Читаем The Haigerloch Project полностью

Sig was concentrating. Something was trying to surface in his mind. Once before he had been confronted with a problem that seemingly had no solution. But it had been there. A “Columbus, egg” solution. Obvious — if you could only think of it. He looked up at Himmelmann.

“Delay,” he said slowly. “Several days ago you mentioned a delay that had occurred at the project. When the pile was — contaminated. By a foreign worker.”

“Yes,” said Himmelmann. “It cannot happen again. Conclusive safeguards make it impossible.”

“Why can't it?” Sig asked. “What if we — pushed it along a little?”

They stared at him. Even Himmelmann suddenly looked interested. Intrigued.

“What if we contaminated the pile? In such a way it would be almost impossible to discover? Sabotage — without detection of sabotage. What then?”

Himmelmann stared at Sig as if seeing him for the first time. “They would think the pile itself — the geometry of it — was faulty,” he said slowly. “It would take many weeks — perhaps months — to discover the real reason and rectify it. The project would have been brought to a standstill!”

Sig moved closer to Himmelmann.

“Let's go over the reactor set-up once again, Professor,” he said, oblivious to the others. “Maybe we'll get an idea.”

“Of course,” Himmelmann said briskly. “I will describe the test briefly.” He glanced at Dirk. “I will do it so that your friend may understand also.” He smiled his little downward smile. “With my apologies.”

He turned to Sig, suddenly all scientist.

“There is a large aluminum cylinder set into the pit in the cave floor, almost filling it,” he explained with sudden animation. “The smaller magnesium-alloy reactor vessel has been placed inside this cylinder. The space between the two cylinders is packed and lined with graphite blocks. Ten tons of them.”

Sig nodded. “To work as a reflector,” he said.

“Precisely.” Himmelmann went on. “The pit is then pumped full of water containing an anti-corrosive. Above the reactor vessel is suspended a heavy magnesium-alloy lid, also filled with graphite reflectors. From this lid hang more than a hundred chains of six-centimeter uranium cubes in eights and nines suspended on fine alloy wires. Through a chimney opening in this lid, the neutron source and the heavy water can be introduced.”

“The lid is secured to the reactor vessel itself?” Sig asked.

“It is. It is firmly bolted on…. During the test the neutron source will be lowered through the lid chimney shaft into the heart of the pile. And the heavy water will slowly be pumped in.” He looked gravely at them. “The neutron multiplication levels will be constantly monitored. On the instrumentation panels in the adjoining control room. There is no doubt that the pile will go critical. We will shut down the chain reaction with blocks of cadmium metal if it threatens to get out of control.”

Dirk frowned. He looked from one to the other. “You lost me,” he said. “What exactly does happen?”

“I will explain,” Himmelmann said. “The object of the reactor is to achieve intense neutron multiplication. A neutron is one of the components of the nucleus of an atom. Neutrons are required to initiate the fission process. This occurs when a free neutron collides with the nucleus of a heavy element. A few extra neutrons break off and fly away with fantastic speed, and the nucleus splits into two nuclei of lighter elements with the release of — eh — substantial amounts of energy. Creating the potentials for a nuclear explosion. In fission an amount of energy is produced that is a hundred million times greater than in the ordinary burning of an atom…. The most fissionable material is uranium. U-235. The nucleus of a U-235 atom contains a hundred and forty-three neutrons. The hanging uranium cubes in the pile emit the necessary extra neutrons. These neutrons must be slowed in order to achieve fission. The heavy water accomplishes this neutron-slowing. Heavy water is a variety of ordinary water. It contains hydrogen atoms of double the usual atomic weight and is therefore about ten percent heavier. It effects the slowing down without capturing or absorbing the neutrons, allowing the build-up to continue until the pile becomes self-sustaining. Goes critical.” He looked at Dirk with his caustic smile. “Is that clear?”

“Sure,” Dirk said. “I couldn't have put it better myself.”

“That's where we come in,” Sig said enthusiastically. “If we can contaminate the heavy water so that the neutrons will be absorbed — the pile will fail!” He was getting fired with the problem. “That is essentially what is done by the cadmium blocks the professor said would be used to check the chain reaction. Of course, we can't use cadmium blocks. They would be detected at once. Besides — they would have to be introduced during the test, which is obviously impossible….”

He suddenly brightened. He turned to Himmelmann. “The heavy water,” he asked eagerly. “Where is it stored? Before it is pumped into the pile?”