High Temperature Water Environments Research Articles

Irradiation techniques under high pressurized water using hybrid type saturated temperature capsule in the JMTR

The IASCC is one of the major concerns on the integrity of in-core materials not only for the LWRs but also for the materials to be cooled by water in fusion reactor. It is desired to irradiate test materials in a high temperature water environment in order to investigate simultaneous effects of irradiation and corrosive environments, which are essential for the study of IASCC. In the JMTR, an irradiation rig named the SATCAP was developed and applied for the IASCC study. Inside of this capsule, cooling water is boiling during irradiation due to heat generated by gamma heating, thus the temperature of the specimens is kept nearly at saturation temperature of water. Recently a new hybrid type SATCAP with electric heaters and vacuum control systems was developed to improve temperature control capability of the original SATCAP. A design and results of performance test of the new hybrid type SATCAP are reported.

Wear of Power Plant Components Due to Impact and Sliding

In nuclear power plants, major tribological problems can occur among the interacting components, such as those in the control assembly, the reactors and the steam generators, due to a combination of impact and sliding motion. Many experimental wear tests have been performed in either room temperature or simulated high pressure, high temperature water environments to study the effects of materials and various operating parameters on wear. Although several successful numerical models are now available for the prediction of dynamic responses during component interaction, only empirical models having limited practical applications are available for wear damage prediction. In recent years, with the advances in tribology and the availability of sophisticated instruments for metallurgical analysis, there have been attempts to develop predictive wear models based on the more fundamental aspects of wear particle formation and detachment. This review article gives a comprehensive account of the past and present work on wear of power plant components. It also includes a brief review of the general wear processes and wear mechanisms. There are 162 references.

Low cycle fatigue behaviour of TZM molybdenum alloy in divertor water coolant

Load controlled low cycle fatigue (LCF) tests on TZM Mo-alloy have been conducted up to specimen rupture, using two triangular load waveforms of 17 and 20 kN amplitudes, and in high temperature water (250°C), either deaerated or containing separate additions of oxygen (10 −5 M/l), hydrogen (10 −3 M/l) and hydrogen peroxide (10 −4-10 −5 M/l), in order to simulate the coolant chemistry inside the divertor tubings during fusion reactor operation. Extensions of TZM fatigue lives, compared to those obtained in the 20 kN experiments, were found to occur in all aqueous environments under the 17 kN cyclic load amplitude test, which induced a lower total strain range. It was also observed that, independently of the stressing conditions, the environments in terms of their deleterious effects on the LCF performances of TZM alloys, could be ranked in the following order: oxygenated water < deaerated water < hydrogenated water. Conflicting results were conversely obtained in hydrogen peroxide solutions, where the fatigue resistance was the lowest under 20 kN loading, but became the highest at a reduced amplitude of 17 kN. On the basis of visual assessments, and TZM open circuit potential values, continuously recorded during testing against an Ag/AgCl reference electrode, an idea about the corrosion behaviour of TZM alloy in high temperature water environments was proposed. Qualitative fractographic analysis was performed by scanning electron microscopy (SEM), to identify the predominant failure modes and suggest, in connection with the electrochemical evaluations, candidate cracking mechanisms, which accounted, reasonably, for the fatigue life data.

Chemical Processing in High-Pressure Aqueous Environments. 5. New Processing Concepts

A combination of fundamental and applied process research at Pacific Northwest National Laboratory resulted in the development of several new processing concepts. These concepts have in common the use of high-temperature pressurized water as a unique reaction medium for carrying out chemical reactions. Typical operating conditions of these processes range from 300 to 360 °C and have pressures to above 200 bar. Investigation of the process chemistry and engineering for these new processing concepts required the development and scale-up of several high-pressure reactor systems which are described. Several new processes involving catalysts and the distinctive properties of pressurized water were patented as part of this effort. These processes, which are at various stages of development, address a broad mix of energy and environmentally related problems. Chemical processing in a high-temperature liquid water environment remains a relatively untapped area for commercial application.

