concrete shield

They crowded behind a thick metal and concrete shield that cut them off from direct sight of the set up.

The core was surrounded by a heavy concrete shield which also served as a secondary containment vessel.

Giant concrete shield plugs are in place over the vessel, and a giant crane 30 feet above is silent.

Lyman is concerned about the strength of the steel containment vessel and the concrete shield building around the AP1000.

An October 2011 shutdown of the plant for maintenance revealed a 30 foot long hairline crack in the concrete shield building around the containment vessel.

In 2003, the concrete shield thrown up to block radiation escaping the Chernobyl nuclear power station after it exploded in 1986 was collapsing and needed urgent reinforcement.

And even if the vessel had cracked, any radioactive material released would still have had to get through a four-foot concrete shield and a steel containment shell outside that to reach the environment.

Lyman, John Ma (a senior structural engineer at the NRC), and Arnold Gundersen (an anti-nuclear consultant) are concerned about what they perceive as weaknesses in the steel containment vessel and the concrete shield building around the AP1000.