Improvement of nuclide leaching resistance of paraffin waste form with low density polyethylene.
Low-level liquid borate wastes have been immobilized with paraffin wax using a concentrate waste drying system (CWDS) in Korean nuclear power plants. The possibility for improving chemical durability of paraffin waste form was suggested in this study. A small amount of low density polyethylene (LDPE) was added to increase the leaching resistance of the existing paraffin waste form. The influence of LDPE on the leaching behavior of waste form was investigated by performing leaching test according to ANSI/ANS-16.1 procedure during 325 days. It was observed that the leaching of nuclides immobilized within paraffin waste form made a marked reduction although little content of LDPE was added to waste form. The acceptance criteria of paraffin waste form associated with leachability index (LI) and compressive strength after the leaching test were fully satisfied with the help of LDPE.
Leaching characteristics of paraffin waste forms generated from Korean nuclear power plants.
Leaching tests of paraffin waste forms including boric acid, cobalt, strontium and cesium were performed to investigate the leaching characteristics of paraffin waste forms which had been generated in Korean nuclear power plants. The leaching tests were conducted according to ANSI/ANS-16.1 test procedure and the cumulative fractions leached (CFLs) of boric acid, cobalt, strontium and cesium were obtained. The compressive strength before and after the leaching test was measured for various waste forms with different mixing ratios of boric acid to paraffin. It was observed that boric acid and other nuclides immobilized within paraffin waste forms were congruently released and the leaching rates were influenced by reacted layer depth as the dissolution reaction progressed. A shrinking core model based on the diffusion-controlled dissolution kinetics was developed in order to simulate the test results. The CFLs and the leaching rates were well expressed by the shrinking core model and the cross-sectional view of specimen after the test demonstrated the applicability of this model with the shrinking dissolution front to the leaching analysis of paraffin waste forms.
The Common European Framework of Reference for Languages, the European Language Portfolio, and language learning in higher education
Abstract This article explains the relevance of the Common European Framework of Reference for Languages (CEFR) and the European Language Portfolio (ELP) to language learning in higher education, especially as regards the definition of aims and learning outcomes and the promotion of students' capacity to manage their own learning. After providing some historical background, the article expounds the CEFR's action-oriented approach, explores it conceptualisation of progression in language learning and its implications for language teaching, and suggests how it can be applied to the design, implementation and assessment of language learning programmes in higher education. It then introduces the ELP, explains how it can be used in conjunction with the CEFR to support coherent programme delivery while promoting reflective learning and student autonomy, and concludes by considering the role of self-assessment in the university's assessment framework. The article ends with a cautionary tale.