On the one-year anniversary (I know you're getting sick of the phrase..) of the Fukushima I Nuclear Power Plant accident, the US Nuclear Regulatory Commission has issued orders to improve safety of the commercial nuclear power plants in the US.
From the NRC's press release on March 9, 2012, they are:
The first Order requires the plants to better protect safety equipment installed after the 9/11 terrorist attacks and to obtain sufficient equipment to support all reactors at a given site simultaneously.
The second Order requires the plants to install enhanced equipment for monitoring water levels in each plant’s spent fuel pool.
The third Order applies only to U.S. boiling-water reactors that have “Mark I” or “Mark II” containment structures. These reactors must improve venting systems (or for the Mark II plants, install new systems) that help prevent or mitigate core damage in the event of a serious accident.
Plants have until Dec. 31, 2016, to complete modifications and requirements of all three Orders.
There are evidences that the venting may have caused the hydrogen explosions of the reactor buildings because the vent pipes were connected to the pipes for the gas management systems BEFORE they connected to the exhaust stacks. At least part of hydrogen and other gasses, instead of dispersing into the atmosphere through the exhaust stacks, may have come back into the reactor buildings via the gas management system pipes, the Nuclear and Industrial Safety Agency admitted in December last year, 9 months after the explosions.
About the "enhanced equipment" to monitor water levels in the SFPs, I wonder what happens if station blackout happens and the operator cannot read any instrument, as it happened at TEPCO's plant.
Order No.3 requires the installation of new venting systems for Mark II containment structures. Fukushima Reactor 6 is Mark II. I actually do not know if Reactor 6 has the venting system.
If anyone knows the link to the details of these NRC orders, please post on the comment section. I want to know the details. I haven't found it, but I haven't looked carefully enough on the NRC site.