A new uniform process for the solution chlorination of PVC, PE, and natural rubber has been developed with initiation by y-irradiation or radical initiators (azocompounds). The solvent used is dichloromethane instead of the industrially used tetrachloroethane or tetrachloromethane. The reaction is carried out in an autoclave with stirrer at temperatures between 70 and 100 "C and pressures from 4 to 7 bar. As a result of the simultaneous chlorination of the solvent, trichloromethane is formed and only less than 1 wt.-Yo tetrachloromethane. Characterization of the chlorinated polymers by DSC and NMR measurements showed no differences to conventionally chlorinated products.
ZUSAMMENFASSUNG:Es wird ein neuer und einheitlicher ProzeD fur die Liisungschlorierung von PVC, PE und Naturkautschuk mit Initiierung durch y-Strahlung oder radikalische Initiatoren (Azo-Verbindungen) beschrieben. Dichlormethan wird an Stelle der industriellen Liisungsmittel Tetrachlormethan oder -ethan verwendet. Die Reaktion wird in einem Riihrautoklaven bei 70-100°C und 4-7 bar durchgefuhrt. Bei der gleichzeitig stattfindenden Chlorierung des Liisungsmittels entsteht als Hauptprodukt Trichlormethan und weniger als 1 Gew.-Yo Tetrachlormethan. Die Charakterisierung der chlorierten Polymeren durch DSC-und NMR-Messungen ergab keine Unterschiede zu konventiell hergestellten Proben.
High-burnup (<50 MWd/kgU) spent fuel samples of various sizes were exposed to NaCl solutions under static, anaerobic and reducing conditions. The accumulated corrosion time was about 200 days. Gas phase and leach solutions were analyzed. By dissolving mm sized fragments in large volumes of solution, saturation effects were avoided and upper limits for intrinsic dissolution rates of about 5-20 mg/(m2d) were measured. Surface area normalized reaction rates were significantly lower when using fine grained fuel powder (estimated sample surface area to solution volume ratio S/V ca. 3000 m-1), indicating saturation effects. The maximum concentrations of Pu and Am in the tests are close to reported solubility limited concentrations in pure 5m NaCl solutions in the absence of radiolysis effects. The presence of iron effectively reduces the solution concentration of all measured radionuclides (except Cs).
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