Walter Hälg was born in 1917 in Basel. He received his PhD from the University of Basel in 1943. After some years at the 'Physikalisches Institut' in Basel he moved to the AG Brown Boveri Co in Baden (BBC), the predecessor of the current ABB. During his time with BBC, he worked on the development of the Swiss heavy water reactor DIORIT in Würenlingen, which went critical on August 26, 1960. Afterwards Walter Hälg moved to ETH Zurich, became full professor for nuclear reactor technology and established neutron scattering in Switzerland. He retired in 1984.
For many years he was member and head of the research commission of ETH Zurich. He was honorary member of the Swiss Neutron Scattering Society, of the distinguished Physical Society of Zurich and donator of the European Neutron Scattering Association (ENSA)Walter Hälg prize.