Process reactor elements

The maximum heat flux achievable with nucleate boiling is known as the critical heat flux. In a system where the surface temperature is not self-limiting, such as a nuclear reactor fuel element, operation above the critical flux will result in a rapid increase in the surface temperature, and in the extreme situation the surface will melt. This phenomenon is known as burn-out . The heating media used for process plant are normally self-limiting for example, with steam the surface temperature can never exceed the saturation temperature. Care must be taken in the design of electrically heated vaporisers to ensure that the critical flux can never be exceeded. 

C. D. Hylton, R. E. Leuze, W. H. Lewis and W. R. Whitson ORNL Metal Recovery Plant Processing Clementine Reactor Fuel Elements. Terminal Report. Report ORNL-1941 (7. Sept. 1955) [Deklassifiziert mit Loschungen als ORNL-1941 (Del.)]. 

Sherwin-Williams has developed such a polymer process control system. The methodology used to accommodate the contrasting requirements has two key elements. First, the software is based on a simple architecture that places the definition of changing reactor hardware elements and characteristics in easily modified configuration files (5). Second, the language uses a small number of basic commands to describe formulations and reactor control. Complex operations are described by reference to commands tables (macros) built using several basic commands or other macros. 

Removal of H2S and acid gases from the hydrogenation reactor process stream and also from the raw gases obtained from gasification of the heavy residual is required. The incentive for H2S removal and recovery of elemental sulfur in this case is environmental. 

NS flooding in the process of SNF unloading Activity escape from fuel of unsealed assemblies mid as a result of reactor s elements, metal mid water shielding tank, and pressure hull corrosion... 

Metering of the individual reactor feed gas constituents to generate the desired feed gas composition actually occurs on dedicated feed gas mixing boards located within the AIMS chassis. The process elements contained on this board are shown within the dashed sub-region in Fig. 12.6. 

The sea bed functions as a giant anaerobic reactor where element cycles are coupled in a way that differs fundamentally from the cycles in the oxic ocean. The microbiological and geochemical processes of sulfur transformation thereby play key... 

The reprocessing of used reactor fuel elements involves solvent extraction processes with organic solvents. In these processes the solvents are subjected to high radiation fields with subsequent decomposition of the organic solvent. The design of chemical reprocessing systems must take into account any interference by the radiolytic products (Ch. 20). 

Once the radioactive fission products are isolated by one of the separation processes, the major problem in the nuclear chemical industry must be faced since radioactivity cannot be immediately destroyed (see Fig. 10-7c for curie level of fission-product isotopes versus elapsed time after removal from the neutron source). This source of radiation energy can be employed in the food-processing industries for sterilization and in the chemical industries for such processes as hydrogenation, chlorination, isomerization, and polymerization. Design of radiation facilities to economically employ spent reactor fuel elements, composite or individually isolated fission products such as cesium 137, is one of the problems facing the design engineer in the nuclear field. 

N Reactor fuel elements were discharged to the spent fuel basin via a large tunnel-like canal located at the outlet face of the N Reactor. During this transfer process, a large quantity of reactor primary-cooling-circuit water, containing considerable amounts of suspended and soluble metals and metal oxides was added to the spent fuel storage basin. Excess basin water was routed to the 116-N-l and/or 116-N-3 cribs via the basin overflow weirs and a... 

High-level waste from the isolation of plutonium-239 contains massive amounts of plutonium-238 formed by various nuclear reactions in reactor fuel elements. A rough estimate indicates that as of 1985 there may be as much as 2 tons of plutonium-238 mixed with heavier plutonium isotopes in stored spent fuel elements and process residues accumulated in the USA and by the European Economic Community [5]. 

The case offered is concerned with a facility to store reactor fuel elements pending further processing. Its safe operation requires that fuel elements are cooled. The primary coolant is pressurised CO . This is provided to the facility from a redundant supply via some 13 valves. The valves are used for filling various parts of the facility, contfolling pressures and blowing down. 

Neutron Activation Analysis Few samples of interest are naturally radioactive. For many elements, however, radioactivity may be induced by irradiating the sample with neutrons in a process called neutron activation analysis (NAA). The radioactive element formed by neutron activation decays to a stable isotope by emitting gamma rays and, if necessary, other nuclear particles. The rate of gamma-ray emission is proportional to the analyte s initial concentration in the sample. For example, when a sample containing nonradioactive 13AI is placed in a nuclear reactor and irradiated with neutrons, the following nuclear reaction results. 

One of the most significant sources of change in isotope ratios is caused by the small mass differences between isotopes and their effects on the physical properties of elements and compounds. For example, ordinary water (mostly Ej O) has a lower density, lower boiling point, and higher vapor pressure than does heavy water (mostly H2 0). Other major changes can occur through exchange processes. Such physical and kinetic differences lead to natural local fractionation of isotopes. Artificial fractionation (enrichment or depletion) of uranium isotopes is the basis for construction of atomic bombs, nuclear power reactors, and depleted uranium weapons. 

Nuclear Applications. Powder metallurgy is used in the fabrication of fuel elements as well as control, shielding, moderator, and other components of nuclear-power reactors (63) (see Nuclearreactors). The materials for fuel, moderator, and control parts of a reactor are thermodynamically unstable if heated to melting temperatures. These same materials are stable under P/M process conditions. It is possible, for example, to incorporate uranium or ceramic compounds in a metallic matrix, or to produce parts that are similar in the size and shape desired without effecting drastic changes in either the stmcture or surface conditions. OnlyHttle post-sintering treatment is necessary. 

Manufacture. Phosphoms sulfides are manufactured commercially by direct reaction of the elements. Elemental phosphoms and sulfur are measured into a reaction vessel containing a heel of molten phosphoms sulfide. The reaction can be batch or continuous. The ratio of phosphoms to sulfur in the feed determines which phosphoms sulfur compound (Table 5) is formed. The reaction temperature can be the boiling point or lower. For the boiling reactor (27,28), the phosphoms sulfide product is first purified by distillation and then condensed to a Hquid. Alternatively, the Hquid product can be formed directly in a nondistiUed process (29—31), which may involve a subsequent distillation step (30), and in which the phosphoms is often cleaned up prior to use (30—32). For either process, the Hquid phosphoms sulfide product is soHdified, and usually sized to form a commercial material. 

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