Development of an irradiation system of low-energy protons - To study the mechanism of the effects of neutrons for biological system-

中子的相对生物学效力比伽马射线和β射线高得多。作为中子照射的例子，我们有在广岛和长崎以及东海村事故中的原子弹幸存者的经验。中子在进入人体时反冲氢原子中的质子，氢原子作为主要成分。这种反冲质子带有电荷。因此，作为结果，它们产生自由基，其诱导DNA双链断裂。这种质子反冲在中子剂量中所占的百分比为70-80%，这取决于中子能量。几乎所有这些损伤都将被修复;然而，其中一些损伤将无法修复，因此被认为是诱发癌症的损伤。最近一些科学家提出，许多这样的损伤是在附近产生的，并且在这种情况下，DNA的损伤变得非常大，并且很有可能无法修复。这被称为“集群模式”。在另一种情况下，中子发生核反应并产生Ra。 关于我们 放射活性它们发射粒子，伽马射线和中子。本研究的目的是利用洋葱根尖细胞进行质子辐照，以寻找这部分中子的辐照效应。质子由广岛大学放射生物学和医学研究所的Shenkel型静电加速器产生。辐照系统已经完成，但强度和均匀性的调整尚未完成。因此，我们进行了中子辐照实验，不仅利用洋葱根尖细胞，但种子本身。辐照后的种子进行培养，观察根尖细胞微核。用中子发生器产生的0.2MeV、0.5MeV、0.8MeV和1.0MeV的单能中子和平均能量为2.1MeV的中子辐照Cf-252，观察根尖细胞微核。中子RBE值的测定结果表明，干种子辐照的RBE值分别为216、186、180、174和150;萌发细胞辐照的RBE值分别为45.3、39.1、36.0、31.4和18。少

Relative biological effectiveness of neutrons is much higher than gamma- and beta-rays. As such cases of neutron exposure, we have experiences of atomic bomb survivors in Hiroshima and Nagasaki, and Tokai-mura accident. Neutrons when coming into human body recoil protons in hydrogen atoms which are included as a main component. Such recoil protons have charges. Therefore, as a consequence, they produce radicals, which induce DNA double strand breaks. The percentage of such proton recoils in neutron dose is 70-80% which depends on neutron energies. Almost all of such damages will be repaired; however, some of them will not be fixed, by which damages it is thought to induce cancers consequently. Recently some of the scientists proposed mat many of such damages are produced near by and that in such cases damages of DNA are become very large, which have large possibility not to be repaired. This is called as "cluster model". As the other case, neutrons have nuclear reaction and produces ra … More dioactivity. They emit particles, gamma rays and neutrons. The purpose of this study is to irradiate protons to find this part of radiation effects of neutrons using onion root top cells. Protons were produced by the Shenkel type electrostatic accelerator at Research Institute for Radiation Biology and Medicine, Hiroshima University. The irradiation system have been finished however adjustment for intensity and uniformity have not been done. Therefore we performed neutron irradiation experiment using not only onion root top cells but seeds themselves. After the irradiation seeds, they are incubated and micronucleus of the root tip cells are observed. We observed micronucleus of the root top cells by using monoenergetic neutrons of 0.2MeV, 0.5MeV, 0.8MeV and 1.0MeV from the neutron generator and average energy of 2.1MeV neutrons in Cf-252. The results of neutron RBE values are 216, 186, 180, 174 and 150 for dry seed irradiation, and 45.3, 39.1, 36.0, 31.4 and 18 for germination cells, respectively. Less