What I am suggesting is the construction of a border barrier whose most effective component is an extremely intense field of nuclear radiation (produced by the operation of underground nuclear reactors), sharply confined to the barrier zone, which practically guarantees the death of anyone attempting to breach the barrier...

Briefly, this is how such a barrier scheme would work:

During peacetime, the reactors (employed underground, for protection and safety) are operated on a continual basis, as are our power reactors. The neutrons produced by the fission reactions escape into a solution containing an element that, upon absorbing the neutrons, becomes highly radioactive and emits gamma rays (very high energy X-rays) at extremely high intensity. The radioactive solution is then passed into a series of pipes running along the barrier length in conjunction with conventional obstacle components—mines, Dragon's Teeth, tank traps, barbed wire, etc. To the rear of the pipes and obstacle belts is a system of conventional defensive fortifications. (The obstacles, the firepower from the fortifications, and tactical air power all serve to impede the rate of advance of the attacker, increasing the attacker's exposure to the gamma radiation. Vice versa, by quickly incapacitating the attacker, the radiation serves to make it difficult, or even impossible, for the attacker to remove the obstacles and assault the fortifications.) The width of the entire defensive system need be no more than a few miles.

The gamma ray field in the immediate vicinity of the obstacle zone readily can be sufficiently intense that several minutes' exposure will produce incapacitation and ultimately death. However, at a distance of, say, 1,000 yards from the pipes, the radiation intensity is so reduced that people are perfectly safe. In fact, a person could stand all day at this distance without putting himself in jeopardy.