[en] Studies on the radiation sensitivity of the phosphine-resistant strain of Tribolium costaneum (x 5.9) showed that resistance to phosphine did not involve any change in their sensitivity to radiation. Further investigations on the interaction between gamma radiation and phosphine fumigation on the susceptible strain of this insect by bioassay tests revealed that there was no interaction between the two treatments whether radiation preceded or followed fumigation. (author)

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[en] Design of Advanced Heavy Water Reactor (AHWR) is in progress. It consists of vertical pressure tubes with boiling light water coolant flowing through the tubes and heavy water moderator in the calandria. In PHWRs, core heat removal is through forced circulation of the coolant by PHT pumps. In AHWR, no PHT pumps are used and core heat is carried away by natural circulation of the coolant due to density difference between steam/water mixture inside the core and the water region outside the core. This passive means of core heat removal results in a number of benefits viz. (a) extra length of piping, valves, instruments, power supply and control systems for functioning of instruments are eliminated, (b) plant layout is simplified, (c) maintenance of valves and instruments is reduced. Natural circulation in AHWR is achieved by keeping the steam drum at a sufficient height above the core to get the required driving force. The loop height depends on many factors i.e. channel power, V_c/V_f ratio (ratio of coolant volume to fuel volume) and core height. The effect of these parameters on the loop height to establish natural circulation have been studied and presented. (author)

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[en] The polarographic reduction of UO₂²⁺ and Th⁴⁺ ions in methyl-3-mercaptopropionate has been found to be irreversible and diffusion controlled in 0.1 M NaClO₄, 0.002% Triton X-100 and 25% ethanol. The values of kinetic parameters-transfer coefficient (αn), formal rate constant (ksub(f,h)deg) for the electrode reaction are determined by Koutecky's method as extended by Meites and Israel. The free energy, enthalpy and entropy of activation have also been reported. (author)

[en] For Advanced Heavy Water Reactor (AHWR), removal of decay heat and containment heat is being considered by passive means. For this, special type of isolation condensers are designed. Isolation condensers when submerged in a pool of water, are the best choice because condensation of high temperature steam is an extremely efficient heat transfer mechanism. By the use of isolation condensers, not only heat is removed but also pressure and temperature of the system are automatically controlled without losing the coolant and without using conventional safety relief valves. In this paper, design optimisation studies of isolation condensers of different types with natural circulation for the removal of core decay heat for AHWR is presented. (author)

[en] Advanced and innovative reactor systems are considering the use of large pools as heat sink for various safety functions like decay heat removal or containment cooling. These designs generally have heat exchangers immersed in the pool or alternatively, pool water passing through the heat exchangers. For enhanced safety and reliability, preferred heat transfer mode is considered to be passive i.e. natural convention so that heat sink availability is maintained even in absence of failure of power supply and active components. However, heat transfer by natural convection to large pools poses a problem to the designer i.e. thermal stratification. As a result of natural convection, hot layers of water may accumulate over the relatively cold one and in turn inhibit the natural convection itself. Not only the heat transfer performance may get deteriorated but some parts of the pool like concrete wall may be subjected to high temperature which is not desirable. Employing shrouds around the heat source in the pools is one of the simplest ways of suppressing the thermal stratification. This paper discusses the assessment of a few schemes of shrouds conceived to suppress the thermal stratification in large pools with immersed heat exchangers and promote the mixing across the pool by natural circulation. (author)