The requirement of natural uranium as the initial inventory for the 540 MWe PHWR is about 110 T of UO2 which is equivalent to 97 T of uranium metal i.e. about 180 TU/GWe. For the existing PHWRs of 220 MWe size this number is about the same. For the future 700 MWe PHWRs, as the core remains the same as that of the 540 MWe reactor, the initial inventory per GWe is lower, about 138 TU/GWe. As the total PHWR capacity would consist of roughly equally of the two designs, an average value of about 160 TU/GWe has been taken in the present study.

The annual fuel operational requirement depends on the power, the burn-up, the capacity factor and the thermal to electrical energy conversion efficiency. It is about 150 TU for 1 GWe power, 6,700 MWd/T burn-up, 80% capacity factor and 0.29 thermal to electrical energy conversion efficiency. The discharged fuel contains about 3.5 kg plutonium. Out of this plutonium, only about 75% is the fissile component. Depleted uranium would constitute the major fraction (about 0.988) of the discharged fuel. It would be used mainly in FBRs.

· For the 1 GWe LWR, the fuel discharge rate is estimated to be 25 T per year at 35,000 MWd/T burn-up, 0.33% thermal to electrical energy conversion efficiency and 80% capacity factor. The discharged fuel contains about 1% plutonium, of which two-third will be the fissile component .

· For the 1 GWe FBR the fuel discharge rate is estimated to be 10.81 T per year at 67,500 MWd/T burn up, at 0.42 thermal to electrical energy conversion efficiency and 80% capacity factor. The fissile component in discharged fuel will be 1.081 times of that of the fissile component of the fuel loaded in the reactor. This number viz., 1.081 has been calculated by INFCE based on 0.75 capacity factor. Larger the capacity factor larger would be this number. Use of this number in the present study is conservative.

· It is assumed that the technology of Pu-U metal based FBRs having the fissile growth rate of 8.1 %/yr, would have been developed by 2020 (Table 12).

· The critical fissile mass required for the above FBR and associated fuel cycle is about 3.7 T for one-year out of pile period. The critical mass may vary with the isotopic composition of the plutonium used i.e. whether it is plutonium discharged from PHWR, LWR or FBR, but this consideration is beyond the scope of the present estimates and is assumed to have negligible effect.

· Metal-fuelled FBRs of 4 GWe capacity or more will be installed annually from 2021 till the plutonium inventory from PHWR discharged fuel lasts and then as many as possible FBRs will continue to be added from the plutonium further bred in PHWRs as well as FBRs. Similarly, FBRs will be installed from the plutonium generated in LWRs and also from the plutonium bred in FBRs themselves.

· The depleted uranium discharged from the PHWRs will be used in the FBRs as initial inventory and as makeup requirements i.e. the difference between the feeds and the discharges. The total cycle inventory would be approximately 130 T per GWe and the annual makeup requirement would be about 1.1 T per GWe. It strictly applies for the INFCE reference oxide design only but has been taken to be applicable for the metal design as well. It may have little effect on the present estimates based on the metal design. Accordingly about 35,750 T of the depleted uranium would be tied up in FBRs. The annual makeup requirement after 2052 would be about 300 T per year, whereas nearly 24,000 T would be the inventory in hand. It would be sufficient for the life time of the FBRs.

· INFCE data is based on a burn up of 100,000MWd/T. It is expected that by 2020, R&D will be completed to ensure that fuel burn up is 200,000 MWd/T and this might also increase fissile material growth by reducing cycle losses. Use of INFCE data for the present study is conservative.