Norman R. Seidle, 68, a retired security engineer with the old Atomic Energy Commission, died of kidney failure Dec. 30 at a convalescent center in Lewes, Del.

He came to Washington while serving in the Army during World War II. He served with the Manhattan project directed by Maj. Gen. Leslie R. Groves that developed the atomic bomb.

Mr. Seidle traveled to atomic research facilities at Oak Ridge, Tenn., and Hanford, Wash., where as a security engineer he helped determine the safety of personnel from radioactive contamination.

He joined the Atomic Energy Commission in 1947 and worked there until retiring in 1972.

Mr. Seidle was a native of La Grange, Ill., and earned a degree in industrial engineering at the University of Pittsburgh.

Mr. Seidle lived in Chevy Chase before retiring to Delaware in 1972.

He was a member of All Saints Episcopal Church in Chevy Chase, where he had been a member of the vestry, acolyte master, and head usher.

He is survived by his wife, Virginia, of the home in Rehoboth Beach, Del., a son, Norman R. Ill, of Gaithersburg; a daughter, Florence Gene Wixson, of Germantown, Md.; a brother, Dr. Charles A., of Rockport, Mass., and six grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the memorial fund of All Saints Episcopal Church in Rehoboth Beach or All Saints Episcopal Church in Chevy Chase.