What is the required setting for the safety relief valve (SRV) when no feedwater pump is present?

The correct answer reflects the standard practice for setting the safety relief valve (SRV) in situations where a feedwater pump is absent. Setting the SRV at 94% of the lowest supply pressure ensures that the valve is adequately calibrated to protect the system from overpressure conditions while still allowing for proper operation.

This percentage takes into account the need for the system to maintain a specific pressure threshold to prevent any potential hazards that might arise due to excessive pressure in the boiler system. Such calibration prevents the risk of over-pressurization that could lead to safety failures, ensuring that the SRV functions effectively under varying operational conditions.

The other choices do not meet the recommended safety standards and may subject the system to undue risks. The percentages suggested by those options either do not provide sufficient margin for safety or would not effectively address the potential fluctuations in pressure if no feedwater pump is present.