Hydrogen generation, and its venting from nuclear reactors

Abstract

Reactor fires and explosions are centred around the use of graphite as a neutron moderator, and the high temperature generation of hydrogen in reactions of steam and zirconium. An alternative to uncontrolled, excessive, build-up of pressure within the reactor, is the provision of a buffer vessel, within which there is permeable membrane separation of hydrogen from radioactive products. Possible rates of production of hydrogen are compared with the rates at which it might be separated and then flared in lifted jet flames, giving high burn rates. There are few data on the behaviour of H2 flares in air cross flows, and this is synthesised from available data for other flammable gases. Destruction of hydrogen lifted jet flames by the cross flow of atmospheric air would seem to be less likely than for hydrocarbon jet flames. The H2 relationships are different from those of the hydrocarbons, due to the higher chemical reactivity of H2, its small laminar flame thickness, reduced air requirement, higher acoustic velocity, and minimal flame lift-off distance. Flaring with micro-tubes might be advantageous for integrating flaring with membrane hydrogen separation, whilst high mass flow rates can be achieved with large diameter flares in the lifted flame, supersonic regime.