Radioactivity Originating from the Chinese Nuclear Test Explosions Observed in Seoul District in 1964-1967

中共 核實驗에 의한 서울地區의 放射線 汚染度 評價

Artificial and natural radioactivity in airborne, rain-out and fallout dusts in Seoul district in the period of 1963-1967 were studied by measuring gross-activity and by analyzing nuclides by means of $\\gamma$-spectrometry. Short-lived radium and thorium decay products give rise to most of the airborne activity unless the fission product concentration is extremely high and it is likely to be said activity remaining after a few days is attributable to fission products. Of seven Chinese nuclear explosions performed at Lop Nor, Sinkiang Province, two exhibited the activity of extremely high concentration of fission product and reached Seoul district around 30 hours after the explosion. The activity was followed by a sudden decrease in less than a week, in contrast to the long-lasted activity of low concentration originating from the huge tests performed by the United States and the USSR in 1956-1962. The radioactive environmental contamination in Seoul district, due to the Chiness nuclear test explosions, largely depends on the height above the earth at which the nuclear explosion is performed and the type of nuclear device as well as the weather system at the time and immediately after the explosion, especially the jet stream in middle latitude in the upper troposphere.

1963年에서 1967年에 걸쳐 서울地區의 人工放射能과 自然放射能을 全放射能의 測定과 放射性核種의 分析을 통하여 硏究하였다. 核分裂生成物의 濃度가 적을때는 \ulcorner은 半減期를 갖는 라듐이나 토리음의 崩壞生成物이 浮游塵의 大部分을 차지하고 있었으며 核分裂生成物에 依한 放射能은 試料 採取후 며칠 지나야 正確히 評價할수 있었다. 7次에 걸친 中共의 核實驗의 結果 두차례의 强放射能이 爆發후 30時間을 前後하여 서울地區에 나타났으며 이들은 1956年에서 1962年 사이에 美國과 蘇聯에서 행한 實驗과 比較할 때 높은 比放射能을 보였으나 持續時間은 아주 짧아서 1週內에 急激히 減少하였다. 이로 보아서 서울地區의 放射能汚染은 中共의 核實驗인 境遇 核實驗의 規模와 實驗高度 및 爆發前後의 氣象條件, 特히 高層對流圈의 제트氣流에 依해서 많은 影響을 받음을 알았다.