A system of monitoring a black cell environment using sensors is presented, in which the sensors can be easily replaced during a sealed period of the black cell environment. The black-cell monitoring system includes at least one sealed vessel that is disposed within the black cell environment. The vessel is configured to store a hazardous mixed substance and is sealed from the external environment for a pre-determined amount of time. The black-cell monitoring system also includes at least one tubing that extends from the outside of the vessel to the inside of the vessel. The black-cell monitoring system also includes a fiber optic cable that is disposed within the lumen of the tubing. At least a portion of the fiber optic cable is disposed within a portion of the tubing located inside the sealed vessel.