| Since nuclear physics applications used more widely today, industry specially fornuclear power factory, its rapidly development calls people’s focus on safety, asnuclear physics development the nuclear accidents are inevitable, especially withsome nuclear accident’s characteristics: It’s more difficult to protect, complexity bio-effects of the human body to produce non-random effects and random effects, andmore difficult to measure issues dose. So for radiation accidents, especially forcriticality accident, to give out people a series of complex dosimetry problems. Andfor these problems, more difficult problems has been hold up that the neutronprotection and issues dose calculation, because neutrons has hard to protecte, and it ishard to calculate the issues dose after neutron accident occurred. There are twoimportant points for nuclear protection: First, to develop protective details for thepublic or staff whom may be suffered from external nuclear exposure. Second, after anuclear accident occurred, to determine the issues absorbed dose promptly andaccurately. For the second point:to determine the absorbed dose, this kind of methodhas been developed since1960s by researchers from all over the world, and theprinciple of this measurement method is: when the body suffered neutron’sirradiation,the element Na in the blood will have an react with neutron called23Na(n,γ)24Na reaction and produced the two kinds of γ-ray particles with energy of2.76MeV to1.38MeV, neutrons absorbed dose is determined by measuring theintensity of these rays, although the development of this method for many years, andthere are a lot of progresses, but due to the complex physiological characteristics ofthe human body ’s own section of the neutron and the different elements in the humanbody, there is still a lot of difficulties to be resolve. with the development ofcomputer speed and mathematical softwares, another method has been developed inthe1970’s: Using computer phantom and use appropriate software to simulatenuclear radiation physics to calculate the body absorbed dose of radiation underdifferent conditions, thus providing for the practical work reference and comparison.This study focuses on calculate neutron flux-dose conversion factors proposed by the ICRU designed after a nuclear accident can get absorbed into the body bymeasuring various organs neutron flux dose.The rule of radiation protection and dose calculation now in most countries of theworld are based on organizations ICRP and ICRU ‘s publications and reports, ICRPand ICRU also used computer phantom with Monte Carlo method software to dealwith it, in this study the main research directions is for the use the phantom that ICRPand ICRU ever used and sophisticated mannequins are calculated, and arecompared with the ex-reports or publications, propose appropriate suggestions andcomments. In this study, the main research contents, methods and results are in thefollowing:1.Using the current most complex voxel phantom “VIP MAN” and Monte Carlomethods software “MCNP” series to calculate the issue dose,then follow the methodthat ICRP74Reports mentioned how to calculated the neutron flux-dose coefficientfactor to compute it.2.Using “VIP MAN” to calculate24mainly issues’ neutron flux-dosecoefficient factor.3.Using the results to compare with ICRP74Report’s results, and give out thedetailed discuss: for most organs, the date can match with ICRP74Reports, but someorgan has a big difference with Reports which are: kidney, lung, stomach, thyroid.These organ’s neutron flux-dose coefficient factor are less than ICRP74Reportsbecause of the difference build principle.In this study, there are several innovations have been made:1. Using voxel phantom to do this study, this kind of technology can match betterwith the real human being organs than the former digital phantom.2.Using results compared with the ICRP report which is the internationalstandard data and give some advices: we may need reduce some organ’s neutronflux-dose coefficient factor which are kidney, lung, stomach, thyroid:.By using voxel phantom "VIP MAN" to do this simulation, and compared it withauthority organization, we can find that most of the data is consistent withauthoritative data, for those date which has big difference with authoritative data, thepaper were given a reasonable explanation. By analyzing the results we can seen thatfor the thyroid gland, lung, liver, stomach and other organs, it may be required somemodifications whit their neutron flux-dose conversion factor in use.This paper deficiencies as follow: Since the “VIP MAN” phantom’s date arebased on real model of the human body which it’s representative need to be re-evaluated, and uses one Monte Carlo software to do this study, so come only with acertain representation of data, in the hope to be able to use other software for furthersimulation. |
PDF Full Text Request