| As if there aren't already enough compelling reasons to immediately retire BWR Mark 1 reactors like the ones at Fukushima and at Vermont Yankee, Arnie Gundersen of Fairewinds Associates has just identified a doozy of a containment flaw that had previously escaped detection!
Analyzing data from the first day of the Fukushima accident, after the tsunami but before the explosions; and comparing those numbers to data collected during a test forty years earlier at the Brunswick facility in North Carolina, Arnie noticed a striking similarity which suggests an entirely unanticpated explanation for how those explosions came to pass.
In the scenario proposed by Fairewinds, as cooling failed at Fukushima, there was an accompanying build-up of contaminated hydrogen gas in the containment vessel. After about eight hours, the pressure build-up in the vessel so far exceeded it's designed capacity that it actually stretched retaining bolts on the vessel "lid," creating a space through which volatile gas escaped into the reactor. A single spark was all it took to set off a blast, ripping through the reactor and rocketing contaminated debris and gases into the atmosphere.
When the possibility of a hydrogen explosion in the Mark 1 was finally recognized in the 1980's, a design modification involving a vent was made to all containments for that generation of reactors. This modification has come to be widely accepted as a permanent fix for the problem.
It turns out that, even though the vent appears to have functioned properly at Fukushima, it never could have prevented the exact problem that precipitated the explosions that occurred there!
The potential for a similar chain of events linked to that single design flaw still exists in all Mark 1BWR reactors that remain online today.
The Nuclear Regulatory Commission has long maintained its official position that the original design flaw in this generation of reactors was resolved through the vent modification, and that the containment vessel could not be breached.
This new evidence suggests otherwise.
Have a look at the brief and very straightforward explanation that Arnie Gundersen provides for this phenomenon:
New Containment Flaw Identified in the BWR Mark 1 from Fairewinds Energy Education on Vimeo. |
