Thermo-physical behavior of borosilicate glasses in the presence of high-level radioactive liquid waste constituents
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Thermo‑physical behavior of borosilicate glasses in the presence of high‑level radioactive liquid waste constituents J. Selvakumar1,2 · Sourav Maity1 · S. Rajasekaran1 · S. Chitra1 · Biplob Paul1 Received: 23 October 2019 / Accepted: 28 November 2019 © Akadémiai Kiadó, Budapest, Hungary 2019
Abstract Elemental composition of high-level radioactive liquid waste (HLW) from samples of various batches was assessed by using side-on-view inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Under robust condition (Mg ratio, 10.2 ± 0.4 at RF power 1.3 kW), t he plasma excitation temperature (Texe, 9925 ± 1950 K) was calculated using the Boltzmann plot method. Thermal behavior of major constituents (> 1 g L−1) of HLW, such as nitrates of Na+, Fe3+, Cs+, Nd3+, and UO22+, were studied using simultaneous thermal analyzer. Subsequently, the thermal stability of five and seven components borosilicate glasses was studied in detail with the above nitrates individually added as additives. Vapor pressure of sodium metaborate (NaBO2, one of the major vapor species from the glass melt in the off-gas system during vitrification of HLW) was estimated using transpiration thermogravimetry. Based on mass loss, the equilibrium vapor pressures (2.51–26.37 Pa) over a temperature span of 1233.15–1343.15 K were estimated. The molar enthalpy of vaporization (ΔvapH°) for sodium metaborate was calculated to be 287.84 ± 0.94 kJ mol−1 using the experimental data. Keywords High-level radioactive liquid waste (HLW) · Inductively coupled plasma-atomic emission spectroscopy (ICPAES) · Plasma temperature · Sodium borosilicate glass · Thermogravimetric analysis (TGA) · Vapor pressure
Introduction Vitrification is an established technology for the effective management of high-level radioactive liquid waste (HLW) [1]. The outcome of vitrification is a solid, immobilized 20–30 mass% of waste oxides in a borosilicate glass matrix [1–3]. Detailed chemical, radiochemical and thermochemical analyses of waste are vital to optimize the waste loading and to achieve glass formulations with desired properties of the conditioned product for safe management. It involves an analysis of various elements and isotopic composition in the multi-elemental matrix of HLW. The radioactivity of strong gamma-emitting fission products and the acidity of HLW cause several complications during estimation. Hence, advanced methods using a combination of techniques have * J. Selvakumar [email protected] 1
Waste Immobilization Plant, Integrated Nuclear Recycle Plant, Nuclear Recycle Board, Bhabha Atomic Research Centre, Kalpakkam 603 102, India
Homi Bhabha National Institute, Anushakthinagar, Mumbai, Maharashtra 400 094, India
2
to be applied for the estimation of the target element in the presence of other elements. At high temperatures in a melter [2], the nitrates and oxides of HLW constituents interact with the base glass and alter the durability and physical properties of the matrix [1–5]. To the nuclear waste managers, a durable product is one t
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