Traditional gamma safeguards measurements have usually been performed using a segmented gamma scanning (SGS) system. The accuracy of this technique relies on the assumption that the sample matrix and the activity are both uniform for a segment. Waste barrels are often highly heterogeneous, span a wide range of composition and matrix type. The primary sources of error are all directly or indirectly related to a non-uniform measurement response associated with unknown radioactive source spatial distribution and heterogeneity of the matrix. These errors can be significantly reduced by some imaging techniques that measure exact spatial locations of sources and attenuation maps. In this paper we describe a joint R&D effort between the Lawrence Livermore National Laboratory (LLNL) and the Institute of Nuclear Techniques (INT) of the Technical University, Budapest, to compare results obtained by two different gamma-ray nondestructive assay (NDA) systems used for imaging waste barrels. The basic principles are the same, but the approaches are different. Key factors to judge the adequacy of a method are the detection limit and the accuracy. Test drums representing waste to be measured are used to determine basic parameters of these techniques.

The performance of the NIF baseline design has been modeled in two transverse dimensions using the Fourier optics code PROP92 and the nonlinear harmonic conversion code THG4DO1. The results obtained are in good agreement with those of the ID versions of these codes which were used during the design optimization, yielding good confidence that a near- optimal design has been chosen. We project that this design is able to fulfill NIF`s three major mission specifications without component damage. Further modeling, including the effects of air- path turbulence, quasi-static thermal deformations, SSD, and sensitivity to misalignment and component tolerances is ongoing.

Existing Housing - Much of the older multifamily housing stock in the United States includes units in structures with uninsulated masonry walls. Included in this stock are two- and three-story walk-up apartments, larger apartment complexes, and public housing (both high- rise and townhouse). This older multifamily housing has seen years of heavy use that may have left the plaster wall marred or damaged. Long- term building settlement or movement may have cracked the plaster, sometimes severely. Moisture from invented kitchens and baths may have caused condensation on uninsulated exterior walls. At best this condensation has left stains on the paint or wallpaper. At worst it has supported mold and mildew growth, fouling the air and creating unhealthy living conditions. Deteriorating plaster and flaking paint also result from wet walls. The presence of flaking, lead-based paint in older (pre-1978) housing is a major public health concern. Children can suffer permanent mental handicaps and psychological disorders if they are subjected to elevated levels of lead, while adults can suffer hypertension and other maladies. Studies have found that, in some urban communities with older housing stocks, over 35% of children tested have elevated blood lead levels (Hastings, et al.: 1997). Nationally, nearly 22% …

The Beamlet laser is a single-aperture prototype for the National Ignition Facility (NIF). We have recently installed and activated a 55 m{sup 3} vacuum vessel and associated diagnostic package at the output of the Beamlet that we are using to characterize target plane irradiance at high power. Measurements obtained both with and without a kinoform diffractive optic are reported. Dependences on critical laser parameters including output power, spatial filtering, and wavefront correction are discussed and compared with simulations.

Colloidal suspensions of Si0{sub 2} in ethanol prepared by the ammonia catalyzed hydrolysis of tetraethyl silicate (TEOS) in ethanol have been routinely used for over 10 years to prepare antireflective (AR) coatings on the fused silica transmissive optical components of high power fusion lasers. Very high purity coatings are required to avoid laser damage and these are obtained when the TEOS is fractionally distilled under N{sub 2} prior to use. Recently we found that products from aerial oxidation of distilled TEOS, had a significant effect on the particle size of our coating suspensions to the detriment of the optical performance. We require particle sizes less than 20 nm to avoid light loss due to scatter and contaminated TEOS gave suspensions with much higher particle sizes. Oxidation products were identified by GC mass spectroscopy and included acetaldehyde, acetic acid, silicon acetates and reaction products of these compounds with ethanol. Acetic acid and silicon acetates were found to be the major cause of large particle formation. These could be removed by careful redistillation preferably in the presence of a small quantity of magnesium ethoxide. Storage in sealed containers over N{sub 2} avoided further problems.

This paper will discuss some basic technical information resources that would be helpful to the novice nuclear criticality safety specialist. These include bibliographic and benchmark compilations, handbooks, and online resources. The specialist should also be familiar with benchmark quality experimental data needed for code validation. This paper will also discuss the critical experiment data obtained in the 1950s and 1960s at the Lawrence Livermore National Laboratory.

Optical component specifications for the high-average-power lasers and transport system used in the Atomic Vapor Laser Isotope Separation (AVLIS) plant must address demanding system performance requirements. The need for high performance optics has to be balanced against the practical desire to reduce the supply risks of cost and schedule. This is addressed in optical system design, careful planning with the optical industry, demonstration of plant quality parts, qualification of optical suppliers and processes, comprehensive procedures for evaluation and test, and a plan for corrective action.

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UNiGe crystallizing in the orthorhombic TiNiSi-type of structure orders magnetically below T{sub N}= 50 K with an additional magnetic phase transition at 42 K. Both structures (below 42 K commensurate antiferromagnetic, between 42 K and T{sub N} incommensurate) are non- collinear with significant a-axis component ({mu}{sub x} = 0.35 {mu}{sub B}U at 20 K). The magnetic properties are highly anisotropic both in the ordered and the paramagnetic state. There are two metamagnetic transitions both with the field applied along the b- and the c-axis. While the magnetic structure above the second metamagnetic transition is forced ferromagnetic for both field orientations, for the field applied along the a-axis the magnetization curve at 4.2 K is linear up to 38 T and no change in magnetic structure is observed.