Samples of seaweed including kelp have been showing signs of radioactive fallout including high radiation levels. I realize that many health care advisors have been recommending sea vegetables of various kinds as a means to counteract the effects of radiation. Brown seaweed alginates have been shown to chelate heavy metals. And spirulina as well chlorella and seaweed have been recommended to supply iodine and to eliminate toxins, both of which are helpful for radiation exposure. But you do not want to eat seaweed grown near the Fukushima nuclear disaster which has been dumping thousands of tons of radioactive water into the ocean around Japan on a daily basis for nearly two months. This radioactivity has contaminated sea life there. It is not safe to eat fish, shellfish, shrimp, or seaweed grown in these waters. Similarly, krill oil is also produced in Japan. You want to be sure that fish oil and krill oil supplements come from Arctic or Antarctic waters free of radiation.
Unless you know your source, stop eating all of these products that may have been grown in Japan. Some supplement manufacturers are now testing their products for radioactivity. If you are considering taking a supplement that contains seaweed or algae, then contact the manufacturer to get assurance that their product has no possibility of containing radioactive materials.