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Plutonium Fission in the Oklo Natural Reactor

Description: The Oklo natural reactor was discovered in 1972. Experimental evidence has indicated that the fuel source was primarily 235U with a small contribution of 7 to 9 percent from the fission of 239Pu. This article's reevaluation of data indicates that 239Pu was an important source of fuel in some areas of the reactor. A small portion of xenon and krypton released from Oklo sample 1348 appears to have originated from a source enriched in 239Pu. That fuel source may have been the core of a natural bre… more
Date: August 18, 1980
Creator: Holloway, R. W.
Partner: UNT Libraries Government Documents Department
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Highest temperatures recorded by the Oklo mineral phase assemblages and rock textures

Description: Biotite-bearing pelitic phase assemblages are observed in reactor zones 2 and 5 and up to at least 4 m outside of zone 2, indicating a minimum temperature in these regions of about 400/sup 0/C. Rock textures suggest that still higher temperatures may have been reached within the reactors.
Date: January 1, 1977
Creator: Vidale, R.
Partner: UNT Libraries Government Documents Department
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Nuclear waste criticality analysis quarterly progress report, 1 July 1995--30 September 1995

Description: Control of criticality in spent nuclear fuel is necessary during all phases of fuel management during storage, transportation, and permanent disposal. Work completed to date is described. Tasks in the original proposal include: seek coverage by an approved quality control program, review documents related to criticality, attend criticality meetings and workshops, and maintain an expertise in criticality. Current work is covered by Univ. of Nevada QA plan, however, coverage under a more thorough… more
Date: October 19, 1995
Creator: Culbreth, W.G.
Partner: UNT Libraries Government Documents Department
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Nuclear waste criticality analysis. Quarterly progress report, 1 October--31 December 1995

Description: The work to date includes the preparation of a report related to criticality in spent fuel, a report on the Oklo reactors and their relevance to Yucca Mountain, and the creation of a computer program to model the Oklo reactors. The objective of the program includes a computational model of the only known natural analogue to an underground nuclear waste repository and the possible application of the model to predict the long-term behavior of Yucca Mountain. A final summary of all work completed … more
Date: January 19, 1996
Creator: Culbreth, W.G.
Partner: UNT Libraries Government Documents Department
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Nuclear waste criticality analysis. Final report, 1 July 1995--30 June 1996

Description: The natural reactors that occurred in Gabon, Africa over 2 billion years ago present an interesting analog to the underground repositories proposed around the world for the long-term storage of high-level spent nuclear fuel. Many articles have been written concerning the low migration rates of actinides and fission products from the Oklo reactor sites, but Oklo also presents researchers with an opportunity to discover the conditions that led to nuclear criticality in uranium oxides with low enr… more
Date: July 3, 1996
Creator: Culbreth, W.G.
Partner: UNT Libraries Government Documents Department
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2. 05 x 10/sup 9/ age of the Oklo uranium deposit

Description: U and Pb isotopic data on samples (10 to 100 gram) 2 to 10 m away from the borders of the Oklo reactor zones indicate a primary age of 2.05 x 10/sup 9/ years for the Oklo deposit and a secondary age of 0.375 x 10/sup 9/ years. All samples show effects of Pb loss; the average loss is 50 percent. Both the U--Pb and Pb isotopic data are consistent with a model of a primary 2.05 x 10/sup 9/ year age of the deposit, continuous volume diffusion of Pb from uraninite, and either continuous or recent lo… more
Date: January 1, 1977
Creator: Gancarz, A. J.
Partner: UNT Libraries Government Documents Department
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Oklo: natural fission reactor program. Progress report, July 1-September 30, 1979

Description: Nearly 200 samples were collected at the Oklo mine in Gabon this quarter for shipment to the United States to continue studies of lead, ruthenium, and technetium migration around natural fission reactors. The first analyses of samples collected near a rich uranium ore body in Canada show the presence of radiogenic lead in pyrite and sandstone materials. Analyses of additional samples are underway to permit the interpretation of the data in terms of transport paths. A technique was developed thi… more
Date: January 1, 1980
Creator: Norris, A. E.
Partner: UNT Libraries Government Documents Department
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Retention of reactor products in the Oklo natural fission reactor

