Baltimore Gas & Electric Co., sensitive about the recent nuclear accident at Three Mile Island in Pennsylvania, spent a large chunk of its annual meeting today seeking to reassure shareholders that such a disaster is not likely in Maryland-while also assuring them the company intends to use nuclear power anyway.

The baltimore utility presented a 45-minute slide show on the Three Mile Island accident and explained how nuclear power works. Company officials also answered numerous questions from shareholders about nuclear accidents.

"The industry has never said that an accident could not happen. What we said is that the probability of an accident affecting the public in any serious fashion was extremely unlikely," said the utility's president, Bernard C. Trueschler. "We have not changed our position on that.

"The management of the company believes that the lessons to be learned from the accident at Three Mile Island will contribute to enhancing the overall safety of nuclear power," Trueschler said in his annual report to the shareholders. ". . . Nothing has happened that makes us retreat from our assertions that nuclear power is economical, environmentally benign and safe."

BG&E's Calvert Cliffs nuclear power plant, located on a 1,135-acre site in Southern Maryland, last year supplied 57 percent of BG&E's customer's total electric requirements and saved the company 16 million barrels of oil, representing $190 million, Trueschler said.

"Since the initial operation of Calvert Cliffs in 1975 the fuel cost savings have exceeded half a billion dollars," he added.

In addition, the demand for electricity increases continuously, the BG&E president said. "Our 10-year projections indicate an annual growth in electric sales of about 4 1/2 percent. This projection was substantiated in 1978 when the sales increased 4.6 percent."

Some shareholders were not convinced. One person wanted to know what danger existed in storing nuclear fuel rods that been used at the plant. The used rods, Trueschler said were placed in swimming pool-type storage tank for six to eight months.

"Are operating personnel adequately trained to react under a severe emergency?" another shareholder asked. Trueschler said they were.

"I do not suggest that management is too complacent," another shareholder said, "but I haven't heard what steps have been taken since the (Three Mile Island) incident to check on safety here. The board and management should report to us."

Trueschler assured the man that the board would "act and react vigoriously" and said steps are being taken to prevent a nuclear accident.

In response to a question about nuclear accident insurance that would pay utility costs while a defective reactor is out of commission. Trueschler replied that no such insurance is available.

On the natural gas side, Trueschler said that the company has been reassured by its sole natural gas supplier that deliveries for the remainder of the year will be about 13 percent more than last year. The company also has removed its five-year-old moratorium on new gas use and customers.

To meet the increasing demand for electricity, the company has under construction two electric generator units at its Brandon Shores plant. The plant was originally designed to burn oil, but because of new federal regulations it may be forced to convert to coal, Trueschler said. The company has petitioned the Fourth U.S. Circuit Court of Appeals to review the regulations. Mandatory conversion would cost the company between $200 million and $500 million, Trueschler said.