PHOTONEUTRON AND CAP TURE GAMMA DOSE CAL CU LA TIONS FOR A RA DIO THER APY ROOM MADE OF HIGH DEN SITY CON CRETE

Neu tron and cap ture gamma ray dose equiv a lent along the maze and en trance door of a ra di a tion ther apy room made of high den sity con crete was cal cu lated us ing an a lyt i cal and Monte Carlo meth ods. The room ge om e try and the 18 MV pho ton beam of a Varian 2100C/D linac were sim u lated us ing MCNPX MC code. Four an a lyt i cal meth ods in clud ing Ker sey, French, Mc Call, and Wu-McGinley meth ods were used in the cur rent study. Av er age dif fer ence of 13-30% was seen be tween an a lyt i cal and MC meth ods along the maze for photoneutron cal cu la tions. The dif fer ence be tween Wu-McGinley and MC meth ods was about 17% for cap ture gamma ray cal cu la tions. It was con cluded that the an a lyt i cal meth ods over es ti mate both neu tron and cap ture gamma ray dose equiv a lents com pared to MC. More over, it was shown that the an a lyt i cal meth ods can be used as con ser va tive es ti ma tors for neu tron and cap ture gamma cal cu la tions.