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Abstract-The optimization of thermal column collimator has been studied which resulted epithermal neutron beam for in vivo and in vitro trials of Boron Neutron Capture Therapy (BNCT) at Kartini Research Reactor of 100 kW by means of Monte Carlo N-Particle Extended (MCNP-X) codes. The design criteria were based on recommendation from the International Atomic Energy Agency (IAEA). MCNP-X calculations indicated by using 5 cm thickness of Ni as collimator wall, 30 cm thickness of Al as moderator, 20 cm thickness of 60Ni as filter, 2 cm thickness of Bi as γ-ray shielding, 3 cm thickness of 6Li2CO3-polyethylene as beam delimiter, and for in vivo in vitro trials purpose, aperture was designed 8 cm radius size, an epitermal neutron beam with an intensity 1.13E+09 n.cm-2.s-1, fast neutron and γ-doses per epithermal neutron of 1.76E-13 Gy.cm2.n-1 and 1.45E-13Gy.cm2.n-1,minimum thermal neutron per epithermal neutron ratio of 0.008,and maximum directionality of 0.73, respectively could be produced. The results have passed all the IAEA's criteria.

The optimization of collimator has been studied which resulted epithermal neutron beam for Boron Neutron Capture Therapy (BNCT) using Monte Carlo N Particle Extended (MCNPX). Cyclotron 30 MeV and 9 Be target is used as a neutron generator. The design criteria were based on recommendation from IAEA. Mcnpx calculations indicated by using 25 cm and 40 cm thickness of PbF2 as reflector and back reflector, 15 cm thickness of TiF3 as first moderator, 35 cm thickness of AlF3 as second moderator, 25 cm thickness of 60 Ni as neutron filter, 2 cm thickness of Bi as gamma filter, and aperture with 20 cm of diameter size, an epithermal ne utron beam with an intensity 1.21 × 10 9 n.cm -2 .s -1 , fast neutron and gamma doses per epithermal neutron of 7.04 × 10 -13 Gy.cm 2 .n -1 and 1.61 × 10 -13 Gy.cm 2 .n -1 , minimum thermal neutron per epithermal neutron ratio of 0.043, and maximum directionality of 0.58, respectively could be produced. The results have not passed all the IAEA's criteria in fast neutron component and directionality.

The objectives of this research were to ?nd (1) the optimum boron dose for treating rhab- domyosarcoma in the head and neck regions and (2) the effective irradiation time to treat rhab- domyosarcoma in the head and neck regions. This research used the particle and heavy ions transport code system (PHITS) to simulate the neutron source and BNCT doses. The neutron source used was Kartini Reactor. The simulation was carried out by creating the geometry of cancer tissue in the head and neck regions. Boron concentration variance was 30, 35, 40, 45, and 50 µg/g tissue. The output of PHITS was a neutron ?ux and neutron dose. The neutron ?ux value was used to acquire the alpha dose, proton dose, and gamma dose inside the tissue. The results showed that (1) the optimum boron dose for treating rhabdomyosarcoma in the head and neck regions was 50 µg/g tissue and (2) the effective irradiation time was 7 hours and 4 minutes, which was acquired with a boron concentration of 50 µg/g tissue. The higher the boron concentration level, the higher the dose rate, the quicker the irradiation time, and the lower the radiation dose received by healthy tissues.

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 befor e. This internal dose analyze include interaction between neutron and air. The air contains N2 (72%), O2 (20%), Ar (0.93%), CO2, Neon, Kripton, Xenon, Helium and 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 3,16x10 7 Neutron/cm 2 s. 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 80,1x10 -2 reaction/cm 3 s for carbon-14 and 8,75x10 -5 reaction/cm 3 s. Internal dose exposed to the radiation worker is 9.08E-9 µSv.

A research of design of double layer collimator using 9 Be(p,n) neutron source has been conducted. The research objective is to design a double layer collimator to obtain neutron sources that are compliant with the IAEA standards. The approach to the design of double layer collimator used the MCNPX code. From the research, it was found that the optimum dimensions of a beryllium target are 0.01 mm in length and 9.5 cm in radius. Collimator consists of a D2O and Al moderator, Pb and Ni as a reflector, and Cd and Fe as a thermal and fast neutron filter. The gamma filter used Bi and Pb. The quality neutron beams emitted from the double layer collimator is specified by five parameters: epithermal neutron flux 1 ×10 9 n/cm 2 s; fast neutron dose per epithermal neutron flux 5 ×10 13 Gy cm 2 s; gamma dose per epithermal neutron flux 1×10 13 Gy cm 2 s; ratio of the thermal neutron flux of epithermal neutron flux 0; and the ratio of epithermal neutron current to total epithermal neutron 0.54.

<span>This research aims to determine the amount of radiation dose rate that can be accepted and the irradiation time that is required from Boron Neutron Capture Therapy (BNCT) cancer therapy to treat melanoma skin cancer. This research used the simulation program, MCNPX by defining the geometric dimensions of the tissue component, and describing the radiation source that were used. The outputs obtained from the MCNPX simulation were the neutron flux and the neutron scattering dose that came out from the collimator. The value of neutron flux was used to calculate the dose which comes from the interaction between the neutron and the material in the cancer tissue. Based on the results of the research, the dose rate to treat cancer tissue for boron is 10 μg/g of tumor, which translates to about 0.019241 Gy/second and  requires 25.98 minutes of irradiation time, 15 μg/g of tumor translates to 0.021854 Gy/second and requires 2.,87 minutes, 20 μg/g of tumor translates to 0.022902 Gy/second and requires 21,83 minutes, 25 μg/g of tumor translates to 0.0271275 Gy/second and requires 18.43 minutes, 30 μg/g of tumor translates to 0.0297658 Gy/second and requires 16.79 minutes, and 35 μg/g of tumor translates to 0.0343472 Gy/second and requires 14.55 minutes . The irradiation time needed for cancer tissue is shorter when boron concentration greater at the cancerous tissue.</span>

OPTIMIZATION OF A NEUTRON BEAM SHAPING ASSEMBLY DESIGN FOR BNCT AND ITS DOSIMETRY SIMULATION BASED ON MCNPX.This article involves two main objectives of BNCT system. The first goal includes optimization of 30 MeV Cyclotron-based Boron Neutron Capture Therapy (BNCT) beam shaping assembly. The second goal is to calculate the neutron flux and dosimetry system of BNCT in the head and neck soft tissue sarcoma. A series of simulations has been carried out using a Monte Carlo N Particle X program to find out the final composition and configuration of a beam shaping assembly design to moderate the fast neutron flux, which is generated from the thick beryllium target. The final configuration of the beam shaping assembly design includes a 39 cm aluminum moderator, 8.2 cm of lithium fluoride as a fast neutron filter and a 0.5 cm boron carbide as a thermal neutron filter. Bismuth, lead fluoride, and lead were chosen as the aperture, reflector, and gamma shielding, respectively. Epithermal neutron fluxes in the suggested design were 2.83 x 10 9 n/s cm -2 , while other IAEA parameters for BNCT beam shaping assembly design have been satisfied. In the next step, its dosimetry for head and neck soft tissue sarcoma is simulated by varying the concentration of boron compounds in ORNL neck phantom model to obtain the optimal dosimetry results. MCNPX calculation showed that the optimal depth for thermal neutrons was 4.8 cm in tissue phantom with the maximum dose rate found in the GTV on each boron concentration variation. The irradiation time needed for this therapy were less than an hour for each level of boron concentration. Keywords: Optimization, Beam Shaping Assembly, BNCT, Dosimetry, 30 MeV Cyclotron, MCNPX. ABSTRAK