Preliminary Safety Criteria for Organic Watch List Tanks at the Hanford Site

Condensed-phase, rapid reactions of organic salts with nitrates/nitrites in Hanford High Level Radioactive Waste single-shell tanks could lead to structural failure of the tanks resulting in significant releases of radionuclides and toxic materials. This report establishes appropriate preliminary safety criteria to ensure that tank wastes will be maintained safe. These criteria show that if actual dry wastes contain less than 1.2 MJ/kg of reactants reaction energy or less 4.5 wt % of total organic carbon, then the waste will be safe and will not propagate if ignited. Waste moisture helps to retard reactions; when waste moisture exceeds 20 wt %, rapid reactions are prevented, regardless of organic carbon concentrations. Aging and degradation of waste materials has been considered to predict the types and amounts to organic compounds present in the waste. Using measurements of 3 waste phases (liquid, salt cake, and sludge) obtained from tank waste samples analyzed in the laboratory, analysis of variance (ANOVA) models were used to estimate waste states for unmeasured tanks. The preliminary safety criteria are based upon calorimetry and propagation testing of likely organic compounds which represent actual tank wastes. These included sodium salts of citrate, formate, acetate and hydroxyethylethylenediaminetricetate (HEDTA). Hot cell tests of actual tank wastes are planned for the future to confirm propagation tests performed in the laboratory. The effects of draining liquids from the tanks which would remove liquids and moisture were considered because reactive waste which is too dry may propagate. Evaporation effects which could remove moisture from the tanks were also calculated. The various ways that the waste could be heated or ignited by equipment failures or tank operations activities were considered and appropriate monitoring and controls were recommended

Thermal environment and UV-B radiation indices in the Vojvodina region, Serbia

We considered thermal environment and UV-B radiation indices in the Vojvodina region, Serbia. We derived an empirical formula for estimating the daily sum of the UV-B from global radiation and used this formula to reconstruct the UV-B radiation pattern for 1981–2008. We describe the actual climate conditions for the period 1992−2008. In addition, we applied a statistical downscaling technique on ECHAM5 outputs under the A2 scenario to assess the 2040 climate. The results indicate that a warmer and drier climate in the Vojvodina region can be expected because of the following evidence: an increase in the mean annual temperature (8.6 to 12.3%) and in the frequency of hot days (29.4 to 50%); a decrease in the mean annual precipitation (8.1 to 14.2%) and in the frequency of cold days (11.8 to 27.8%); a higher increase in the mean temperature for the colder period (24.9%) than for the hotter one (6.7%); and a reduction in precipitation during the growing season (15.7%). We have analyzed the thermal environment for the period 1992 −2008 using the wind chill index and the heat index for the winter (December to February) and summer (June to August) periods. In all places, the heat index has a tendency for growth. We determined an increase in the daily UV-B dose in an amount of 3.7% per decade. Even though there is some evidence indicating ozone stabilization, there are no signs of a significant recovery of ozone layer thickness, so it can be expected that UV-B dose levels will remain high in the future