What should always be verified before using a nuclear gauge?

Before using a nuclear gauge, it is crucial to verify the condition of the shielding and the integrity of the source. This step is essential for ensuring safety and compliance with regulatory requirements. The shielding serves to protect operators and personnel from unnecessary exposure to radiation emitted by the radioactive source within the gauge. If the shielding is damaged or the integrity of the source is compromised, there may be an increased risk of radiation exposure, which poses a serious safety hazard.

Checking the shielding's condition helps to confirm that it effectively limits radiation and ensures that any potential leaks from the source are contained. This verification is a fundamental part of safety protocols for nuclear gauge usage and is critical to maintaining a safe working environment.

Other options such as the weight of the gauge, the manufacturer’s location, or the color of the gauge do not have a direct impact on safety or the operational effectiveness of the gauge. Hence, they are not priorities in the context of ensuring proper and safe usage of nuclear gauges.