QUARTERLY PROGRESS REPORT JANUARY, FEBRUARY, MARCH, 1968 REACTOR FUELS AND MATERIALS DEVELOPMENT PROGRAMS FOR FUELS AND MATERIALS BRANCH OF USAEC DIVISION OF REACTOR DEVELOPMENT AND TECHNOLOGY

Progress is reported in these areas: nuclear graphite; fuel development for gas-cooled reactors; HTGR graphite studies; nuclear ceramics; fast-reactor nitrides research; non-destructive testing; metallic fuels; basic swelling studies; ATR gas and water loop operation and maintenance; reactor fuels and materials; fast reactor dosimetry and damage analysis; and irradiation damage to reactor metals

Laser-Based Ultrasound for the Inspection of Gas Pipelines

Ultrasonics has proven to be an effective method for detecting a variety of defects in gas transmission pipes including cracks, wall thinning and corrosion pits. The use of Lamb waves for the detection of defects and in situ process monitoring applications has been successfully pursued for many years [1–6]. The use of a laser-based ultrasound (LBU) inspection technique to detecti defects is attractive because of the potential for rapid inspection of large areas and because it is noncontact with large standoff distances. Owing to its noncontacting and remote nature, the LBU technique is being investigated as an alternative technology to piezoelectric transducers or electromagnetic acoustic transducers (EMATs) for the rapid nondestructive inspection of pipelines. Currently, the preferred methods for introducing ultrasonic waves into the pipe are by using a piezoelectric transducer in a liquid-filled wheel or an EMAT. In field use, the wheel or the EMAT is attached to a moveable platform (known as a pig), which travels along the length of the transmission line. The wheel must maintain contact with the pipe wall during the inspection. Although the EMAT is a noncontact sensor, it must be operated close to the pipe’s surface. The contact and near-contact requirements can result in a loss of data when pipe irregularities such as dents or joints between sections cause the wheel or the EMAT to lift off from the surface of the pipe. The liquid-filled wheel uses longitudinal waves that propagate into the wall of the pipe. For a complete inspection of the pipe’s circumference, many wheels must be used. The EMAT generates a Lamb wave in the wall of the pipe that can be directed either circumferentially or axially along the pipe. Although the LBU technique also uses Lamb waves, unlike EMAT systems, the detection sensitivity of the LBU system does not decrease with increased separation from the part. However, a potential difficulty for LBU techniques is that Lamb waves are a family of guided waves that exist in plate-like structures, and a large number of modes of vibration may coexist in a given plate thickness. A laser that has been focused to a spot or line represents a broadband Lamb wave source in both the temporal and spatial frequency domains, which leads to the simultaneous excitation of many modes. Consequently, LBU techniques for generating Lamb waves have generally been pursued only when the lowest order symmetric or asymmetric mode was needed, probably because these modes are generated and detected with the greatest efficiency and thus offer a de facto mode selection mechanism since these modes dominate the others that may be present. We previously demonstrated [7] a mechanism for efficiently generating and selecting a single Lamb wave mode using simulated arrays. In this paper, we describe the implementation of a laser array for the generation of Lamb waves. We also present some preliminary results of a study of the characteristics of Lamb wave modes to identify suitable modes for detecting defects in pipelines. The features that are important include the generation and detection efficiency of the Lamb wave modes, the mode’s energy distribution, and the velocity dispersion of the waves

Wave interaction with defects in pressurised composite structures

There exists a great variety of structural failure modes which must be frequently inspected to ensure continuous structural integrity of composite structures. This work presents a Finite Element (FE) based method for calculating wave interaction with damage within structures of arbitrary layering and geometric complexity. The principal novelty is the investigation of pre-stress effect on wave propagation and scattering in layered structures. A Wave Finite Element (WFE) method, which combines FE analysis with periodic structure theory (PST), is used to predict the wave propagation properties along periodic waveguides of the structural system. This is then coupled to the full FE model of a coupling joint within which structural damage is modelled, in order to quantify wave interaction coeffcients through the joint. Pre-stress impact is quantified by comparison of results under pressurised and non-pressurised scenarios. The results show that including these pressurisation effects in calculations is essential. This is of specific relevance to aircraft structures being intensely pressurised while on air. Numerical case studies are exhibited for different forms of damage type. The exhibited results are validated against available analytical and experimental results

Hanford Works Report HW-43031

Ultrasonic equipment has been developed for nondestructive testing of Hanford fuel elements. The ultrasonic method has replaced the Frost Test for bonding layer inspection in the Hanford canning line, and provides more accurate and reliable results at lower cost. The method has also been adopted to the testing of new fuel elements for which no other method is available

Tof-vis, software for interactive exploration of time-of-flight data.

TOF-VIS, Software for Interactive Exploration of Time-of-Flight Data TOF-VIS is a fast, highly interactive program for examining time-of-flight neutron scattering data. All spectra from an experiment are displayed simultaneously as an image. The data can be displayed in terms of time-of-flight, energy, wave-vector, or lattice spacing. TOF-VIS has beer? used for examining data from IPNS and ISIS, and has been useful for diagnosing problems with instruments and detectors as well as for making a quick evaluation of the quality of the data. Hard copy output to a variety of devices using routines built on PGPLOT is now available. TOF-VIS is portable to VMS and UNIX, and is currently implemented primarily using object-based methods in This report was prepared as an account of work sponsored by an agency of the US Government. Neither the US Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the US Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the US Government or any agency thereof. The TOF-VIS main or ''image'' view shows the set of spectra as an image in which rows of the image correspond to spectra from different detectors ordered by detector number or by detector as graphs in the other views. The values of the time, energy, wave-vector, lattice spacing and ''Q'' split into three levels: an interface layer, a translation layer, and an application layer. The interface The heart of the application layer is the concept of a spectrum ''object''. Each spectrum is an instance of a spectrum object