某核电厂在线式硼表测量准确度超标原因分析及改造研究
Reason Analysis for Unsatisfactory of Accuracy and Improvement of Accuracy of On-line Boron Meter in a Nuclear Power Plant
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摘要: 为查明AREVA NP GmbH供货的在线式硼表(BCMS)测量准确度超标原因,研究提高BCMS测量准确度的方案。根据BCMS工作原理,从中子测量和总硼浓度计算环节对影响BCMS测量准确度的因素进行了分析,并统计分析了BCMS的测量数据;选择测量准确度高于BCMS的离线式硼表(OFBM)为对标对象,在同等统计误差分析条件下对二者的测量准确度进行了对比;以中国核动力研究设计院研制的在线式硼表(ONBM)为参考,量化分析了被测管道尺寸对BCMS中子计数率的影响。结果表明:BCMS在制造厂测试和在核电厂运行期间均存在测量准确度超标问题;BCMS测量准确度超标是由其中子测量装置在固定计数时长内测得的累积中子计数率过低所致;BCMS中子源与中子探测器之间有聚乙烯损耗中子的缺陷。提出了通过切削聚乙烯屏蔽层,同时更换高热中子灵敏度探测器提高BCMS测量准确度的改造方案。Abstract: In order to find out the reason for the unsatisfactory of measurement accuracy of the online type boron meter (BCMS) supplied by AREVA NP GmbH, the scheme to improve the BCMS measurement accuracy was studied. According to the working principle of BCMS, the factors affecting the measurement accuracy of BCMS were analyzed in terms of the neutron measurement and total boron concentration calculation, and the measurement data of BCMS is statistically analyzed; the offline type boron meter(OFBM) with measurement accuracy higher than that of BCMS was selected as the comparison object, and the comparison of the measurement accuracy between BCMS and OFBM was made under the same statistical error analysis condition; the online type boron meter (ONBM) developed by Nuclear Power Institute of China was selected as the reference, and the quantitative analysis of the effect of the measured pipe size on the BCMS neutron count rate was made. The results show that: the unsatisfactory of measurement accuracy existed both in the manufacture factory test and in the nuclear power plant operation of BCMS, which was caused by the extremely low value of the cumulative neutron count rate measured by its neutron measurement device within a fixed counting time; and the loss neutron by polyethylene exists between the neutron source and the neutron detector of BCMS. A modification scheme to improve the BCMS measurement accuracy was proposed, i.e., to cut the polyethylene shielding layer and replace with the higher thermal neutron sensitivity detector .
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Key words:
- Boron meter /
- Neutron /
- Count rate /
- Boron concentration /
- Accuracy
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