Characterization and Qualification of New TATB and Kel-F 800 for LX-17

The project would (1) compare new FK-800 with old Kel-F 800 and KF-800 lots currently available at LLNL, (2) compare and characterize new TATB with old TATB, (3) formulate new FK-800 with wet-aminated TATB and new TATBs in according to HAAP slurry coating procedure into LX-17-2, and (4) evaluate the mechanical and detonation performance characteristics of this insensitive high explosive (IHE). Priorities will be to prove that these new materials can be formulated, pressed to density and machined; and that they contain no impurities which might cause compatibility issues. Since 3M [1, 2], LANL [7], Pantex [8] and AWE [9, 10] are currently evaluating the new FK-800, we plan to share data rather than repeating their work. Our effort is briefly described: Task 1--Evaluation of newer characterization methods to identify structural variations between old and new Kel-F 800 including: Rheological and mechanical properties, copolymer content, degree of crystallinity, and interfacial interactions with TATB. Task 2--Evaluate TATBs using scattering techniques to replace sieving operations called out in the specification [12] for particle size distribution measurements. Use SEM and OM for morphological differences between the old and new explosives. Evaluate the compaction characteristics of new TATB. Task 3--Formulation of new LX-17-2 (with new FK-800 and/or new TATB) Task 4--Evaluate mechanical and performance properties of LX-17-2. At a minimum, compressive strength, dynamic mechanical behavior and a 2-inch cylinder shot should be performed and compared with existing data for LX-17-1

Comparison of New and Legacy TATBs

Two newly synthesized versions of the insensitive high explosive (IHE) 1,3,5-triamino-2,4,6-trinitrobenzenes (TATBs) were compared to two legacy explosives currently used by the Department of Energy. Except for thermal analysis, small scale safety tests could not distinguish between the different synthetic routes. Morphologies of new TATBs were less faceted and more spherical. The particle size distribution of one new material was similar to legacy TATBs, but the other was very fine. Densities and submicron structure of the new TATBs were also significantly different from the legacy explosives. Pressed pellets of the new explosives were less dense. Recrystallization from sulfolane improved the density and thermal stability of both new TATBs, though the morphology of the recrystallized TATB was nearly hexagonal platelets

What Have We Learned From Decades of CRT, And Where Do We Go From Here?

The Chemical Reactivity Test, or CRT, has been the workhorse for determining short-to-medium term compatibility and thermal stability for energetic materials since the mid 1960s. The concept behind the CRT is quite simple. 0.25 g of material is heated in a 17 cm{sup 3} vessel for 22 hours at 80, 100, or 120 C, and the yield of gaseous products are analyzed by gas chromatography to determine its thermal stability. The instrumentation is shown in Figure 1, and the vessel configuration is shown in Figure 2. For compatibility purposes, two materials, normally 0.25 g of each, are analyzed as a mixture. Recently, data from the past 4 decades have been compiled in an Excel spreadsheet and inspected for reliability and internal consistency. The resulting processed data will be added this year to the LLNL HE Reference Guide. Also recently, we have begun to assess the suitability of the CRT to answer new compatibility issues, especially in view of more modern instrumentation now available commercially. One issue that needs to be addressed is the definition of thermal stability and compatibility from the CRT. Prokosch and Garcia (and the associated MIL-STD-1751A) state that the criterion for thermal stability is a gas yield of less than 4 cm{sup 3}/g for a single material for 22 hours at 120 C. The gases from energetic materials of interest ordinarily have an average molecular weight of about 36 g/mol, so this represents decomposition of 0.5-1.0% of the sample. This is a reasonable value, and a relatively unstable energetic material such as PETN has no problem passing. PBX 9404, which yields 1.5 to 2.0 cm{sup 3}/g historically, is used as a periodic check standard. This is interesting in itself, since the nitrocellulose in the 9404 is unstable and probably has partially decomposed over the decades. However, it is not clear whether this aging of the standard would lead to more or less gas, since the initial gaseous degradation products are captured by the DPA stabilizer. Clearly this is an issue that needs reconsideration. The criterion for compatibility is less clearly correct. Although some LLNL reports say that generation of gas in excess of the materials by themselves is an indication of incompatibility, LLNL reports invariably say that materials are compatible if they generate less than 1 cm{sup 3}/g of gas. There are two problems with this criterion. First, it is not stated whether the gas yield is per gram of energetic material or mixture. Second, a material that generates >2 cm{sup 3}/g by itself could never pass the compatibility tests as stated, because even a mixture of equal masses of that material with a completely inert material would generate >1 cm{sup 3}/g of gas per mixture. Furthermore, Prokosch states that a yield equal to or less than from the materials individually means that no reaction has occurred. Clearly, less gas can not be generated unless some type of interaction has occurred. An obvious example would be mixing CaO with a CO{sub 2}-generating energetic material. In the absence of any direct action of the CaO on the energetic material, the CO{sub 2} product would be captured by the CaO, thereby decreasing the gas yield and liberating considerable heat. In a large, closed volume, this could tip the balance to thermal runaway

