Remediation of radioiodine using polyamine anion exchange resins

Two weak base anion exchange resins, Lewatit A365 and Purolite MTS9850, have been tested for the removal of aqueous iodide from conditions simulating nuclear waste reprocessing streams. pH variation and relevant co-contaminant addition (nitrate, molybdate and iodine) allowed for assessment of iodide extraction behaviour of each resin. Isotherm experiments were performed and maximum uptake capacities obtained exceed current industrial adsorbents, such as silver-impregnated zeolites. Maximum loading capacities, determined by Dubinin–Radushkevich isotherm, were 761 ± 14 mg g−1 for MTS9850 and 589 ± 15 mg g−1 for A365. Uptake for both resins was significantly suppressed by nitrate and molybdate ions. The presence of dissolved iodine in the raffinate however, was found to increase iodide uptake. This was explained by characterisation of the spent resin surface by infrared and Raman spectroscopy, which determined the presence of triiodide, indicating charge-transfer complex formation on the surface. Dynamic studies assessed the effect of co-contaminants on iodide uptake in a column environment. Data was fitted to three dynamic models, with the Dose-Response model providing the best description of breakthrough. In all cases iodide breakthrough was accelerated, indicating suppression of uptake, but capacity was still significant

Assessment of Night Vision Problems in Patients with Congenital Stationary Night Blindness

Congenital Stationary Night Blindness (CSNB) is a retinal disorder caused by a signal transmission defect between photoreceptors and bipolar cells. CSNB can be subdivided in CSNB2 (rod signal transmission reduced) and CSNB1 (rod signal transmission absent). The present study is the first in which night vision problems are assessed in CSNB patients in a systematic way, with the purpose of improving rehabilitation for these patients. We assessed the night vision problems of 13 CSNB2 patients and 9 CSNB1 patients by means of a questionnaire on low luminance situations. We furthermore investigated their dark adapted visual functions by the Goldmann Weekers dark adaptation curve, a dark adapted static visual field, and a two-dimensional version of the ‘‘Light Lab’’. In the latter test, a digital image of a living room with objects was projected on a screen. While increasing the luminance of the image, we asked the patients to report on detection and recognition of objects. The questionnaire showed that the CSNB2 patients hardly experienced any night vision problems, while all CSNB1 patients experienced some problems although they generally did not describe them as severe. The three scotopic tests showed minimally to moderately decreased dark adapted visual functions in the CSNB2 patients, with differences between patients. In contrast, the dark adapted visual functions of the CSNB1 patients were more severely affected, but showed almost no differences between patients. The results from the ‘‘2D Light Lab’’ showed that all CSNB1 patients were blind at low intensities (equal to starlight), but quickly regained vision at higher intensities (full moonlight). Just above their dark adapted thresholds both CSNB1 and CSNB2 patients had normal visual fields. From the results we conclude that night vision problems in CSNB, in contrast to what the name suggests, are not conspicuous and generally not disabling

Thorium fuel has risks

Thorium is being touted as a potential wonder fuel. Proponents believe that this element could be used in a new generation of nuclear-power plants to produce relatively safe, low-carbon energy with more resistance against potential nuclear-weapons proliferation than uranium. Although thorium offers some benefits, we contend that the public debate is too one-sided: small-scale chemical reprocessing of irradiated thorium can create an isotope of uranium that could be used in nuclear weap-ons, raising proliferation concerns