Production study of gadolinium-153

Production of gadolinium-153 for use in atmospheric density gages based on gamma backscatter measurement

Geochemistry and deposition of Be-7 in river‐estuarine and coastal waters

The atmospheric flux of cosmogenic Be-7 (53.3-day half-life) and the mode of ?Be deposition in river- estuarine and coastal environments have been examined. The atmospheric flux of ?Be commonly sup- ports inventories ranging from 1.0 to 2.0 pCi/cm 2 (1 pCi = 0.037 Bq). Beryllium 7 concentrations in water phase samples, collected across salinity gradients in several estuaries along the eastern coastline of the United States, range from 0.03 to 0.53 pCi/L and primarily reflect variations in Be-7supply and sorption kinetics. The major process controlling the concentration of Be-7 on estuarine suspended particles appears to be the length of time that these particles remain in the water column. Field particle-to- water distribution coefficients for Be-7have a median value of about 4 x 10 \u27• but range over an order of magnitude reflecting short-term variations in 7Be input, particle dynamics, and particulate iron content rather than equilibrium sorption-desorption responses to changes in water salinity or particle type. Residence times of 7Be in the water column range from a few days in estuarine areas of rapid fine-particle deposition, to several weeks in high-energy environments where pronounced sediment resuspension reintroduces deposited 7Be back into the water column. Inventories of ?Be in sediments range-from nondetectable to 3.3 pCi/cm 2, with the highest inventories in areas where fine particles are accumulating rapidly. Such sites are also major repositories for other particle-reactive substances. A ?Be budget for the James estuary indicates that less than 5% of the expected ?Be input is in the water column and that the short-term estuarine trapping efficiency for atmospherically derived ?Be is somewhere between 50 and 100%

Chromium-51 in the Columbia River and adjacent Pacific Ocean

Radioactive chromium-51, a waste byproduct from operation of nuclear reactors at Hanford, Washington, has been followed down the Columbia River and into the Pacific Ocean. Chemical factors influencing the partitioning of ⁵¹Cr between solution and sediment have been considered. Chromium-5l, in a hexavalent oxyanion when introduced into the Columbia River, largely remains in solution in a hexavalent anion during its passage through the lower river and after its entrance into the Pacific Ocean. A minor fraction of Hanford-induced ⁵¹Cr becomes attached to suspended particles and bottom sediments. Reduction of Cr(VI) to Cr(III) apparently precedes or accompanies sorption. Iron oxides appear to be the most important sorption substrate. Sediment organic matter acts both as a reducing agent, making ⁵¹Cr less soluble, and as a sorption substrate. Ion exchange on sediment particles is not important in retention of ⁵¹Cr by Columbia River sediment. Chromium-51 is a sensitive and unique tracer for Columbia River water at sea and has been used to trace the Columbia River plume up to 525 km away from the mouth of the river. Dispersion of ⁵¹Cr by the Columbia River system would be adversely affected by: 1) lowered pH; 2) presence of particulate organic wastes; 3) increased temperature; 4) increased biological oxygen demand. These factors would increase the rate of uptake of ⁵¹Cr by sediments and thus increase the steady-state inventory of ⁵¹Cr on the bottom of the river

Control of radionuclide migration in soil by the application of dc electric current

Shallow land burial in humid regions as a disposal method for low-level solid waste provides the potential for water-driven migration of leachable radionuclides present in the waste. A number of methods to control this migration have been suggested and studied. One such method involves the use of a dc electric current to move ions countercurrent to the water flow. Laboratory studies using trays of soil indigenous to the Oak Ridge National Laboratory (ORNL) low-level burial grounds have shown /sup 137/Cs, /sup 90/Sr, and /sup 99/Tc ions can be moved countercurrent to a water flow using small dc currents of 20 mA at 40 volts. A field test of the method has been under way for over one year in an ORNL low-level waste disposal area. Results of the field test are given in this paper

