ABSTRACT
Objective To investigate the radiation dose to operators in the process of 241Am-Be neutron source logging, and discuss neutron source management and protective measures for operators in well logging. Methods Through on-site observation and measurement of 241Am-Be neutron source logging in a company, we obtained the surface γ dose rate and neutron dose rate of the neutron source, as well as the operating time and distance of various processes including source taking, transfer, and loading, calculated the radiation dose to operators in various processes, and analyzed the source and proportion of the personal effective dose to operators. Results The effective doses of neutron irradiation and γ irradiation were 94.17 μSv and 2.72 μSv, respectively, for the combined processes of source tank inspection, transfer, and detection; 36.66 μSv and 24.08 μSv, respectively, for source loading and unloading; and 130.83 μSv and 26.80 μSv, respectively, for the whole neutron source logging process. The total annual effective dose of neutron source logging was 15.78 mSv, as estimated by logging 100 times per year. Conclusion In the process of 241Am-Be neutron source logging in the company, the effective dose to operators mainly arises from neutron irradiation. Therefore, it is necessary to strengthen neutron source management and take effective protective measures against neutron radiation.
ABSTRACT
Objective To design and build a set of experimental equipment for neutron radiation irradiation by using the 241Am-Be neutron source. Methods In the preliminary work, the spatial distribution data of the neutron energy spectrum and the gamma energy spectrum inside and outside the device were simulated by Monte Carlo method, and the changes of radiation fluence rate with spatial distribution was studied. The model of the 241Am-Be neutron device was established, and the neutron transport process in the irradiation field was studied using the method of shadow cone, inverse square law and other data analysis methods. Results Based on the simulation results, the normalized effective does of fast neutron fluence at the measurement point is about 72.9 pSv/n, and the one of photon fluence is about 3.04 pSv/γ. The ratio of effective dose of photon fluence to neuteon is about 4.17%. Conclusion Using Monte Carlo method, a standard model of 241Am-Be neutron source was constructed, the shadow cone design was optimized, and the feasibility of using the shadow cone conversion method to establish a standard neutron source radiation device was discussed.