Discovery and discussion of 7Be and another full-energy peak in water from 3D water phantom of a proton therapy system
10.13491/j.issn.1004-714X.2022.03.009
- VernacularTitle:某质子治疗系统三维水箱测量用水中7Be和另一全能峰的发现与探讨
- Author:
Jiaang XU
1
;
Jing SU
1
;
Qiang FU
2
;
Gang SONG
1
;
Nan MIN
1
;
Xiaoshan WANG
1
;
Yingmin CHEN
1
Author Information
1. School of Preventive Medicine Sciences (Institute of Radiation Medicine), Shandong First Medical University (Shandong Academy of Medical Sciences), Jinan 260062 China.
2. Qingdao Municipal Hospital, Qingdao 266011 China.
- Publication Type:OriginalArticles
- Keywords:
Proton accelerator;
Water in 3D water phantom;
Gamma energy spectrum;
7Be activity concentration;
Induced radioactivity
- From:
Chinese Journal of Radiological Health
2022;31(3):306-310
- CountryChina
- Language:Chinese
-
Abstract:
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.
