The element beryllium is particularly useful due to its ability to act as a neutron reflector or lens.
12.
The purpose of the neutron reflector was to reduce the mass required for the plutonium core to attain criticality.
13.
A bare critical mass of plutonium at normal density and without additional neutron reflector material is roughly 10 kilograms.
14.
Because the core was surrounded by a good neutron reflector, at explosion it comprised almost 2.5 critical masses.
15.
Other controls include the size and shape of the reactor and the presence of neutron reflectors in and around a core.
16.
Ishfaq Ahmad where he immersed himself in work on the physics calculations in the initiator, and helping designing the neutron reflector.
17.
The purpose of the neutron reflector is to improve neutron economy in the reactor, and hence to increase the maximum neutron flux.
18.
The core is surrounded by a steel neutron reflector which increases reactivity and saves ~ 0.1wt % U-235 enrichment.
19.
The molten fluoride fuel can not itself reach criticality but only reaches criticality by the addition of a neutron reflector such as pyrolytic graphite.
20.
Beryllium and graphite blocks or plates may be added to the core as neutron reflectors and neutron absorbing rods pierce the core for control.
