بررسي تضعيف فوتوني در حفاظ هاي بتن سنگين حاوي سنگ دانه هاي هماتيتي و باريتي به صورت چند لايه و مخلوط Investigation of gamma ray attenuation in multi layered and mixture heavyweight concrete shields containing hematite and barite aggregate

چكيده انگليسي :

Investigation of gamma ray attenuation in multi layered and mixture heavyweight concrete shields containing hematite and barite aggregates Taban Shams t shams@cv iut ac ir April 20 2016 Department of Civil Engineering Isfahan University of Technology IUT Isfahan 84156 83111 Iran Degree M Sc Language Persian Supervisor s Name Dr Mohammad Reza Eftekhar Email address eft@cc iut ac ir Dr Ahmad Shirani Shirani@cc iut ac irAbstract Nowadays with the growing use of nuclear technology in various fields protection against nuclear radiation is one of the most important issues receiving special attention Therefore the use of shields that can attenuate and absorb harmful radiations has been considered at the same time such shields should display desirable mechanical and physical properties while being economical In this regard concrete shields are one of the best and most widely used This research aimed at constructing and testing concrete shields of heavy concrete with barite and hematite graining in separate mixed and multi layered cases Then nuclear and mechanical properties of these shields were compared with each other and with those of existing conventional concrete shields In addition the use of different percentages of heavy aggregates and their effect on protecting absorbing and attenuating radiation were investigated hence the effect of increase or decrease in thickness of shield and the useful part of the building as well as its cost effectiveness was explored too In this research the multi layered concrete shield was obtained by putting together the layers of barite and hematite concrete and the mixture concrete shield was prepared from combining barite and hematite aggregates in the form of hematite barite concrete In order to achieve the objectives of the study concrete samples in five general categories were produced These were conventional concrete samples including two conventional concrete wet and dry samples barite concrete samples including both barite concrete 50 and barite concrete 100 samples of hematite concrete including hematite concrete 50 and hematite concrete 100 and the mixed samples of barite and hematite including barite hematite 50 and barite hematite 100 After the preparation of the samples nuclear testing was employed to measure the linear attenuation coefficient for gamma rays with energies of 1173 and 1332 keV as emitted by cobalt 60 radiation source These are energies emitted in radiotherapy and radiology centers as done using the HPGe detector To determine the linear attenuation coefficient in each group of concrete shields 5 samples in different thicknesses totaling 40 were prepared Also to measure the compressive strength of each of concrete samples 3 cubic samples totaling 21 were obtained Structural and nuclear testing results indicated that increasing barite and hematite aggregates either individually or in combination led to the increase in the linear attenuation coefficient and compressive strength So the use of different volume percentages of hematite heavy aggregates instead of conventional aggregates showed that obtained concrete had good mechanical strength It also increased absorption and suppression of harmful radiation thus reducing the thickness of the shield and increasing the useful space The impact of hematite aggregates on increasing the absorption and attenuation was greater than that of barite aggregates But replacing the layers of concrete containing the mentioned aggregates had no effect on the absorption and attenuation Also under the same conditions in terms of the amount of ingredients used concrete density and energy of initial rays the function of uniform concrete shields in the absorption and attenuation of initial rays was slightly better as compared to a layered concrete shield Keywords Nuclear radiation concrete shield heavy aggregate hematite aggregate barite aggregate layered mixure attenuation of radiation

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