As you know if you visit this page frequently, the nuclear industry seems to have a problem with keeping containment doors closed. The reason why both doors to a containment area are not supposed to be open simultaneously is to prevent the release of radiation in case of on acccident. One thing I had suggested was something that would prevent one of the doors from being opened if the other door was also open. Apparently, these systems exist, but they sometimes don’t work.
The Dresden nuclear power plant in Illinois reported to the NRC on Friday:
“At 0151 [CDT] on March 27, 2014, indication was received in the Control Room that two Secondary Containment doors, in the 2/3 Diesel Generator Interlock, were opened simultaneously. An equipment operator, in the field at the time of the event, reported that while opening the reactor building side interlock doors, individuals were able to open the diesel side interlock doors. The interlock mechanism preventing both doors from operating simultaneously did not operate as expected.”
Another thing this report calls into question is something that the nuclear industry says when there is a fire or explosion in the diesel generator room, for example. Nuclear operating companies always insist that the problem was on the “non-nuclear” side of the plant. What this report from Dresden indicates is that the only thing separating the nuclear and non-nuclear side of the plant is sometimes a single room, with a pair of doors where the interlock may or may not allow the doors to be open at the same time.