Transient Evolution of Inter Vessel Gap Pressure Due to Relative Thermal Expansion Between Two Vessels

In a typical liquid metal cooled fast breeder reactor (LMFBR), a cylindrical sodium filled main vessel, which carries the internals such as reactor core, pumps, intermediate heat exchangers etc. is surrounded by another vessel called safety vessel. The inter vessel gap is filled with nitrogen. During a thermal transient in the pool sodium, because of the relative delay involved in the thermal diffusion between MV and SV, they are subjected to relative thermal expansion or contraction between them. This in turn results in pressurisation and depressurisation of inter vessel gap nitrogen respectively. In order to obtain the external pressurization for the buckling design of MV, transient thermal models for obtaining the evolutions of MV, SV and inter gap nitrogen temperatures and hence their relative thermal expansion and inter vessel gap pressure have been developed. This paper gives the details of the mathematical model, assumptions made in the calculation and the results of the analysis.

Molecular evolution of methanogens based on their metabolic facets

The information provided by completely sequenced genomes of methanogens can yield insights into a deeper molecular understanding of evolutionary mechanisms.This review describes the advantages of using metabolic pathways to clarify evolutionary correlation of methanogens with archaea and prokaryotes.Metabolic trees can be used to highlight similarities in metabolic networks related to the biology of methanogens.Metabolic genes are among the most modular in the cell and their genes are expected to travel laterally,even in recent evolution.Phylogenetic analysis of protein superfamilies provides a perspective on the evolutionary history of some key metabolic modules of methanogens.Phage-related genes from distantly related organisms typically invade methanogens by horizontal gene transfer.Metabolic modules in methanogenesis are phylogenetically aligned in closely related methanogens.Reverse order reactions of methanogenesis are achieved in methylotrophic methanogens using metabolic and structural modules of key enzymes.A significant evolutionary process is thought to couple the utilization of heavy metal ions with energetic metabolism in methanogens.Over 30 of methanogens genomes have been sequenced to date,and a variety of databases are being developed that will provide for genome annotation and phylogenomic analysis of methanogens.Into the context of the evolutionary hypothesis,the integration of metabolomic and proteomic data into large-scale mathematical models holds promise for fostering rational strategies for strain improvement.