What is the initial requirement for starting up a unit after a trip?

The initial requirement for starting up a unit after a trip is that all operational 'permissives' must be met. Permissives are a set of conditions or criteria that must be satisfied in order to ensure the safe and reliable operation of the equipment before a restart can occur. These conditions are put in place to prevent damage to the equipment and ensure safety for operating personnel.

Permissives often include checks on temperature, pressure, levels, and operational status of various components. If any of these conditions are not met, it indicates that the system may not be ready for operation, potentially leading to secondary trips or unsafe conditions. Therefore, ensuring all operational permissives are met is critical for a safe and effective start-up process.

Meeting the other choices, such as resetting all manual systems, verifying power supply, and confirming readiness from engineers, may also be necessary steps; however, they are generally subsequent to ensuring that all operational permissives are satisfied first. This hierarchy emphasizes the importance of safety and operational integrity in the restart process after an unexpected shutdown.