Calculation of neutron flux and spectrum in three north beam tubes of Tehran research reactor for BNCT, by MCNP

In order to investigate the possibility of using the T.R.R beam tubes in BNCT, it is necessary to select the best one from three north beam tubes. This beam tube should have more flux and better spectrum compared to others. So, after simulation of the last configuration of reactor’s core (NO.55) by MCNP4C code, the neutron flux and spectrum were calculated at the start, middle, and end of each three north beam tubes (B1, B2, B3). Because of the relation between these parameters and the state of core, this calculation was done in three different situations of reactor’s core: BOC, MOC and EOC. The analyses of results showed that the neutron spectrum is almost the same in all of the beam tubes, but the neutron flux in northwest beam tube is better than the others .So, this beam tube is more proper to be used in BNCT.