Metal Gaskets Research Articles

Japanese perspectives and research on packaging, transport and storage of spent fuel

The present paper gives an overview of Japanese experimental studies of dual-purpose metal casks. The studies included: cask drop without impact limiters, drop of a heavy weight onto a cask due to building collapse, burial of a cask in debris from building collapse, tipping over of a cask during an earthquake, long-term containment of metal gaskets and transportability of casks after long-term storage. Most of the studies employed full-scale casks for the experiments.

Measuring the Thickness of a Metal Gasket Squeezed between the Anvils of a High-Pressure Cell while Preparing It for an Experiment

A simple method for preparing metal gaskets used in high-pressure anvil cells is described. The preparation is carried out in one indentation cycle without additional assembly and disassembly of the cell.

384. 使用済燃料輸送・貯蔵キャスクの長期密封性能試験

The use of transport/storage cask for spent fuel storage is considered to be rational and economical. Since the storage duration may continue for 40 years or so, the function of sealing radioactive materials in the casks must be reliable for long-term. Long-term containment test of full-scale spent fuel transport/storage cask models have been in progress since 1990 in CRIEPI, Japan. It has been 11 years since it started. The results so far demonstrate and confirm very reliable containment performance of the cask lid structure with metal gaskets. Using the test data it is predicted by Larson-Miller Parameter (LMP) method that the containment system will keep its integrity at least for 40 years.

Long-Term Containment Performance Test Facilities for Spent Fuel Transport/Storage Casks (CRIEPI, Japan)

Long-term containment tests of full-scale transport/storage cask models have been in progress since 1990 at CRIEPI, Japan. The results demonstrate and confirm the very reliable containment pelformance of the cask lid structure with metallic gaskets.

Application of Metallic Gaskets in SOFC Stacks

Application of Metallic Gaskets in SOFC Stacks

The Strength of Joints Combining Adhesives with Bolts. Case where Adherends are Pipe Flanges of which the Interfaces are Bonded Partially.

The stresses of joints combining the bonding force of adhesives with the clamping force of bolts is analyzed using axisymmetrical theory of elasticity and FEM, when an internal pressure is applied to the combination joint in which two pipe flanges are clamped together by bolts and nuts with an initial clamping force after being joined by anaerobic sealant. The anaerobic sealant is applied at the interfaces partially instead of formed gaskets in pipe flange connections. In the numerical calculations, the effect of the bonding area and position and Young's modulus of sealant on the contact stress at the interfaces are clarified. In addition, using the interface stress distribution, the strength of the combination joint is predicted. Experiments were performed and the analytical results are consistent with the experimental results concerning the variation in axial bolt force and the strength of combination joints. It is found that the joint strength changes as the bolt pitch circle diameter, the bonding position and its area, the initial clamping force and the adhesive material properties change. Furthermore, it is seen that the sealing performance of such combination joints in which the interfaces are bonded partially is improved over that of pipe flange connection with metallic gaskets.

The Strength of Joints Combining Adhesives with Bolts. Case where Adherends are Pipe Flanges of which the Interfaces are Bonded Partially.

The stress of joints combining the bonding force of adhesives with the clamping force of bolts is analyzed using axisymmetrical theory of elasticity and FEM, when an internal pressure is applied to the combination joint in which two pipe flanges are clamped together by bolts and nuts with an initial claming force after being joined by anaerobic sealant. The anaerobic sealant is applied at the interfaces partially instead of formed gaskets in pipe flange connections. In the numerical calculations, the effects of the bonding area and position and Youngs' modulus of sealants (epoxy adhesive) on the contact stress at the interfaces are clarified. In addition, using the interface stress distribution, the strength of the combination joint is predicted. Experiments were performed and the analytical results are consistent with the experimental results concerning the variation in axial bolt force and the strength of combination joints. It is found that the joint strength changes as the bolt pitch circle diameter, the bonding position and area, the initial clamping force and the adhesive material properties change. Furthermore, it is seen that the sealing performance of such combination joints in which the interfaces are bonded partially is improved over that of pipe flange connections with metallic gaskets.

Radio Frequency Heating Coils for Shock Wave Experiments

ABSTRACTRadio-frequency eddy current heating of metallic samples in shock wave, ultrasonic and diamond anvil apparatus provides a methodology for obtaining hot samples or hot metallic gaskets (containing a sample) and yet not heating the entire target, ultrasonic assembly or diamond cell. Analysis of a previous design of a radio-frequency (∼0.5 MHz) coil demonstrated that the center of 13 mm diameter shock wave experiment sample discs were underheated and the experimental temperatures achieved resulted from conduction of heat from the overheated sample edges relative to the center of the sample. We show, using the Biot-Savant law, that the ratio of magnetic field in the center to that at the edge of the sample, f, can be maximized to a value of f=1.8, by decreasing the radius of the heater coil, relative to the 13 mm diameter of sample. A simple analysis provides the thermal gradient across the sample thickness. An electric skin depth for iron of ∼1 mm for the 0.45 MHz frequency of the heater power supply of our system is obtained. This leads to a maximum temperature gradient of ∼52 K over the 4 mm thickness of the shock wave sample discs.

