Boiling Water Reactor Observations

Elbows at Boiling Water Reactors on February 6, 1997 [5.21] which notes that the riser elbow cracking observed at both BWRs occurred in the weld heat-affected zone of the riser elbow to thermal sleeve attachment weld appears to be characteristic of IGSCC. 

The extensive IGSCC (intergranular stress corrosion cracking) of sensitized Type 304 SS observed in Boiling Water Reactor (BWR) primary coolant circuits over the past three decades has prompted examination of the stress corrosion cracking of possible stmctural... 

Polyterpene resins are related to the oldest reported polymerization, as they were first observed in 1789 by Bishop Watson by treatment of turpentine with sulfuric acid [92]. Commercial polyterpene resins are synthesized by cationic polymerization of /3- and a-pinenes extracted from turpentine, of rf,/-limonene (dipentene) derived from kraft-paper manufacture, and of d-limonene extracted from citrus peels as a by-product of juice industry [1,80,82,93]. The batch or continuous processes are similar for the three monomers. The solution polymerization is generally performed in mixed xylenes or high boiling aromatic solvent, at 30-55° C, with AlCl3-adventi-tious water initiation. The purified feedstream (72-95% purity, depending on monomer) is mixed in the reactor with solvent and powdered A1C13 (2—4 wt% with respect to monomer), and then stirred for 30-60 min. After completion of the reaction, the catalyst is deactivated by hydrolysis, and evolved HC1 is eliminated by alkaline aqueous washes. The organic solution is then dried, and the solvent is separated from the resin by distillation. 

The feed consists of 3 to 7% HNO3, 59 to 67%H2S04, and 28 to 37% water. Sulfuric acid is necessary to adsorb the water and energy generated by the heat of reaction. The plant, which produces 15,000 lb nitrobenzeneUi, requires one or two operators per shift together with a plant supervisor and part-time foreman. This exothermic reaction is carried out essentially adiabatically, so that the temperature of the feed stream rises from 90°C to 135°C at the exit. One observes that the nitrobenzene stream from the separator is used to heat the benzene feed. However, care must be taken so that the temperature never exceeds 190°C, where secondary reactions could result in an explosion. One of the safety precautions is the installation of rehef valves that will rupture before the temperature approaches 190°C, thereby allowing a boil-off of water and benzene, which would drop the reactor temperature. 

Figure 3.7 shows the results obtained in the batch process at 87 °C according to literature procedures [50]. A mixture of water and p-dioxane as a solvent system was chosen to allow for homogenous reaction conditions using a Pd(0) catalyst Reaction times of 8 and Ih were observed for bromo- and chlorobenzaldehyde, respectively, until the (nonisolated) GC yield reached about 90%. The maximum reaction temperature was limited in these experiments by the boiling point of the mixture at ambient pressure. The same reaction was performed in the MMRS, which was equipped with a backpressure controller, so that the reactor could be operated at elevated temperatures and pressures. Conditions could be achieved with temperatures above the boiling point of the mixture under ambient pressure, which are often referred to as superheated conditions. The setup allowed quick variation... 

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