yes. He banged his hand on his faceplate in an
unconscious attempt to wipe it off. He cursed silently, and wiped it off
on the inside of his helmet again. This time, two drops ran down the
inside of his faceplate.

"Still don't work," said Cade.

"Keep trying," Cowalczk ordered. "Lehman, get a Geiger counter and come
with me, we've got to fix this thing."

Lehman and Cowalczk, who were already suited up started across to the
reactor building. Cade, who was in the pressurized control room without
a suit on, kept working the switch back and forth. There was light that
indicated when the valve was open. It was on, and it stayed on, no
matter what Cade did.

"The vat pressure's too high," Cade said.

"Let me know when it reaches six pounds," Cowalczk requested. "Because
it'll probably blow at seven."

The vat was a light plastic container used only to decant sludge out of
the water. It neither needed nor had much strength.

"Six now," said Cade.

Cowalczk and Lehman stopped halfway to the reactor. The vat bulged and
ruptured. A stream of mud gushed out and boiled dry on the face of the
Moon. Cowalczk and Lehman rushed forward again.

They could see the trickle of water from the discharge pipe. The motor
turned the valve back and forth in response to Cade's signals.

* * * * *

"What's going on out there?" demanded McIlroy on the intercom.

"Scale stuck in the valve," Cowalczk answered.

"Are the reactors off?"

"Yes. Vat blew. Shut up! Let me work, Mac!"

"Sorry," McIlroy said, realizing that this was no time for officials.
"Let me know when it's fixed."

"Geiger's off scale," Lehman said.

"We're probably O.K. in these suits for an hour," Cowalczk answered. "Is
there a manual shut-off?"

"Not that I know of," Lehman answered. "What about it, Cade?"

"I don't think so," Cade said. "I'll get on the blower and rouse out an
engineer."

"O.K., but keep working that switch."

"I checked the line as far as it's safe," said Lehman. "No valve."

* * * * *

"O.K.," Cowalczk said. "Listen, Cade, are the injectors still on?"

"Yeah. There's still enough heat in these reactors to do some damage.
I'll cut 'em in about fifteen minutes."

"I've found the trouble," Lehman said. "The worm gear's loose on its
shaft. It's slipping every time the valve closes. There's not enough
power in it to crush the scale."

"Right," Cowalczk said. "Cade, open