共查询到20条相似文献,搜索用时 15 毫秒
1.
Xingcai Guan Masanobu Manabe Isao Murata Tieshan Wang 《Journal of Nuclear Science and Technology》2013,50(4):503-508
Boron neutron capture therapy (BNCT) is a promising cancer therapy. Epi-thermal neutron (0.5 eV < En < 10 keV) flux intensity is one of the basic characteristics for modern BNCT. In this work, based on the 71Ga(n,γ)72Ga reaction, a new simple monitor with gallium nitride (GaN) wafer as activation material was designed by Monte Carlo simulations to precisely measure the absolute integral flux intensity of epi-thermal neutrons especially for practical BNCT. In the monitor, a GaN wafer was positioned in the center of a polyethylene sphere as neutron moderator covered with cadmium (Cd) layer as thermal neutron absorber outside. The simulation results and related analysis indicated that the epi-thermal neutron flux intensity could be precisely measured by the presently designed monitor. 相似文献
2.
3.
A. Couture 《Atomic Data and Nuclear Data Tables》2007,93(5):807-830
We simulated the response of a 4π calorimetric γ-detector array to decays of radioactive isotopes on the s-process path. The GEANT 3.21 simulation package was used. The main table contains estimates on the maximum sample size and required neutron flux based on the latest available neutron capture cross-section at 30 keV. The results are intended to be used to estimate the feasibility of neutron capture measurements with 4π arrays using the time-of-flight technique. 相似文献
4.
Kenichi Yoshioka Tsukasa Kikuchi Satoshi Gunji Hironori Kumanomido Ishi Mitsuhashi Takuya Umano 《Journal of Nuclear Science and Technology》2013,50(6):606-614
We have developed inexpensive and easy-handling measurement methods on intra-pellet neutron flux. A foil activation method with metallic foils, which were fabricated by punching out technique and etching technique to reduce fabrication error and positioning error, was used for the intra-pellet neutron flux distribution measurement. The developed method was applied to measure intra-pellet neutron flux distributions in a reduced–moderation light water reactor (LWR) lattices, and uncertainty of the distributions was estimated to be 1% to 2%. Measured values were analyzed with a continuous energy Monte Carlo code. Comparison of measurements and analyses revealed that the developed method is useful for the validation of an advanced fuel design method considering neutron behavior in fuel pellets. 相似文献
5.
6.
A. Mameli A. Fidanzio S. Cilla L. Grimaldi G. Giannini P. Totaro L. Azario 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(16):3656-3660
PhoNeS (photo neutron source) is a project aimed at the production and moderation of neutrons by exploiting high energy linear accelerators, currently used in radiotherapy. A feasibility study has been carried out with the scope in mind to use the high energy photon beams from these accelerators for the production of neutrons suitable for boron neutron capture therapy (BNCT). Within these investigations, it was necessary to carry out preliminary measurements of the thermal neutron component of neutron spectra, produced by the photo-conversion of X-ray radiotherapy beams supplied by three LinAcs: 15 MV, 18 MV and 23 MV. To this end, a simple passive thermal neutron detector has been used which consists of a CR-39 track detector facing a new type of boron-loaded radiator. Once calibrated, this passive detector has been used for the measurement of both the thermal neutron component and the cadmium ratio of different neutron spectra. In addition, bubble detectors with a response highly sensitive to thermal neutrons have also been used. Both thermal neutron detectors are simple to use, very compact and totally insensitive to low-ionizing radiation such as electrons and X-rays. The resultant thermal neutron flux was above 106 n/cm2s and the cadmium ratio was no greater than 15 for the first attempt of photo-conversion of X-ray radiotherapy beams. 相似文献
7.
8.
Neutron capture therapy with Sulfur-33, similar to boron neutron capture therapy with Boron-10, is effective in treating some types of tumors including ocular melanoma. The key point in sulfur neutron capture therapy is whether the neutron beam flux and the resonance capture cross section of ~(33)S(n;α)~(30) Si reaction at 13.5 keV can achieve the requirements of radiotherapy. In this research,the authors investigated the production of 13.5 keV neutron production and moderation based on an accelerator neutron source. A lithium glass detector was used to measure the neutron flux produced via near threshold~7 Li(p,n)~7 Be reaction using the time-of-flight method. Furthermore, the moderation effects of different kinds of materials were investigated using Monte Carlo simulation. 相似文献
9.
Computational studies are performed for choosing an optimal material and dimensions of a moderator for forming a beam of epithermal neutrons for boron-neutron-capture therapy based on a proton accelerator and the reaction 7 Li(p, n)7 Be as the neutron source. It is shown that the best material for this is magnesium fluoride. An optimal configuration is proposed for a combined moderator consisting of magnesium fluoride and teflon. The computational results are compared with the experimental data.Translated from Atomnaya Énergiya, Vol. 97, No. 3, pp. 195–200, September, 2004. 相似文献
10.
为了探讨利用D-D中子源评估硼中子俘获治疗(Boron Neutron Capture Therapy,BNCT)中子通量探测器性能的可能性,本文利用蒙特卡罗模拟程序MCNP5(Monte Carlo N Particle Transport Code, version 5)设计了基于D-D中子源的BNCT慢化体,并最终给出了一种"5 cm聚乙烯(Polyethylene,PE)+24 cm氟化钛(TiF3)+22 cm氟化镁(MgF2)"的组合作为慢化层、20 cm的镍(Ni)作为反射层以及0.03 cm的镉(Cd)作为热中子吸收层的慢化体设计方案。模拟计算结果表明:D-D中子源经设计的慢化体慢化后形成的中子场可以用于BNCT中子通量探测器性能的实验测试。 相似文献
11.
