Allowable Leak Rate Research Articles

Final design of the Fiber-Optic Current Sensor bundle in the ITER buildings

The Fiber-Optic Current Sensor (FOCS) will be used in ITER to measure the total plasma current using Faraday effect. Sensing spun fibers will be placed around the Vacuum Vessel (VV) on a poloidal loop in two different VV sectors. To link the loop fibers with the reading instruments, placed several tens of meters away in electrical cabinets, a fiber bundle link is needed. This fiber bundle would start from the tokamak building port-cell, cross several rooms and end in the ITER diagnostics building. The design of such bundle needs to fulfil the unique requirements of ITER buildings, some of them related to safety, such as non-propagation of smoke and fire, as well as maximum allowable leak rate, between two separate rooms. To this regard, the FOCS fiber bundle is classified as a Safety-Relevant (SR) component. To fulfil these requirements, and at the same time achieve a good design using as many Commercial Off The Shelf (COTS) components as possible, the fiber bundle design entailed a complete qualification procedure, aimed at benchmarking the use of the selected components against the required constraints. This paper presents the final design and qualification of the FOCS fiber bundle, from the applicable requirements to the final technical solution, benchmarked through careful qualification tests. Being the first work addressing qualification of safety-relevant fiber bundles in ITER buildings, this work is also considered to be relevant for current and future diagnostics in ITER using similar components.

Corrections to Graham’s Law of Effusion for Predicting Leak Rates Through Hermetic Seals

Graham’s law of effusion has been used for decades to facilitate the prediction of the flow rates of gases penetrating into hermetically sealed devices. Typically, a trace gas such as He is used as a measure of gas flow into or out of a device. He flow is then related via Graham’s law to the flow of an unwanted gas, and this in turn is used to predict the service lifetime of the device based on the maximum allowable leak rate. As hermetically sealed devices become smaller and lower leak rates are required, there is evidence to suggest that Graham’s law is inaccurate. We evaluate Graham’s law by measuring the flow rates of noble gases (He, Kr, and Xe) and diatomic gases (D2 and N2) through realistic leaks. Our findings indicate that Graham’s law is not always accurate, and the incorporation of a relative tangential momentum accommodation coefficient into Graham’s law leads to improved correlation between different gases and thus improved predictions of service lifetime.

A Simple Method of the Load Factor and Design Based on an Allowable Leak Rate for Bolted Pipe Flange Connections with Gaskets under Internal Pressure

A Simple Method of the Load Factor and Design Based on an Allowable Leak Rate for Bolted Pipe Flange Connections with Gaskets under Internal Pressure

651 許容漏えい量を考慮した内圧を受ける金属平型ガスケット付き管フランジ締結体のボルト初期締付け力決定法

651 許容漏えい量を考慮した内圧を受ける金属平型ガスケット付き管フランジ締結体のボルト初期締付け力決定法

Study on Plugging Criteria for Thru-wall Axial Crack in Roll Transition Zone of Steam Generator Tube

The stream generator tubes represent an integral part of a major barrier against the fission product release to the environment. So, the rupture of these tubes could permit flow of reactor coolant into the secondary system and injure the safety of reactor coolant system. Therefore, if the crack was detected during In-Service Inspection of tubes the cracked tube should be evaluated by the pulgging criteria and plugged or not. In this study, the fracture mechanics evaluation is carried out on the thru-wall axial crack due to Primary Water Stress Corrosion Cracking in the roll transition aone of steam generator tube to help the assurence the integrity of tubes and estabilish the plugging criteria. Due to the Inconel which is used as tube material is more ductile than others, the plastic instability repture theory was used to calculate the critical and allowable crack length. Based on Leak Before Break concept the leak rate for the critical crack length and the allowable leak rate are compared and the safety of tubes was given.

Detecting leaks in geomembranes : Laine, D L; Darilek, G T Civ Engng, N YV63, N8, Aug, 1993, P50–53

A field-tested leak-location survey, now commercially-available, can provide construction quality assurance or solve a leakage problem in lined landfills, impoundments or tanks. A liner leak in a waste containment facility can be costly. The facility owner may face environmental cleanup costs and a loss of revenue while the leakage problem is being solved. Also, a new facility that exceeds the allowable leak rate, as defined in the design/operating permit, may not be accepted by the facility owner until the leakage problem is solved. This start-up delay may cause additional expenses or penalties for the general contractor, liner installer, and design engineering firm. This leak location method involves connecting an electrical power supply to electrodes placed above and below a geomembrane to detect areas of localized electrical-current flow through leaks in the liner. If there are no leaks in the geomembrane, a very low current will flow across the liner producing relatively uniform voltage distribution in the material above the liner. If the liner has a leak, the current flows through the leak, causing an anomaly in the electrical distribution. Leaks are located by searching for these areas.

On the penetration of gases and water vapour into packages with cavities and on maximum allowable leak rates : D. Stroehle. 15th A. Proc. Reliab. Phys. IEEE (1977) Nevada. p. 101

On the penetration of gases and water vapour into packages with cavities and on maximum allowable leak rates : D. Stroehle. 15th A. Proc. Reliab. Phys. IEEE (1977) Nevada. p. 101

Model calculations for maximum allowable leak rates of hermetic packages

Calculations are presented which apply to electronic packages prefilled with helium for leak testing. Depending on the geometry of the leak, the leak rate of the package, while in use in air at ambient pressure, may be equal to or less than that measured while it is tested in vacuum. Two principal flow mechanisms are identified: viscous (including slip), driven by the difference in total pressure between the inside and outside of the package; and diffusive (diffusion and molecular flow), driven by the difference in partial pressure of helium. Air leaks into the package at a rate comparable to the rate at which helium escapes by diffusive flow. An equation is presented which relates leak rate to leak geometry for a capillary leak, and generalization to other leak shapes is made. It is shown that for a 100−cm3 package, with a maximum allowable leak rate of 5×10−6 atm cm3 sec−1, if pressurized to 1 atm (gauge) with helium, most of the pressurization will be lost within a year. If unpressurized, water vapor will accumulate at nearly 3000 ppm/yr. A more stringent standard is proposed of 10−7 atm cm3 sec−1 for a package of this size when pressurized to 1 atm (gauge), or 10−8 atm cm3 sec−1 if unpressurized. The concept is introduced of the ’’marginal gross leaker,’’ defined as a package with the largest leak rate undetectable by a gross−leak test, taken here to be 10−3 atm cm3 sec−1. It is shown that the maximum allowable length of time after filling and sealing a 100−cm3 package with such a leak rate, before it loses enough helium to erroneously pass a helium leak test is 6 days if the standard is 5×10−6 atm cm3 sec−1, and 9 days if the standard is 10−7 atm cm3 sec−1.