The effect of carbon on grain boundary diffusivity in Ni-16Cr-9Fe alloys

It is well known that alloy 600 is susceptible to intergranular stress corrosion cracking (IGSCC) in high temperature water environments. Over the past three decades, extensive research has been conducted on Ni-Cr-Fe-C alloys in order to determine the influences of microstructural changes on IGSCC behavior. Although solid solution carbon appears to be beneficial in increasing IGSCC resistance, the mechanism for the improved behavior is unknown. This study focuses on the effect of solid solution carbon on grain boundary diffusivity, in an effort to explain the observed differences in boundary deformation accommodation mechanisms between high purity and carbon doped Ni-Cr-Fe alloys.

A fractographic assessment of sulphide inclusion distributions and their influence in promoting environmentally assisted crack growth in ferritic pressure vessel steels

The present study was aimed at fractographically assessing the extent of the sulphur concentration that is needed to initiate environmentally assisted crack (EAC) growth in fatigue crack growth tests on pressure vessel steels in a high temperature water environment. A relationship has been established between the extent of sulphide segregation within a cluster and the propensity towards the initiation of EAC growth. Also the EAC growth has been shown to be a function of K max at which the cluster occurred on the fatigue fracture surface. In terms of sulphur concentration, EAC growth occurred at sulphur concentrations of around 7000 ppm at K max values of 80 MPa√ m while at lower values (viz. 40 MPa√ m ) concentrations approaching 35 000 ppm were required to initiate EAC growth. Under an ideal sulphide distribution it was suggested that no EAC growth was possible. Finally the sulphur anion concentration levels for both EAC and non-EAC growth, assessed from the present fractographic evaluation, have exhibited good commonality with those predicted from a slip dissolution model which characterised fatigue phenomena in high temperature water environments.

Ceramic coating for valve seats and stems by plasma chemical vapor deposition

Abstract To extend the lifetime of the valve seats and stems used in nuclear power plants, we have developed a unique ceramic coating technique using plasma chemical vapor deposition (CVD). Multilayer coatings of Al 2 O 3 /TiN/TiC, Al 2 O 3 /TiC and TiN/TiC were deposited onto Stellite and stainless steel substrates. The mechanical and physical properties of the coatings were evaluated by various methods. The coated specimens showed good wear resistance in a high-temperature water environment. Corrosion resistance was evaluated in an autoclave at a temperature of 548 K for 200 h. The coated specimens showed excellent performance in reducing the cobalt level dissolved in the testing solution. The weight loss of the multilayer-coated AISI403 specimen, as evaluated by a cavitation erosion test, was less than 1% of that of the uncoated AISI403. However, for the coated Stellite-padded AISI316L substrate, the weight loss was almost the same as that of the uncoated specimen.

A probabilistic assessment for the stress corrosion cracking lifetime of sensitized 304 stainless steel in sodium chloride solutions.

Since stress corrosion crack initiation/propagation process is essentially a stochastic one, a series of uniaxial constant load tests have been conducted on sensitized 304 stainless steel specimens in neutral chloride solutions to examine the effects of stress, temperature, crevice and chloride ion concentration on probability distribution of intergranular stress corrosion cracking lifetime. By examining the effects of various acceleration factors, the lifetime distribution can be satisfactorily presented by the exponential probability distribution model as that of sensitized stainless steels in high-temperature and high-purity water environment systems. The tendency of both the location parameter, i.e., lower limit of lifetime distribution, and the scale parameter, i.e., standard deviation of lifetime distribution, to increase with decreasing stress, temperature and chloride ion concentration, also the ratio of those two parameters is constant.

