Nuclear weapons, 4th generation or even more advanced weapons, are ideal because they
are extremely small with very predictable profiles. After decades of underground nuclear testing this science has been refined to an extraordinary level of competence.
With nano-technology the various control systems necessary to a nuclear device are infinitesimally smaller than those we’re familiar with from the 1960s.
Advanced nuclear grenades, nuclear weapons the size of apples or grapefruits as Dr. Busby states, are the most secretive technological advancement in real world weapons systems. Nuclear devices as described herein were the only possible way to destroy the buildings without having enormous chunks of building debris fly all over NYC and smash down on dozens of surrounding buildings.
Theses enormous structures had to be turned to dust. Destruction was kept to a minimum although overall it was still quite devastating. It could have been monumentally worse had standard explosives been used: