CONTAINMENT SHELL
The primary function of the containment shell is to surround the primary system and provide complete containment of any radioactive matter that might escape from the system. The design pressure of the vessel was determined by postulating the instantaneous release and expansion of the entire contents of the primary system. This approach is highly conservative because of the improbability of a large rupture.
A study has been made concerning the penetration of the vessel wall by a piece of debris in an explosion. An analysis of the penetrating power of high-speed components indicated that the shell would contain the largest missile that could be expected.
The shell is cylindrical in shape, 35 feet in diameter by 50.5 feet long, and is centrally located on the ship’s bottom.
The containment shell is sealed at all times during plant operation. Entry to the shell will be made only after the reactor has been shut down, the shell purged with air, and the radiation level has dropped below 200 mr per hour.
The bottom half of the shell rests in a cradle of steel surrounded by a 48-inch-thick wall of reinforced concrete.
The top half of the containment shell is covered by a 6-inch layer of lead plus a 6-inch layer of polyethylene. During normal power operation, this reduces the radiation level to less than 0.6 mr per hour at the nearest point of access by the crew.