We’re sorry to dwell on unpleasant news of disasters and danger around the world, but it’s been a bad week. (To add to the sorrow, there have been large bombings in Riyahd and Baghdad. And Jerry Orbach of “Law and Order” died of prostate cancer, if you haven’t heard. Gothamist has a touching tribute here.)

Just as the world is dealing with a major international natural disaster that has killed perhaps more than 100,000 people, the Post reminds us of the threat of a manmade disaster: nuclear terror. As the capital city of a much-hated nation, Washington, D.C., faces the uncomfortable threat of being in terrorists’ crosshairs. The Post begins a three-day series on perceived and actual threats from nuclear terrorism and other mass casualty dangers. From the “About the Series” description:

While the dangers certainly are real, there is considerable disagreement among security experts about the probabilities for “catastrophic terrorism.” In the case of nuclear and biological weapons, the subjects of articles today and tomorrow, there are technical and scientific hurdles that have proved daunting, even for nations with sizable budgets and state-of-the-art facilities. Chemical weapons, which will be explored in an article Friday, would be somewhat easier to devise or obtain, but also far less likely to yield huge numbers of casualties. A radiological device would have similar limitations for terrorists.

From the first part, here’s a graphic from the Post about the difficult challenges nuclear terrorists would face to execute their sinister plots.