One of the most important features of the SAVANNAH is her radiation
shielding. The main sources of radiation during operation of the
SAVANNAH’s power plant are the reactor itself and the primary coolant
loop lines. The primary coolant which passes through the reactor core is
irradiated, and itself becomes a source of radiation. Both the reactor
and the coolant emit neutrons and gamma rays. There are also radiation
sources of lesser magnitude including process piping, hold-up tanks,
pumps, and demineralizers.
The objective of radiation shielding on the SAVANNAH is twofold: First,
it limits the radiation dose outside the containment to prescribed safe
levels, and second, it reduces the activation of structure within the
containment shell by reactor core neutrons. The latter consideration is
necessary in order that the reactor plant be accessible for maintenance
within 30 minutes after shutdown.
The shielding is divided into a primary shield, which surrounds the
reactor itself, and a secondary shield, which surrounds the entire
containment shell.