ABSTRACT: Radiotherapy is used of X-rays directly on target to destroy cancer cells and minimize the impact of radiation on healthy cells. Old radiotherapy treatment depends on several factors, such as location, type and stage of cancer, and whether radiotherapy is the treatment of single or combined with other types of cancer treatment, such as chemotherapy or surgery. Based Studies were carried out to analyze internal dose for radiation worker at Boron Neutron Capture Therapy (BNCT) facility base on Cyclotron 30 MeV with BSA and room that actually design before. This internal dose analyze include interaction between neutron and air. The air contain nitrogen (72%), oksigen (20%), argon (0,93%), carbon dioxide, neon, kripton, xenon, helium dan methane. That internal dose to the worker should be bellow limit dose for radiation worker amount of 20 mSv/years. From the particle that are present in the air, only nitrogen and argon can change into radioactive element. Nitrogen-14 activated to carbon-14, nitrogen-15 activated to nitrogen-16, and argon-40 activated to argon-41. Calculation using tally facility in Monte Carlo N Particle version Extended (MCNPX) program for calculated flux neutron in the air 3,16 x 107 Neutron.cm-2.detik-1. room design in cancer facility have a measurement of length 200 cm, width 200 cm and high 166,40 cm. flux neutron can be used to calculated the reaction rate which is 80,1 x 10-2 reaction.cm-3.detik-1 for carbon-14 and 8,75 x 10-5 reaction.cm-3.detik-1. internal dose exposed to the radiation worker is 5,893 x 10-11 Sv.years-1.