Fatigue crack growth behaviour of pressure vessel steels and submerged arc weldments in a high-temperature pressurized water environment: Liaw, P. K., Logsdon, W. A. and Begley, J. A.Metall. Trans. A Oct. 1989 20A, (10), 2069–2085

In this study, the methods for constructing accurate and consistent geometrical and finite element (FE) models for general cracked tubular Y-joints are described. Firstly, geometrical analysis of welded tubular joint is given and it is then extended to the modelling of general cracked Y-joints. The concept of crack surface and a simple mapping approach are suggested to model either through-thickness or surface cracks which can be of any length and located at any position along the brace–chord intersection. Secondly, the geometrical model developed will be used in the generation of consistent FE meshes. The basic concepts used for the design and generation of three-dimensional FE meshes will be described. This will include the meshing procedures for discretization of tubular joints with through-thickness and surface cracks which are frequently regarded as one of the most difficult steps in the construction of tubular joint models. Finally, some mesh generation examples for uncracked and cracked Y-joints will be presented to demonstrate the use of the purposed geometrical model and mesh generation scheme developed.

炭化ケイ素および安定化ジルコニアの高温水中における腐食挙動

Many kinds of advanced cermaics, which have been recently developed, are considered to have much possibility for engineering applications as structural materials in high temperature water environments. In the previous report, fundamental corrosion behaviors of 14 kinds of sintered polycrystalline ceramics in 290°C high purity water with or without dissolved oxygen were clarified. In the present study, pH and immersion time dependences of corrosion behaviors of sillicon carbide and stabilized zirconia were discussed. Silicon carbide showed high corrosion resistivity, and the corrosion rate increased at higher pH and oxygenated solution. Time dependence of corrosion weight loss obeyed a power law with the power of 0.7 to 1.3 depending on pH value. Surface silica layer formation was not detected by X-ray diffractometry and Auger electron spectroscopy. These results suggest simultaneous hydrothermal oxidation and dissolution, rather than two step oxidation and dissolution with a protective silica layer. Stabilized zirconia with 6mol% and 8mol% of yttria also showed excellent corrosion resistance, especially the corrosion weight loss for 8mol% yttria stabilized zirconia was below the detection limit in oxygen-free neutral and pH 10 solution.

Prediction of changes in elastic moduli due to water-rock interaction during operation of granitic hdr geothermal system

Young's modulus of granitic rock samples under the simulated conditions of a geothermal reservoir, such as a pressurized high temperature water environment up to 350°C, was measured by means of the compliance calibration technique. The results obtained indicate a significant change in modulus with increasing test temperature and exposure time in a hydrothermal environment, which can be considered as a consequence of an increase in microcrack aperture due to chemical dissolution. The applicability of the laboratory results to hot dry rock geothermal field data is also demonstrated.

Fatigue crack growth behavior of pressure vessel steels and submerged arc weldments in a high-temperature pressurized water environment

The fatigue crack growth rate (FCGR) properties of SA508 C1 2a and SA533 Gr A C1 2 pressure vessel steels and the corresponding automatic submerged are weldments were developed in a high-temperature pressurized water (HPW) environment at 288 °C (550°F) and 7.2 MPa (1044 psi) at load ratios of 0.02 and 0.50. The HPW enviromment FCGR properties of these pressure vessel steels and submerged arc weldments were generally conservative, compared with the approrpriate American Society of Mechanical Engineers (ASME) Section XI water environmental reference curve. The growth rate of fatigue cracks in the base materials, however, was considerably faster in the HPW environment than in a corresponding 288°C (550°F) base line air environment. The growth rate of fatigue cracks in the two submerged are weldments was also accelerated in the HPW environment but to a significantly lesser degree than that demonstrated by the corresponding base materials. In the air environment, fatigue striations were observed, independent of material and load ratio, while in the HPW environment, some intergranular facets were present. The greater environmental effect on crack growth rates displayed by the base materials, as compared with the weldments, was attributed to a different sulfide composition and morphology.

