[en] Section 208 of the Energy Reorganization Act of 1974 identifies an abnormal occurrence as an unscheduled incident or event that the Nuclear Regulatory Commission determines to be significant from the standpoint of public health or safety and requires a quarterly report of such events to be made to Congress. This report covers the period from January 1 through March 31, 1990. for this reporting period, there were 10 abnormal occurrences. One involved the loss of vital ac power with a subsequent reactor coolant system heat-up at the Vogtle Unit 1 nuclear power plant during shutdown. The event was investigated by an NRC Incident Investigation Team (IIT). The other nine abnormal occurrences involved nuclear material licensees and are described in detail under other NRC-issued licenses: eight of these involved medical therapy misadministrations; the other involved the receipt of an unshielded radioactive source at Amersham Corporation in Burlington, Massachusetts. The latter event was also investigated by an NRC IIT. No abnormal occurrences were reported by the Agreement States. The report also contains information that updates a previously reported abnormal occurrence