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Laboratory evaluation of colloidal actinide transport at the Waste Isolation Pilot Plant (WIPP): 1. crushed-dolomite column flow...

Description: Colloid-facilitated transport of Pu, Am, U, Th, and Np has been recognized as a potentially important phenomenon affecting the performance of the Waste Isolation Pilot Plant (WIPP) facility being developed for safe disposal of transuranic radioactive waste. In a human intrusion scenario, actinide-bearing colloidal particles may be released from the repository and be transported by brines (approximately 0.8 to 3 molal ionic strength) through the Culebra, a thin fractured microcrystalline (mean grain size 2 micrometers) dolomite aquifer overlying the repository. Transport experiments were conducted using sieved, uniformly packed crushed Culebra rock or nonporous dolomite cleavage rhombohedra. Experiments with mineral fragments and fixed and live WIPP-relevant bacteria cultures showed significant levels of retardation due to physical filtration effects. Humic substances were not attenuated by the Culebra dolomite. Comparison of elution curves of latex microspheres in columns prepared with microcrystalline rock and nonporous rock showed minimal effect of Culebra micropores on colloid transport. These data form part of the basis to parameterize numerical codes being used to evaluate the performance of the WIPP.
Date: December 31, 1996
Creator: Yelton, W.G.; Behl, Y.K.; Kelly, J.W.; Dunn, M.; Gillow, J.B.; Francis, A.J. et al.
Partner: UNT Libraries Government Documents Department

Transport code for radiocolloid migration: with an assessment of an actual low-level waste site

Description: Recently, there is increased concern that radiocolloids may act as a rapid transport mechanism for the release of radionuclides from high-level waste repositories. The role of colloids is, however, controversial because the necessary data and assessment methodology have been limited. Evidence is accumulating to indicate that colloids are an important consideration in the geological disposal of nuclear waste. To quantitatively assess the role of colloids, the TRACR3D transport code has been enhanced by the addition of the population balance equations. This new version of the code can simulate the migration of colloids through combinations of porous/fractured, unsaturated, geologic media. The code was tested against the experimental laboratory column data of Avogadro et al. in order to compare the code results to both experimental data and an analytical solution. Next, a low-level radioactive waste site was investigated to explore whether colloid migration could account for the unusually rapid and long transport of plutonium and americium observed at a low-level waste site. Both plutonium and americium migrated 30 meters through unsaturated volcanic tuff. The nature and modeling of radiocolloids are discussed along with site simulation results from the TRACR3D code. 20 references.
Date: December 31, 1984
Creator: Travis, B.J. & Nuttall, H.E.
Partner: UNT Libraries Government Documents Department

Performance assessment modeling of radionuclide transport: Matrix/Fracture and colloidal transport

Description: Several total system PA analyses have been completed to investigate the performance of light water reactor (LWR) SNF or alternative waste forms in a geologic repository. These analyses contained either no modeling or simple modeling of fracture flow and transport; and none considered radio-colloid facilitated transport. This paper summarizes the work completed to develop a transport model which considers fracture, matrix, and radio-colloid transport; this model is used to evaluate the transport of SNF radionuclides at the Yucca Mountain site.
Date: April 1, 1996
Creator: Nutt, W.M. & Hill, R.N.
Partner: UNT Libraries Government Documents Department

A modeling study of contaminant transport resulting from flooding of Pit 9 at the Radioactive Waste Management Complex, Idaho National Engineering Laboratory

Description: A simulation study was conducted to determine if dissolved-phase transport due to flooding is a viable mechanism for explaining the presence of radionuclides in sedimentary interbeds below the Radioactive Waste Management Complex. In particular, the study focused on {sup 241}Am migration due to flooding of Pit 9 in 1969. A kinetically-controlled source term model was used to estimate the mass of {sup 241}Am that leached as a function of a variable surface infiltration rate. This mass release rate was then used in a numerical simulation of unsaturated flow and transport to estimate the advance due to flooding of the {sup 241}Am front down towards the 110 ft interbed. The simulation included the effect of fractures by superimposing them onto elements that represented the basalt matrix. For the base case, hydraulic and transport parameters were assigned using the best available data. The advance of the {sup 241}Am front due to flooding for this case was minimal, on the order of a few meters. This was due to the strong tendency for {sup 241}Am to sorb onto both basalts and sediments. In addition to the base case simulation, a parametric sensitivity study was conducted which tested the effect of sorption in the fractures, in the kinetic source term, and in the basalt matrix. Of these, the only case which resulted in significant transport was when there was no sorption in the basalt matrix. The indication being that other processes such as transport by radiocolloids or organic complexation may have contributed. However, caution is advised in interpreting these results due to approximations in the numerical method that was used incorporate fractures into the simulation. The approximations are a result of fracture apertures being significantly smaller than the elements over which they are superimposed. The sensitivity of the {sup 241}Am advance to the assumed ...
Date: September 1, 1992
Creator: Magnuson, S. O. & Sondrup, A. J.
Partner: UNT Libraries Government Documents Department