圧力容器用低合金鋼の高温高圧水中における低サイクル疲労挙動

Low cycle fatigue behaviour of low alloy steels JIS SFVQ1A (equivalent to ASTM A508 cl. 3) and SQV2A (A533B cl. 1) for reactor pressure vessel was investigated in high temperature pressurized water environment. Total strain range, strain rate and dissolved oxygen (DO) concentration were varied from 0.5% to 2.2%, 0.1%/s to 0.001%/s and 10 ppb to 8 000 ppb, respectively. Fatigue tests in ambient air and 561K air were also conducted for comparison. Reduction of fatigue life in high temperature water environment was observed. It decreased with decreasing total strain range and rather longer fatigue lives than those in air were observed at lower total strain range. SQV2A steel showed a distinct strain rate dependence of fatigue life compared to SFVQ1A steel, while both steels showed a similar DO concentration dependence. It was found that fatigue cracks initiated at surface corrosion pits due to MnS inclusion and the low cycle fatigue behaviour of both steels depended on their sulphur contents. It can be conclusively remarked that the materials tested possess a plenty of safety margin in high temperature water environment by judging from the fact that the present data fell on the points far above the design fatigue curve in the ASME Code Sec.III.

Stress corrosion cracking behavior of granite under pressurized high temperature water environments and crack propagation resistance.

In the development of design and control methodolgy for hot, dry rock (HDR) geothermal reservoir cracks, a full understanding of the environmentally assisted cracking behaviors of rock under the reservoir conditions is a prerequisite. In this stdy, the significance of time-dependent material degradation is demonstrated, which is induced by the water-rock interactions. In a 350°C, 18 MPa water environment, pre-immersion of 2 inch CT specimens of granite is given for different periods using an autoclave, after which the ultrasonic wave velocity measurements and fracture toughness tests are performed. The results show that the hydrothermal environment causes the time-dependent material degradation throughout the specimens tested, and that the crack propagation resistance of the granite is also time-dependent and decreases with increasing immersion time. Based on the experimental results, an immersion time-dependent crack growth model is proposed and applied to simulate the stress corrosion cracking test which has been conducted in the 350°C, 18 MPa water. It is shown that the proposed model allows us to predict the stress corrosion cracking behaviors under the pressurized high-temperature water environments.

Evaluation of environment assisted fracture of granite under the simulated geothermal reservoir condition and design of artificial subsurface crack.

Environment sensitive fracture is one of the important phenomenon in designing fractures for geothermal energy extraction. Material degradation and environment assisted cracking, stress corrosion cracking (SCC) under constant applied load and corrosion fatigue (CF) under alternating load were investigated in a pressurized high temperature water environment. The test results obtained were applied to two kinds of rock mass according to the permeability, that is, impermeable rock mass and permeable rock mass. In the case of a permeable rock mass, material degradation caused by permeation can reduce maximum pressure for hydraulic fracturing. Crack propagation due to degradation as well as due to SCC and /or CF during long-term service performance is found to be of importance for predicting the stability over the lifetime of the geothermal reservoir. In the case of an impermeable rock mass, conventional fracture mechanics can provide a safe evaluation.

Notch Fatigue Crack Initiation in High Temperature Water Environments: Experiments and Life Prediction

Test results, experimental techniques and analytical interpretations are reported from notched compact type (CT) tests of SA 333 Gr. 6 carbon steel to determine quantitatively fatigue initiation lives in high temperature oxygenated water. Parameters explored include environments of air, 0.2 ppm O2 and 8 ppm O2-water at 10.3 MPa (1500 psi), temperatures of 149, 232 and 288° C, frequencies of 0.00021, 0.0021 and 0.021 Hz, notch radii of 0.051 and 0.51 mm and R-values of 0.2, 0.5 and 0.8. Pseudostress amplitudes were calculated elastically and by Neuber notch analysis procedures using a worst case notch concept. Results were compared to ASME Section III fatigue data curves. Test results showed that the fatigue initiation life of carbon steel is substantially lowered as oxygen level is raised, as frequency is lowered or as temperature is raised. No frequency or temperature effect occurred in air. To a lesser extent, a decreasing notch radius or an increased R-value degrade the initiation life. Results compare favorably with interpretations based on environmental fatigue crack growth of this material.

