Isolation of long-lived radioisotope produced by HIroshima atomic bomb

对先前残余放射性的测量进行了精确的回顾。在超过1 km地面范围（GR）的样品中，测量值与计算值之间的差异是显著的。本文改进了加速器质谱法（ams）中氯离子的分离方法，使之可在不经海盐稀释的情况下从岩石样品中分离氯离子。它将对大于1km gr的岩石样品中<36>Cl/Cl的ams有用。在获得大于1km gr的岩石样品后将进行隔离。混凝土样品中氯含量超过100ppm。将粉状样品用8 ml / lg的纯水洗涤两次，除去雨水中的氯离子。然而，从混凝土中提取的AgCl样品含有其他元素。排除元素的工作正在进行中。超过1km GR的瓷砖中氯含量低于20ppm，因此氯样品的ams实验很困难。从1公里范围内的混凝土和瓦片中也可以得到^<41>Ca ams的钙样品。钙样品的测量要求在^<41>Ca ams范围内提高检测效率。从1公斤混凝土中分离铕也在进行中，以确定^<152>Eu/Eu。初步研究表明，传统的NaI （Tl）探测器可用于测量来自无天然放射性同位素的分离铕样品的^<152>Eu伽马射线。中子的影响将通过同位素比率的测量和蒙特卡罗计算来评估，正如我们之前的研究所示。^<*)>^*Ruhm， W., Kato， K., Korschinek， G., Morinaga， H., Nolte， E.（1995）从一个地点的放射性核素测量推断出的广岛原子弹的中子谱和产率。中国生物医学工程学报，2016,33(2):444 - 444。

The previous measurements of residual radioactivity were precisely reviewed. The discrepancies between measured and calculated isotope ratios are significant in samples beyond 1 km ground range (GR). The chloride isolation method used for our previous investigations of accelarator mass spectrometry (ams) has been improved, and is available for isolating chloride ions from rock sample without dilution by sea salt. It will be useful for the ams of ^<36>Cl/Cl in rock samples beyond 1 km GR.The isolations will be performed after obtaining rock samples beyond 1 km GR.Concrete samples contained chlorine more than 100 ppm. The chloride ions from rain water were excluded by washing the powdered sample by pure water of 8 ml per lg sample, twice. The AgCl samples from concrete, however contains other element. The exclusion of the element is in progerss. Tiles beyond 1 km GR contained chlorine less than 20 ppm, and hence the ams experiment for the chloride sample is difficult. Calcium samples for ^<41>Ca ams were also produced from concrete and tiles beyond 1 km range. The measurements of the calcium samples require increase of the detection efficiency in ^<41>Ca ams. Europium isolation from a 1 kg concrete is also in progress for determining ^<152>Eu/Eu. A preliminary study revealed that a conventional NaI (Tl) detector was useful for measurements of ^<152>Eu gamma rays from the isolated europium samples without natural radio isotope. The neutron fluences will be evaluated by the measurements of isotope ratios and Monte Carlo calculations, as shown in our previous investigation. ^<*)>^*Ruhm, W., Kato, K., Korschinek, G., Morinaga, H., Nolte, E.(1995) Neutron spectrum and yield of the Hiroshima A-bomb deduced from radionuclide measurements at one location. International Journal of Radiation Biology, 68,97-103.