Development and radiotherapeutic application of /sup 211/At-labeled radiopharmaceuticals. Progress report, March 1, 1981-February 28, 1982

Description: This project is concerned with developing the potential of alpha-emitting radionuclides as agents for radiotherapy. Alpha-emitters seem ideally suited for his application because their high linear energy transfer and short range permit the deposition of considerable energy in a very small volume of tissue. Unlike the beta particles of /sup 131/I which have a range of about 1 to 2 mm in tissue, 5 to 7 MeV alpha particles would traverse only a few cell diameters. Among the available alpha-emitters, /sup 211/At appears most promising for therapeutic applications because, (1) it has some chemical similarities to iodine, an element that can readily be incorporated into numerous proteins and peptides, (2) it has a half-life that is long enough to permit chemical manipulation yet short enough to minimize destruction of healthy cells due to degradation of the label over time, (3) it can be produced conveniently using a cyclotron, and (4) alpha emission is associated with 100% of its decays with no accompanying beta emission. In the past year the evaluation of an astatine-tellurium colloid as an agent for the destruction of malignant ascites has been completed. The therapeutic efficacy of /sup 211/At-tellurium colloid has been compared with that of several beta-emitting radiocolloids. Studies on the application of monoclonal antibodies as carriers for selective delineation and destruction of malignant cell populations have also been initiated.
Date: January 1, 1981
Creator: Adelstein, S.J.; Zalutsky, M. & Bloomer, W.
Partner: UNT Libraries Government Documents Department

Ruthenium-97 labeled compounds: a new class of radiopharmaceuticals. [Preparation, tissue distribution, and imaging studies]

Description: The excellent physical properties of 2.9 day ruthenium-97 (216 KeV ..gamma.., 86%) combined with its chemical reactivity were exploited for the design of versatile new radiopharmaceuticals. Complexes of ruthenium (III and IV) with citrate, DTPA, MDP, EHDP, PYP, ethylenediaminetetramethylene phosphonate (EDTMP), and oxine 7-carboxylic acid acetate, and of ruthenium (II) with 1,10-phenanthroline and 3,4,7,8-tetramethyl 1,10-phenanthroline were prepared and studied. Preparation of a ruthenium--sulfur colloid was achieved and its application in lymphangiography was demonstrated. Ruthenium chloride clears from the blood slowly; at 24 hr, the activity remains diffused all over the body including muscle, and excretion is only partial. Ru-DTPA and Ru-citrate both are eliminated rapidly via the kidneys. Ru-EHDP and Ru-EDTMP clear fast from the blood and localize in bone. The oxine complex showed excellent promise as a hepatobiliary agent; excretion via the kidneys was negligible. Several complexes of Ru (II) and ammine-Ru (III), especially with nitrogen heterocycles such as pyridines, phenanthrolines, and purine bases are under evaluation in animal tumor models. Uptake of ruthenium phosphate compounds in experimental myocardial infarcts shows promise. BLIP production of Ru-97 has been achieved using the Rh-103 (p, 2p5n) Ru-97 reaction (> 100 mCi/day). These results reinforce our optimism regarding the potential of ruthenium-97 in nuclear medicine, in particular when periodic or delayed scans are either necessary or desirable in order to diagnose or monitor the progress of disease.
Date: January 1, 1978
Creator: Srivastava, S C; Som, P; Meinken, G; Sewatkar, A & Ku, T H
Partner: UNT Libraries Government Documents Department