Formation of diffusion barrier coating on superalloy 690 substrate and its stability in borosilicate melt at elevated temperature

Dutta, R.S.; Yusufali, C.; Paul, Bhaskar; Majumdar, S.; Sengupta, P.; Mishra, R.; Kaushik, C.P.; Kshirsagar, R.J.; Kulkarni, U.D.; Dey, G.K.

doi:10.1016/j.jnucmat.2012.08.012

Cited by 17 publications

(3 citation statements)

References 33 publications

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“…To achieve this, a 'multiple barrier system' concept is followed which constitutes an 'engineered barrier system' and a 'natural barrier system'. The general practice is to immobilize the high-level liquid waste within borosilicate (Hench et al, 1984;Kaushik et al, 2006;Ojovan and Lee, 2007;Mishra et al, 2007Mishra et al, , 2008Sengupta et al, 2014) and/or phosphate (Kim and Day, 2003;Sengupta, 2012) or aluminosilicate glass (Sengupta et al, 2011a) matrices prepared in metallic melter or Joule heated ceramic melter pots (Dutta et al, 2013;Haldar et al 2014;Sengupta, 2011;Sengupta et al, 2006Sengupta et al, , 2007Sengupta et al, , 2008Sengupta et al, , 2009Sengupta et al, , 2011bKain et al, 2005). However, laboratory based studies are also being pursued to explore the potential of glass ceramics (Donald et al, 1997;Goswami et al, 2007;Lee et al, 2006;Sharma et al, 2004) and crystalline inert matrices (Haldar et al, 2015;Grover et al, 2006Grover et al, , 2007Grover et al, , 2008Grover et al, , 2010Jafar et al, 2014a,b) for this purpose.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of actinides within speleothems

et al. 2016

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Stalagmites and stalactites, as observed within natural caves, may develop inside geological repositories during constructional and post-operational periods. It is therefore important to understand actinide sorption within such materials. Towards this, experimental studies were carried out with 233U, 238Np (VI), 238Np (IV), 239Pu and 241Am radiotracers using natural speleothem samples collected from the Dharamjali cave of the Kumaon Lesser Himalayas, India. Petrological/mineralogical studies showed that natural speleothems have three general domains: (1) columnar calcite; (2) microcrystalline calcite; and (3) botryoidal aragonite – each with ferruginous materials. Results showed that all domains of speleothems can take up >99% actinides, irrespective of valence state and pH (1–6 range) of the solution. However, distribution coefficients were found to be at a maximum in aragonite for most of the actinides. Such data are very important for long-term performance and safety assessments of the deep geological repositories planned for the disposal of high-level nuclear wastes.

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Section: Introductionmentioning

confidence: 99%

Adsorption of actinides within speleothems

et al. 2016

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“…During plant scale vitrification process, “yellow phase” being lighter in density than borosilicate melt accumulates on/within the top part of the melt surface and hence prevents easy release of gaseous reaction products from the molten mass. This lowers overall efficiency in melting/mixing rates (yellow phase being good conductor of heat), promotes corrosion/plugging of vitrification furnace components (including off‐gas handling system), and causes short circuiting (yellow phase is good conductor of electricity) of the melter electrodes . In short, sulfate separation from waste glassmelt poses severe safety risks.…”

Section: Introductionmentioning

confidence: 99%

Vanadium in Borosilicate Glass

et al. 2014

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Understanding the role of V 2 O 5 within borosilicate glass matrices is important for the development of novel matrices toward immobilization of sulfate containing high-level nuclear wastes. Present investigation shows, within sodium barium borosilicate glass matrix V 2 O 5 can be homogeneously added up to 5 mol% and beyond which it separates out into three phases, for example, (i) silica (ii) Barium (Ba) -Vanadium (V) oxide, and (iii) glass matrix. 29 Si MAS NMR (Nuclear Magnetic Resonance) studies of the samples show that below 5 mol% V 2 O 5 addition, silicate network is dominantly constituted of Q 2 and Q 3 structural units, whereas above this, the network gets more polymerized through formation of Q 3 and Q 4 units. In case of borate network, 11 B MAS NMR investigations revealed that the concentration of BO 4 [(0B, 4Si)] unit increases gradually up to 5 mol% and then it decreases at the cost of BO 4 [(1B, 3Si)], BO 3 (symmetric) and BO 3 (asymmetric) units. Micro-Raman analyses of the samples showed that with additions of V 2 O 5 in diluted concentrations, amorphous silicate network remained unaltered, whereas some amplification in signals corresponding to ring-type metaborate and VO 5 units exists. It is therefore apparent from both MAS-NMR and micro-Raman studies that with V 2 O 5 additions within the solubility limit (≤5 mol%), borate network gets depolymerized leading to decrease in hardness from an average value of 5.0-4.2 GPa.(1) V 2 O 5 as Amorphous Network Modifier The idea of using V 2 O 5 within glass matrices to enhance sulfate solubility was first put forward by Russian scientists. 35 According to them, the match between sulfate crystallochemical parameters and glass structure plays a crucial role in determining sulfate solubility. The important parameters which decide such compatibility include (i) cation-oxygen binding energy; (ii) Dietzel field strength (z c /a 2 , where "z" is charge of the cation and "a" is sum of cation radius and O 2À radius); (iii) z c /k bond strength, where "k" is the coordination number of the cation; and (iv) size and polarization of the polyhedra. 12,35 These considerations yielded following cation distribution series: L. Pinckney-contributing editor Manuscript No. 34981.

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“…To avoid such situations, 'preventive management strategy', either through development of diffusion barrier coating on Alloy 690 or through its compositional modification appear to be more appropriate ones. Towards the first option, the authors have already successfully developed (i) Ni-YSZ composite [17] and (ii) Ni-aluminide [18] coatings on the laboratory scale specimens. However, considering the harsh environment experienced by the Superalloy within vitrification furnaces, it is thought worthwhile to explore the alloy modification route as well [19,20].…”

Section: Introductionmentioning

confidence: 99%