The Mechanisms for Hydrothermal Leaching of Nuclear Waste Glasses: Properties and Evaluation of Surface Layers

1981 ◽  
Vol 11 ◽  
Author(s):  
GÜnter Malow
Keyword(s):  
Environmental Parameters ◽  
Specific Weight ◽  
Deionized Water ◽  
High Level Waste ◽  
Surface Layers ◽  
Leach Rate ◽  
Weight Losses ◽  
Corrosion Mechanisms ◽  
High Level ◽  
Glass Compositions

Remobilization of solidified high-level waste by corrosion and transport of radionuclides by groundwater are the only likely events for radioactivity to find its way back to the environment. The interaction of the waste form with aqueous solutions is the most important mechanism and must be known for safety and risk analysis. It has been shown that the activity release depends on a number of experimental and environmental parameters. The corrosion mechanisms of the waste forms control the leach rate of individual components. Of particular importance to the resistance against water attack of various glass compositions is the formation of layers on the glass surface. The results for leaching in deionized water reveafed that the mechanism was strongly influenced by the formation of a surface layer which determined the further attack on the glass. In this work the specific weight losses of the glass after leaching in rock salt and MgCl2–MgSO4-NaCl-KCl solutions were measured and surface layers investigated.

Effects of Alpha, Gamma, and Alpha-Recoil Radiation on Borosilicate Glass Containing Savannah River Plant Defense High-Level Nuclear Waste

1981 ◽  
Vol 6 ◽  
Author(s):  
Ned E. Bibler
Keyword(s):  
Borosilicate Glass ◽  
Deionized Water ◽  
Savannah River ◽  
Γ Radiation ◽  
Leach Rate ◽  
Geologic Storage ◽  
Savannah River Plant ◽  
Pb Ions ◽  
High Level ◽  
Doped Glass

ABSTRACTAt the Savannah River Plant, the reference process for the immobilization of defense high-level waste (DHLW) for geologic storage is vitrification into borosilicate glass. During geologic storage for 106y, the glass would be exposed to ∼3 × 1010 rad of β radiation, ∼1010 rad of γ radiation, and 1018 particles/g glass for both α and α-recoil radiation. This paper discusses tests of the effect of these radiations on the leachability and density of the glass. No effect of the radiations was detected that reduced the effectiveness of the glass for long-term storage of DHLW even at doses corresponding to 106 years storage for the actual glass. For the tests, glass containing simulated DHLW was prepared from frit of the reference composition. Three methods were used to irradiate the glass: external irradiations with beams of ∼200 keV or Pb ions, internal irradiations with Cm–244 doped glass, and external irradiations with Co–60 γ rays. Results with both Xe and Pb ions indicate that a dose of 3 × 1013 ions/cm2 (simulating >106 years storage) does not significantly increase the leachability of the glass in deionized water. Tests with Cm–244 doped glass show no increase in leach rate in deionized water up to a dose of 1.3 × 1018 α and α-recoils/g glass. The density of the Cm–244 doped glass has decreased by 1% at a dose of 1018 particles/g glass. With γ-radiation, the density has changed by <0.05% at a dose of 8.5 × 1010 rad. Results of leach tests in deionized water and brine indicated that this very large dose of γ-radiation increased the leach rate by only 20%. Also, the leach rates are 3 to 4 times lower in brine.

scholarly journals High Waste Loading Glass Formulations for Hanford High-Aluminum High-Level Waste Streams

2011 ◽  
Author(s):  
Albert A. Kruger
Keyword(s):  
Previous Experience ◽  
High Level Waste ◽  
Waste Streams ◽  
Testing Program ◽  
Glass Formulation ◽  
Waste Loading ◽  
Production Requirement ◽  
High Level ◽  
Glass Compositions ◽  
High Aluminum