Description: Analysis of the fission product distribution in the Oklo reactor and its environs support the conclusions that a mineral such as uraninite can retain its integrity and composition to a remarkable degree while immersed in natural ground water. The transport of uranium out of the principal reactor zones averaged no more than 20 percent in the most affected regions with a fractional loss of uranium of 10/sup -10/ per year. (JSR)
Date: January 1, 1976
Creator: Cowan, G. A.
Partner: UNT Libraries Government Documents Department
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Uranium mill monitoring for natural fission reactors

Description: Isotopic monitoring of the product stream from operating uranium mills is proposed for discovering other possible natural fission reactors; aspects of their occurrence and discovery are considered. Uranium mill operating characteristics are formulated in terms of the total uranium capacity, the uranium throughput, and the dilution half-time of the mill. The requirements for detection of milled reactor-zone uranium are expressed in terms of the dilution half-time and the sampling frequency. Dete… more
Date: December 1, 1977
Creator: Apt, K.E.
Partner: UNT Libraries Government Documents Department
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Investigations of the natural fission reactor program. Progress report, October 1977--September 1978

Description: The U.S. study of the Oklo natural reactor began in 1973 with the principal objectives of understanding the processes that produced the reactor and that led to the retention of many of its products. Major facets of the program have been the chemical separation and mass spectrometric analysis of the reactor components and products, the petrological and mineralogical examination of samples taken from the reactor zones, and an interdisciplinary modeling of possible processes consistent with reacto… more
Date: October 1, 1978
Creator: Cowan, G.A. & Norris, A.E. (eds.)
Partner: UNT Libraries Government Documents Department
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Investigations of the Natural Fission Reactor Program. Progress report, October 1976--September 1977

Description: During Fiscal Year 1977, efforts of the Natural Fission Reactor Program have been directed toward (1) further measurements and predictions of reactor product migration at Oklo, (2) uraninite solubility studies, (3) radiogenic equilibria studies of natural Pu, Ra, and Th in U ores, (4) search for evidence of other natural fission reactors, and (5) supportive analytical measurements and procedures development.
Date: November 1, 1977
Creator: Apt, K.E. (ed.)
Partner: UNT Libraries Government Documents Department
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Natural repository analogue program. Progress report, January 1-March 30, 1982

Description: Lead and uranium isotopic abundances in rocks from the Oklo mine show large deficiencies of radiogenic lead in the mineralized regions and enormous excesses of this element outside the uraniferous zones. A fracture lined with secondary minerals and its host rock from distances as far as approx. 13 meters away contain lead that was deposited contemporaneously. The isotopic composition of lead in these samples varies systematically as a function of distance from the fracture. This regularity may … more
Date: June 1, 1982
Creator: Curtis, D.B. (comp.)
Partner: UNT Libraries Government Documents Department
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Migration paths for Oklo reactor products and applications to the problem of geological storage of nuclear wastes

Description: Escape of the products from the Oklo reactor proceeds, first, by escape from the uraninite (UO/sub 2/) grains and, second, by transport out of the gangue. Escape from the grain by fission recoil accounts for prompt deposition in the gangue of 5 to 10 percent of the products. Escape by volume diffusion is very slow. The rate of loss by diffusion was highest during the operating period of the reactor and may have been of the order of 10/sup -6/ fraction/a for the most volatile elements. The least… more
Date: January 1, 1977
Creator: Cowan, G.A.
Partner: UNT Libraries Government Documents Department
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Natural repository analogue program. Progress report, October 1-December 31, 1981

Description: The final draft of a paper entitled The Oklo Reactors: Natural Analogs to Nuclear Waste Repositories has been submitted for publication. This paper discusses the chemical stability of the fossil reactors with respect to uranium, neodymium, ruthenium, and technetium, the transport of elements in the geologic environment at Oklo; and the geochemical conditions that may have influenced these processes. Measurements of barium isotopic ratios limit the abundance of fissiogenic barium to <10/sup -7/ … more
Date: March 1, 1982
Creator: Curtis, D.B. (comp.)
Partner: UNT Libraries Government Documents Department
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Pb migration in the OKLO uranium deposit

