On nuclear power

As a nuclear engineer, I appreciate Engr. S.A. Mansoor's promotion of Pebble Bed Reactors (PBRs) for heat or power generation (Dec. 13). It is one of the six concepts being investigated for Generation IV rectors (current reactors operating round the world being of the Generation II and III type). Generation IV reactors are not expected to be available for commercial operation before 2030.
Although promising in principle, the PBR has significantly less production scale experience than Light Water Reactors (LWRs). The two PBRs (15 Mwe and 300 Mwe) in Germany were shut down in late 1980s and the South African demonstration project has been indefinitely postponed due to financial constraints in Sep. 2009. On the other hand, of the 436 reactors currently operating world-wide, 356 reactors are LWRs. Since Bangladesh should invest in a proven technology, the decision of the current government to negotiate with Russia for a proven Generation III type LWR is a step in the right direction.
Incidentally Engr. Mansoor may note that both PBR and LWR use U-235 as reactor fuel. U-236 does not occur in nature and cannot be used as a reactor fuel as it is not a fissionable material. U-238 is a fertile material that is converted into a fissionable material (Pu-239) when bombarded with neutrons in a reactor.