NEUTRON AND GAMMA SPECTRUM ANALYSIS OF KARTINI RESEARCH REACTOR

OPTIMIZATION OF BIOLOGICAL SHIELD FOR BORON NEUTRON CAPTURE CANCER THERAPY (BNCT) AT KARTINI RESEARCH REACTOR.A study to optimize a model of neutron radiation shielding for BNCT facility in the irradiation room has been performed. The collimator used in this study is a predesigned collimator from earlier studies. The model includes the selection of the materials and the thickness of materials used for radiation shield. The radiation shield is required to absorb leaking radiation in order to protect workers at the threshold dose of 20 mSv/year. The considered materials were barite concrete, paraffin, stainless steel 304 and lead. The leaking neutron radiation dose rates have been determined using Monte Carlo N Particle Version Extended (MCNPX) with a radiation dose limit rate that is less than 10 µSv/hour. This dose limit is in accordance with BAPETEN regulation related the threshold dose for workers, in which the working duration is 8 hours per day and 5 days per week. It is recommended that the best model for the irradiation room has a dimension 30 cm width, 30 cm length, 30 cm height and a main layer of irradiation room shielding made from the material paraffin which is 68 cm thickness on the left side and bottom of the irradiation room, 70 cm thickness on the right side of the iradiation room, 45 cm thickness on the front of the irradiation room and 67 cm thickness on the top of the irradiation room. The additional layers of 15 cm and 10 cm thickness are used along with paraffin in order to reduce the intensity of primary radiation from piercing the beamport after two primary layers. There is no neutron radiation leakage in this model. Keywords: Radiation shielding, BNCT, MCNPX, radiation dose rate, piercing beamport. ABSTRAK OPTIMASI PERISAI RADIASI NEUTRON FASILITAS RUANGAN IRADIASI UNTUK BORON NEUTRON CAPTURE CANCER THERAPY (BNCT) DENGAN SUMBER BEAMPORT TEMBUS REAKTOR KARTINI. Telah dilakukan pemodelan perisai radiasi neutron untuk fasilitas Boron Neutron

The purpose of this study is to know the concentration of boron and irradiation times which optimizes the treatment of breast cancer using the BNCT method. This research was conducted by using MCNPX simulation which outputs are flux neutron, neutron scattering dose and gamma dose. The neutron source used is the BSA D-D Neutron generator model. The independent variable of this research is the boron concentration injected into the cancer. The dependent variable is the total dose rate and irradiation time which determines the effectiveness of  BNCT therapy. The controlled variables are the output of the neutron flux, dose and gamma neutron scattering dose. The results showed that in the range of 70-150 µg/g, the dose rate received by cancer increases with increasing the concentration of boron-10. If the dose rate is increased, the irradiation time interval will be faster. The Boron dose of 70 μg/g and the dose rate of irradiation 0.00293603 Gy/sec needs an irradiation time of 409.43 minutes; the boron dose of 90 µg/g and the dose rate of irradiation 0.00241049 Gy/sec needs an irradiation time of 345.71 minutes; the boron dose of 110 µg/g and the dose rate of irradiation 0.00271236 Gy/sec needs an irradiation time of 307.24 minutes; the boron dose of 130 µg/g and the dose rate of irradiation 0.00303389 Gy/sec needs an irradiation time of 274.67 minutes; and the boron dose 150 µg/g and the dose rate of irradiation 0.00334565 Gy/sec needs an irradiation time of 249.08 minutes. The Optimum concentration of boron is 150 µg/g with irradiation time of 249.08 minutes.