Protection against fatigue damage with respect to the environmental influence of LWR operating conditions

As nuclear power plant operation proceeds, a certain number of isolated leakages and cracks are found in pipes and components. Considering the extensive design and analysis efforts made, it is at least the early occurrence of the incidents in relation to the design lifetime of the material that is surprising. In the Federal Republic of Germany, a tremendous effort has been directed towards the development of optimized steels with respect to fracture toughness and weldability, the manufacturing of integral forged products (forged-on nozzles, seamless pipes and elbows), and the reduction of peak stresses by an advanced design (basic safety concept). The design of the areas of cold water injection has been improved to prevent temperature stratification. The safety of pipes and components has been considerably improved by these developments. Pipes and components previously affected by material, design and manufacturing problems have been replaced by components built to the new high standard of quality. An area which still deserves attention with respect to the lifetime of a plant is the protection against fatigue damage. The present design fatigue curve (ASME Section III or KTA 3201.2) only allows a generic assessment of the safety against cyclic loadings. In most cases, this concept has proved its worth and is sufficiently safe. In some cases, however, and especially in the presence of a corrosive environment, a detailed investigation is necessary. The design fatigue curve can no longer be applied if cracks form in the protective magnetite layer and, owing to this, strain-induced corrosion cracking occurs. The concept developed in this paper defines a number of correction factors which take into account the effects of a high-temperature water environment as a function of the duration of the strain cycle. It is based on work presented by General Electric. The concept developed allows a more detailed assessment of the local conditions and, consequently, serves as a useful tool for both the designer and the operator of the plant.

Surface Crack Growth Behavior of Structural Metals in High Temperature Water Environments

This paper reports on a study of surface crack growth of two nuclear structural steels, SA333 Gr6 carbon steel used for piping and SA533 Grade B pressure vessel steel, both tested under cyclic loads in 288°C (550°F), 0.2 ppm oxygen water at 10.34 MPa (1500 psi). Results are compared with tests on compact type (CT) specimen geometries tested in similar environments. It was found that, for the frequencies employed, the crack growth rates for the two specimen geometries were not widely different, despite the high net mean stresses employed in the surface crack geometries. However, substantial differences were noted in the crack velocity response under static loading for the two geometries, suggesting that such differences can be expected in low frequency loading more typical of service conditions, raising questions about the applicability of CT geometry test results for the materials, temperatures and environments used in this study. Temperature effects, air environments and R-value effects for surface crack geometries are also reported.

Fatigue crack initiation at notches in SA 333 piping steel

AbstractIn this paper are reported two recent investigations into crack initiation at notch roots using techniques developed for remote monitoring of crack growth in high–temperature water environments. In the first, a notched compact–type specimen of a carbon steel, SA 333 Gr. 6, was monitored for crack initiation (defined as a 0·076 mm crack at the notch root) in a variety of water chemistries and testing conditions. The mechanical conditions at the notch root have been analysed using the Neuber–notch method, enabling a direct comparison to be made with the strain–controlled fatigue data curves used for a smooth specimen in the ASME Boiler and Pressure Vessel Code, Section III. In the second investigation a different method was considered for monitoring crack initiation. A modification of the electrical–potential technique, called the reversing dc electrical potential method, was used to obtain quantitative information on the initiation and early growth of small surface cracks in notched bars of a high–...

ZIRCADYNE 704

Abstract ZIRCADYNE 704 is a zirconium-tin-iron-chromium alloy. Zircadyne 704 can contain up to 4.5% hafnium which is naturally present in the zirconium ore. The hafnium is very similar to zirconium metallurgically and chemically and is not detrimental to the corrosion resistance of Zircadyne 704 in chemical applications. Zircadyne 704 is used for high-pressure, high-temperature water and steam environments such as those in the nuclear power industry. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fatigue. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Zr-9. Producer or source: Teledyne Wah Chang Albany.