NDT, Radiography. Bio accumulation is a serious issue, but it only affects chemicals such as lead, toxins, etc; not radiation. Radiatio, to put simply is really intense rays of light from the a different part of the spectrum. But same as turning off a light, once the source is gone so is the radiation. It does not stay in what was exposed. The harm comes from what the radiation did while it was present. It can mutate cells, kill them out right and more on a very short order. The radiation from Japan could very well have hindered plankton's ability to reproduce, or similar but that would not be passed on to whatever consumes it. Same with salmon, the radiation could of stunted their growth (I doubt it but haven't look into it), but would have no affect on a fisherman who consumes it.