Engineering task plan for five portable exhausters

Exhausters will be employed to ventilate certain single-shell tanks (SSTs) during salt well pumping campaigns. Active ventilation is necessary to reduce the potential flammable gas inventory (LANL 1996a) in the dome space that may accumulate during steady-state conditions or during/after postulated episodic gas release events. The tanks described in this plan support the activities required to fabricate and test three 500 cfm portable exhausters in the 200 W area shops, and to procure, design, fabricate and test two 1000 cfm units. Appropriate Notice of Construction (NOC) radiological and toxic air pollutant permits will be obtained for the portable exhausters. The portable exhauster design media to be employed to support this task was previously developed for the 241-A-101 exhauster. The same design as A101 will be fabricated with only minor improvements to the design based upon operator input/lessons learned. The safety authorization basis for this program effort will follow SAD 36 (LANL 1996b), and each tank will be reviewed against this SAD for changes or updates. The 1000 cfm units will be designed by the selected offsite contractor according to the specification requirements in KHC-S-O490. The offsite units have been specified to utilize as many of the same components as the 500 cfm units to ensure a more cost effective operation and maintenance through the reduction of spare parts and additional procedures

Edge plasma modeling of limiter surfaces in a Tokamak divertor configuration

During the startup phase of a tokamak the plasma configuration may evolve from a limiter to a divertor configuration. Some of the particle and heat flux from the core will be deposited on material surfaces near the separatrix instead of the divertor plates. Examples of such surfaces include the center-post in most tokamaks, baffles near the x-point that create closed divertors, and outboard limiter surfaces. Two-dimensional edge plasma models for tokamak divertor configurations typically give detailed information about the particle and heat fluxes on the divertor plates, but yield little or no information about fluxes on these other localized surfaces near the core plasma. To realistically model the startup phase of a tokamak it is necessary to compute the plasma interaction with both limiter and divertor surfaces. The UEDGE code [l] has been modified to include these limiter surfaces. In this report we present simulation results for an idealized ITER [2] startup configuration with variations in the limiter penetration depth and surface shape

Progress on coupling UEDGE and Monte-Carlo simulation codes

Our objective is to develop an accurate self-consistent model for plasma and neutral sin the edge of tokamak devices such as DIII-D and ITER. The tow-dimensional fluid model in the UEDGE code has been used successfully for simulating a wide range of experimental plasma conditions. However, when the neutral mean free path exceeds the gradient scale length of the background plasma, the validity of the diffusive and inertial fluid models in UEDGE is questionable. In the long mean free path regime, neutrals can be accurately and efficiently described by a Monte Carlo neutrals model. Coupling of the fluid plasma model in UEDGE with a Monte Carlo neutrals model should improve the accuracy of our edge plasma simulations. The results described here used the EIRENE Monte Carlo neutrals code, but since information is passed to and from the UEDGE plasma code via formatted test files, any similar neutrals code such as DEGAS2 or NIMBUS could, in principle, be used

On the homomorphism order of labeled posets

Partially ordered sets labeled with k labels (k-posets) and their homomorphisms are examined. We give a representation of directed graphs by k-posets; this provides a new proof of the universality of the homomorphism order of k-posets. This universal order is a distributive lattice. We investigate some other properties, namely the infinite distributivity, the computation of infinite suprema and infima, and the complexity of certain decision problems involving the homomorphism order of k-posets. Sublattices are also examined.Comment: 14 page

Modeling and Reasoning over Distributed Systems using Aspect-Oriented Graph Grammars

Aspect-orientation is a relatively new paradigm that introduces abstractions to modularize the implementation of system-wide policies. It is based on a composition operation, called aspect weaving, that implicitly modifies a base system by performing related changes within the system modules. Aspect-oriented graph grammars (AOGG) extend the classic graph grammar formalism by defining aspects as sets of rule-based modifications over a base graph grammar. Despite the advantages of aspect-oriented concepts regarding modularity, the implicit nature of the aspect weaving operation may also introduce issues when reasoning about the system behavior. Since in AOGGs aspect weaving is characterized by means of rule-based rewriting, we can overcome these problems by using known analysis techniques from the graph transformation literature to study aspect composition. In this paper, we present a case study of a distributed client-server system with global policies, modeled as an aspect-oriented graph grammar, and discuss how to use the AGG tool to identify potential conflicts in aspect weaving

Culture and change blindness

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91933/1/culture_change_blindness.pd

Models and applications of the UEDGE code

The transport of particles and energy from the core of a tokamak to nearby material surfaces is an important problem for understanding present experiments and for designing reactor-grade devices. A number of fluid transport codes have been developed to model the plasma in the edge and scrape-off layer (SOL) regions. This report will focus on recent model improvements and illustrative results from the UEDGE code. Some geometric and mesh considerations are introduced, followed by a general description of the plasma and neutral fluid models. A few comments on computational issues are given and then two important applications are illustrated concerning benchmarking and the ITER radiative divertor. Finally, we report on some recent work to improve the models in UEDGE by coupling to a Monte Carlo neutrals code and by utilizing an adaptive grid