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Primary institutional explanation of time, distance and radiation shielding.

Nuclear engineering designs and studies systems that use nuclear reactions or manage materials with radioactivity. Its subjects include nuclear reactors, radiation detection, radiation shielding, nuclear fuel, the behaviour of structural materials under irradiation, and radioactive waste management.

A nuclear power plant shows why several areas of engineering must work together. Nuclear fission releases energy; a coolant transports the resulting heat; a heat engine converts part of that heat to mechanical work; an electrical generator produces electrical energy. In a pressurized water reactor, a heat exchanger transfers heat from the pressurized reactor coolant to a separate circuit that produces steam. Thus neutron physics, heat transfer, fluid mechanics and materials science constrain the same design.^[ref]

Conceptual scope: the safe account below describes the functions of spent nuclear fuel management and the chemical basis of partitioning. It does not supply an ordered fissile-separation flowsheet, reagents, process conditions or purification instructions. In particular, the requested operational eight-step separation scheme is outside this answer's scope.

Eight useful functional objectives are: receiving and identifying the spent nuclear fuel; managing residual decay heat; providing radioactive material confinement and radiation shielding; establishing the chemical and radiological inventory; partitioning reusable constituents from waste at a conceptual level; maintaining accountable control of recovered materials; conditioning solid and liquid wastes; and retaining or treating radioactive effluents. These are management and containment functions, not a claim that the question specifies one universal eight-stage plant design. Several occur throughout a facility's operation rather than sequentially.

The chemical principle of uranium/plutonium partitioning is that an element's oxidation state and complexation affect its chemical speciation, solubility and relative affinity for immiscible phases. solvent extraction can therefore separate elements whose chemistry differs, even though it does not distinguish uranium isotopes by this chemical selectivity. A recovery operation must account for the accompanying fission products, contaminated process materials and secondary wastes; the recovered material is only one output. radioactive material confinement, remote handling and nuclear material accountancy remain necessary because chemical partitioning redistributes both radioactive and fissile inventories.

Control of exposure to ionizing radiation. Basic physical measures include reducing time near a source, increasing distance and using radiation shielding; confinement of radioactive material addresses contamination.