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测量自来水的放射性浓度是自来水系统及环境监测部门的日常必须的测量项目之一,其数值作为判断水质是否合格,能否饮用,是否污染的重要依据,为此监测单位的测量结果的报出是否准确、可靠的数据直接影响对饮用水水质的评价和国民的身体健康息息相关。为此在水中总放射性测量中涉及的衰变数、粒子的计数、光子的计数都是随机量。在完全相同的测量条件下,测量多次,每次得到的计数是不同的,评价测量结果的水平如何,用不确定度来说明。不确定度愈小,测量的水平愈高,质量愈高,其使用价值愈高;反之,不确定度愈大,测量水平愈低,质量愈低,其使用价值也愈低。在实际测量中,当样品计数率和低本底α和β测量仪的本底计数率相近时怎样报告结果,应该考虑计算评定合成标准不确定的问题。
Measuring the radioactive concentration of tap water is one of the daily routine measurements required by the tap water system and environmental monitoring department. The values are used as an important basis for judging whether the water quality is acceptable, drinkable or not, and whether the report of the measurement results of the monitoring unit is Accurate and reliable data directly affect the evaluation of drinking water quality and national health are closely related. The decay numbers, particle counts, and photon counts involved in total radioactivity measurements in water for this purpose are all random quantities. Under exactly the same measurement conditions, the measurement is repeated several times and the count obtained each time is different. The level of the measurement result is evaluated and the uncertainty is used to describe it. The smaller the uncertainty, the higher the level of measurement, the higher the quality, the higher the value of its use; the other hand, the greater the uncertainty, the lower the measurement level, the lower the quality, the lower the value of its use. In actual measurements, the question of how to report the results when the sample count rate is similar to the background count rate of the low background α and β meters should be taken into account when calculating the uncertainty of the composite standard.