[Qbert]

“Why is a roof crack meaningful?”

—If this article is correct, then spent fuel of the Mark 1 design reactor No. 4 is located as follows:

“This diagram shows where spent fuel pools are located in the boiling water reactor system at Fukushima, a 1970s design by General Electric known as the Mark 1. As the graphic shows, while the spent fuel lies under a deep pool of water, it is outside the concrete-and-steel containment designed to trap radiation leaks.”

http://www.allheadlinenews.com/briefs/articles/90040199?Spent%20Fuel%20Now%20Focus%20at%20Japanese%20Reactor%2C%20Highlighting%20Concerns%20About%20Plant%20Design

—This diagram shows what lies above the pool:

http://www.propublica.org/documents/item/ucs-spent-fuel-report#document/p6

[winoneforthegipper]

Good stuff! Had not seen that diagram.

[D-fendr]

Thanks for your post. I’ve also watched another report.

They were considering using helicopters through the roof to cool, but decided against it. So, not sure if roof integrity is a hindrance or an opportunity.

If the roof crack significance is an avenue for leakage, I would think the large holes in the walls would be enough anyway.

Perhaps it is a worry of roof collapse.

Or maybe the headline of roof crack is of little meaning other than another excuse for a headline.

I appreciate the information and effort of your post.