\ell {\text{n}}\frac{{\text{c}}}{{\sqrt {{\text{Rh}}} }})\frac{{{\text{c}}^{\text{2}} }}{{{\text{Rh}}}} + ...$$     

A circumferential crack in a pressurized cylindrical shell

Following an earlier analysis of an axial line crack in a cylindrical shell, the stresses for a finite circumferential crack are presented. The inverse square root singularity of the stresses peculiar to crack problems is obtained in both the extensional and bending components. Furthermore, the initial curvature may be related to that found in an initially flat plate by a factor of the form

$$\frac{{{}^\sigma shell}}{{{}^\sigma plate}} \approx 1 + (a + b \ell n \frac{c}{{\sqrt {Rh} }})\frac{{c^2 }}{{Rh}} + ...$$     

Fluid fracture interaction in pressurized reinforced concrete vessels

The water penetration and flow through cracks in reinforced concrete structures are investigated experimentally and numerically. First, wedge-splitting tests of reinforced concrete under strain control were performed. These specimens were subjected to a mechanical load, as well as to an internal hydrostatic pressure. Pressure along the propagating crack and flow rates were measured. Then, nonlinear fracture mechanics-based finite element simulations were performed. From this study, it was determined that the rebars on the outer side of the wall in concrete containment vessels are more effective in preventing leakage than are the inner ones. Furthermore, it was once again determined that the presence of a hydrostatic pressure reduces not only the fracture energy of concrete but also the bond between reinforcement and concrete. Finally, two analytical models are proposed.