Reevaluation of the Dosimetry System 1986 (DS86) -collection and measurements-

本研究的目的是（1）收集原子弹照射量，（2）测量~（18）<15i>Eu，（3）讨论中子感生放射性（~（18）<152>Eu和~（18）<60>Co）的DS 86测量值与DS 86计算值之间的矛盾。原子弹暴露材料的收集工作进行得很成功。在2km的地面范围内采集了15个标本（14个来自广岛，1个来自长崎）。对1000 m范围内的样品进行了122 keV和344 keV的γ射线<152>测量。在广岛大学工学部对超过1000 m的部分进行了化学浓缩和测量，并通过MCNP程序的所谓“基准测试”开始对这些数据进行分析。我们<252>在我们的研究所利用了^ Cf裂变中子，它们在四种材料（花岗岩、含B的聚乙烯、水和氯化铵）中降解。在这些材料中，测量了热中子和快中子。用MCNP程序计算了相应的热中子和快中子产额，并与实验结果进行了比较。我们发现良好的拟合在15%以内，直到1/1000的退化，这对应于1500米的地面范围在广岛。我们正在使用MCNP在Hiroshma中进行输运计算，并几乎找到了DS 86矛盾的原因。我们将在不久的将来举行的美日联合会议上讨论我们的解决办法。

The aim of this study was (1) to collect A-bomb exposed speciments, (2) to measure ^<15i>Eu and (3) to discuss the DS86 contradiction of neutron induced radioactivites ( ^<152>Eu and ^<60>Co) between the measured data and the calculation based on DS86. The collection of the A-bomb exposed materials was performed successfully. We collected 15 specimens (14 from Hiroshima and 1 from Nagasaki) within 2 km ground range. The samples within 1000 m were powdered 122 keV and 344 keV gamma rays from ^<152>Eu were measured. Those more than 1000 m were chemically concentrated and measured at Faculty of Engineering, Hiroshima University.Analysis of these data was begun by so called "benchmark test" of the MCNP code. We utilized ^<252>Cf fission neutrons at our institution and they were degraded in four materials (granite, polyethylene with B, water and ammonium chloride). In these materials thermal and fast neutrons were measured. The yield of the corresponding thermal and fast neutrons were calculated by the MCNP code and compared with the experimental results. We found good fit within 15% until 1/1000 degradation, which correspond to 1500 m ground range in Hiroshima. We are performing the transport calculation in Hiroshma using the MCNP and are almost finding the cause of DS86 contradiction. We will discuss our solution at the US-Japan joint meeting, which will be held in near future.