The AP1000 doesn't have a single containment.
Like all reactors it has a sealed fuel assembly (containment #1), reactor pressure vessel (containment #2) and a steel containment structure (containment #3).
NRC regulations require that all reactors built in the US (past and future) have 3 levels of containment.
![](https://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Containment_Building.jpg/300px-Containment_Building.jpg)
Traditional (GenII) PWR:
fuelassembly(#1)-reactor(#2)-SteelContainment(#3)-Concrete
AP1000
fuelassembly(#1)-reactor(#2)-SteelContainment(#3)-Space-Concrete
The only difference between the AP100 and a Gen II PWR is that there is a space between the concrete missile shield and the steel containment structure to facilitate passive cooling. This feature along with others makes the reactor safer because it is able to cool without any electrical power.
As usual the anti-nukkers need to rely on lies to continue their luddite agenda.