Study of monitoring the neutron dose on radiation workers at Linac operation with photon energy ≥ 10 MV

Abstract

The use of Linac for radiotherapy is starting to use a lot of high-energy photons of 10 MV; in addition, some use 15 MV for patient therapy in routine use, there is also the use of 6 MV. The purpose of this study is to obtain an overview and information of the neutron dose that has the potential to provide additional doses for radiation workers operating the Linac 10 MV aircraft. Based on the Regulation of the Head of BAPETEN No. 3 of 2013, Article 48 paragraph (2) states that in the operation of Linac with X-ray photon energies above 10 MV, must coat the shield wall with a neutron-absorbing material. The statement follows the IAEA-TecDoc 1891 that neutrons will have the potential to have a significant radiological impact on workers if routinely operated at energies above 10 MV, so must consider protection for workers. The results of a survey from 27 hospitals, obtained information through filling out questionnaires and discussions and validated with B@LIS Pendora, it found that the trend of annual doses received by each profession in the operation of Linac 6 MV, 10 MV, and 15 MV was less than one mSv, only partially small worker dose that is above one mSv (above the 90th percentile). This study concluded that the presence of neutrons in Linacs up to 10 MV was deemed not to have a significant radiological impact on workers. The recommended criteria/mechanism for monitoring worker neutron doses in Linacs up to 10 MV could be based on if the safety study results obtained a dose received by workers 1.5 mSv/year. Then, there is no need to monitor the neutron dose. If the measurement results of exposure to neutron and gama radiation around the Linac space are 7.5 microSv/hour, there is no need for neutron monitoring. In Linacs above 10 MV, if the annual effective dose is 1.5 mSv/year, there is no need to monitor the dose of special neutron personnel. Still, routine radiation exposure monitoring may be considered every two years. Keywords: Neutron Dose, Radiation Worker, Linac, Dose Monitoring.