A review of radiation effects in nuclear reactor materials has been made; the irradiation effects have been correlated with the crystal structure of the materials. Five phenomena, irradiation hardening, irradiation embrittlement, irradiation creep, irradiation growth and void swelling that occur in materials by neutron irradiation in a reactor environment have been discussed with a view to explaining the physics of the phenomena and the engineering consequences. Metallurgical approaches for improving the irradiation performance of materials and for developing new alloys with better resistance to radiation damage have been pointed out.

The ushering in of the era of high technology in our country witnessed the emergence and growth of several new technologies which are either totally unconventional or less common in otherwise well known and established areas of industrial practice. A vivid example of the second category of advances is found in the development of extractive processes for obtaining the less common metals particularly required for service in nuclear, aerospace and electronics industries. In this paper, the growth of research and development in rare metals extraction in India is surveyed from its infancy in the fifties to the present stature of a firm footed technology accredited with several directed achievements and well-developed maturity.

The discovery of the phenomenon of superconductivity by Kamerlingh Onnes in 1911 was the first indication of the possibility of electrical conduction without any associated Joule loss. The technological application of the property (which was essentially manifested at liquid helium temperatures) had to await the development of stable superconducting materials capable of withstanding high currents and large magnetic fields. Although many materials — elements, alloys, ternary chalcogenides, and recently oxides — have been found to be superconducting, only a few of them have received attention for significant applications. This is based on three important parameters namelyT_c, the transition temperature,H_c2, the upper critical field andJ_c, the critical current density.T_c andH_c2 are considered intrinsic to the material, whileJ_c is influenced by the microstructure, and has to be optimised during fabrication of the material in the useful form. On these considerations, Nb-Ti, Nb₃Sn and V₃Ga have emerged as proven materials for significant applications while PbMo₆S₈ is still under development. Despite the fact that all these materials have to be used only at liquid helium temperatures on account of their lowT_c, major developments have taken place in harnessing particularly the niobium alloys to produce superconducting magnets.

Towards the end of 1986, a break-through has been achieved in the direction of raising theT_c. Many ceramic oxides, notably Y₁Ba₂Cu₃O₇, have exhibitedT_c in the vicinity of 100 K. These materials have also been shown to have highH_c2, about 180 Tesla. Attempts are now being made to realise a highJ_c. It is too early to say whether such materials can be fabricated in suitable forms capable of carrying high currents.

Among the major areas in which superconducting materials have so far been used, mention should be made of superconducting magnets for high energy particle accelerators, magnetohydrodynamic power generation, magnetic resonance imaging, and fusion research programmes. In other potential applications such as motors and magnetically levitated transportation, economic break-even has not been achieved, mostly on account of the need to use liquid helium. The discovery of the high temperature superconductors capable of operating at liquid nitrogen temperatures thus promises a revolution in electrical technology.

The paper reviews the development and applications of superconducting materials, with reference to work being done in India.

Titanium has been finding increasing usage as a structural metal in aerospace and many non-aerospace sectors mainly due to its light weight, high strength and outstanding corrosion resistance properties. India is very fortunate to possess the world’s largest and richest mineral deposit for this metal. Early studies on the metal extraction during mid ’60s at the Bhabha Atomic Research Centre, Bombay and pilot plant studies at the Nuclear Fuel Complex, Hyderabad resulted in the establishment of a ‘Technology Development Centre’ at Defence Metallurgical Research Laboratory (DMRL), Hyderabad. DMRL has already demonstrated titanium sponge production feasibility in 2,000 kg batches by the conventional Krcll process and is presently engaged in the development of the more energy saving ‘combined process technology’ in 4,000 kg batches. Fused salt electrolysis is widely employed to produce magnesium metal in integrated titanium plants so as to regenerate magnesium from the by-product magnesium chloride. DMRL has developed magnesium electrolysis technology in a 30 kA monopolar, modular type cell and is now developing the multipolar cell technology in 7kA, 22·2 V, two-module cell equipped with five bipoles in each module. This paper traces the developmental efforts on titanium metal extraction in India and describes the current efforts underway at DMRL for developing the latest energy efficient and cost effective technologies for the large scale production of both titanium and magnesium metals.