scholarly journals Discovery of fissionogenic Cs and Ba capture five years after Oklo reactor shutdown

2018 ◽  
Vol 115 (35) ◽  
pp. 8676-8681 ◽  
Author(s):  
Evan E. Groopman ◽  
David G. Willingham ◽  
Alex P. Meshik ◽  
Olga V. Pravdivtseva
Keyword(s):  
Nuclear Reactor ◽  
Metal Sulfide ◽  
Fission Products ◽  
Naval Research ◽  
Reactor Accident ◽  
Nuclear Waste Storage ◽  
Waste Storage ◽  
Reactor Shutdown ◽  
Ultra Trace ◽  
High Level

Understanding the release and sequestration of specific radioactive signatures into the environment is of extreme importance for long-term nuclear waste storage and reactor accident mitigation. Recent accidents at the Fukushima and Chernobyl nuclear reactors released radioactive 137Cs and 134Cs into the environment, the former of which is still live today. We have studied the migration of fission products in the Oklo natural nuclear reactor using an isotope imaging capability, the NAval Ultra-Trace Isotope Laboratory’s Universal Spectrometer (NAUTILUS) at the US Naval Research Laboratory. In Oklo reactor zone (RZ) 13, we have identified the most depleted natural U of any known material with a 235U/238U ratio of 0.3655 ± 0.0007% (2σ). This sample contains the most extreme natural burnup in 149Sm, 151Eu, 155Gd, and 157Gd, which demonstrates that it was sourced from the most active Oklo reactor region. We have discovered that fissionogenic Cs and Ba were captured by Ru metal/sulfide aggregates shortly following reactor shutdown. Isochrons from the Ru aggregates place their closure time at 4.98 ± 0.56 y after the end of criticality. Most fissionogenic 135Ba and 137Ba in the Ru migrated and was incorporated as Cs over this period. Excesses in 134Ba in the Ru point to the burnup of 133Cs. Cesium and Ba were retained in the Ru despite local volcanic activity since the reactor shutdown and the high level of activity during reactor operation.

scholarly journals Selection of Barrier Metals for a Waste Package in Tuff

1983 ◽  
Vol 26 ◽  
Author(s):  
E. W. yyRussell ◽  
R. D. McCright ◽  
W. C. O'Neal
Keyword(s):  
Nuclear Waste ◽  
Lawrence Livermore National Laboratory ◽  
Near Field ◽  
National Laboratory ◽  
Test Site ◽  
Management Program ◽  
Nuclear Waste Storage ◽  
Waste Storage ◽  
High Level ◽  
Selection Of

ABSTRACTThe Nevada Nuclear Waste Storage Investigations (NNWSI) project under the Civilian Radioactive Waste Management Program is planning a repository at Yucca Mountain at the Nevada Test Site for isolation of high-level nuclear waste. Lawrence Livermore National Laboratory is developing designs for an engineered barrier system containing several barriers such as the waste form, a canister and/or an overpack, packing, and near field host rock. In this paper we address the selection of metal containment barriers.

Summary of Results From the Series 2 and Series 3 NNWSI Bare Fuel Dissolution Tests

1987 ◽  
Vol 112 ◽  
Author(s):  
C. N. Wilson
Keyword(s):  
Spent Nuclear Fuel ◽  
Fine Particles ◽  
Fission Products ◽  
Test Site ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Nuclear Waste Storage ◽  
Waste Storage ◽  
Rate Of Increase ◽  
In Series

AbstractThe Nevada Nuclear Waste Storage Investigations (NNWSI) Project is studying dissolution and radionuclide release behavior of spent nuclear fuel in Nevada Test Site groundwater. Specimens prepared from pressurized water reactor (PWR) fuel rod segments were tested for multiple cycles in J-13 well water. The Series 2 tests were run in unsealed silica vessels under ambient hot cell air (25°C) for five cycles for a total of 34 months. The Series 3 tests were run in sealed stainless steel vessels at 25°C and 85°C for three cycles for a total of 15 months. Selected summary results from Series 2 and Series 3 tests with bare fuel specimens are reported.Actinide concentrations tended to saturate and then often decreased during test cycles. Uranium concentrations in later test cycles ranged from 1 to 2 μg/ml in the Series 2 Tests versus about 0.1 to 0.4 μg/ml in Series 3 with the lowest concentrations occurring in the 85°C tests. Formation of a calciumuranium-silicate phase identified as uranophane in the 85°C Series 3 Tests is thought to have limited uranium concentration in these tests. Americium-241, Pu-239 and Pu-240 activities measured in filtered solution decreased to less than 1 pCi/ml in the 85°C tests. Preferential release of fission products Cs, I, Sr and Tc, and activation product C-14, was indicated relative to the actinides. Tc-99 and Cs-137 activities measured in solution after Cycle 1 increased linearly with time, with the rate of increase greater at 85°C than at 25°C. Continuous preferential release of soluble fission products is thought to result primarily from the dissolution of fine particles of fission product phases concentrated on grain boundaries.

