[en] Interaction study in thoria/zircaloy-2 system is important for the understanding of in-reactor behavior of fuel/clad assembly in future reactors. In the present investigation, experiments were carried out at elevated temperature (1100-1250deg C) under vacuum condition to understand the mode of interaction. It is observed that thoria got reduced under the experimental conditions. (author)

[en] Reprocessing of spent nuclear fuels does fetch multiple benefits in terms of lower environmental stress/risk and more economical nuclear power generation. (i) Recycling of uranium (²³⁵U, ²³³U), and/or plutonium (²³⁹Pu) as nuclear fuel components for further energy generation; usage of (ii) ¹³⁷Cs and ⁹⁰Sr for cancer treatment; (iii) ²³⁸Pu, ²⁴⁴Cm for Radioactive Thermoelectric Generator; (iv) ²⁴¹Am for safety (e.g. smoke detector) and security applications; (v) recovery of expensive platinum group of elements etc are the few advantages associated with closed nuclear fuel cycles. However, besides all these beneficial features, reprocessing of spent fuels also generates High-Level Nuclear Wastes, which contain as high as 99% of radioactivity witnessed in a given fuel cycle

[en] Natural allanite grains collected from Jojjuru, Andhra Pradesh were analysed for their actinides and lanthanides content. It is seen that allanite show the excellent capacity of retaining significant amount of actinides and lanthanides over millions of years and can be potential host for immobilisation of actinides and lanthanides rich nuclear waste. (author)

[en] Satisfying the growing requirement in an environment friendly way is one of the most important tasks we need to accomplish these days. Considering the restricted non-renewable energy resources and limited technological progresses achieved in the renewable energy sectors in India, nuclear energy appears to be one of the most lucrative solutions towards the forthcoming energy crisis. Successful implementation of nuclear energy program however requires careful execution of high level nuclear waste management activities. One very important aspect of this process is to identify and develop suitable inert matrix(ces) for conditioning of nuclear waste(s) using natural analogue studies. And this establishes the very vital linkage between geochemical studies and nuclear waste immobilization. One good example of such an interdisciplinary approach can be seen in the methodologies adopted for immobilization of sulfate bearing high level nuclear wastes (SO₄-HLW). It has been reported on several occasions that sulfur-rich melt get separated from silicate melt within magma chamber. Similar process has also been witnessed within vitrification furnaces whenever an attempt has been made to condition SO₄-HLW within borosilicate glass matrices. Since such liquid-liquid phase separation leads to multiple difficulties in connection to radionuclide immobilization and plant scale vitrification processes, solutions were sought from natural analogue studies. Such as integrated approach ultimately resulted in establishing two different methodologies e.g. (i) modifying the borosilicate network through introduction of Ba²⁺ cation; a process being followed in India and (ii) using phosphatic melt as a host instead of borosilicate melt; a process being followed in Russia. Detail of these two routes and the geochemical linkage in nuclear waste immobilization will be discussed.(author)

[en] Thorium based fuels are being used for nuclear reactors. The structural stability of fuel-clad assemblies in reactor systems depend upon the nature of interdiffusion reaction between fuel-cladding materials. Interdiffusion reaction thorium and various cladding materials is presented in this paper. (author)

[en] Highlights: • Management of radioactive Ni based metallic wastes. • Microstructure of Ni/NiO–perovskite composite. • Interaction of Ni/NiO–perovskite composite with simulated high level waste glass melt. - Abstract: Management of nickel – based radioactive metallic wastes is a difficult issue. To arrest the release of hazardous material to the environment it is proposed to develop perovskite coating for the metallic wastes. Polycrystalline BaCe_0_._8Y_0_._2O_3_−_δ perovskite with orthorhombic structure has been synthesized by sol–gel route. Crystallographic analyses show, the perovskite belong to orthorhombic Pmcn space group at room temperature, and gets converted to orthorhombic Incn space group at 623 K, cubic Pm3m space group (with a = 4.434 Å) at 1173 K and again orthorhombic Pmcn space group at room temperature after cooling. Similar observations have been made from micro-Raman study as well. Microstructural studies of BaCe_0_._8Y_0_._2O_3_−_δ–NiO/Ni composites showed absence of any reaction product at the interface. This suggests that both the components (i.e. perovskite and NiO/Ni) of the composite are compatible to each other. Interaction of BaCe_0_._8Y_0_._2O_3_−_δ–NiO/Ni composites with simulated barium borosilicate waste glass melt also did not reveal any reaction product at the interfaces. Importantly, uranium from the waste glass melt was found to be partitioned within BaCe_0_._8Y_0_._2O_3_−_δ perovskite structure. It is therefore concluded that BaCe_0_._8Y_0_._2O_3_−_δ can be considered as a good coating material for management of radioactive Ni based metallic wastes

[en] Highlights: ► Technical review. ► High level nuclear waste immobilization within phosphate glasses. ► Integration of data from laboratory scale experiments, plant scale observations and natural rock information. - Abstarct: Immobilization of phosphate containing high level nuclear wastes within commonly used silicate glasses is difficult due to restricted solubility of P₂O₅ within such melts and its tendency to promote crystallization. The situation becomes more adverse when sulfate, chromate, etc. are also present within the waste. To solve this problem waste developers have carried out significant laboratory scale research works in various phosphate based glass systems and successfully identified few formulations which apparently look very promising as they are chemically durable, thermally stable and can be processed at moderate temperatures. However, in the absence of required plant scale manufacturing experiences it is not possible to replace existing silicate based vitrification processes by the phosphate based ones. A review on phosphate glass based wasteforms is presented here.

[en] Identification of proper materials for plant scale vitrification furnaces, engaged in immobilization of high level nuclear waste has always been a great challenge. Fast degradation of pour spout materials very often cause problem towards smooth pouring of waste-glass melt in canister and damages bellow kept in between. The present experimental study describes the various reaction products that form due to interaction between waste-glass melt and potential bellow liner materials such as copper, stainless steel and nickel based Superalloys (Alloy 690, 625). The results indicate that copper based material has lesser tendency to form adherent glassy layer.

[en] Joule heated ceramic melters are widely used for conditioning of high level liquid waste (HLW). In general alloy 690 is used to fabricate the metallic components of ceramic melter. For uninterrupted operation of vitrification plant, longevity assessment of metallic components used is essential. Vitrification of HLW is a complex process and it induces a harsh environment within the melter, which includes borosilicate melt pool in the bottom, gaseous cap in the top etc. In the present study, coupons of alloy 690, alloy 625 (Ni based superalloys), copper, stainless steel etc were dipped in borosilicate melt at 1223K for varying period of time. The cross sections of polished coupons have been studied with the help of optical microscope and electro-optical instruments like scanning electron microscope and electron probe micro analyser. Emphases were given to the microstructural and compositional changes of metal/alloys and borosilicate glasses near the interface

[en] Micro-Raman spectroscopy was used to evaluate the radiation damage in metamict form of gadolinite and defects formed in halite single crystals. The metamict mineral of gadolinite was investigated in order to study its structural variation in metamict form and recrystallized form. However, types of defects which are originally present in halite crystals responsible for its gradual colour variation are identified using Micro-Raman spectra (author)