A special report shall be provided, as required in Article 16, in the following cases:
if, as a result of any unusual incident or circumstances, it is considered that there has been or might be an increase or a loss of nuclear material, including during transfer to or from the installation; in such case, the special report shall include a description of the incident or circumstances, the weights of uranium, thorium and plutonium, in accordance with the categories listed in Article 21(2), point (b), the weight of the fissile isotopes in the case of enriched uranium, as well as a description of how the weights were established, and any further actions taken, including to avoid recurrence of a loss;
if the containment has unexpectedly changed, to a point where an unauthorised removal of nuclear material has become possible; in such case, the special report shall include a description of the incident or circumstances, and it may also include a description of any actions taken to reduce the risk of unauthorised removal and to avoid recurrence.
The operators concerned shall provide those special reports as soon as they have become aware of any such increase or loss or of any such sudden unexpected change, or of anything which leads them to consider that there has been such an occurrence. The causes for such unusual occurrences shall also be stated as soon as they are known.
For each installation, further details on the information to be provided may be specified in the particular safeguard provisions referred to in Article 8.