Final answer:
A simulator shielding survey should be completed upon the installation of a new radiation therapy simulator, after major modifications, or to comply with regulatory standards to ensure adequate protection from ionizing radiation.
Step-by-step explanation:
A simulator shielding survey should be completed when a new radiation therapy simulator is installed, or when significant modifications have been made to an existing system or its environment. This survey ensures that the shielding is adequate to protect patients, staff, and the general public from unnecessary exposure to ionizing radiation. The survey checks whether the barriers, walls, and the control booth are providing sufficient protection according to regulatory standards. Local regulations may require periodic reevaluation to confirm continuous safety.