Tuesday, April 5, 2011
How high is the radiation from Japan's leaking Fukushima Daiichi complex?
As I noted on March 29th, radioactive cesium from Japan already rivals Chernobyl.
Greenpeace has measured very high levels of radiation some 40 killometers from Fukushima:
The Japan Times reports that there are extremely high levels of radiation in and around the nuclear plants:
Radioactive iodine-131 readings taken from seawater near the water intake of the Fukushima No. 1 nuclear plant's No. 2 reactor reached 7.5 million times the legal limit, Tokyo Electric Power Co. admitted Tuesday.
The sample that yielded the high reading was taken Saturday, before Tepco announced Monday it would start releasing radioactive water into the sea [see this for background], and experts fear the contamination may spread well beyond Japan's shores to affect seafood overseas.
The unstoppable radioactive discharge into the Pacific has prompted experts to sound the alarm, as cesium, which has a much longer half-life than iodine, is expected to concentrate in the upper food chain.
According to Tepco, some 300,000 becquerels per sq. centimeter of radioactive iodine-131 was detected Saturday, while the amount of cesium-134 was 2 million times the maximum amount permitted and cesium-137 was 1.3 million times the amount allowable.
The level of radioactive iodine in the polluted water inside reactor 2's cracked storage pit had an even higher concentration. A water sample Saturday had 5.2 million becquerels of iodine per sq. centimeter, or 130 million times the maximum amount allowable, and water leaking from the crack had a reading of 5.4 million becquerels, Tepco said.
Masayoshi Yamamoto, a professor of radiology at Kanazawa University, said the high level of cesium is the more worrisome find.
"By the time radioactive iodine is taken in by plankton, which is eaten by smaller fish and then by bigger fish, it will be diluted by the sea and the amount will decrease because of its eight-day half-life," Yamamoto said. "But cesium is a bigger problem."
The half-life of cesium-137 is 30 years, while that for cesium-134 is two years. The longer half-life means it will probably concentrate in the upper food chain.
Yamamoto said such radioactive materials are likely to be detected in fish and other marine products in Japan and other nations in the short and long run, posing a serious threat to the seafood industry in other nations as well.
Indeed, high levels of radioactive cesium above the legal limits have already been detected in small fish called "sand lances" off the coast of Ibaraki, almost 100 miles south of Fukushima.
And NHK news points out that radiation levels are so high in some locations that they are literally "immeasurable":
A radiation monitor at the troubled Fukushima Daiichi nuclear power plant says workers there are exposed to immeasurable levels of radiation.
The monitor told NHK that no one can enter the plant's No. 1 through 3 reactor buildings because radiation levels are so high that monitoring devices have been rendered useless. He said even levels outside the buildings exceed 100 millisieverts in some places.