Environmental assessment of Las Vegas Wash and Lake Mead artificial wetlands demonstration project

The effective use of artificial wetlands for treatment of municipal wastewater is well documented; however, design and economic data for artificial wetlands development are limited (Gersberg et al., 1984a). This is due partly to regional differences in climate, soils, and vegetation and partly to the desired waste treatment. As a result, specific treatment levels and cost benefits relative to the use of an artificial wetlands for a particular site cannot be evaluated adequately without a pilot demonstration project. Las Vegas Wash receives sewage effluent from the Las Vegas metropolitan area and has been designated as a wetlands community park. Las Vegas Wash is located in the Mojave Desert and a wetlands in this area is very unique. Unfortunately, the existing wetlands have been essentially lost due to erosion. Wetlands restoration is currently under consideration for both sewage treatment and erosion control. The effort proposed here is for a pilot wetlands demonstration for treatment of sewage effluent in Las Vegas Wash. Historically, substantial reductions in nutrient concentrations occurred in the Las Vegas Wash. These reductions were due to some combination of mechanisms associated with but not directly related to the historical wetlands as described in the Historical Background section of this proposal. The proposed demonstration will be an artificial (managed) wetlands; and therefore, it will not functionally be representative of the historical wetlands in Las Vegas Wash

Intercomparison and validation of computer codes for thermalhydraulic safety analysis of heavy water reactors

Activities within the frame of the IAEA’s Technical Working Group on Advanced Technologies for HWRs (TWG-HWR) are conducted in a project within the IAEA’s subprogramme on nuclear power reactor technology development. The objective of the activities on HWRs is to foster, within the frame of the TWG-HWR, information exchange and co-operative research on technology development for current and future HWRs, with an emphasis on safety, economics and fuel resource sustainability. One of the activities recommended by the TWG-HWR was an international standard problem exercise entitled: “Intercomparison and validation of computer codes for thermalhydraulics safety analyses”. Intercomparison and validation of computer codes used in different countries for thermalhydraulics safety analyses will enhance the confidence in the predictions made by these codes. However, the intercomparison and validation exercise needs a set of reliable experimental data. The RD-14M Large-Loss Of Coolant Accident (LOCA) test B9401 simulating HWR LOCA behaviour that was conducted by Atomic Energy of Canada Ltd (AECL) was selected for this validation project. This report provides a comparison of the results obtained from six participating countries, utilizing four different computer codes. General conclusions are reached and recommendations made. The IAEA expresses its appreciation to the CANDU Owners Group (COG) for releasing the experimental data to the international community, and to D. Richards of AECL, Canada for leading the activity. The IAEA officer responsible for this publication was R. Lyon of the Division of Nuclear Power