Investigation of Three Efficiency Calibration Methods for Off-line Noble Gas Effluent Monitor

Three alternative efficiency calibration methods were introduced and employed to calculate the efficiency curve for detecting a simulated gas source with known activity by a HPGe detector. The dimension parameters of the model utilized by Monte Carlo (MC) method were based on the parameter values supplied by its manufactory. The result of MC method is unreliable and its maximal relative deviation reaches 130% compared with the experimental results. Both numerical integration (NI) method and representative point (RP) method utilized a multiγ point-like standard source as well as MC simulation. When the energy range of γ-ray is 60-1 836 keV, the relative deviations of RP method are within ±6% while those of NI method are within ±4%. The NI and RP methods satisfy the uncertainty requirement in field work, while RP method is much easier to be implemented.