
9.6 Collimated Neutron Beams
459
Without any shielding, the dose is 3.71 × 10
−15
Sv/source particle. With a
shielding consisting of multiple layers of steel totaling 30cm thickness inter-
spersed with several layers of polyethylene totaling 20cm thickness, the dose
drops to 3.68 × 10
−17
Sv/emitted neutron at π radians opposite the shield open-
ing. e layered shielding approach is more eective at reducing dose equiva-
lent and neutron uence than shields made out of single continuous layers
of the same material and thicknesses. Adding boron to the polyethylene and
substituting tungsten for steel would make the shielding more eective but
wou ...