Putting a CD in a microwave oven for just one second is sufficient evidence that a strong time-varying EM field is devastating to a CD. The question I don't know is how close one would need to be to a nuclear explosion to have EM pulses that can do this to the CD.
Of course, if you are too close to the detonation the CD gets destroyed by heat or from the building crumbling around it. So the question is whether the EM pulse outside the blast and heat damage regions is sufficient to cause melting in the thin metallic foil of the CD. We know the EM pulse beyond the blast/heat zone is sufficient to ruin transistors; especially CMOS transistors. But CMOS is destroyed at much lower fields than a CD would be.
We also know the government has researched and built different types of nuclear weapons. A weapon (and its detonation height) can be designed to maximize blast, or maximum heat, or maximize neutrons, or maximum EM pulse, etc. Two CDs equidistant from two different weapons might be destroyed in different ways. A weapon designed to maximum EM pulse might make the CD look like it came out of a microwave oven, whereas a weapon designed for blast/heat might make the CD look like it came out of an incinerator.
In the end, I personally can answer the question in the following way.
(1) A strong enough EM can certianly destroy a CD.
(2) Blast and heat can destroy a CD.
(3) Whether the CD could have survived the blast/heat but it got clobbered by the EM pulse depends on things like
(a) How far is it from the center of the detonation?
(b) What type of building is it housed in?
(c) What orientation does it have with respect to the EM pulse propagation?
(d) What type of nuclear device was detonated?
Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817