The threat of terrorist attack on spent nuclear fuel pools may be real but I think this article is probably over the top.

1) In order to drain a pool one would have to penetrate already-obnoxious nuclear plant security and one would have to have the technical expertise to get all the right valves open with the safety and backup systems deactivated. These pools are inside a secure area in the auxiliary building. They are not out in the open like an easy target to hit.

2) The fuel you would expose would have to be pretty much fresh out of the reactor. Fuel bundles recently placed in the spent fuel pool have generally been in a reactor for 3 to 4 years and are pretty much "burned out" in a nuclear sense. While they still produce a fair amount of heat initially, the intensity drops off pretty rapidly over the next year. In any given pool, most of the bundles will be really old with only a few having much heat. In some plants the aged bundles are removed from the pool and stored on dry racks.

3) Even if water is removed from a fresh bundle, the zirc would melt rather than ignite. Zirc presents an appreciable fire danger when it is being machined because those chips come off quite hot. But there you are looking at intense heat in the tiny area where the bit is peeling off metal shavings. The shavings can ignite but the block won't. (We machine zirc under a cooling bath.)

I'm not a spent fuel expert but there are same guys down the hall who are.