Study On The Safety Of Industrial Irradiation Transport Package

In the transportation of nuclear material, some transportation accidentsoccur, which leads to radioactive material transportation package damages andthe leakage of nuclear. They are serious accidents, and cause casualties andenvironmental pollution serious consequences. Therefore, except for enhancingthe radioactive material transportation regulation and other relevant laws, theability of radioactive material transportation package on coping with accidentshas become a focus of nuclear industry and the Ministry of EnvironmentalProtection.Radioactive material transportation package is an important containerwhich can guarantee nuclear material no leaking after the accident occurring. Itsstructural strength, impermeability and thermal shock resistance are vital to thetransportation task. According to the GB11806-2004, package requiresmechanical test and thermal test at the design stage, the package could beapproved to product as long as test results reaching the evaluation standard.Finite element method was used in the simulation of mechanical and thermaltests in this paper. The simulation of mechanical test include:1) this paper established asimplified radioactive material transportation package full-scalethree-dimensional finite element model.2) First of all，the implicit algorithmwas applied to calculate the pre-stress of bolt. Secondly, using nonlineardynamic explicit algorithm, this paper gave the finite element simulation ofmechanics test including impacting rigid target surface in normal conditions andaccident conditions with apex angle, side and top3drop orientations. Thesimulation of thermal stress test include:1) in no-solarization case, solarizationcase and heating test case,10°wedge structure which between2ribbed slabs asthe research object was simulated for thermal test by Abaqus/Standard modelusing steady algorithm and transient algorithm.2)In this paper the thermal stressof package in3above-mentioned cases was analyzed by using sequentialcoupling method.Mechanical test simulation results include:1) in the normal operatingcondition, the apex orientation leaded the package to have the biggestdeformation, and large plastic deformation of7ribbed slabs, meanwhile, the lidwarped down25mm along the circumferential60°range, and M10boltsdeformed obviously, while M24bolts were intact;2)in the accident condition,the apex orientation leaded the package to have the most serious damages, andlarge plastic deformation of11ribbed slabs, meanwhile, there were7M10boltsdamaged, the lid warps down55mm along the circumferential90°range.There was a little dislocation between pressure plate and flange. The drum’s shoulder region which was impacted had a serious buckling. Damping ringtended to turn into oval. M24bolts had a little deformation mainly induced bythe shear force, but M24bolts were still undamaged;3)in various cases aboutthe package, the dynamic response of package were evaluated according to theprinciple of package design. The apex angle drop was the most dangerousorientations, but the sealing and the safety of package can be guaranteed.Thermal stress test simulation results include:1) we obtained the packageof temperature distribution through calculations，the temperature increasingcurve of lead parts and package’s outside and inside wall in various cases: thehighest temperature of lead part was114.3℃in no-solarization case, the highesttemperature of lead part was109℃in solarization case, the highest temperatureof lead part was233.2℃in heating test case. According to the curves, it could bedraw that lead part’s temperature don’t beyond its melting point in whatevercases.2) Then, we analyzed the thermal stress of package under hightemperature shock: the maximum thermal stress of package which is249.5MPain heating test case, was less than the allowable design value in the outside wall.The evaluation result was that package meets the design requirements of thermalprotection aspect.The finite element calculation results show that the package meet thedesign requirements in the mechanical and thermal protection. The package canguarantee radioactive material safe whatever cases the package suffered. Thisstudy also provides guidance for the optimization radioactive material transportation package structure and subsequent tests.