Tokyo: Radioactive fallout from Operation Castle, a series of thermonuclear tests the United States conducted at Bikini Atoll in the South Pacific in 1954, reached an extensive area, including the mainland United States and Latin America, Japanese researchers said here.
The extent of the fallout, which also reached Japan, was
confirmed in a declassified document downloaded from the US
Energy Department in March and gives credence to a claim that
radioactivity found in rainfall in Japan at the time came from
the nuclear tests.
``Because there is a possibility that agricultural
products may have been contaminated, investigations should
swiftly be conducted on the (fallout`s) impact on residents,``
Masatoshi Yamashita, one of the researchers, said of the
A Japanese tuna fishing boat, the Fukuryu Maru No. 5 from
Shizuoka Prefecture, was hit by radiation from a U.S. hydrogen
bomb test at the atoll in March 1954, but a total of 856
Japanese fishing boats had fish confirmed contaminated with
radiation by the end of 1954.
Yamashita, who heads the secretariat of an organization
in Kochi Prefecture that helps survivors of the U.S. nuclear
tests, said that while many fishing boats other than the
Fukuryu Maru were apparently exposed to radiation, ``The true
extent (of the exposure) has yet to be revealed.``
According to the document -- excerpts of a report made by
the US Atomic Energy Commission in conjunction with the U.S.
Weather Bureau in 1955 and declassified in 1984 -- the total
amount of radioactive fallout from Operation Castle between
March and May of 1954 was estimated at 22.73 mega-curies based
on the readings of radioactivity at 122 locations over
roughly four months from the end of February 1954.
The document said that the fallout tended to remain in
the tropical region but streamed into the temperate region
when seasons changed, with the largest amount of fallout in
the southwestern region of the United States,
outside the tropical region, or about five times that which
fell over Japan.