使用済燃料貯蔵キャスクの長期密封性能評価手法の開発

One of the characteristics of the cask storage method of spent fuel is that containment of radioactive materials is assured by the storage cask itself. Thus, the seal structure of the cask is designed to have a highly reliable multi-barrier system using metallic gaskets instead of the conventional rubber gaskets. Although, it has been reported that the containment feature of the metallic gaskets is influenced by the plastic deformation and stress relaxation of the gaskets for a short-term usage, no research report has been pulblished on the containment feature of the metallic gaskets for a long-term usage. In this paper, the stress relaxation features of the metallic gaskets is investigated which will directly influence the long-term sealability of the storage cask, at first. Next, the relationship between the temperature/time dependence of the plastic deformation and the containment features of the metallic gaskets. Finally, an evaluation method of the long-term sealability from experimental data of a short-term behavior of the metallic gaskets is proposed.

An Analysis of Pipe Flange Connections Using Epoxy Adhesives/Anaerobic Sealant Instead of Gaskets

Abstract This paper deals with the strength and the sealing performance of pipe flange connections combining the bonding force of adhesives with the clamping force of bolts. The epoxy adhesives or anaerobic sealants are bonded at the interface partially instead of gaskets in pipe flange connections. The stress distribution in the epoxy adhesives (anaerobic sealant), which governs the sealing performance, and the variations in axial bolt force are analyzed, using an axisymmetrical theory of elasticity, when an internal pressure is applied to a connection in which two pipe flanges are clamped together by bolts and nuts with an initial clamping force after being joined by epoxy adhesives or anaerobic sealant. In addition, a method for estimating the strength of the combination connection is demonstrated. Experiments are performed and the analytical results are consistent with the experimental results concerning the variation in axial bolt force and the strength of combination connections. It can be seen that the strength of connections increases with a decrease in the bolt pitch circle diameter. Furthermore, it is seen that the sealing performance of such combination connections in which the interface is bonded partially is improved over that of pipe flange connections with metallic gaskets.

Simple device for drilling holes in metal gaskets for diamond anvil cell experiments

With a spring-loaded platform mounted on a precision minidrilling machine, it is possible to rapidly and inexpensively drill sharp sample holes down to about 100 μm in hardened metal gaskets for diamond anvil cell experiments.

The performance of the vacuum system of the 800 MeV proton synchrotron, ISIS

The neutron source, ISIS, is the world's leading pulsed neutron facility, primarily used for condensed matter research using slow neutron scattering techniques. The source is based on the bombardment of a uranium or tantalum target by an 800 MeV high intensity proton beam from a rapid cycling synchrotron. A brief description is given of the vacuum system of the synchrotron and beam line to the target. Key factors in the design of the system are reliability and minimum maintenance, to reduce exposure of operators to radiation. Ceramic vacuum chambers make up two thirds of the ring to reduce eddy current losses in the pulsed magnets: all other chambers are constructed from stainless steel. Metal gaskets are used in all de-mountable joints. The system is pumped with triode sputter ion pumps and roughed by a carbon vane, dry combination claw and roots, and turbomolecular pumps. The entire system is free from hydrocarbons. The performance of the system is reported including an analysis of breakdown. Since operation began in 1984 there have been few failures apart from those caused by beam heating in the extracted beam line, which has caused leaks in joints. As diagnostics and beam control have improved, these occurrences have become increasingly rare. This has resulted in a vacuum system virtually fault and maintenance free.

A Stress Analysis of Pipe Flange Connections

The use of pipe flange connections is standardized in the codes of JIS, ASME, DIN and so on. However, these codes are almost entirely dependent on experience, and subsequently some problems concerning pipe flange connections have been encountered. In the present paper, the distribution of contact stresses which governs the sealing performance is analyzed as a three-body contact problem, using an axisymmetrical three-dimensional theory of elasticity. The effects of the stiffness and the thickness of raised face metallic gaskets on the contact stresses and the effective gasket seating width are shown by numerical calculation. Moreover, stresses produced on the hub, the load factor (the relationship between an increment of bolt axial force and an internal pressure), and the maximum stress caused in bolts are analyzed. For verification, experiments are carried out. The analytical results are satisfactorily consistent with the experimental results.

