Gun Liner Emplacement Using Elastomeric Materials

The development of a process to emplace a refractory metal liner inside a gun tube is described. The process consists of filling the liner with an elastomeric material and then slipping this arrangement into the gun tube whose inner diameter is close to the outer diameter of the liner. The ends of the liner are plugged with plastic disks and pressure is applied to the elastomeric material by a load frame. This pressure can produce a residual internal stress within the steel gun tube that produces a frictional bond between the liner and gun tube. Initial efforts have resulted in bond strengths over 3 ksi (21 MPa). In addition, by tailoring the degree of lubrication between the elastomeric material and the liner, a graded autofrettage can be produced in the steel gun tube.

An Ultrasonic Phased Array Evaluation of Intergranular Stress Corrosion Crack (IGSCC) Detection in Austenitic Stainless Steel Piping Welds

Research is being conducted for the U.S. Nuclear Regulatory Commission at the Pacific Northwest National Laboratory to assess the effectiveness and reliability of advanced nondestructive examination (NDE) methods for the inspection of light water reactor (LWR) components and challenging material/component configurations. This study assessed the effectiveness of far-side inspections on wrought stainless steel piping with austenitic welds, as found in thin-walled, boiling water reactor (BWR) component configurations, for the detection and characterization of intergranular stress corrosion cracks (IGSCC).

Failure Criterion for Varying Strain Rates

Strain rate affects the behaviors of engineering structural materials, such as metals and composites, in terms of their stiffness and strength. In particular, yield and failure strengths and strains depend on the strain rate applied to the materials. When a structural material is subjected to a typical dynamic loading, the material usually undergoes various strain rate loading conditions. Then, the main question is whether the material is going to fail or not. To the authors’ best knowledge, there has been no failure criterion proposed for a varying strain rate loading condition. This paper presents a failure criterion under non-uniform strain rate conditions. Experiments were also conducted to support the proposed failure criterion using aluminum alloy AA3003-H14. This study also investigated the failure envelopes in terms of strain rates and the normalized failure strengths. Furthermore, evaluations of various stressstrain relations under different strain rate loading conditions were also undertaken.

Life Assessment of Full-Scale EDS Vessel Under Impulsive Loadings

The Explosive Destruction System (EDS) was developed by Sandia National Laboratories for the US Army Product Manager for Non-Stockpile Chemical Materiel (PMNSCM) to destroy recovered, explosively configured, chemical munitions. PMNSCM currently has five EDS units that have processed over 1,400 items. The system uses linear and conical shaped charges to open munitions and attack the burster followed by chemical treatment of the agent. The main component of the EDS is a stainless steel, cylindrical vessel, which contains the explosion and the subsequent chemical treatment. Extensive modeling and testing have been used to design and qualify the vessel for different applications and conditions. The high explosive (HE) pressure histories and subsequent vessel response (strain histories) are modeled using the analysis codes CTH and LS-DYNA, respectively. Using the model results, a load rating for the EDS is determined based on design guidance provided in the ASME Code, Sect. VIII, Div. 3, Code Case No. 2564. One of the goals is to assess and understand the vessel’s capacity in containing a wide variety of detonation sequences at various load levels. Of particular interest are to know the total number of detonation events at the rated load that can be processed inside each vessel, and a maximum load (such as that arising from an upset condition) that can be contained without causing catastrophic failure of the vessel. This paper will discuss application of Code Case 2564 to the stainless steel EDS vessels, including a fatigue analysis using a J-R curve, vessel response to extreme upset loads, and the effects of strain hardening from successive events.

Parametric Study on Determining Optimal Eddy Current Testing Method for Inspection of Steam Generator Tubes in SMART Plant

The SMART (System-integrated Modular Advanced ReacTor) is small sized integral type pressurized water reactor designed by KAERI (Korea Atomic Energy Research Institute), Korea. But, shape of steam generator (SG) in SMART plant differs from those in operated nuclear power plants (NPPs). Especially, SG tubes in SAMRT plant is helical type with around 600 mm of innermost diameter and thickness of 2.5 mm which is thicker than general NPPs one. For providing integrity of SG tube in SMART plant, new types of ECT method are needed because eddy current testing (ECT) is one of widely adopted method for inspection of SG tubes in NPPs. Therefore, in this study, we investigate optimal conditions or parameters for detecting and evaluating of flaws in the SG tubes in SMART plant by simulation of ECT signals with various testing condition or parameter such as frequency, coil gap and etc. From the simulated ECT signals optimal eddy current test condition or parameters are proposed.

Ultrasound Imaging Using Multilayer Synthetic Aperture Focusing

Synthetic aperture focusing techniques (SAFT) have already been studied within several fields of non-destructive testing, but so far only with a single, relatively homogenous medium. In this article, we modify the original time-domain SAFT in order to image the interior of a multilayer structure. Standard focusing techniques assume that the wave velocity is constant within the volume to be imaged. The concept of the root-mean-square (RMS) velocity is used here to modify the classical delay-and-sum algorithm to handle layers with differing wave velocities. A scheme for iteratively using this to estimate the interfaces between the layers is also presented. The proposed method is demonstrated on ultrasonic B-scans of two test objects immersed in water, and it is shown that the increased lateral resolution and signal-to-noise ratio of standard SAFT is extended to the multilayer case. The increased resolution also makes it possible to accurately estimate the interfaces between consecutive layers, as long as the preceding interfaces are relatively smooth.

