The Effect of Gamma Radiation on the Dissolution of High-Level Waste Glass in Boom Clay

2000 ◽  
Vol 663 ◽  
Author(s):  
K. Lemmens ◽  
P. Van Iseghem
Keyword(s):  
Bubble Formation ◽  
Bentonite Clay ◽  
High Level Waste ◽  
Glass Mass ◽  
Γ Radiation ◽  
Boom Clay ◽  
Leach Rate ◽  
The Media ◽  
Ph Decrease ◽  
High Level

ABSTRACTThe effect of γ-radiation on the dissolution of candidate high-level waste glasses was investigated in potential disposal environments at 90°C. The media consisted of mixtures of Boom Clay, bentonite clay and cement with clay water. During the experiments the pH of Boom Clay decreased, probably mainly by radiolytical oxidation of pyrite. The addition of bentonite, cement and glass buffered the pH decrease. Under radiation the glass mass losses decreased, whereas the leach rate of soluble elements was not influenced or appeared to increase. This is explained through the radiolytical acidification, and possibly by bubble formation in the glass.

Leaching of Np and Tc From Doped Nuclear Waste Glasses in Clay Media: The Effects of Redox Conditions

2002 ◽  
Vol 713 ◽  
Author(s):  
Véra Pirlet ◽  
Karel Lemmens ◽  
Pierre Van Iseghem
Keyword(s):  
Specific Activity ◽  
Solubility Limit ◽  
Redox Conditions ◽  
Metal Corrosion ◽  
High Level Waste ◽  
Test Medium ◽  
Static Tests ◽  
Boom Clay ◽  
The Media ◽  
High Level

ABSTRACTBoom Clay is the candidate geologic formation in Belgium for disposal of vitrified high level waste. In the waste glass, 237Np and 99Tc are some of the principal radionuclides. The leaching behaviour of these nuclides has been studied in dissolution tests involving glass doped with 237Np and 99Tc and was found to depend strongly on the redox conditions of the media contacting the glass. Static tests with the reference R7T7 glass and the reference PAMELA SM539 glass were performed in two clay media that may interact with the glass during the geological disposal. The first test medium consisted of FoCa-clay (Fourges-Cahaignes-clay), which is an oxidised clay. The second test medium was a mixture of backfill material, consisting mainly of FoCa-Clay, with metal corrosion products and Boom Clay. Lower Np and Tc concentrations were found in Boom Clay compared to FoCa-clay. In FoCaclay, Np and Tc were predominately in their oxidised form. Although Tc is mostly present in the soluble pertechnetate form, the Np concentrations are lower than expected for the chemistry of Np(V) in the medium. The concentrations of the radionuclides are steady-state concentrations rather than thermodynamic concentrations. Different mechanisms can be invoked to explain these Np concentrations. In Boom Clay, the measured Np concentrations are close to the solubility limit whereas the Tc concentrations are slightly higher than those calculated in Boom Clay at thermodynamic equilibrium. The initial specific activity of the radionuclide in the glass was found to influence the soluble concentration. Np and Tc were not found to be retained in the glass reaction layer for both media.

Neptunium Speciation in Humic Acid-rich Clay Water upon Interaction With Radioactive Waste Glass Samples

2002 ◽  
Vol 757 ◽  
Author(s):  
V. Pirlet ◽  
P. Van Iseghem
Keyword(s):  
Humic Substances ◽  
Humic Acids ◽  
Specific Interaction ◽  
Waste Glass ◽  
High Level Waste ◽  
Boom Clay ◽  
Dissolution Tests ◽  
Vis Spectroscopy ◽  
Doped Glasses ◽  
High Level

ABSTRACTOrganic complexes of actinides are known to occur upon interaction of high level waste glass and Boom Clay which is a potential host rock formation for disposal of high level waste in Belgium. The solubility and mobility of 237Np, one of the most critical radionuclides, can be affected by the high dissolved organic carbon content of the Boom Clay porewater through complexation with the humic substances. The influence of humic substances on the Np behaviour is considered through dissolution tests of Np-doped glasses in Boom Clay water and through fundamental study of the specific interaction between Np(IV) and the humic acids using spectroscopic techniques. High Np(IV) concentrations are found in the glass dissolution tests. These concentrations are higher than what we should expect from the solubility of Np(OH)4, the solubility limiting solid phase predicted under the reducing conditions and pH prevailing in Boom Clay. Studying the specific interaction of Np(IV) with humic acids in Boom Clay porewater, high soluble Np concentrations are also measured and two main tetravalent Np-humate species are observed by UV-Vis spectroscopy. The two species are interpreted in terms of mixed hydroxo-humate complexes, Np(OH)xHA with x = 3 or 4. These species are the most likely species that can form according to the pH working conditions. Using thermodynamic simplified approaches, high complexation constants, i.e. log β131 and log β141 respectively equal to 46 and 51.6, are calculated for these species under the Boom Clay conditions.Comparing the spectroscopic results of the dissolution tests with the study of the interaction of Np(IV) with humic substances, we can conclude that the complexation of Np(IV) with the humic acids may occur and increases the solubility of Np(OH)4 upon interaction of a Np-doped glass and the Boom Clay porewater.

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.

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.

The investigation of the neptunium complexes formed upon interaction of high level waste glass and Boom Clay media

1998 ◽  
Vol 271-273 ◽  
pp. 267-271 ◽  
Author(s):  
V. Pirlet ◽  
P. Van Iseghem ◽  
A. Dierckx ◽  
J.-F. Desreux
Keyword(s):  
Waste Glass ◽  
High Level Waste ◽  
Boom Clay ◽  
High Level

Safety Assessment of Geological Disposal of High-Level Radioactive Waste in Boom Clay: Relation With the Radionuclide Inventory

2009 ◽  
Author(s):  
Pierre Van Iseghem ◽  
Jan Marivoet
Keyword(s):  
Radioactive Waste ◽  
Safety Assessment ◽  
High Level Waste ◽  
Spent Fuel ◽  
Geological Disposal ◽  
High Level Radioactive Waste ◽  
Boom Clay ◽  
High Level ◽  
Clay Formation ◽  
Parameter Values

This paper discusses the impact of the parameter values used for the transport of radionuclides from high-level radioactive waste to the far-field on the long-term safety of a proposed geological disposal in the Boom Clay formation in Belgium. The methodology of the Safety Assessment is explained, and the results of the Safety Assessment for vitrified high-level waste and spent fuel are presented. The radionuclides having the strongest impact on the dose-to-man for both HLW glass and spent fuel are 79Se, 129I, 126Sn, 36Cl, and 99Tc. Some of them are volatile during the vitrification process, other radionuclides are activation products, and for many of them there is no accurate information on their inventory in the waste form. The hypotheses in the selection of the main parameter values are further discussed, together with the status of the R&D on one of the main dose contributing radionuclides (79Se).

Properties of Bentonite Clay as Buffer Material in High-Level Waste Geological Disposal. Part I: Chemical Species Contained in Bentonite

1987 ◽  
Vol 76 (2) ◽  
pp. 221-228 ◽  
Author(s):  
Masanori Takahashi ◽  
Masayuki Muroi ◽  
Atsuyuki Inoue ◽  
Masahiro Aoki ◽  
Makoto Takizawa ◽  
...  
Keyword(s):  
Chemical Species ◽  
Bentonite Clay ◽  
High Level Waste ◽  
Geological Disposal ◽  
Buffer Material ◽  
High Level
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