Dunno who the 'concerned' was, but a lot of speculation has been posted; it is the later posts that are based more on actual findings.
In any case, it is the vents that are supposed to keep the vessel from blowing its top.
As Tepco reported May 18: "Tokyo Electric Power (TEPCO) has now finally confirmed that meltdowns occured in reactor No. 1, 2 and 3 all of which suffered hydrogen explosions that blew away their containment buildings-.... thanks to the failed General Electric hydrogen vents." Several news reports indicating that similar vents were on U. S. reactors.
Bellona and bloomberg.com among others discussed the problem.
Entergy Corp. (the second-largest U. S. nuclear operator, and Duke Energy Corp. said the industry may need to retrofit reactors or bolster safety systems after a pressure-relief system failed in Japan, contributing to the worst nuclear disaster since Chernobyl- report in bloomberg.com.
"The U.S. Nuclear Regulatory Commission is "looking at effectiveness of containment venting strategies," Charlie Miller, head of the post-Fukushima safety review, said at a May 12 agancy meeting.

Entergy "fully expects" the U.S. Nuclear Regulatory Commission to order new equipment installed and new procedures to be adopted as a result of the accident in Japan, said Jim Sheets, a spokesman for the New Orleans-based company that owns 11 reactors. Exelon Corp. owns the largest number of U.S. reactors. Another Entergy executive said there were multiple explanations for the failure of the venting systems.
The U.S. has 104 reactors in 31 states. At least 5 are in areas possibly subject to serious earthquakes. www.worldnuclear.org