Description: U-Pb and Pb isotopic data are presented which indicate that Pb is lost from host uraninite by diffusion, and that not only in situ uranogenic Pb but also the initial Pb is lost by diffusion. The conglomerate underlying the U deposit contains excess Pb and is both a transport zone and the repository for the Pb. 2 figures.
Date: January 1, 1979
Creator: Gancarz, A. J. & Curtis, D. B.
Partner: UNT Libraries Government Documents Department
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Natural repository analouge program. Progress report, January 1-March 31, 1981

Description: Samples from Oklo Reactor zone-9 (ORZ-9) have been analyzed for the isotopic abundances of Nd, Ce, Ru, and Mo. Interpretation of the Nd data has begun as part of the effort to reconstruct the operating parameters of the reactor. The study of ORZ-9 and the peripheral rocks is being enhanced by additional analytical capabilities. A procedure was developed to measure uranium isotopic ratios with high precision. This new method was used for the analysis of rocks peripheral to ORZ-9. Two rocks conta… more
Date: May 1, 1981
Creator: Curtis, D.B. (comp.)
Partner: UNT Libraries Government Documents Department
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Non-destructive field measurement of the ratio /sup 235/U//sup 238/U in depleted to moderately enriched uranium

Description: The exploration of a natural reactor site is expedited by prompt measurement of /sup 235/U to /sup 238/U ratios near the mining operation. An instrument has been constructed which uses the relative fission rates of /sup 235/U and /sup 238/U in fast and moderated neutron spectra to measure the isotopic ratio. This device can be placed in the field and allows continuous monitoring of ore as a rich deposit of uranium is mined. With rapid return of isotopic information to the operator it is possibl… more
Date: January 1, 1977
Creator: Balagna, J.P. & Cowan, G.A.
Partner: UNT Libraries Government Documents Department
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Natural repository analogue program. Progress report, July 1-September 30, 1981

Description: A report on the immobilization of uranium in the earth's crust has been completed. Techniques have been developed to do a comprehensive mass inventory of the Oklo reactor zones. These techniques were applied to a compilation of data from Oklo zones 2 and 3-4. The study shows large deficiencies of neodymium, ruthenium, and mass 99 elements (/sup 99/Tc or /sup 99/Ru) in the reactor zones. The extent of these deficiencies are correlated with the intensity of the nuclear reactions. Analyses of ores… more
Date: March 1, 1982
Creator: Curtis, D.B. (comp.)
Partner: UNT Libraries Government Documents Department
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Oklo natural fission reactor program. Progress report, April 1-August 31, 1980

Description: An interim report has been published on the redistribution of uranium, thorium, and lead in samples representing several million cubic meters of sandstone and metamorphosed sediments in the Athabasca Basin which is located in the northwest corner of the Canadian province of Saskatchewan. The region of study includes zones of uranium mineralization at Key Lake. Mineralization occurs at the unconformity between the Athabasca sandstone and the underlying metasediments and in fault zones within the… more
Date: December 1, 1980
Creator: Curtis, D.B. (comp.)
Partner: UNT Libraries Government Documents Department
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Technical Division quarterly progess report, July 1--September 30, 1977

Description: Results are presented on the fluidized-bed calcination of simulated radioactive waste from the reprocessing of spent commercial nuclear fuel, on the post treatment of the calcine, and on the removal of actinide elements from the waste prior to calcination. Other programs include the development of storage technology for {sup 85}Kr waste; a study of the hydrogen mordenite catalyzed reaction between NO{sub x} and NH{sub 3}; the adsorption and storage of {sup 129}I on silver exchanged mordenite; p… more
Date: October 1, 1977
Creator: Slansky, Cyril M.; Musgrave, B. C.; Dickey, B. R. & Rohde, K. L.
Partner: UNT Libraries Government Documents Department
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Technical Division quarterly progress report, October 1--December 31, 1976

Description: The first in a series of quarterly progress reports on ERDA budgeted activities subcontracted to Allied Chemical Corporation at the Idaho National Engineering Laboratory is presented. The work is performed by the Technical Division and is divided into three subjects. Fuel cycle research and development includes fluidized-bed calcination and post treatment of commercial nuclear fuel process waste; the storage of fission product noble gas; the catalyzed reaction between NO/sub x/ and NH/sub 3/; t… more
Date: March 1, 1977
Creator: Slansky, C. M. (ed.)
Partner: UNT Libraries Government Documents Department
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