The explosion hazard associated with the use of liquid nitrogen in a radiation environment in fusion facilities has been investigated. The principal product of irradiating liquid nitrogen is thought to be ozone, resulting from the action of radiation on oxygen impurity. Ozone is a very unstable material and explosions may occur as it rapidly decomposes to oxygen. Occurrences of this problem in irradiated liquid nitrogen systems are reviewed. An empirical expression, from early experiments, for the yield of ozone in liquid nitrogen-oxygen mixtures exposed to gamma radiation is employed to assess the degree of ozone explosion hazard expected at fusion facilities. The problem is investigated for the Compact Ignition Tokamak (CIT) as a particular example. a On assignment from the Canadian Fusion Fuels Technology Project (CFFTP).