RESUMEN
Objective To discuss 7Be and a 77.2 keV full-energy peak with short half-life found in the water sample from the 3D water phantom of a proton therapy system. Methods We measured the water sample from the 3D water phantom of a proton therapy system according to Determination of Radionuclides in Water by Gamma Spectrometry (GB/T 16140—2018). Results The activity concentration of 7Be in the water sample was 1.30 × 101 Bq·L−1 on December 24, 2018; 4.3 × 101 Bq·L−1 on March 22, 2019; and 1.41 × 101 Bq·L−1 at the time of sampling on December 19, 2018. On December 24, 2018, the net peak area of the 77.2 keV full-energy peak in the sample was 683 ± 45, and the measurement time was 26123.02 s; on March 22, 2019, the net peak area decreased to the background level of 194 ± 49, and the measurement time was 86400.00 s. Conclusion In the 3D water phantom of the proton therapy system, 7Be can be generated from the spallation reaction between high-energy neutrons and oxygen in water. In addition, we find a full-energy peak at 77.2 keV with short half-life. The activity concentration of 7Be in the water sample is lower than the exemption level, but the activity concentration at sampling may not be the maximum activity concentration in the process of quality control. The inductive radionuclide 7Be produced in the 3D water phantom should be identified and properly evaluated in the assessment of occupational radiation hazards of proton therapy system.
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Objective:To monitor and analyze the activity concentrations of 7Be and 210Pb in atmospheric aerosol in Beijing from 2017 to 2020. Methods:Totally 1 074 atmospheric aerosol samples were collected by high flow air sampler (SnowWhite) including 275 in spring, 266 in summer, 262 in autumn and 271 in winter and subjected to analysis by low background high-purity germanium gamma-ray spectrometery (ORTEC) to determine the activity concentrations of 7Be and 210Pb. Results:The activity concentrations of 7Be in atmospheric aerosol were from 0.56 to 14.84 mBq/m 3, with an avearage of 6.84 mBq/m 3, and from 0.01 to 9.37 mBq/m 3 for 210Pb, with an avearage 3.19 mBq/m 3. The differences in activity concentrations of 7Be and 210Pb in atmospheric aerosol among differernt seasons were statistically significant ( F=32.66, 93.93, P<0.05). Activity concentration of 7Be was highest in spring, followed by autumn, and lowest in summer and winter. Activity concentration of 210Pb ranged from winter, autumn, spring to summer in descending order. Conclusions:The activity concentrations of 7Be and 210Pb in atmospheric aerosol in Beijing from 2017 to 2020 fluctated within the range of normal level.