The total estimated quantity of uranium in oceans is around four and a half billion tonnes. Harvesting uranium from seawater is much less taxing to the environment. Thus, when uranium is harvested from seawater with near-zero environmental burdens, it will become a totally green fuel in the hands of humankind, as uranium generates primary calories without giving CO2 emissions and leaves no mill tailings at the recovery site while recovering it for use in reactors. To extract uranium from seawater, a contactor assembly that contains radiation-grafted polyacrylamid oxime (PAO) is used to trap the loosely bonded uranyl ion. Some of the design constraints for contractor assembly are the maximisation of the grafted sheet area and strength to withstand extreme marine conditions. The material should be compatible with the hot processing chemicals and be extremely cost effective, as well as lightweight. Design also has to take into account the ease of loading/unloading of grafted sheet modules, ease of replacement of grafted sheets, fixing of cage modules in seabed and load equilibrium even in high and low tide. This paper will cover the various challenges involved in designing a contactor assembly.