Study On The Analytical Method Of Ra-228 In Water Samples

Ra is widely distributed in nature,and Ra has similar chemical properties to elements in the same family,such as Ca,Sr and Ba,so Ra and Ca have similar metabolic behavior inside human body.Ra obtained through drinking water is easily deposited in human bones,resulting continuous internal irradiation of human body.These Ra isotopes uniformly accumulate in bones and muscle tissues,increasing the exposure dose.Among the Ra isotopes,Ra-228 has a half-life of 5.75 years,which is a highly toxic nuclide,so it is significant to monitor Ra-228 in water.In this study,Ra-228 analysis method based on high purity germanium(HPGe)y-spectrometry and liquid scintillation spectrometry(LSC)was established.In the method of y-spectrometry analysis of Ra-228 in water,the water sample to be tested is enriched by Fe(OH)3-CaCO3 carrier method,and then Ra-228 is carried by Ba(Ra)SO4 co-precipitation method.The sample was prepared by Ba(Ra)SO4 co-precipitation,using the Ba-133 tracer method,and the Ra-228 sample after loading was placed for more than 30h.After Ra-228/Ac-228 reached the radioactive equilibrium,it was indirectly measured by measuring the Ac-228(Full energy peak=911keV).The activity of Ra-228 was determined and the yield was calculated.In the method of LSC analysis of Ra-228 in water,Ra-228 in water was enriched by Pb(Ra)SO4 co-precipitation method,and separation and purification of Ra-228 by Ba(Ra)SO4 co-precipitation method.The yield was calculated from the concentration of stable barium in the solution before and after separation carried out by atomic absorption spectrometry(AAS for short).The isolated and purified Ra-228 was placed for about 20 days,and the third generation decayer Ra-224 of Ra-228 is attenuated completely.At this time,Ra-228 and Ac-228 have reached the radioactive equilibrium.After mixing with the scintillation liquid,they were measured on the LSC.The total counts after Ra-228/Ac-228 radioactivity equilibrium was measured to determine the activity of Ra-228.The method of y spectrometry analysis Ra-228 can realize the rapid measurement of Ra-228 in water.The pre-treatment method is simple,and the enrichment efficiency is as high as 96.0%.The detection efficiency of y energy spectrum for Ac-228 is 3.6%,but the method has a high detection limit of 54.7 mBq/L.In the method of LSC analysis of Ra-228,the sample needs to be placed for about 20 days to measure.The detection efficiency of LSC for Ra-228/Ac-228 is 72.6%.The method has a lower detection limit of 7.4 mBq/L.The research results of this study provide two methods for the analysis of Ra-228 in water,realizing the measurement of Ra-228 in water under different conditions.