Kemp had his arm inside
the hole and was peering past it as he finished the cut.

"Done, sir," he said, and adjusted the flame to a spout of red fire. He
thrust the torch into the hole and quickly withdrew it as pieces of
thorium flew out. A stream of water hosed into the tube would have washed
them out the same way.

Rip took a block of plutonium from Dominico and handed it to Kemp. "Cut a
plug and fit this into it. Then cut a second plug for the other piece.
They have to match perfectly, and you can't put them together to try out
the fit. If you do, we'll have fission right here in the open."

Kemp searched and found a piece he had cut in making the tube. It was
perfectly round, ideal for the purpose. He sliced off the inner side where
it tapered to a cone, then, working only by eye estimate, cut out a hole
in which the wedge of fission material would fit. He wasn't off by a
thirty-second of an inch. Skillful application of the torch melted the
thorium around the wedge and sealed it tightly.

Koa was ready with a sheet of nuclite. Trudeau arrived with a long pole he
had made by lashing two crate sticks together.

Rip gave directions as they formed a cylinder of nuclite. Kemp spot-welded
it, and they pushed it into the hole, forming a lining.

Nunez found a small piece of material in one of the earlier craters. It
would provide some neutrons to start the chain reaction. Rip added it to
the front of the plutonium wedge along with a piece of beryllium from the
bomb, and Kemp welded it in place.

They put the thorium block which contained the plutonium into the hole,
the plutonium facing outward. Trudeau rammed it to the bottom with his
pole. The neutron source, the neutron reflector, and one piece of
fissionable material were in place.

Kemp sliced another round block of thorium out of a near-by crystal and
fitted the second wedge of plutonium into it. At first Rip had worried
about the two pieces of plutonium making a good enough contact, but Kemp's
skillful hand and precision eye removed that worry.

The torchman finished fitting the plutonium and carried the block to the
tube opening. He tried it, removed a slight irregularity with his torch,
then said quietly, "Finished, sir."

Rip took over. He slid the thorium-plutonium block into the tube, took a
rocket head from Santos and used it to push the block in farther. When the
rocket head was about four inches inside the tube, its wires trailing out,
Rip calle