Calibration and evaluation of neutron survey meters used at linac facility

Calibrated survey meters from the Neutron Laboratory of the Instituto de Radioprotecao e Dosimetria (IRD) were used to determine the ambient dose-equivalent rate in a 15 MV linear accelerator treatment room at the Instituto Nacional do Cancer (INCa). Three different models of neutron survey meters were calibrated using four neutron radionuclide neutron sources: (AmBe)-Am-241(alpha,n), Cf-252(f,n), heavy-water moderated Cf-252(f,n), and (PuBe)-Pu-238(alpha,n). All neutron sources were standardized in a Manganese Sulphate Bath (MSB) absolute primary system. The response of each of these instruments was compared with reference values of ambient dose-equivalent rate. The results demonstrate the complexity of making measurements in the mixed neutron/photon field produced in electron linear accelerator radiotherapy treatment rooms. (C) 2010 Elsevier Ltd. All rights reserved.