Optimization Of Preparation Technology Of Enriched Boron-10 Boric Acid

Boron has two stable isotopes,19.78%of ¹⁰B and 80.22%of ¹¹B,in which ¹⁰B is a good neutron absorber.Boric acid was dissolved in the reactor coolant and used widely as a soluble reactive control agent in pressurized water reactor?PWR?due to this property.Currently,enriched boric acid?EBA?,replacing natural boric acid to apply to EPR?Europe pressure reactor?and AP1000,has been used in many nucl ear power plants.However,EBA mainly rely on import in China due to the difficulty of producing enriched ¹⁰B.Thus,it is valuable to study the preparation of EBA.This paper deals with the basic question about the production of EBA from boron trifluoride methanol as reactant as follows.In this paper,firstly,based on the hydrolysis reaction of boron trifluoride,the process of preparing high purity 10B boric acid by one-step method with calcium carbonate as a fluorine removal agent was discussed.The effects of reaction time,raw material ratio of solid to liquid,the water volume and other factors on the product purity and yield were investigated.H₂O₂ is added to reduce the content of Fe²⁺in the product as an innovative operation.Secondly,two processes for preparing ¹⁰B boric acid were summarized,through the comparison of six kinds of methods and the material and energy balance of the two methods.It is more valuable to determine the calcium carbonate in one step method.Meanwhile,the process flow charts of the two methods were drawn.Based on the above research,aiming at the problem of the one-step product purity is not high enough;the effect of the traditional purification method is compared.The purification effect of recrystallization method is the best,which is optimized for the anti solvent recrystallization with acetone as the solvent.The purity can be increased to 99.98%.At last,the author explored the preparation of nuclear grade boric acid by the method of melt crystallization.Effect of the cooling rate,feeding rate and other factors on crystal layer growth rate and separation efficiency were analyzed,moreover,the effects of transpiration process on separation efficiency and yield were investigated.The final product boric acid purity can reach more than 99.99%.Boric acid produced by traditional production technology is always accompanied by natural abundance,and the purity is mostly analytical reagent,no complete high purity boric acid production process for reference.There is no uniform standard for the content of impurity ions in boric acid.This paper describes the technology and influence factors of high purity boric acid,and some process steps were optimized,the pilot production process of high purity boric acid was established,at the same time,the production process of nuclear grade boric acid is given,which provides a theoretical reference for the production of 10B boric acid with different purity in the industry,which has great significance in the industry.