This post provides justification for the sole sourcing of Sentry 110 Cobalt Exposure Device. The PNSY Radiography Program owns and uses this Exposure Device in their work to expose radiography films t... This post provides justification for the sole sourcing of Sentry 110 Cobalt Exposure Device. The PNSY Radiography Program owns and uses this Exposure Device in their work to expose radiography films to inspect production welds and base materials for NDT (Nondestructive Testing) inspection. Please see attached limited source justification document for details.