直接熔融热电离质谱法测定硼硅玻璃中硼同位素比值

Determination of Boron Isotope Ratio in Borosilicate Glass by Direct Melting with Thermal Ionization Mass Spectrometry

硼硅玻璃是目前压水堆应用最多的可燃毒物材料,产品中硼同位素组成的准确测定对燃耗预估及产品质量判定具有重要意义。文章基于直接熔融热电离质谱法,首先探讨了硅元素对硼酸中硼同位素测量结果的影响,结果表明:Si/B质量比小于9时,硅对NIST 951a硼酸标准物质测量结果无显著干扰,采用直接熔融热电离质谱法测定核电用硼硅玻璃中硼同位素比值具有可行性;随后,详细分析了Na/B摩尔比、甘露醇和石墨加入量3个参数对测试结果的影响,得到的最佳参数为Na/B摩尔比9、加入甘露醇及3μL石墨发射剂;最后,采用优化测试参数,对实际硼硅玻璃样品进行了测试,并以NIST 951a硼酸标准物质为外标对测量结果进行分馏校正,结果发现分馏校正后样品的不确定度来源主要是标准物质。研究成果可满足硼硅玻璃的燃耗预估及产品质量的快速判定需要。

Borosilicate glass is the most widely used burnable poison material in PWR.The boron isotope composition in the product can be used for fuel consumption estimation and product quality determination.In this paper,boron isotope composition was studied based on direct melt thermoelectric ionization mass spectrometry.First,we discussed the influence of silicon impurity on the measurement results of boron isotope in boric acid.The results showed that silicon had no significant interference to the measurement results of NIST 951a boric acid standard material when Si/B mass ratio was less than 9,which verified the feasibility of the direct melt thermoelectric ionization mass spectrometry for the determination of boron isotope composition in borosilicate glass.Then,the effects of three parameters,namely the molar ratio of Na/B,mannitol and graphite addition amount were analyzed in detail,and the best analysis condition were obtained as that the molar ratio of Na/B was 9 and the graphite addition amount was 3μL with the addition of mannitol.Based on the above optimal test parameters,the actual borosilicate glass samples were tested,the correction of mass fractionation was carried out using NIST 951a boric acid as the external standard to obtain the final determination value of boron isotope ratio of samples.It was found that the uncertainty of the sample after fractionation correction was mainly from the standard material.The research results can provide reference for the burn-up estimation of borosilicate glass and the quick determination of product quality.