Spent fuel cladding corrosion under tuff repository conditions: initial observations

The Westinghouse Hanford Company program is investigating corrosion and stress corrosion cracking of Zircaloy-2 and 4 in two model tuff repository environments using an experimental approach in which the repository environment is reproduced as accurately as possible, including temperature, radiation field, water chemistry and materials associations. Post-experimental sample evaluation utilizes or will utilize sophisticated SEM/STEM, Auger surface analysis/ion milling, and trace element release to detect, locate and measure the effects of corrosion. The experiments themselves are being conducted using actual spent fuel and repository materials at repository conditions. The short experimental time (i.e., one year) is being compensated for by sensitive measuring techniques. Characterization of any corrosion found will be used to understand the mechanisms involved for extrapolation purposes. The initial evaluation of samples from two, six, and 12-month electrochemical corrosion experiments indicated no Zircaloy-4 corrosion at a detection sensitivity of 1 to 2 {mu}m of corrosion per year. To improve the sensitivity of the experiment, baseline conditions (e.g., beginning with a polished metal surface) will need to be established that are expected to make it possible to resolve corrosion on the scale of hundreds of angstroms. Examples are the development of such measurements as film depth determination via Auger surface analysis/ion milling and Zr and {sup 14}C released into the aqueous corrosion environment. Characterization of any corrosion found will be used to understand the mechanisms involved. This will allow extrapolation of results to predict cladding lifetime under repository conditions. 3 refs

An Automatic System for Sampling Processing Waste Water

The composition of waste water from food processing and other plants varies with time. A composite sample composed of smaller samples taken at different times will represent an average condition of these flows. The sampling system described in this paper will gather subsamples over a 24-hour or longer period and keep the composite sample frozen until ready for laboratory analysis. This system will work equally well on pressurized pipelines or ponded water. The parts cost per controller is approximately $80.00 plus the price of a freezer, associated plumbing, and a pump if the water sample is not in a pressurized pipeline

Convex Hull Representations Of Models For Computing Collisions Between Multiple Bodies

In this paper, we consider a collision detection problem that frequently arises in the field of robotics. Given a set of bodies with their initial positions and trajectories, we wish to identify the first collision that occurs between any two bodies. or to determine that none exists. For the case of bodies having linear trajectories, we construct a convex hull representation of the integer programming model of S.Z. Selim and H.A. Almohamad [European Journal of Operational Research 119 (1) (1999) 121-129], and compare the relative effectiveness in solving this problem via the resultant linear program. We also extend this analysis to model a situation in which bodies move along piecewise linear trajectories, possibly rotating at the end of each linear segment. For this case, we again compare an integer programming approach with its linear programming convex hull representation, and exhibit the effectiveness of solving a sequence of mathematical programs for each time segment over a global programming scheme which considers all segments at once. We provide computational results to illustrate the effect of various numbers of bodies present in the collision scenarios, as well as the times at which the first collision occurs

Convex Hull Representations Of Models For Computing Collisions Between Multiple Bodies

In this paper, we consider a collision detection problem that frequently arises in the field of robotics. Given a set of bodies with their initial positions and trajectories, we wish to identify the first collision that occurs between any two bodies. or to determine that none exists. For the case of bodies having linear trajectories, we construct a convex hull representation of the integer programming model of S.Z. Selim and H.A. Almohamad [European Journal of Operational Research 119 (1) (1999) 121-129], and compare the relative effectiveness in solving this problem via the resultant linear program. We also extend this analysis to model a situation in which bodies move along piecewise linear trajectories, possibly rotating at the end of each linear segment. For this case, we again compare an integer programming approach with its linear programming convex hull representation, and exhibit the effectiveness of solving a sequence of mathematical programs for each time segment over a global programming scheme which considers all segments at once. We provide computational results to illustrate the effect of various numbers of bodies present in the collision scenarios, as well as the times at which the first collision occurs

Radar Pulse Interleaving For Multi-Target Tracking

In a multifunction radar, the maximum number of targets that can be managed or tracked is an important performance measure. Interleaving algorithms developed to operate radars exploit the dead-times between the transmitted and the received pulses to allocate new tracking tasks that might involve transmitting or receiving pulses, thus increasing the capacity of the system. The problem of interleaving N targets involves a search among N! possibilities, and suboptimal solutions are usually employed to satisfy the real-time constraints of the radar system. In this paper, we present new tight 0-1 integer programming models for the radar pulse interleaving problem and develop effective solution methods based on Lagrangian relaxation techniques

Radar Pulse Interleaving For Multi-Target Tracking

In a multifunction radar, the maximum number of targets that can be managed or tracked is an important performance measure. Interleaving algorithms developed to operate radars exploit the dead-times between the transmitted and the received pulses to allocate new tracking tasks that might involve transmitting or receiving pulses, thus increasing the capacity of the system. The problem of interleaving N targets involves a search among N! possibilities, and suboptimal solutions are usually employed to satisfy the real-time constraints of the radar system. In this paper, we present new tight 0-1 integer programming models for the radar pulse interleaving problem and develop effective solution methods based on Lagrangian relaxation techniques

Explosive Percolation in the Human Protein Homology Network

We study the explosive character of the percolation transition in a real-world network. We show that the emergence of a spanning cluster in the Human Protein Homology Network (H-PHN) exhibits similar features to an Achlioptas-type process and is markedly different from regular random percolation. The underlying mechanism of this transition can be described by slow-growing clusters that remain isolated until the later stages of the process, when the addition of a small number of links leads to the rapid interconnection of these modules into a giant cluster. Our results indicate that the evolutionary-based process that shapes the topology of the H-PHN through duplication-divergence events may occur in sudden steps, similarly to what is seen in first-order phase transitions.Comment: 13 pages, 6 figure

Forgotten fatalities: British military, mining, and maritime accidents since 1900.

Background Comparative long-term trends in fatal accident rates in the UK’s most hazardous occupations have not been reported. Aims To compare trends in fatal accident rates in six of the most hazardous occupations (the three armed forces, merchant shipping, sea fishing and coal mining) and the general British workforce during peacetime years since 1900. Methods Examinations of annual mortality reports, returns, inquiry files and statistics. The main outcome measure was the fatal accident rate per 100 000 population employed. Results These six occupations accounted for ~40% of all fatal accidents in the British workforce. Fatal accident rates were highest in merchant shipping to 1914 (400–600 per 100 000) and in the Royal Air Force and sea fishing by the early 1920s (around 300 per 100 000). Since the 1950s sea fishing has remained the most hazardous occupation (50–200). Widespread reductions in fatal accident rates for each occupation have been greatest in recent years in the three armed forces and merchant shipping. Compared with the general workforce, relative risks of fatalities have increased in recent decades in all these occupations except shipping. Conclusions All six occupations still have high fatal accident rates. The greatly increased fatalities in sea fishing generally and in the Royal Air Force during its early years reflect, for different reasons, cultures of extreme risk-taking in these two sectors. Reductions in fatality rates in the armed forces over the last 20 years are due largely to decreases in land transport accidents