Radiation Protection Design And Evaluation Of Protective Effect For Medical Electronic Linear Accelerator

Recently, medical electronic linear accelerator has become a major facility for radiotherapy. Even though medical electronic linear accelerator has varies advantages, its harm to human cannot be ignored. Radiation is harmful to human beings, Rays could lead to large molecules and water molecules to produce ionization in human body, because of the ionization rays have on material. Thus humans who exposed in rays would have different symptoms, such as headache, weakness, anemia and so on. In order to protect people from those possible effects, it is necessary to keep medical electronic linear accelerator under protection according to laws and regulations.This paper will focus on the legal and standard guidance perspectives to determine the feasibility of radiation protection design for medical electronic linear accelerator, to ensure the radiation complies with the safety standards and to strictly monitor the construction of the treatment rooms, as well as to ensure the project complies with construction standards. First of all, research shall be conducted to select the project site. After the determination of the accelerator model and its parameter, Simple formula estimation methods will be used to determine whether the design of the machine room, including the thickness of the room wall, room door design and ventilation system, complies with design standards to block out radiation. After the establishment of the project, tests will be conducted on the accelerator to ensure normal performance.Finally,FJ-347 X-γdosimeter and 190N+RP-N neutron dosimeter will be used to test the effectiveness of protection.It has been proved by calculation and experiments that the forecast data of the thickness and width of the main shield of treatment room is a little bit higher than the results calculated, which means it satisfied requirements of optimization of protection principle. It is expected that treatment room and simulation room could be operated under the data limitation given in evaluation in this design. The door of the treatment room is made up of 16 mmPb lead board, which used to block stray X-Ray and Capture γ-Ray, and 120 mm thick paraffin to block neutron, which contains 30 percent boron. If 17 mmPb and 130 mm thick paraffin contain B(30%)could reach the requirements that dose and dose rate outside less than 2.5μSv/h and dose constraint, the design is qualified. The ventilation system in this project can ventilate the treatment room 10 times per hour higher than national standard of 4 times per hour. Thus design of ventilation ducts is reasonable. Trace X – ray and neutron are detected in Part of the monitoring points outside the accelerator room, however, other experimental points haven’t. The result shows that the annual radiation dose of staff at each point under observation are lower than Target dose management. Thus this accelerator room is qualified and protection result is perfect.