Fermi National Laboratory

Volume 22  |  Friday, August 20, 1999  |  Number 16
In This Issue  |  FermiNews Main Page

How hot was it?

by Judy Jackson

In Chicagoland, the last week in July was a scorcher. The heat boiled up to a peak of 102° on Friday, July 30, and the dew point stuck for five hours at 82 degrees, giving the air the approximate consistency of simmering cottage cheese. Out on the prairie at Fermilab, it was really, really hot.

How hot was it?

It was so hot we shut the Tevatron off to save power to help keep Chicago from an electrical blackout.

It was so hot that Wilson Hall began rocking and rolling. The High Rise’s two independent but connected towers move slightly, in response to temperature extremes, causing cracking and spalling (or chipping) concrete. (Fermilab, the joke goes, operates DOE’s "Concrete Spallation Source.”) An extensive renovation beginning this fall will address this problem, but in the meantime, the cracks opened up.

"We have been monitoring the building motion in Wilson Hall since 1997, watching the cracks over the course of the year,” said Fermilab engineer Elaine McCluskey. "In the recent heat wave, the cracks opened more than ever before. In summer, we generally see the cracks open up to a width of three to four millimeters. This time they reached a width of five millimeters, 20 to 25 percent more than we have seen. In the winter the cracks will close up again.”

It was so hot that keeping the Tevatron cold (when it was operating) was a challenge. The accelerator’s superconducting magnets operate at close to absolute zero.

"The bigger the difference between the outside temperature and the temperature required for operating the Tevatron,” said Fermilab cryogenics expert Jay Theilacker, "the more refrigeration we need, the harder the cryogenic systems have to work, and the more it costs in cryogens, like liquid nitrogen and liquid helium. It takes more compressor power to reach our fixed cold-capacity requirement.”

It was so hot, we ate lunch with the lights off in the Wilson Hall cafeteria, which was actually rather pleasant.

It was so hot, the cooling water lost its cool. Much of the cooling on the Fermilab site starts with Casey’s Pond, a pastoral pool from which huge 400-horsepower pumps circulate water throughout the laboratory to cool accelerators, machinery, buildings and people. On Fry Day, the 30th, hot machinery and hot weather brought the temperature in Casey’s Pond to 84 degrees. The pumping process added still more energy, and the pond could not shed its heat.

"When the humidity is very high, as it was in the recent heat wave, evaporation does not take place, so the pond cannot cool off,” said Pump House building manager Cliff Worby. "It’s the sweating effect.”

It was so hot, the fish in Casey’s Pond began to die. A species called the quill back (Carpiodes cyprinus) is especially sensitive to the lower oxygen levels in hotter water, and many died. This was bad news for the quill backs but good news for the herons, egrets and raccoons who flocked to the ponds for a hot fish dinner,

It was so hot, the Computing Division made a plan to start shutting down if it got any hotter.

"The Casey’s Pond cooling water input to Feynman Computing Center reached 87 degrees,” said Matthias Kasemann, head of the Computing Division. "If it reaches about 90 degrees, then it does not cool anymore. If computing equipment gets too hot, things begin to fail, power supplies burn up, and systems trip off. As the temperature of the cooling water began to rise, we devised a plan to begin shutting off equipment, starting with systems that aren’t being used for current operations.”

In the end, the heat wave broke and the computers kept running, but "we came close,” Kasemann said.

How hot was it?

It was so hot the Fermilab buffalo stood in the shade and didn’t move— a strategy with much to recommend it if and when the weather once again becomes too darn hot.



last modified 8/20/1999   email Fermilab