12.
H. Tanaka Y. Sakurai S. Masunaga G. Kashino T. Mitsumoto H. Tsutsui K. Ono 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(11):1970-1977
At Kyoto University Research Reactor Institute (KURRI), 275 clinical trials of boron neutron capture therapy (BNCT) have been performed as of March 2006, and the effectiveness of BNCT has been revealed. In order to further develop BNCT, it is desirable to supply accelerator-based epithermal-neutron sources that can be installed near the hospital. We proposed the method of filtering and moderating fast neutrons, which are emitted from the reaction between a beryllium target and 30-MeV protons accelerated by a cyclotron accelerator, using an optimum moderator system composed of iron, lead, aluminum and calcium fluoride. At present, an epithermal-neutron source is under construction from June 2008. This system consists of a cyclotron accelerator, beam transport system, neutron-yielding target, filter, moderator and irradiation bed.In this article, an overview of this system and the properties of the treatment neutron beam optimized by the MCNPX Monte Carlo neutron transport code are presented. The distribution of biological effect weighted dose in a head phantom compared with that of Kyoto University Research Reactor (KUR) is shown. It is confirmed that for the accelerator, the biological effect weighted dose for a deeply situated tumor in the phantom is 18% larger than that for KUR, when the limit dose of the normal brain is 10 Gy-eq. The therapeutic time of the cyclotron-based neutron sources are nearly one-quarter of that of KUR. The cyclotron-based epithermal-neutron source is a promising alternative to reactor-based neutron sources for treatments by BNCT. 相似文献
13.
14.
硼中子俘获治疗(Boron Neutron Capture Therapy,BNCT)是一种具有广阔前景的癌症治疗方法。氘氚中子源是未来可供选择的BNCT中子源之一,由于氘氚中子源产生的中子能量为14.1 MeV,不能直接用于BNCT,需要进行束流慢化整形。使用蒙特卡罗模拟程序MCNP5设计了相应的束流整形组件(Beam Shaping Assembly,BSA),模拟验证了用半径为14 cm的天然铀球做中子倍增层的优越性,计算结果表明:采用50 cm厚的BiF3和10 cm厚的TiF3组合慢化层,17 cm厚的AlF3补充慢化层,0.2 mm厚的Cd热中子吸收层,3.5 cm厚的Pb作为γ屏蔽层,以及10 cm厚的Pb反射层,获得了较为理想的治疗中子束,输出中子束的空气端参数满足国际原子能机构(International Atomic Energy Agency,IAEA)的建议值。 相似文献
15.
Tetsuo Matsumoto 《Progress in Nuclear Energy》2000,37(1-4):327-332
Neutron beam designs were studied for TRIGA reactor with a view to generating thermal, epithermal and fast neutron beams for both medical neutron capture therapy (NCT) and industrial neutron radiography (NR). The beams are delivered from thermal and thermalizing columns, and also horizontal beam hole. Several prospective neutron filters (high-density graphite (G), bismuth (Bi), single-crystal silicon (Si), aluminum (Al), aluminum oxide (Al2O3), aluminum fluoride (AlF3) and lead fluoride (PbF2)) were examined for obtaining sufficiently intense neutron beam for various applications. Monte Carlo calculations indicated that with a suitable neutron filter arrangement, thermal and epithermal neutron beams attaining 2×109 and 7×108 n cm−2S−1, respectively, could be obtainable from thermal and thermalizing columns with the reactor operating at 100 kW. These neutron beams could be adopted for boron neutron capture therapy. Compared with these columns, horizontal beam port would deliver neutron fluxes of 10−2 10−3 lower intensity, but produced thermal and neutron beams would be adequate for different application of nondestructive inspection by neutron radiography. 相似文献
16.
M. Thellier E. Hennequin C. Heurteaux F. Martini M. Pettersson T. Fernandez J.C. Wissocq 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1988,30(4):567-579
Theoretical models are proposed for the calculation of the local concentrations, in a specimen, of nuclides such as 6Li, 10B, 14N or 17O, from the corresponding local densities of tracks on the detectors. Several different cases have been studied: i) one or several types of particle involved, ii) initial energy of the particles below, or above the “upper threshold of detection”, iii) possible nonnegligible abrasion of the detectors during etching and iv) contribution of background tracks originating from the detectors themselves. The theoretical equations have been applied to the interpretation of experimental data. 相似文献
17.
Institute of General Nuclear Physics, Russian Scientific Center of the Kurachatov Institute. Translated from Atomnaya Énergiya, Vol. 74, No. 5, pp. 394–400, May, 1993. 相似文献
18.
19.
20.
《Annals of Nuclear Energy》2005,32(12):1391-1406
Using the basic theory developed in our earlier work (Cassell, J.S., Williams, M.M.R., 2005. Particle flux in an annular gap about a sphere, Annals of Nuclear Energy 32, 457, we have evaluated the neutron flux across a spherical void due to a point source in a moderating and absorbing medium. Neutron motion in the moderator is described by diffusion theory and that in the void by the free streaming Boltzmann transport equation. An explicit solution is obtained in the form of an infinite series. This is evaluated numerically for a number of practical cases and comparison is made with an exact transport calculation using a Monte Carlo code. The hybrid method is seen to be highly accurate. 相似文献