The closed-beam radiation-producing device enclosure, sample chamber, or other similar closure must be interlocked with the X-ray tube high voltage supply or a shutter in the primary beam, or both, so that no X-ray beam can enter the sample or object chamber while the chamber is open unless the interlock has been conspicuously and deliberately defeated. The interlock required by this section must be of fail-safe design or have adequate administrative controls to ensure that operations will only continue with a proper functioning interlock.
25 Pa. Code § 227a.32