What is the most efficient state of a nuclear power plant BOL, MOL, or EOL? Explain. Describe the difference between BOL, MOL, and EOL in terms of reactor core reactivity, specifically the "power coefficient." Describe the difference between BOL, MOL, and EOL in terms of Boron efficiency? Explain the thermodynamics of the thermal energy transfer (heat exchange) between the fuel elements and water-boron mixture in BOL, MOL, and EOL? Explain the thermodynamics of the thermal energy transfer (heat exchange) between the fuel elements and control rods in BOL, MOL, and EOL?