바로가기  >

Residual gamma effective dose rate and accumulated dose as a function of decay time just after 1 fraction irradiation with maximum energy (430 MeV/u) and the beam intensity of 1 x 109 particles per second in normal operation in the treatment room

Abstract
PURPOSE:
An optimized air ventilation system design for a treatment room in Heavy-ion Medical Facility is an important issue in the aspects of nuclear safety because the activated air produced in a treatment room can directly affect the medical staff and the general public in the radiation-free area.

METHODS:
Optimized design criteria of air ventilation system for a clinical room in 430 MeV/u carbon ion beam medical accelerator facility was performed by using a combination of MCNPX2.7.0 and CINDER'90 codes. Effective dose rate and its accumulated effective dose by inhalation and residual gamma were calculated for a normal treatment scenario (2 min irradiation for one fraction) as a function of decay time. Natural doses around the site were measured before construction and used as reference data.

RESULTS:
With no air ventilation system, the maximum effective dose rate was about 3 μSv/h (total dose of 90 mSv/y) and minimum 0.2 μSv/h (total dose of 6 mSv/y), which are over the legal limits for medical staff and for the general public. Although inhalation dose contribution was relatively small, it was considered seriously because of its long-lasting effects in the body. The integrated dose per year was 1.8 mSv/y in the radiation-free area with the 20-min rate of air ventilation system.

CONCLUSION:
An optimal air ventilation rate of 20 min is proposed for a clinical room, which also agrees with the best mechanical design value.

Author information

Kum O1.
1
School of Electrical, Electronics, and Computer Engineering, Kyungpook National University, 80 Daehakro, Bukgu, Daegu, 41566, Korea.