摘要：The effects of the dose rate and the energy of fission neutrons using an iron block on tumorigenesis in B6C3F1 mice were examined. Six-week-old female animas were divided into 4 groups and exposes to 252 Cf neutron irradiation at dose rates of 0.05 cGy/min, with (Group 1) or without (Group 2) filtering through a 10 cm thick iron block, 0.8 cGy/min (Group 3) or 0 (Group 4 controls). Total neutron exposure was 50 cGy in each of groups 1-3 and total irradiation dose was 56, 75 and 75 cGy in Groups 1-3, respectively. Total tumor incidences or multiplicity were significantly higher in Group 3 than in Group 1. A similar tendency was observed as compared to Group 2, ovarian and Harderian gland tumors being mainly affected and adrenal tumors were significantly higher in Group 2 than in Group 1. The results indicated a clear increase in tumorigenesis with the higher dose rate and no filtering influence of iron was evident, despite the drop in neutron energy level.
