The FBI yesterday arrested a 39-year-old old man in Wilmington N.C., on charges he attempted to extort $100,000 from the General Electric Co. in return for 150 pounds of uranium he said he stole from the company plant.

The arrested man was identified as David L. Dale, a temporary worker for a GE subcontractor. Authorities said he threatened to mail samples of the uranium to President Carter, newspaper editors, congressional leaders and public advocacy personalities like Ralph Nader if he was not given $100,000 in small bills by Feb. 1.

In a letter found outside the door of the GE plant manager last Monday, Dale allegedly said that if he did not receive the money by the end of this week he would disperse the uranium powder through one or more unnamed large American cities in an attempt to cause a panic in the population.

By Last night, the uranium the letter said had taken from the GE plant was still unaccounted for. The letter said the uranium was in a pair of containers weighing 75 pounds apiece. It gave the serial numbers of the can. GE said yesterday the cans were missing from its plant in Wilmington.

Joseph M. Hendrie, chairman of the Nuclear Regulatory Commission, described the missing uranium as a brown powder that contains about three percent by weight of an isotope of uranium known as U-235. Mildly radioactive on its own, the uranium is used in nuclear power plants to bring about a chain reaction to produce nuclear fission.

Hendrie called the uranium a "minimal health hazard." He said an individual would have to eat several pounds of it or "remain in a visible cloud of a large amount of it for longer than 10 minutes" to suffer any radiation damage.

The FBI said Dale, who holds a bachelor's degree from the University of Miami, was hired as a laboratory assistant at the General Electric plant two months ago. Prior to being hired at the plant where uranium fuel is prepared, Dale worked as a boat captain in Puerto Rico and the Netherlands Antilles in the Caribbean.

Of utmost importance to U.S. nuclear officials was whether security procedures that led to Dale's hiring and the alleged theft of the uranium may have been week or may have broken down.

Since the missing uranium was not the kind that can be used to make a bomb, security procedures at the plant are not as strict as they would be at a factory handling nuclear weapons-grade uranium. Nonetheless, even plants handling "low enriched uranium" operate under more than routine industrial security arrangements.

"The stuff is worth several hundred dollars a pound," a spokesman for the NRC said last night. "For that reason alone, the security measures surrounding it are more than just business-as-usual things."

The FBI said a sample of the stolen material had been sent in a small bottle to the managing editor of the Wilmington Star-News. In the letter found at the plant, Dale apparently threatend to mail at least a dozen small bottles of the brown powder to public officials like President Carter in an attempt to embarrass General Electric.

In GE's Wilmington plant at any time there are apparently thousands of the paint-bucket-sized cans filled with low-enriched uranium awaiting shipment out of the plant to be fabricated elsewhere into fuel bundles for GE power reactors. The two cans whose serial numbers were identified by Dale were apparently the only cans missing.

"I want to congratulate the FBI on its prompt and successful action in this case," Said Rep. Morris K. Udall (D-Ariz.), chairman of one three congressional subcommittees charged with oversight in matters concerning the NRC. "Whilw this theft did not create a significant danger to the public, it should remind us that widespread use of nuclear materials in our military programs and civilian power production brings dangers and risks to our society and the necessary precautions made."

If convicted on extortions charges, Dale would face a sentence of up to 20 years in prison together with a fine of $10,000.