Unusual occurrences
Article 15
A special report shall be made in the following cases: (a) if, as a result of any unusual incident or circumstances, it is believed that there has been or might be an increase or a loss of nuclear material in excess of the limits specified for these purposes in the particular safeguard provisions referred to in Article 6; (b) if the containment has unexpectedly changed from that specified in the particular safeguard provisions referred to in Article 6, to a point where an unauthorised removal of nuclear material has become possible. The persons or undertakings concerned shall submit these reports as soon as they have become aware of any such loss or increase or sudden change in the containment conditions, or of anything which leads them to believe that there has been such an occurrence. The causes shall also be stated as soon as they are known.