A man who dubbed himself "Dr. Chaos" was sentenced to 13 years in prison Thursday for storing a cache of cyanide in a CTA Blue Line tunnel under the Loop.

Joseph D. Konopka, 26, apologized at his sentencing hearing for the disruption he caused on a Saturday night in March 2002, when police shut down the Blue Line and Red Line for three hours after learning of the cyanide.

Prosecutors said they believe Konopka, a former computer worker from De Pere, Wis., is the first person to be convicted and sentenced for possession of a chemical weapon.

Before imposing a sentence, U.S. District Judge Wayne Andersen asked Konopka why he kept the cyanide, which he had found in an abandoned South Side warehouse in the summer of 2001.

"I have several reasons, but no good reasons," Konopka answered.

Konopka, a thin, plainspoken man who made a hobby of foraging through empty buildings and tunnels, also said he contemplated using the chemical to commit suicide at one point.

Attorney Matthew Madden said his client thought the chemicals were a "unique, cool thing to have" and sometimes showed them off to others. "He never imagined it as a chemical weapon because he didn't think of it as a weapon," Madden said.

Konopka, who pleaded guilty in November to two counts of possessing a chemical weapon, faces additional prison time for separate crimes in Wisconsin.

He was arrested March 9, 2002, along with a 15-year-old boy in a steam tunnel at the University of Illinois at Chicago. Authorities found a cyanide capsule on Konopka and the boy later told police more chemicals were stashed in the subway.

Konopka, who was living near the location where the chemicals were found, had homemade keys to various areas of the CTA system, burglary tools, sketches of CTA stations, a Global Positioning System device and a radio scanner programmed with Commonwealth Edison frequencies.

Authorities recovered nearly a pound of sodium cyanide and about a quarter-pound of potassium cyanide from an underground CTA substation near the Blue Line's Washington-Dearborn stop.

"These chemicals could easily have been converted to a lethal gas," said Assistant U.S. Atty. M. David Weisman.

The judge, who at several points acknowledged Konopka's intelligence, also ordered mental health and chemical dependency treatment.

The incident involving Konopka exposed vulnerabilities to the CTA rail system. A CTA spokeswoman said Thursday workers have since sealed up rooms no longer in use and changed locks. Anyone caught trespassing is arrested.

Konopka is scheduled to be sentenced April 11 in Milwaukee as part of a plea agreement on charges of vandalism to a TV station transmitter, electric power substations and natural gas pipelines.

Prosecutors have agreed to recommend a 20-year prison sentence on the Wisconsin charges. A judge will determine whether any of the two sentences will be served concurrently.