According to Project on Government Oversight's Senior Investigator, Peter Stockton, this incident "is a new twist in the long history of screw-ups by Los Alamos." I can't really blame him for saying that when testing a gun results in several million dollars of structural damage, propels doors away from the building, and leaves pieces of the weapon spread out on the ground outside. Geez.
Update: Wired reports that they've received an email from National Nuclear Security Administration spokesman Damien LaVera which implies that what we've first heard might not be the exact story:
Here are the facts: On December 16, Los Alamos conducted a standard proof test on a new design for a catch tank in the target chamber for one of our large bore powder guns (LBPG). These types of experiments are routine and responsible. The LBPG is used to conduct measurements of material properties at pressures needed for understanding nuclear weapons performance. During this particular test, unexpected explosive damage occurred and, because that damage could result in $1 million in damages, an investigation was automatically triggered. That investigation will seek to identify the cause of the incident and any changes in procedures that might be required. NNSA, Los Alamos, and all of our facilities take their commitment to safety very seriously. It is important to note that no personnel were injured from this event, no hazardous or radioactive materials were involved, and that lab's incident response mechanisms appear to have performed as intended.