Effects of Residual Stresses on the High Cycle Fatigue Behavior of Ti-6Al-4V

Axial force-controlled fatigue tests are conducted at various stress ratios (R) on Ti-6Al-4V specimens prepared by two different manufacturing techniques (hard turning plus polishing with and without vacuum stress relieve anneal carried out after polishing). Residual stress is measured by using X-ray diffraction. Results indicate that the surface compressive residual stress lead to an increase of fatigue limit at a given life and stress ratio. This effect decreases with increasing stress ratio R. At R = 0.6, the effect of surface residual stress on fatigue limit fades away. In addition, the location of crack initiation shifts from surface to interior when the stress ratio changes from −1 to 0.6.

Research Activities in the European Union on Ageing Management for Long Term Operation of Nuclear Power Plants

The energy supply of the future in the EU will be a mix of renewable, fossil and nuclear. There are 145 nuclear power reactors in operation in 15 out of the 27 EU countries, with installed power ∼132 GWe. The age distribution of current nuclear power plants in EU is such that in 2010 most of them will have passed 20-years and approximately 25% of them 30 years of age. The decrease of energy supply from nuclear generated electricity can not always be compensated in a reliable and economical way within a short time span. For this situation utilities may be keen to upgrade the reactor output and /or to ask their regulatory bodies for longer term operation. Under the research financed in the Euratom part of the Research Directorate (RTD) of the European Commission several projects explicitly address the safe long term operation of nuclear power plants (NULIFE, LONGLIFE) and the topics proposed in the 2010 call explicitly address issues concerning component ageing, in particular non metallic components, i.e. instrumentation and cables (I&C) and concrete ageing. This paper presents an overview of the plans for long term operation (LTO) of nuclear power plants in the EU. Special emphasis is given on research activities on component ageing management and long term operation issues related to safety.

Analysis of the Dynamic Response of a Controlled Detonation Chamber

Detonation chambers (either mobile or fixed) are used worldwide for a wide range of applications. At present, a 1/7 scale model of a 1 ton detonation chamber is available for extended testing in Belgium. The chamber is a single wall cylindrical vessel with semi-elliptical ends. Each time an explosive charge is fired in the vessel, that vessel is submitted to a number of deformation cycles. A series of strain gages measure the deformation of the vessel walls. Experimental peak strains and vibration frequency can be compared to predicted values based on simple formulas. Measured values are reasonably close to the estimated values. The influence of the shape of the charge is studied. The shape has an important influence on the chamber response. For a fixed charge mass, a spherical charge causes less deformation than a cylindrical charge and is therefore advantageous from a fatigue point of view.

The Application of Harmonic Finite Elements in the Seismic Response Spectrum Analysis of a Skirt Supported Vessel

This paper describes the finite element considerations employed in a seismic response spectrum analysis of a skirt supported, liquid containing pressure vessel. Like many axisymmetric cylindrical vessels, the gross seismic response to an input response spectrum can be categorized by a simplified lump mass model that includes both the mass of the vessel proper in combination with the associated mass of multiple fluid levels. This simplified response may be utilized to determine the initial sizing of the supporting configuration, such as a skirt, but lacks the ability to properly address the fluid-structure interaction that creates sloshing loads on the vessel walls. The most obvious method to address the fluid-structure interaction when considering the finite element method is to build a three-dimensional model of the vessel proper, including, but not limited to the shell courses, the top and bottom heads (for a vertical vessel), and the support skirt. The inclusion of the fluid effects may now be incorporated with a “contained fluid” finite element, however, for vessels of any significant volume, the number of finite elements can easily exceed 100,000 and the number of degrees of freedom can sore from as few as 300,000 to as many as 500,000 or more. While these types of finite element analysis problems can be solved with today’s computer hardware and software, it is not desirable in any analysis to have that volume of information that has to be reviewed and approved in a highly regulated nuclear QA environment (if at all possible). With these items in mind, the methodology described in this paper seeks to minimize the number of degrees of freedom associated with a response spectrum analysis of a liquid filled, skirt supported vertical pressure vessel. The input response spectra are almost always provided in Cartesian coordinates, while many, if not most liquid containing pressure vessels are almost always axisymmetric in geometry without having benefit of being subjected to an axisymmetric load (acceleration in this case) due to the specified seismic event. The use of harmonic finite elements for both the vessel structure and the contained fluid medium permit the efficiencies associated with an axisymmetric geometry to be leveraged when the seismic response spectrum is formulated in terms of a Fourier series and combined to regain the effects of the two orthogonal, horizontally applied accelerations as a function of frequency. The end result as discussed and shown in this paper is a finite element model that permits a dense mesh of both the fluid and the structure, while economizing on the number of simultaneous equations required to be solved by the chosen finite element analysis.