Sediment quality and ecorisk assessment factors for a major river system

Sediment-related water quality and risk assessment parameters for the Columbia River were developed using heavy metal loading and concentration data from Lake Roosevelt (river km 1120) to the mouth and adjacent coastal zone. Correlation of Pb, Zn, Hg, and Cd concentrations in downstream sediments with refinery operations in British Columbia suggest that solutes with K{sub d}`s > 10{sup 5} reach about 1 to 5 {mu}g/g per metric ton/year of input. A low-suspended load (upriver avg. <10 mg/L) and high particle-surface reactivity account for the high clay-fraction contaminant concentrations. In addition, a sediment exposure path was demonstrated based on analysis of post-shutdown biodynamics of a heavy metal radiotracer. The slow decline in sediment was attributed to resuspension, bioturbation, and anthropogenic disturbances. The above findings suggest that conservative sediment quality criteria should be used to restrict additional contaminant loading in the upper drainage basin. The issuance of an advisory for Lake Roosevelt, due in part to Hg accumulation in large sport fish, suggests more restrictive controls are needed. A monitoring strategy for assessing human exposure potential and the ecological health of the river is proposed

Ecological studies of radioactivity in the Columbia River Estuary and adjacent Pacific Ocean : progress report 1 July 1971 through 30 June 1972

The progress report that follows includes research results ranging from unproved ideas to scientific papers published during the tenure of this contract. The end of the contract year finds several facets of our work in various states of preparation, therefore the reader is cautioned that all except the published papers are subject to revision

Evaluation of DOE Radionuclide Solubility Data and Selected Retardation Parameters: Description of Calculational and Confirmatory Experimental Activities

An experimentally oriented program has been initiated to support the NRC analysis and licensing activities related to high-level nuclear waste repositories. The program will allow the NRC to independently confirm key geochemical values used in the site performance assessments submitted by the DOE candidate repository site projects. Key radionuclide retardation factor values, particularly radionuclide solubility and sorption values under site specific geochemical conditions, are being confirmed. The initial efforts are being directed toward basalt rock/groundwater systems relevant to the BWIP candidate site in the Pasco Basin. Future work will consider tuff (NNWSI candidate site in Yucca Mountain) and salt (unspecified ONWI bedded or domal salt sites) rock/groundwater systems. Initial experimental results with technetium have confirmed the BWIP values for basalt/groundwater systems under oxic redox conditions: high solubility and no sorption. Under reducing redox conditions, however, the experimental work did not confirm the proposed technetium values recommended by BWIP. In the presence of hydrazine to establish reducing conditions, an apparent solubility limit for technetium of about 5E-7 mol/L was encountered; BWIP recommended calculated values of 1E-12 or greater than or equal to 1E-14 mol/L. Experimental evidence concerning sorption of reduced technetium species is incomplete at this time. Equilibrium speciation and saturation indices were calculated for well water data sets from BWIP using the computer code PHREEQUE. Oversaturation was indicated for hematite and quartz in all data sets. Near surface samples were undersaturated with respect to calcite, but most deep samples were oversaturated with respect to calcite and other carbonate minerals

Ecological studies in radioactivity in the Columbia River Estuary and adjacent Pacific Ocean : progress report 1 July 1972 through 31 March 1974

This report presents progress accomplished during the 20-month period from 1 July 1972 through 31 March 1974 as part of the program "Ecological Studies of Radioactivity in the Columbia River Estuary and Adjacent Pacific Ocean". This program is a continuing study supported by the Division of Biomedical and Environmental Research of the U.S. Atomic Energy Commission under Contract AT(45-1)-2227, Task Agreement 12 with Oregon State University. The report format is one which has evolved in recent years. In this introductory section we attempt to describe the history and goals of the program and to identify the major physical facilities which are dedicated primarily to the program. This presentation is followed by identification of students associated with the program and then the results of recently completed thesis research. Next, staff participation in meetings is recounted. The various research projects which are underway but for which final papers have not been written are then described. In the Research in Progress section we indicate the rationale and approach to specific research projects and keep the reporting of data and conclusions to a minimum. The largest section of the report is Research Completed, wherein we reproduce manuscripts which have been submitted for publication and reprints of papers published. Papers included as reprints may have been printed in earlier progress reports as manuscripts. Although a certain amount of repetition therefore occurs, in many cases the text of published papers varies from the text originally submitted. Finally, we include a bibliography of publications from the program