Reevaluation of Dosimetry System 1986 (DS86) - Clarification of its cause and deduction of new dose -

研究内容包括：(1)收集原子弹暴露的岩石、屋顶瓦片和瓦片；(2)测量原子弹中子引起的低水平放射性；(3)通过模拟实验对计算机代码（MCNP）进行基准测试；(4)考虑测量数据与基于DS86的计算结果的差异，并澄清其原因。(1)至(3)条款直到去年才令人满意地完成，在本财政年度，我考虑了其差异的原因。这个差异首先是由我们组发现的。主要的问题是在广岛原子弹的中子中，在1.5公里处，DS86的计算仅为测量值的10-30%。我们在本研究中检查的术语如下：A；爆炸点b处中子的能谱。中子在空气中的输运计算。c .计算机代码（MCNP）的基准测试。不同高度的空气密度（包括湿度）测量。e .通过模拟实验和计算验证土壤表面的活化。f .伽马射线数据和计算的比较。作为结论，我们发现问题在于广岛的A项。即(a)在长崎，所有项（从a到F）都是正确的。(b)在广岛，从b到F是正确的。因此A项是错的。(c)对我们来说，核查A一词是不可能的，因为它包括原子弹爆炸的过程。因此，我做了很多输运计算，改变了DS86的基本假设，试图找到最好的假设来解释差异。根据计算结果，我发现了DS86的假设，即“在a弹体破裂之前，中子完全通过厚铁材料（约20厘米厚的铁）发射”。可能出错了。我假设5-15%的中子是通过将原子弹体水平分开的裂缝释放出来的。根据这一假设，几乎所有的数据都可以重现。在此之后有必要进行剂量评估。

The study included (1) collection A-bomb exposed rocks, roof tiles and tiles, (2) measurements of low level radioactivities induced by A-bomb neutrons, (3) benchmark test of the computer code (MCNP) by simulation experiments, (4) consideration of discrepancies between the measured data and the calculations based on DS86 and clarification of it cause.The terms from (1) to (3) were satisfactorily completed until the last year and, in this fiscal year, I considered its cause of discrepancy.The discrepancy was firstly found by our group.The major problem was in Hiroshima A-bomb neutrons and at 1.5km DS86 calculations were only 10-30% of the measurements.The terms we checked in this study were as follows :A.The energy spectrum of neutrons at the burst pointB.Transport calculations of the neutrons through air.C.Benchmark test of the computer code (MCNP).D.Measurements of air density (including humidity) by different height.E.Verifications of activations at soil surface by simulation experiments and calculation.F.Comparison of gamma-ray data and calculations.As conclusions we find the problem is in the term A of Hiroshima.Namely, (a) in Nagasaki all terms (from A to F) are correct.(b) In Hiroshima terms from B to F are correct. Thus the term A is wrong.(c) The verification of the term A is impossible for us, since it include the process of the A-bomb detonation.Therefore, I performed many transport calculations changing the basic assumptions of DS86 and tried to find out the best assumption to explain the difference.As the results of the calculations I find out the assumption of DS86, that is, "before the A-bomb body was cracked, neutrons were totally emitted through thick iron material (about 20 cm thick Fe)".might be in error.I assumed 5-15% of the neutrons were emitted through a crack which divide the A-bomb body horizontally.By this assumption almost all data could be reproduced.The dose evaluation will be necessary after this.