The current estimates and glass formulation efforts have been conservative in terms of achievable waste loadings. These formulations have been specified to ensure that the glasses are homogenous, contain essentially no crystalline phases, are processable in joule-heated, ceramic-lined melters and meet WTP Contract terms. The WTP’s overall mission will require the immobilization of tank waste compositions that are dominated by mixtures of aluminum (Al), chromium (Cr), bismuth (Bi), iron (Fe), phosphorous (P), zirconium (Zr), and sulfur (S) compounds as waste-limiting components. Glass compositions for these waste mixtures have been developed based upon previous experience and current glass property models. Recently, DOE has initiated a testing program to develop and characterize HLW glasses with higher waste loadings. Results of this work have demonstrated the feasibility of increases in waste loading from about 25 wt% to 33–50 wt% (based on oxide loading) in the glass depending on the waste stream. It is expected that these higher waste loading glasses will reduce the HLW canister production requirement by about 25% or more.

Determination of the Corrosion Mechanisms of High-Level Waste Containing Glass

1981 ◽  
Vol 11 ◽  
Author(s):  
Horst Scholze ◽  
Reinhard Conradt ◽  
Heinrich Engelke ◽  
Hans Roggendorf
Keyword(s):  
Rock Salt ◽  
High Level Waste ◽  
Extreme Conditions ◽  
Safety Standard ◽  
Waste Forms ◽  
Corrosion Mechanisms ◽  
High Level

The German concept of high level waste final storage provides the use of certain glasses containing radioelement oxides as glass components. These waste forms are to be stored in rock salt formations in order to isolate the waste from the biosphere. The efficiency of this isolation is a most important question. The aim is to achieve a high safety standard that remains valid under extreme conditions such as the uncontrolled water entrance to the deposit.

Dissolution of Synroc in Deionised Water at 150°C

1996 ◽  
Vol 465 ◽  
Author(s):  
Katherine L. Smith ◽  
Michael Colella ◽  
Gordon J. Thorogood ◽  
Mark G. Blackford ◽  
Gregory R. Lumpkin ◽  
...  
Keyword(s):  
High Level Waste ◽  
Solution Ph ◽  
Dissolution Study ◽  
Leach Rate ◽  
Elemental Concentrations ◽  
Icp Ms ◽  
Before And After ◽  
High Level ◽  
Periodic Replacement ◽  
Simulated High Level Waste

ABSTRACTSynroc containing 20 wt% simulated high level waste (HLW) was subjected to two sets of leach tests at 150°C where the leachant was and was not replaced during the test (replacement and non-replacement testing). The leachant was a KH-phthalate buffered solution (pH 4.2). Samples were characterised before and after leach testing using SEM, AEM and SIMS. Elemental concentrations in leachates were measured using ICP-MS. In concert with the findings of i) a dissolution study of perovskite in a flowing leachant and ii) a previous Synroc dissolution study (wherein Synroc containing 10 wt% simulated HLW was subjected to periodic replacement, leach testing in deionised water at 150°C), the results of this study show that when the leachant replacement frequency is varied from 7 d to the duration of the test, there is no effect on leach rate or leaching mechanisms.

Nepheline Crystallization in High-Alumina High-Level Waste Glass

2015 ◽  
Vol 1744 ◽  
pp. 85-91 ◽  
Author(s):  
José Marcial ◽  
John McCloy ◽  
Owen Neill
Keyword(s):  
Nuclear Waste ◽  
Waste Glass ◽  
High Alumina ◽  
High Level Waste ◽  
Interfacial Conditions ◽  
Waste Vitrification ◽  
Cooling Schedules ◽  
High Level Nuclear Waste ◽  
High Level ◽  
Glass Compositions

ABSTRACTThe understanding of the crystallization of aluminosilicate phases in nuclear waste glasses is a major challenge for nuclear waste vitrification. Robust studies on the compositional dependence of nepheline formation have focused on large compositional spaces with hundreds of glass compositions. However, there are clear benefits to obtaining complete descriptions of the conditions under which crystallization occurs for specific glasses, adding to the understanding of nucleation and growth kinetics and interfacial conditions. The focus of this work was the investigation of the microstructure and composition of one simulant high-level nuclear waste glass crystallized under isothermal and continuous cooling schedules. It was observed that conditions of low undercooling, nepheline was the most abundant aluminosilicate phase. Further undercooling led to the formation of additional phases such as calcium phosphate. Nepheline composition was independent of thermal history.