Time resolved transient absorption probing of a laser plasma

The described experimental setup allows the kinetic analysis of a pulsed-laser generated gas-plasma by transient visible absorption spectroscopy at a time resolution of 10 ns and a spectral resolution of 0.3 cm-I. Absorption from the first-4s level manifold towards the 5p level manifold of the argon atom is reported in the spectral range around 420 nm. An example of time dependence is given for the 4s[3/2]~ level population. Since the advent of lasers their ability to generate plasmas has been recognized and widely used and the physical properties of such plasmas extensively studied [I]. Quite a number of those works dealt with rare gas laser plasmas but very few have been devoted to spectroscopical properties of these plasmas. However during the last two decades dense rare gases have attracted considerable attention due to their potentiality as laser media [2]. In this respect a detailed knowledge of plasma kinetics is of great importance. The present report describes a method allowing the kinetic study of a gas plasma by transient visible absorption spectroscopy at high spectral and temporal resolution. The experimental setup is sketched in figure I. The pulsed-laser generated plasma, recently used as a vacuum ultraviolet source [3], is created by focusing the 1064 nm radiation of a pulsed 585-20 Quantel Nd : YAG laser (YAG 1, 350 mJ) at the center of a 6-way gas cell by means of the spherical lens Ll of focal length 20 mm. The stainless steel gas cell, mounted with metallic Helicoflex gaskets from Cefilac, is evacuated with a turbopurnp and refilled before each run with a gas at a pressure typically in the atmospheric range (10~ Pa). This is a very clean technique as the medium is excited far from the cell walls. The probe beam is obtained by irradiating a laser dye cell by part of the frequency tripled radiation at 355 nm of a 2062 JOURNAL DE PHYSIQUE III M 12

On peculiarities of plastic loosening of gasket materials at pressure generation by diamond anvil technique

Abstract In this paper standard gasket materials are studied to estimate the plastic loosening intensity at the deformation centre during uniaxial compression in the diamond-anvil high-pressure apparatus using the mathematical model of plastic yield and stress-strain state parameters of metallic gaskets.

Calculation of the stresses in thin interlayers

An analysis is made of the thermal stresses which develop in thin metal gaskets (interlayers) after welding. The case of diffusion welding is discussed in particular. The problem is solved within the range of applicability of the linear theory of elasticity for dissimilar circular plates arranged symmetrically relative to the middle plane. Relations for the stresses and displacements in the plates are derived without the use of the hypothesis of straight normals or certain other assumptions traditionally used for thin plates. Simple formulas are presented for thin metal interlayers.

Effects of hubs on the characteristics of pipe flange connections.

The use of pipe flange connections is standardised in the codes of JIS, ASME, DIN and so on. However, these codes are almost entirely dependant on experience, and subsequently some problems concerning pipe flange connections have been encountered. In the Present paper, the distribution of contact stresses which governs the sealing performance is analyzed as a three-body contact problem, using an axisymmetrical three-dimensional theory of elasticity. The effects of the stiffness and the thickness of raised face metallic gaskets on the contact stresses and the effective gasket seating width are shown by numerical calculations. Moreover, stresses produced on the hub, the force ratio (the relationship between an increment of bolt axial force and an internal pressure) and the maximum stress caused in bolts are analyzed. For verification, experiments are carried out. The analytical results are satisfactorily consistent with the experimental results.

Effect of surface roughness on compressive stress of static seals. (2nd report Sealing characteristics of metallic gaskets)

In this paper, the effect of surface roughness appearing on a turned sealing surface on compressive stress and compressive force of copper gaskets (a fiat gasket, a ring joint gasket and a copper wire gasket) was studied. The results obtained can be summarized as follows : (I) In the case of a flat gasket or a ring joint gasket, in order to ignore both the surface roughness appearing on a turned sealing surface and the cross section of gasket, the compressive stress for sealing had to be nearly equal to 1.3 times the tensile strength of the copper gasket. (2) In the case of a ring joint gasket or a copper wire gasket, the values of maximum heigh roughness, in which the minimum compressive force for sealing applied, were found in the region between 2μm and 20μm or not less than 110μm respectively

Pressure generation in a diamond anvil apparatus

The behaviour of metal gaskets between diamond anvils in a high pressure apparatus has been studied. Along with the basic function of pressure generation a gasket supports the anvils' working planes' peripheral area. The elastic-plastic deformation mechanics of a 301 stainless steel gasket was investigated while generating pressure up to 65 GPa on a gasket axis.

On the Characteristics of Bolted Joints with Gaskets : Stress Analysis of Metallic Gaskets with Raised Face Interposed between Pipe Flanges

A design of bolted joints with gaskets mainly depends on experience and their sealing performance is not made clear by theoretical analyses. In this paper, discussion is made on the contact stress of bolted joints in the case where metallic gaskets with raised face are interposed between pipe flanges. The distribution of contact stresses of metallic gaskets is analyzed as a three body contact problem by using three-dimensional theory of elasticity. The effects of stiffness, thickness and position of gaskets on the distribution of contact stresses are investigated by numerical computations. Next, the force ratio of bolted joints with gaskets, that is a ratio of an increment of bolt axial force to an external load, is analyzed. Experiments on the force ratio are carried out. Then, it is shown that analytical results are in a fairly good agreement with experimental ones.