Page 174 - Dynamics and Control of Nuclear Reactors

13.3 Characteristics of BWRs 171

FOUR-BUNDLE FUEL MODULE
FUEL ROD
WATER RODS
Care Lattice TIE RODS
FIG. 13.3
Four fuel assemblies (boxed channels) showing the control rod cruciform shaped assembly in
the center of fuel four fuel assemblies.
Courtesy of GE Hitachi Nuclear Energy Americas LLC (GE Nuclear Energy, BWR-6: General Description of a
Boiling Water Reactor).
contains steam separators and driers. The location of control rod assemblies means
that gravity-based insertion is impossible. Insertion from below places the control
rod assembles enter through the subcooled region where control rod worth is greatest
and facilitates refueling from above. The control assemblies contain boron carbide
and are used for reactivity control and power flattening. Burnable poison (oxide of
gadolinium – gadolinia) is mixed with the fuel for shim control.