Simple evaluation method for radiation streaming through bent ducts having arbitrary rectangular sections and a plane radiation source

The simplified method for radiation streaming through bent ducts with a point source was previously derived by an optics analogy considering only components passing through the duct without enormous preparatory calculations. In the present paper, a simplified method for radiation streaming through arbitrary rectangular section bent ducts including slits with a plane source is derived on the basis of the same consideration as earlier. Dose rates estimated by the derived method are compared with experimental values in 90° one-stage, bent square ducts with 10 cm and 20 cm sides, and 2 cm×40 cm, 2.08 cm×40 cm and 5.25 cm×40 cm slits in iron and polyethylene shields with 14 MeV neutron source. The dose rates estimated by the method agree with experimental values within a factor of 2. Regarding the two-stage, 45° bent duct with a diameter of 15 cm and the two-stage, 90° bent square duct with a 1.8 m side, estimated dose rates at the positions of the bend points and the exit agree with the experimental values within a factor of 2. From these results, it is concluded that the derived method is applicable to midway shielding design.