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ID 47361
file
creator
Yamamoto, Masayoshi
Honda, Kouya
Takatsuji, Toshihiro
Sakaguchi, Aya
Hoshi, Masaharu
abstract
Plutonium atomic bomb (A-bomb) was exploded at 503 meters height above Nagasaki City on August 9, 1945. Many studies on radioactive contamination, radiation dose, effect to people and so on have been conducted until now. Local fallout from the A-bomb mainly spread a lot in the east direction centering on Nishiyama area located about 4 km east of the hypocenter.
Like the Hiroshima A-bomb, black rain accompanied by radioactive materials fell shortly after the explosion, but relationship between local fallout fall zone and black rain fall area has not been sufficiently elucidated, which has enhanced the concerns on radiation exposure to the A-bomb survivor. Concerning the black rain due to the Nagasaki A-bomb, it has been said that black rain did not fall across a wide area in a comprehensive way, except for the heavily contaminated Nishiyama area, but fell at various areas with conditions of light rain and/or soaking after the explosion. Among many villages or towns, especially in the Manose District where is a small intermountain village about 7.5 km northeast of the hypocenter, it had always been heard and known that the residents living there encountered black rain and experienced hair loss. In this district, the hair loss of inhabitants occurred actually with high probability, but its reason has not been elucidated well. Therefore, in order to reevaluate the local fallout level in the Manose District by the A-bomb, residual long-lived radionuclides 137Cs and Pu isotopes were measured for soil samples collected at the Manose District including the surrounding areas in July, 2011.
As a result, accumulated levels of 137Cs and 239,240Pu in the Manose District were not so high, each being nearly background (BG) level. The dispersion of local fallout Pu from the A-bomb was reconfirmed by 240Pu/239Pu atomic ratios measured in soil samples at the same time, and was found to be primarily limited in the east direction, especially around the Nishiyama area. Those results were consistent with results obtained so far. Further researches are needed for understanding scientifically the cause of the high incidence rate of hair loss in this district.
description
This research was supported by JSPS KAKENHI Grants Numbers 23406002 (April 2011-March 2014) and 26257501 (April 2014-March 2018).
journal title
Hiroshima Peace Science
volume
Volume 40
start page
17
end page
32
date of issued
2019-03
publisher
広島大学平和センター
issn
0386-3565
2434-9135
ncid
language
eng
nii type
Departmental Bulletin Paper
HU type
Departmental Bulletin Papers
DCMI type
text
format
applicarion/pdf
text version
publisher
rights
Copyright (c) 2019 広島大学平和センター
department
The Center for Peace
Graduate School of Engineering
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