RIVER-RAD: A computer code for simulating the transport of radionuclides in rivers

A screening-level model, RIVER-RAD, has been developed to assess the potential fate of radionuclides released to rivers. The model is simplified in nature and is intended to provide guidance in determining the potential importance of the surface water pathway, relevant transport mechanisms, and key radionuclides in estimating radiological dose to man. The purpose of this report is to provide a description of the model and a user's manual for the FORTRAN computer code

The inverse problem of determining the filtration function and permeability reduction in flow of water with particles in porous media

The original publication can be found at www.springerlink.comDeep bed filtration of particle suspensions in porous media occurs during water injection into oil reservoirs, drilling fluid invasion of reservoir production zones, fines migration in oil fields, industrial filtering, bacteria, viruses or contaminants transport in groundwater etc. The basic features of the process are particle capture by the porous medium and consequent permeability reduction. Models for deep bed filtration contain two quantities that represent rock and fluid properties: the filtration function, which is the fraction of particles captured per unit particle path length, and formation damage function, which is the ratio between reduced and initial permeabilities. These quantities cannot be measured directly in the laboratory or in the field; therefore, they must be calculated indirectly by solving inverse problems. The practical petroleum and environmental engineering purpose is to predict injectivity loss and particle penetration depth around wells. Reliable prediction requires precise knowledge of these two coefficients. In this work we determine these quantities from pressure drop and effluent concentration histories measured in one-dimensional laboratory experiments. The recovery method consists of optimizing deviation functionals in appropriate subdomains; if necessary, a Tikhonov regularization term is added to the functional. The filtration function is recovered by optimizing a non-linear functional with box constraints; this functional involves the effluent concentration history. The permeability reduction is recovered likewise, taking into account the filtration function already found, and the functional involves the pressure drop history. In both cases, the functionals are derived from least square formulations of the deviation between experimental data and quantities predicted by the model.Alvarez, A. C., Hime, G., Marchesin, D., Bedrikovetski, P

Estimated radiation doses from thorium and daughters contained in thoriated welding electrodes

The collective radiation dose commitment to the general U.S. population estimated for the annual distribution, use, and disposal of one million thoriated welding electrodes was found to range between 7.9 x 10/sup 2/ to 6.4 x 10/sup 3/ man-rem to the bone (56 to 5.4 x 10/sup 2/ man-rem to the whole body). These values represent the potential dose received by the general U.S. population over a 50-year period following exposure during one year

Long-term uncertainty in radiological performance assessments of low-level waste facilities at Savannah River Site

Radiological performance assessments are being conducted for the Saltstone Disposal Facility and the E-Area Vaults at the Savannah River Site near Aiken, South Carolina. Saltstone is a solidified waste form which will contain very low levels of radionuclides but considerable levels of nitrate. The E-Area Vaults will contain solid, radioactively contaminated waste. Preliminary results of the assessments indicate that adequate performance will be very sensitive to the degradation scenario adopted for the cover and containment systems for these facilities. 2 refs

Technical considerations related to interim source-term assumptions for emergency planning and equipment qualification. [PWR; BWR]

The source terms recommended in the current regulatory guidance for many considerations of light water reactor (LWR) accidents were developed a number of years ago when understandings of many of the phenomena pertinent to source term estimation were relatively primitive. The purpose of the work presented here was to develop more realistic source term assumptions which could be used for interim regulatory purposes for two specific considerations, namely, equipment qualification and emergency planning. The overall approach taken was to adopt assumptions and models previously proposed for various aspects of source term estimation and to modify those assumptions and models to reflect recently gained insights into, and data describing, the release and transport of radionuclides during and after LWR accidents. To obtain illustrative estimates of the magnitudes of the source terms, the results of previous calculations employing the adopted assumptions and models were utilized and were modified to account for the effects of the recent insights and data

Potential health effects of radon-222 to the general public from uranium milling

This paper presents a discussion of the potential health risk that may result from present and future radon-222 releases at uranium mill tailings piles situated in the United States. These risks are contrasted with the health risk continually present as a consequence of background levels of radon-222 naturally present in the atmosphere. It is estimated that the current risk of lung cancer in the population due to uranium milling is less than 10/sup -4/ times the natural risk. In addition, it is estimated that future risks due to mill tailings will be approximately a factor of 10/sup 5/ lower than the natural radon-222 risk to the general public if stabilization of tailings piles is implemented. Thus, it appears the incremental population risk due to milling is insignificant with respect to the natural risk

Effects of soil matric suction on retention and percolation of Bacillus subtilis in intact soil cores

Bacillus subtilis endospores (resistant to rifampicin) irrigated on the surface of intact soil cores (20 cm diameter x 8 cm length) which were equilibrated under selected suctions, i.e. 0, 0.5, 2, 5, 10 kPa, were then percolated by saturated water flow. The bacterial retention and percolation percentage were significantly correlated with the suctions. The higher retention with higher suction was explained by micropore storage, attachment to static air-water interface (AWI), and irreversible adsorption to soil particles. The bacterial percolation was mainly controlled by initial replacement of pore water storage, and following reversible detachment process. Another sensitivity experiment with four replicates using lincomycin-resistant B. subtilis at 0 and 0.5 kPa suctions revealed that small increase (0 to 0.5 kPa) in soil matric suction incurred a substantial higher level of bacterial retention. Based on our experimental results, soil matric suction was proposed as a comprehensive parameter to monitor bacterial transport and fate for animal waste disposal (irrigation) and subsurface bioremediation