Born in 1952 in Zaragoza, Spain, Dr. Alejaldre received his Doctorate in Electro-physics at the Polytechnical Institute of New York in 1983 and became an Assistant Professor there.

He joined CIEMAT in 1986 and became Head of Theory and Plasma Simulation.

In 1993 he became Director of the Spanish National Laboratory for Magnetic Confinement Fusion, and was head of the CIEMAT-Euratom Association from 1999 to 2004.

Between October 2001 and 2003 he was also Director of ITER Spain, responsible for preparing and presenting Spanish studies for the proposed ITER site in Vandellos.

In 2004 he was appointed Director-General for Technology at the Spanish Ministry of Education and Science.

He was designated as ITER Deputy Director-General for Safety and Security in July 2006.