Development Of Fast-curing Shielding Material Based On Polyurethane And The Key Application Component

With wide application of nuclear technology in different field,the development of new kind irradiation shielding materials was concerned by people deeply.During the maintenance of a nuclear power plant,special-shaped pipe failures often resulted in radioactive water seeping out from cracks,however,it was lack of effective shielding material at present.For this situation,a kind of fast-curing shielding materials which could be spayed at a long distance based on polyurethane was developed.Besides,according to the formula of the shieling composite which had the best comprehensive performance,the key application component,available mixing structure of spry gun,was designed.The main research contents involved were as follows.(1)For the demand of the fast-curing shielding material during the maintenance of a nuclear power plant,the fast-curing shielding composite was fabricated with two-component polyurethane as matrix and PbO,WO3,ZB as fillers.Four different kinds of composites were designed,and curing time,shielding performance,microtopography,flame-retardant performance,thermostability,mechanical property,cohesional strength of these composites were compared and studied.Experimental results showed that,the 4th system composite with reactive flame retardant V-490 and compound catalyst 2 had reasonable fast curing time and the best shielding performance.As the filler content and specimen thickness increased,the shielding performance of composite increased.When the filler content was 60% and the specimen thickness was 12 cm,the composite could almost shield all the rays under the energy of 100 keV and the transmittance of 662 keV was only 45.2%.The flame-retardant performance and thermostability of this composite increased as the filler content increased.Because of the refinement of microstructure,the composite had the best mechanical property.Cohesional strength decreased as filler content increased,but it was higher than 100 keV,the composite still had excellent adhesion property metal surface.(2)For the high filler content and high viscosity of the composite which had the best comprehensive performance,a kind of combined mixing head was designed and developed according to the traditional low and high pressure mixing head of two-component polyurethane spraying equipment.FLUENT in ANSYS was adopted to simulate the flow field and analyze the results.The mixing structure was optimized and improved from the angle of enhancing the blending homogeneity and enlarging the flow velocity of outlet.Experimental results showed that the combined mixing head with 4 mixed element,which nozzle diameter was 2 mm and the compound model of mixed element was ’right-left-right-left’,had the best blending homogeneity and the largest flow velocity of outlet.The range of component A in outlet was only 1.44% and the flow velocity of outlet was 99.59 m/s.In this paper,the research work was derived from the actual needs of nuclear irradiation protection.The fast-curing shielding composite based on polyurethane had fast curing velocity,excellent shielding performance,flame-retardant performance and so on.It provided effective protection for the works in coping with the penetration of nuclear pipe.The combined mixing structure of spray gun had excellent mixing quality and bigger outlet velocity.It supplied the fabrication of spraying equipment with firm foundation.