Uzbekistan approves regulations on hydrogen explosion safety at nuclear power plants

Uzbekistan has approved regulations on protection against hydrogen explosions at nuclear power plants. The decision was adopted on March 19 by the Committee for Industrial, Radiation and Nuclear Safety under the Cabinet of Ministers.

The document was agreed upon with the Ministry of Emergency Situations, the Ministry of Construction and Housing and Communal Services, the National Committee on Ecology and Climate Change, the Atomic Energy Agency under the Cabinet of Ministers, and the Academy of Sciences.

The operating organization is established by the Cabinet of Ministers of Uzbekistan and is designated as responsible for the nuclear installation and/or storage facility. It may operate the facility independently or with the involvement of other legal entities.

The operating organization must ensure that the following situations do not occur at nuclear power plants:

• the formation of explosive hydrogen-containing mixtures within systems, components and rooms confined by a containment barrier during normal operation;
• detonation and deflagration of hydrogen-containing mixtures within confined spaces during design-basis accidents;
• detonation of hydrogen-containing mixtures during beyond-design-basis accidents.

Deflagration during beyond-design-basis accidents is permitted only if the safety systems specified in the plant design fully perform their functions.

During normal operation, the operating organization must prevent the formation of hydrogen-containing mixtures within confined volumes by ensuring:

• compliance of technological processes with the design parameters and operating conditions specified in project documentation;
• the integrity of equipment structures that prevent or minimize the ingress of hydrogen and hydrogen-containing mixtures into confined spaces to levels defined in the plant design;
• the effective operation of systems designed to reduce hydrogen concentrations to non-explosive levels;
• continuous monitoring of hydrogen-containing mixture concentrations.

The document also defines key terms:

• detonation — an explosion process in which a chemical reaction in a combustible gas mixture propagates at a speed exceeding the speed of sound and is associated with a shock wave;
• deflagration — an explosion characterized by the propagation of a reaction front at a speed lower than the speed of sound, resulting in pressure and thermal loads;
• containment barrier — a set of structural elements that isolate space around a nuclear reactor or radioactive material storage facility, forming a boundary defined in the plant design;
• design-basis accidents — accidents anticipated in the plant design, for which safety systems are provided to limit their consequences;
• beyond-design-basis accidents — accidents resulting from events or sequences not provided in the plant design.

The decision entered into force on the date of its official publication.

Earlier, Uzbekistan acceded to the Vienna Convention on Civil Liability for Nuclear Damage, which ensures compensation for citizens in the event of a nuclear incident.