Keep in mind that the favorite method of waste disposal during the early history of nuclear energy was dropping containers into the ocean. This dumping strategy hinged on the dilution of the material in huge quantities of water. The strategy was successful but particularly unpopular.

If the containment on these reactors was lost, the effect would be measurable due to the sensitivity of such detectors, but literally a drop in the bucket of waste disposed of into the ocean.

http://large.stanford.edu/courses/2017/ph241/jones-a2/