Showing papers by "Brit Salbu published in 2001"

High energy X-ray microscopy for characterisation of fuel particles

Abstract: For the first time different high energy microanalysis techniques were combined to characterise individual micrometer sized radioactive particles. It was shown that particle characteristics including weathering rates and mobilisation of associated radionuclides are source specific and release-scenario dependent. Fuel particles released during the explosion are characterised by UO 2 -cores with surrounding layer of reduced U with low weathering rates. In contrast, fuel particles released during the subsequent fire show UO 2 -core with surrounding layers of oxidised U 2 O 5 /U 3 O 8 with high weathering rates

Time and Ph-Dependent Detoxification of Aluminum in Mixing Zones between Acid and Non-Acid Rivers

Abstract: Liming detoxifies aluminum in a time-dependent process following the increase in pH. Transformation of Ali into non-reactive or colloidal forms of Al reduces toxicity. To investigate the effects of pH on the detoxification rate, Atlantic salmon (Salmo salar) parr were exposed in four identical channel-tank setups differing only in mixing ratio (30:70, 16:84 or 6:94) between acid (pH 5.6, total Ali 90 µg Al·L−1) and non-acid water (pH 6.3, total Ali 3 µg Al·L−1). Two channels had identical mixing ratio (30:70), but differed with respect to pH (6.0 or >6.4) due to addition of lime. Fish were exposed for 140 hrs. in waters aged from 1 minute and up to 4 hours after mixing. Ali decreased within minutes after mixing at pH 6.4. The detoxification process required hours at pH 6.0. Al accumulation onto fish gills and fish homeostasis was related to Ali. The data suggest that the detoxification process, and therefore the water body affected by ongoing polymerization, was strongly influenced by pH, where a pH target for liming set at pH 6.4 detoxified water faster than a pH target of pH 6.0.

Water Quality Dependent Recovery from Aluminum Stress in Atlantic Salmon Smolt

Abstract: In Norway, a variable pH target (pH 6.2–6.4 during most of the year, but 6.4 during the smoltification period) is used to reduce the cost of liming salmon rivers. Here we test the adequacy of this liming strategy. Atlantic salmon presmolts exposed to sublethal acidic water (pH 5.9, 210 hrs in water aged from 1 minute up to 2 hours after treatment (in a flow through system). More Al was eliminated from the gills when the fish were exposed to pH 6.3 than to pH 5.8 or 6.0, and when water was aged after pH increase. Recovery, defined as return of normal gill morphology, blood homeostasis and establishment of seawater tolerance was achieved within 210 hrs in channels treated with lime to pH 6.3, while a similar recovery was not obvious at lower pH values. Liming to pH 6.3 detoxified Al better than pH 6.1.

Actinides associated with particles

Abstract: Following nuclear events such as nuclear weapons tests and nuclear accidents, particles containing actinides are released into the environment. Furthermore, actinides associated with colloids and particles are present in effluents from nuclear installations during normal operations. Thus, the presence of radioactive particles in releases from nuclear sources occurs more frequently than is usually anticipated. The composition of radionuclides in particles is, however, source-related, while particle characteristics related to microstructures also depend on release conditions and dispersion processes. Thus, source-term information on actinide speciation, e.g. size distribution pattern, crystallographic structures, binding mechanisms and oxidation states, influencing weathering rates and mobilisation of associated radionuclides in ecosystems is essential for impact assessments. For areas contaminated with particles, impact assessments will suffer from unacceptably large uncertainties unless the impact of particles is taken into account. Therefore, advanced analytical micro-techniques applicable to particle characterisation are greatly needed within radioecology. The present work summarises the available literature related to actinide-containing particles released from specific nuclear sources.

Cesium‐134 as a Tracer to Study Particle Transport Processes within a Small Catchment with a Buffer Zone

Abstract: The purpose of the study is to use soil particles labeled with the radioactive tracer cesium-134 ( 134 Cs) as a method for studying soil erosion and sedimentation pattern within a small catchment with buffer zones Cesium is adsorbed to soil particles, and by measuring changes in the 134 Cs activity on the soil surface, erosion, sedimentation, and pathways for particles can be traced A harrowed area was surface-contaminated with 134 CsCl, while the buffer zone was left uncontaminated A grid net in the tilled plot and buffer zone was established for in situ measurements of the 134 Cs activity after major runoff events from October 1993 to May 1996 In addition, 134 Cs activity and suspended solids in runoff were followed during the events At the end of the experiment, the vertical distribution of 134 Cs in soil profiles and uptake of 134 Cs in vegetation within the buffer zone were determined At the end of the experiment, about 54% of the applied tracer remained at the soil surface Surface soil erosion occurred relatively uniformly across the hillslope due to sheet flow Most of the tracer was transported vertically into the soil profile, probably during the first heavy rainfall 3 wk after application when the soil was newly tilled Sedimentation occurred in the upper part of the buffer zone The correlation between suspended particles in runoff and 134 Cs activity was good (R 2 = 076) The study also demonstrates the benefit of utilizing 134 Cs 2+ tracer for investigating transport pathways for contaminated particles within a hillslope system without disturbing the surface soil system