Pellet bed reactor for nuclear propelled vehicles: Part 1: Reactor technology

The pellet bed reactor (PBR) for nuclear propelled vehicles is briefly discussed. Much of the information is given in viewgraph form. Viewgraphs include information on the layout for a Mars mission using a PBR nuclear thermal rocket, the rocket reactor layout, the fuel pellet design, materials compatibility, fuel microspheres, microsphere coating, melting points in quasibinary systems, stress analysis of microspheres, safety features, and advantages of the PBR concept

Measurements of the Influence of Acceleration and Temperature of Bodies on their Weight

A brief review of experimental research of the influence of acceleration and temperatures of test mass upon gravitation force, executed between the 1990s and the beginning of 2000 is provided.Results of weighing a rotor of a mechanical gyroscope with a horizontal axis, an anisotropic crystal with the big difference of the speed of longitudinal acoustic waves, measurements of temperature dependence of weight of metal bars of non-magnetic materials, and also measurement of restitution coefficients at quasi-elastic impact of a steel ball about a massive plate are given. A negative temperature dependence of the weight of a brass core was measured. All observably experimental effects, have probably a general physical reason connected with the weight change dependent upon acceleration of a body or at thermal movement of its microparticles.Comment: 7 pages, 6 figures. Presented at the 5-th Symposium on New Frontiers and Future Concepts (STAIF-2008

Natural circulation decay heat removal from an SP-100, 550 kWe power system for a lunar outpost

This research investigated the decay heat removal from the SP-100 reactor core of a 550-kWe power system for a lunar outpost by natural circulation of lithium coolant. A transient model that simulates the decay heat removal loop (DHRL) of the power system was developed and used to assess the system's decay heat removal capability. The effects of the surface area of the decay heat rejection radiator, the dimensions of the decay heat exchanger (DHE) flow duct, the elevation of the DHE, and the diameter of the rise and down pipes in the DHRL on the decay heat removal capability were examined. Also, to determine the applicability of test results at earth gravity to actual system performance on the lunar surface, the effect of the gravity constant (1 g and 1/6 g) on the thermal behavior of the system after shutdown was investigated

An investigation of voids formation mechanisms and their effects on freeze and thaw processes of lithium and lithium fluoride

The mechanisms of void formation during the cooldown and freezing of lithium coolant within the primary loop of SP-100 type systems are investigated. These mechanisms are: (1) homogeneous nucleation; (2) heterogeneous nucleation; (3) normal segregation of helium gas dissolved in liquid lithium; and (4) shrinkage of lithium during freezing. To evaluate the void formation potential due to segregation, a numerical scheme that couples the freezing and mass diffusion processes in both the solid and liquid regions is developed. The results indicated that the formation of He bubbles is unlikely by either homogeneous or heterogeneous nucleation during the cooldown process. However, homogeneous nucleation of He bubbles following the segregation of dissolved He in liquid lithium ahead of the solid-liquid interface is likely to occur. Results also show that total volume of He void is insignificant when compared to that of shrinkage voids. In viewing this, the subsequent research focuses on the effects of shrinkage void forming during freezing of lithium on subsequent thaw processes are investigated using a numerical scheme that is based on a single (solid/liquid) cell approach. The cases of lithium-fluoride are also investigated to show the effect of larger volume shrinkage upon freezing on the freeze and thaw processes. Results show that a void forming at the wall appreciably reduces the solid-liquid interface velocity, during both freeze and thaw, and causes a substantial rise in the wall temperature during thaw. However, in the case of Li, the maximum wall temperature was much lower than the melting temperature of PWC-11, which is used as the structure material in the SP-100 system. Hence, it is included that a formation of hot spots is unlikely during the startup or restart of the SP-100 system

Conceptual studies on the integration of a nuclear reactor system to a manned rover for Mars missions

Multiyear civilian manned missions to explore the surface of Mars are thought by NASA to be possible early in the next century. Expeditions to Mars, as well as permanent bases, are envisioned to require enhanced piloted vehicles to conduct science and exploration activities. Piloted rovers, with 30 kWe user net power (for drilling, sampling and sample analysis, onboard computer and computer instrumentation, vehicle thermal management, and astronaut life support systems) in addition to mobility are being considered. The rover design, for this study, included a four car train type vehicle complete with a hybrid solar photovoltaic/regenerative fuel cell auxiliary power system (APS). This system was designed to power the primary control vehicle. The APS supplies life support power for four astronauts and a limited degree of mobility allowing the primary control vehicle to limp back to either a permanent base or an accent vehicle. The results showed that the APS described above, with a mass of 667 kg, was sufficient to provide live support power and a top speed of five km/h for 6 hours per day. It was also seen that the factors that had the largest effect on the APS mass were the life support power, the number of astronauts, and the PV cell efficiency. The topics covered include: (1) power system options; (2) rover layout and design; (3) parametric analysis of total mass and power requirements for a manned Mars rover; (4) radiation shield design; and (5) energy conversion systems

Patterns of sensitization to food allergens among allergic adults and children following-up in Zagazig university hospitals, Egypt

Background: Data regarding food sensitization and food allergy in developing countries are lacking. We sought to explore the frequency and pattern of sensitization to food allergens among a sample of Egyptian allergic patients. Methods: This cross-sectional study included 1373 allergic patients. They were subjected to thorough history taking, skin prick test, serum specific IgE (sIgE) level. Patients with evidence of sensitization to food were subjected to food elimination followed by an open oral food challenge (OFC) test. Results: Four-hundreds and nineteen patients (30.5%) (76 children and 343 adults) had evidence of sensitization to one or more food allergen. Among children, 41 (52.5%) had urticaria, 31 (39.7%) allergic rhinitis, 13 (16.6%) pollen food allergy syndrome, 16 (20.5%) bronchial asthma, 9 (11.5%) eczema and 7 (9%) had GIT symptoms. Among adults, 152 (44.5%) had allergic rhinitis, 149 (43.6%) urticaria and 57 (16.7%) had GIT symptoms. The most common allergens among children were peanut (31; 39.7%), fish (29; 37%), egg (18; 23%), and strawberry (17; 21.79%) while in adult, they were jalapeno pepper (123; 36%), egg (122; 35.7%), tomato (120; 35.1%), peanut (110; 32.2%), and fish (109; 31.9%). Significant associations were found between sensitization to different types of foods including associations between citrus fruits and mango, and between shrimps and crabs (p<0.001). Out of the sensitized 419 patients, 118 (28.2%) had positive OFC test. Conclusion: A significant proportion of both adults and children with allergic disorders are sensitized to foods. Pepper, peanut, egg, fish, tomato, strawberry are the most common foods to which Egyptian patients are sensitized