For better utilization of land and infrastructure, multiple power reactor units are preferably constructed at same site. In the life of reactor, at some stage, it will undergo either major upgradation for plant life management or de-commissioning which requires whole reactor fuel to be discharged irrespective of burn-up. This includes a large amount of fuel, which has not achieved target discharge burn-up. In this paper, novel methodologies are explored and innovative techniques are proposed for ex-core fuel management (ECFM) and in-core fuel management (ICFM) to utilize low burn-up bundles in a twin unit PHWR by inter-unit transfer. This is achieved without any reprocessing of fuel. Using the proposed modified fuel management, a net economic benefit of equivalent fuel saving of ~23% NU of the initial full core load of 37-element bundles in an PHWR-700 is achieved. Additionally, reactor operation of ~60FPDs without using any fresh fuel is also accomplished.