Heterogeneity in clinical practices for post-cardiotomy extracorporeal life support: A pilot survey from the PELS-1 multicenter study

Background: High-quality evidence for post-cardiotomy extracorporeal life support (PC-ECLS) management is lacking. This study investigated real-world PC-ECLS clinical practices. Methods: This cross-sectional, multi-institutional, international pilot survey explored center organization, anticoagulation management, left ventricular unloading, distal limb perfusion, PC-ECLS monitoring, and transfusion practices. Twenty-nine questions were distributed among 34 hospitals participating in the Post-cardiotomy Extra-Corporeal Life Support Study. Results: Of the 32 centers [16 low-volume (50%); 16 high-volume (50%)] that responded, 16 (50%) had dedicated ECLS specialists. Twenty-six centers (81.3%) reported using additional mechanical circulatory supports. Anticoagulation practices were highly heterogeneous: 24 hospitals (75%) reported using patients bleeding status as a guide, without a specific threshold in 54.2% of cases. Transfusion targets ranged from 7 to 10 g/dL. Most centers used cardiac venting on a case-by-case basis (78.1%) and regular distal limb perfusion (84.4%). Nineteen (54.9%) centers reported dedicated monitoring protocols, including daily echocardiography (87.5%), Swan-Ganz catheterization (40.6%), cerebral near-infrared spectroscopy (53.1%), and multimodal assessment of limb ischemia. Inspection of the circuit (71.9%), oxygenator pressure drop (68.8%), plasma free hemoglobin (75%), d-dimer (59.4%), lactate dehydrogenase (56.3%), and fibrinogen (46.9%) are used to diagnose hemolysis and thrombosis. Conclusions: This study shows remarkable heterogeneity in clinical practices for PC-ECLS management. More standardized protocols and better implementation of the available evidence are recommended

Single and multiple impact ignition of new and aged high explosives in the Steven Impact Test

Threshold impact velocities for ignition of exothermic reaction were determined for several new and aged HMX-based solid high explosives using three types of projectiles in the Steven Test. Multiple impact threshold velocities were found to be approximately 10% lower in damaged charges that did not react in one or more prior impacts. Projectiles with protrusions that concentrate the friction work in a small volume of explosive reduced the threshold velocities by approximately 30%. Flat projectiles required nearly twice as high velocities for ignition as rounded projectiles. Blast overpressure gauges were used for both pristine and damaged charges to quantitatively measure reaction violence. Reactive flow calculations of single and multiple impacts with various projectiles suggest that the ignition rates double in damaged charges

Combining two structured domains for modeling various graph matching problems

Graph pattern matching is a central application in many fields. In various areas, the structure of the pattern can only be approximated and exact matching is then too accurate. We focus here on approximations declared by the user within the pattern (optional nodes and forbidden arcs), covering graph/subgraph mono/isomorphism problems. In this paper, we show how the integration of two domains of computation over countable structures, graphs and maps, can be used for modeling and solving various graph matching problems from the simple graph isomorphism to approximate graph matching. To achieve this, we extend map variables allowing the domain and range to be non-fixed and constrained. We describe how such extended maps are designed then realized on top of finite domain and finite set variables with specific propagators. We show how a single monomorphism constraint is sufficient to model and solve those multiples graph matching problems. Furthermore, our experimental results show that our CP approach is competitive with a state of the art algorithm for subgraph isomorphism.Anglai