Calculate the amount of \({ }^{235} \mathrm{U}\) consumed in a year in the Example 6.1. Calculate the burnup in MWd/ \(\mathrm{kg}\) if the reload is 25 tonnes. Also calculate the depletion in \({ }^{235} \mathrm{U}\), if the initial feed was 75 tonnes of \(U\) with an enrichment of \(3 \%\). Estimate the burnup in atom percent.

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6.1 Introduction In nuclear reactors, fuel and structural materials get irradiated by neutrons and gamma dur- ing their residence time and also for a few years when stored just outside the reactor core for cooling before possible reprocessing, recycling, and safe disposal. Energy extracted from a nu- clear fuel is a measure of its potential. Estimation of fuel performance is an essential aspect of reactor design. This chapter gives an exposition to fuel utilization in different thermal and fast reactor systems, fuel burnup aspects, fissile and fertile optimization for maximizing burnup, effect on reactivity coefficients or transient safety parameters due to burnup, fuel management and irradiation cycles, development and solution of buildup and depletion of actinides, and fission products and also advanced fuel cycles. Fuel burnup effects and fuel management prin- ciples for boiling water reactor, pressurized water reactor, pressurized heavy water reactor, and fast breeder reactor are detailed with examples. Fuel cycle physics entails an entire gamut of studies from the front end which deals with efficient use in reactors to the backend where the fuel is safely disposed or reprocessed and recycled to form a closed fuel cycle.