Planning of BNCT using a new medical irradiation facility at JRR4

Abstract

this work. we have compared the dose distributions calculated with these three software packages.Both BNCT_Rtpe/rtt_MC and MCNP are based on the Monte Carlo method, whereas DORT solves the Boltzmann transport equation throughout a deterministic algorithm. Both Monte Carlo applications use similar radiation transport methods; the differences are in the geometry and tally speci®cations. BNCT_Rtpe/rtt_MC can use medical images (MR/CT) in constructing the geometry, whereas in MCNP the tally output options are more¯exible. In both systems, the cross-sectional data are obtained from the ENDF/B (IV/V). In DORT, neutrons and photons are transported to certain discrete directions through each cell of space mesh in the R-Z geometry from the reactor core to the phantom. The solution to the transport equation is iterated until¯uxes will converge to the de®ned accuracy. In this model, the BUGLE-80 cross-section library of 47 neutron and 20 photon energy groups is used.Comparisons were done with calculations of the thermal neutron¯ux in a cylindrical water phantom. Depth dose data as well as x-and y-pro®les at 25 and 60 mm depths were calculated using all three systems mentioned above. For example, the difference between rtt_MC and DOR, at 25 mm depth in the central axis is 1%, but at the phantom surface the difference may be as high as 40%. In the case of pro®les, these two methods agree within 2% when the distance from the central axis is 50 mm or less. In general, all three methods are in good agreement with each other. References 1. Wessol DE et al.. http://id.inel.gov/cart/rtpe-manual. 2. Rhoades WA, Childs RL. (1988) The DORT two-dimensional discrete ordinates transport code. Nucl Sci Engr, 99, 88±89. 3. Briesmeister JF (ed.) (1997) MCNP ± a general Monte Carlo N-particle transport code. Los Alamos National Laboratory Report, LA-12625-M.A new boron neutron capture therapy (BNCT) facility is being planned at the Japanese Atomic Energy Research Institute (JAERI). A former BNCT facility, JRR2, provided thermal neutrons with a neutron¯ux of 1´10 9 n cm A2 s A1 . The new JRR4 facility is intended to generate epithermal and thermal neutrons using various moderators such as heavy water, graphite and alminium. A design optimization study revealed that the thermal mode will provide thermal neutron¯ux (< 0.53 eV) of 0.85´10 9 n cm A2 s A1 and the epithermal mode will provide an epithermal neutron¯ux (0.53±3.35 keV) of 1.7´10 9 n cm A2 s A1 ). Medical facilities will include an operating room, life support monitor; TV monitoring and anesthetic equipment are also planned. The operating room is situated next to the irradiation room (beam port), which facilitates transport of the patient to neutron irradiation. General anaesthesia and life support monitoring will also be available in the irradiation room. The University of Tsukuba teaching hospital for pre-and post-BNCT patient care is also located near JAERI.Regarding the use of epithermal neutrons, which will be predominantly a non-operating method, a new computational dosimetry sys...