want, doe?”
“Harper is relieved from watch. You take over as engineer-of-the-watch. Send
for the standby engineer.”
“Very well.” His voice and manner were phlegmatic, as he accepted the
situation without comment. The atomic engineer whom he had just relieved glanced
from one to the other, then carefully replaced the wrench in its rack.
“Just as you say, Doctor Silard, but send for your relief, too. I shall
demand an immediate hearing!” Harper swept indignantly out, his lead-sheathed boots
clumping on the floorplates.
Doctor Silard waited unhappily for the ensuing twenty minutes until his own
relief arrived. Perhaps he had been hasty. Maybe he was wrong in thinking that
Harper had at last broken under the strain of tending the most dangerous machine in
the world-the atomic breeder plant. But if he had made a mistake, it had to be on
the safe side-slips must not happen in this business; not when a slip might result
in atomic detonation of nearly ten tons of uranium-238, U-235, and plutonium.
He tried to visualize what that would mean, and failed. He had ‘been told
that uranium was potentially twenty million times as explosive as T.N.T. The figure
was meaningless that way. He thought of the pile instead as a hundred million tons
of high explosive, or as a thousand Hiroshimas. It still did not mean anything. He
had once seen an A-bomb dropped, when he had been serving as a temperament analyst
for the Air Forces. He could not imagine the explosion of a thousand such bombs;
his. brain balked. Perhaps these atomic engineers could. Perhaps, with their greater
mathematical ability and closer comprehension of what actually went on inside the
nuclear fission chamber, they had some vivid glimpse of the mind-shattering horror
locked up beyond that shield. If so, no wonder they tended to blow up- He sighed.
Erickson looked away from the controls of the linear resonant accelerator on which
he had been making some adjustment.
“What’s the trouble, doc?”
“Nothing. I’m sorry I had to relieve Harper.”
Silard could feel the shrewd glance of the big Scandinavian. “Not getting
the jitters yourself, are you, doc? Sometimes you squirrel-sleuths blow up, too-”
“Me? I don’t think so. I’m scared of that thing in there-I’d be crazy if I
weren’t.”
“So am I,” Erickson told him soberly, and went back to his work at the
controls of the accelerator. The accelerator proper lay beyond another shielding
barrier; its snout disappeared in the final shield between it and the pile and fed a
steady stream of terrifically speeded up sub-atomic bullets to the beryllium target
located within the pile itself. The tortured beryllium yielded up neutrons, which
shot out in all directions through the uranium mass. Some of these neutrons struck
uranium atoms squarely on their nuclei and split them in two. The fragments were new
elements, barium, xenon, rubidium-depending on the portions in which each atom
split. The new elements were usually unstable isotopes and broke down into a, dozen
more elements by radioactive disintegration in a progressive reaction.
But these second transmutations were comparatively safe; it was the original
splitting of the uranium nucleus, with the release of the awe-inspiring energy that
bound it together-an incredible two hundred million electron volts-that was
important-and perilous.
For, while uranium was used to breed other fuels by bombarding it with
neutrons, the splitting itself gives up more neutrons which in turn may land in
other uranium nuclei and split them. If conditions are favorable to a progressively
increasing reaction of this sort, it may get out of hand, build up in an
unmeasurable fraction of a micro-second into a complete atomic explosion-an
explosion which would dwarf an atom bomb to pop-gun size; an explosion so far beyond
all human experience as to be as completely incomprehensible as the idea of personal
death. It could be feared, but not understood.
Page 16
But a self-perpetuating sequence of nuclear splitting, just wider the level
of complete explosion, was necessary to the operation of the breeder plant. To split
the first uranium nucleus by bombarding it with neutrons from the beryllium target
took more power than the death of the atom gave up. In order that the breeder pile