Bernard L. Hoffman, 51, a nuclear engineer and an executive consultant, died Wednesday at Washington Advertist Hospital after a long illness.

He had been with NUS Corporation of Rockville for 10 years, and recently served as special assistant to the senior vise president, consulting group.

NUS is a consulting and engineering firm working primarily in energy and environmental fields.

Before coming here last July, Mr. Hoffman had been responsible for business development and client liaison for the corporation's international operations, working in California and Spain.

He had been involved in the nuclear power program in Mexico and then served for 3 1/2 years in Madrid.

Born in New York City, Mr. Hoffman held bachelor's and master's degrees in chemical engineering from Columbia University. He also attended the Oak Ridge School of Reactor Technology in Tennessee.

Before joining NUS, he had served as liaison representatives on a demonstration power reactor project in Spain for Atomics International, which is based in California, and that conducted research and development in heat transfer at Columbia University and at the Naval Research Laboratory here in 1964 and 1955.

Mr. Hoffman wrote numerous papers on nuclear energy and held a patent on a portable thermionic generator.

He is survived by his wife, Sherry, of the home in Silver Spring; a son, Jan, attending the University of Guadalajara Medical School in Mexico; a daughter, Susan, a student at Yale University, and his parents, Murray Hoffman, of Los Angeles, and Rose Perlstein, of Miami Beach, Fla.

The family suggests that expressions of sympathy may be in the form of contributions to the Muscular Dystrophy Association for use in research of amyotrophic lateral sclerosis, knownas Lou Gehrig's disease.