Arid geomorphology

1996 ◽  
Vol 20 (1) ◽  
pp. 97-103 ◽  
Author(s):  
Nicholas Lancaster
Keyword(s):  
Great Plains ◽  
Sediment Supply ◽  
Age Dating ◽  
Future Climate Change ◽  
Arid Environments ◽  
Nuclear Waste Storage ◽  
Waste Storage ◽  
Southern Nevada ◽  
High Level ◽  
Soil Forming Processes

Geomorphic research in arid environments continues to attract a wide variety of researchers who employ a range of techniques to understand modem processes and landscape evolution in dry lands. A notable feature of much contemporary research is the collaboration between geomorphologists and those with specialized geochemical and geophysical knowledge, for example in the areas of exposure-age dating. Another significant development is the synergism (at least in the western USA) between environ mental and public policy concerns and fundamental geomorphic research. For example, the need to understand landform development and the history of climate in the region of the proposed high-level nuclear-waste storage facility at Yucca Mountain in southern Nevada has generated important fundamental research on soil-forming processes (Reheis et al., 1995), soil-landscape relations (Peterson et al., 1995), slope stability (Whitney and Harrington, 1993) and evidence for past groundwater discharge conditions (Quade et al., 1995). Similarly, concerns about the response of sensitive semi-arid areas to possible future climate change has stimulated research into the Holocene climatic history and aeolian environments of the Great Plains (Muhs and Maat, 1993; Forman et al., 1995; Loope et al., 1995; Madole, 1995; Muhs and Holliday, 1995; Wolfe et al., 1995) and the Negev Desert (Tsoar, 1995). Of particular importance is the realization that droughts and changes in sediment supply from fluvial systems within the past 150 yr have had effects on dune mobility that are comparable to some inferred Holocene climate changes (Muhs and Holliday, 1995).

scholarly journals Post Emplacement Environment of Waste Packages

1983 ◽  
Vol 26 ◽  
Author(s):  
K. G. Knauss ◽  
V. M. Oversby ◽  
T. J. Wolery
Keyword(s):  
Water Chemistry ◽  
Geographic Location ◽  
High Level Waste ◽  
Nuclear Waste Storage ◽  
Waste Storage ◽  
Reaction Extent ◽  
Waste Repository ◽  
High Level ◽  
Water Ratio ◽  
Topopah Spring Tuff

ABSTRACTExperiments have been conducted as part of the Nevada Nuclear Waste Storage Investigations Project to determine the changes in water chemistry due to reaction of the Topopah Spring tuff with natural groundwater at temperatures up to 150°C. The reaction extent has been investigated as a function of rock-to-water ratio, temperature, reaction time, physical state of the samples, and geographic location of the samples within the tuff unit. Results of these experiments will be used to provide information on the water chemistry to be expected if a high level waste repository were to be constructed in the Topopah Spring tuff.

scholarly journals Fracture failure of granite after varied durations of thermal treatment: an experimental study

2019 ◽  
Vol 6 (7) ◽  
pp. 190144 ◽  
Author(s):  
Gan Feng ◽  
Yong Kang ◽  
Xiao-chuan Wang
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Thermal Treatment ◽  
Shear Failure ◽  
Mode I ◽  
Tensile Shear ◽  
Nuclear Waste Storage ◽  
Reservoir Rocks ◽  
Waste Storage ◽  
High Level

Energy extraction from nuclear materials produces high-level radioactive waste. In geological nuclear waste storage repositories, the decay of radioactive elements generates heat, exposing the reservoir rocks to high-temperature conditions for long periods. To explore the effects of these conditions, this study examines the ability of granite to resist fracturing after thermal treatment for 10 h, 10 days, 30 days and 60 days. The results show that the fracture toughness of the granite remained basically unchanged for up to 10 days of thermal treatment. After thermal treatment for 60 days, the mode I, mode II and mixed-mode (I + II) fracture toughness decreased by 15.39%, 18.09% and 15.17%, respectively, compared with samples heated for 10 h. The change trends of the ability of granite to resist tensile, shear and mixed (tensile + shear) failure with an increased thermal treatment duration were basically consistent. Moreover, there was little change in its brittle fracturing characteristics with an increase in heating duration. Changes caused to the internal microstructure of the granite by high temperature were ongoing even up to 60 days.

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