Long-Term Radioactivity Release from Solidified High-Level Waste - Part II Parametric Study of Waste form Properties, Temperature and Time

1982 ◽  
Vol 15 ◽  
Author(s):  
Friedrich K. Altenhein ◽  
Werner Lutze ◽  
Rodney C. Ewing
Keyword(s):  
Parametric Study ◽  
Computer Code ◽  
Salt Dome ◽  
Waste Form ◽  
Glass Block ◽  
High Level Waste ◽  
Surface Layers ◽  
History Of ◽  
High Level

The computer code QTERM has been used to calculate the total released activity from a single glass block when in contact with brine in a salt dome repository as a function of: (1) waste form properties, (2) leaching mechanisms, (3) retention or precipitation of specific radionuclides in surface layers, (4) thermal history of the repository and (5) decreasing activity as a function of time.

scholarly journals The Reaction of SRL 202 Glass in J-13 and DIW

1992 ◽  
Vol 294 ◽  
Author(s):  
W. L. Ebert ◽  
J. K. Bates ◽  
E. C. Buck
Keyword(s):  
Stainless Steel ◽  
Reaction Rates ◽  
Deionized Water ◽  
High Level Waste ◽  
Similar Reaction ◽  
304L Stainless Steel ◽  
Ph Values ◽  
Stainless Steel Vessel ◽  
J 13 ◽  
High Level

ABSTRACTStatic leach tests were performed in both 304L stainless steel and Teflon vessels using a synthetic high-level waste glass with either deionized water (DIW) or a tuff groundwater solution as the leachant to assess the effects of the vessel and the initial leachant composition on the extent and nature of the glass reaction. The tests were performed using monolith samples at 340 m−1 and crushed samples at 2000 m−1 for times up to 1 year. The results show less silicon is released from the glass into the groundwater solution than into DIW at both high and low glass surface area/leachant volume ratios (SA/V), but the alkali metal and boron releases are not affected by the leachant used. Tests performed in a stainless steel vessel resulted in slightly lower leachate pH values, but similar reaction rates to those performed in a Teflon vessel, as measured by the boron release. Blank tests with DIW or EJ-13 in the vessels showed the Teflon vessels to release small amounts of fluoride (1 to 2 ppm) and to acidify the DIW slightly (4.0 < pH < 5.6). The pH values of blank tests with EJ-13 increased from 8.2 to about 8.6 in steel and to about 9.2 in Teflon vessels. The slightly higher pH values attained in Teflon vessels are attributed to outgassing of CO2 during the test.

Static Leaching of Radioactive Glass Under Conditions Simulating a Granitic Repository for High-Level Waste: Phase 1.

1983 ◽  
Vol 26 ◽  
Author(s):  
Hans-Peter Hermansson ◽  
Hilbert Christensen ◽  
David E Clark ◽  
Inga-Kari Björner ◽  
Hayaichi Yokoyama ◽  
...  
Keyword(s):  
Phase 1 ◽  
High Level Waste ◽  
Borosilicate Glasses ◽  
Joint Research ◽  
Weight Losses ◽  
Infrared Reflection ◽  
Joint Research Project ◽  
Actinide Oxides ◽  
Leaching Experiments ◽  
High Level

ABSTRACTA joint research project with participation from Japan, Switzerland and Sweden is underway at Studsvik (The JSS-project). The project concerns investigations on the leaching of fully radioactive glass (containing 12 wt% fission product oxides and actinide oxides) manufactured by CEA/Marcoule.So far the glass has been leached in doubly distilled water and in silicate water at 90°C. Some leaching experiments involved the presence of crushed Stripa granite in the same containers as the glass.Due to strong radiation and the presence of plutonium the leaching was carried out in a specially designed lead cave using gilded stainless steel containers.Weight losses, pH and elemental mass losses were determined together with infrared reflection spectral changes. These data are compared to those obtained from a simulated nonradioactive glass of nearly the same composition and to similar alkali borosilicate glasses previously investigated at Studsvik.

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