A sheet includes an optical fiber extending across at least a portion of
its surface to detect nuclear radiation. The sheet can line at least a
portion of a shipping container or box. Radiation within or outside the
container or box reduces optical transmissibility of the fiber. The fiber
integrates the radiation over time and/or over the length of the fiber,
making the fiber sensitive to even low-level radiation. Dopants, use of
particular wavelengths of light or temperatures or other mechanisms can
increase the sensitivity of the optical fiber to radiation. The optical
fiber is monitored for a change in its transmissibility. A reduction in
the transmissibility, such as to below a threshold, can trigger an alarm,
such as an annunciator, or send a message that includes information about
the time or the container's contents or location when the radiation is
detected to a central location, such as a ship's control room or port
notification system.