NRC ISSUES ANNUAL REPORT ON ABNORMAL OCCURRENCES FOR FY2011

The Nuclear Regulatory Commission has released its annual report on abnormal 

occurrences for fiscal year 2011, citing 23 events involving radioactive materials and one event a 

commercial nuclear power plant.

An accident or event is considered an abnormal occurrence if it involves a major 

reduction in the degree of protection of public health and safety. Abnormal occurrences can 

include, but are not necessarily limited to, moderate exposure to or release of radioactive 

material licensed by the NRC or a state agency; major degradation of safety-related equipment; 

or major deficiencies in design, construction, use of or management controls for facilities or 

radioactive material at NRC-licensed facilities.

For FY 2011, there was one abnormal occurrence at an NRC-licensed nuclear power 

reactor. This occurred on Oct. 23, 2010, at the Browns Ferry Nuclear Plant, Unit 1, with the 

failure of a low-pressure coolant injection flow control valve, part of the reactor’s residual heat 

removal system. Although no event occurred and the public was never in danger, the NRC 

determined that the valve failure caused a weakness in the licensee’s fire mitigation strategy, 

increasing the likelihood of core damage in event of a major fire. The determination resulted in a 

red finding under the NRC’s Reactor Oversight Process, for a finding of high safety significance.

Of the 23 abnormal occurrences involving radioactive materials, two of the events 

involved exposure of an embryo or fetus, one event involved an exposure to the extremities of a 

radiographer, and a fourth involved a stolen gamma radiography camera. The remaining 19 

events involved misadministration of radioactive material during diagnostic or therapeutic 

procedures. Thousands of such procedures are conducted in U.S. medical facilities each year.

Nine of the abnormal occurrences actually occurred in prior fiscal years, but NRC’s 

investigations were closed during FY 2011.

The report details investigations of each incident by the NRC, Agreement States and 

licensees, as well as measures taken to ensure such incidents do not recur.

A section on “other items of interest” discusses three events that did not meet the criteria 

to be classified as abnormal occurrences but are included in the report because of high public and 

media interest. These are the Japanese event at Fukushima Dai-ichi nuclear plant, flooding at 

Fort Calhoun plant in Nebraska, and the August 2011 earthquake near the North Anna plant in 

Virginia.

NRC NEWS

U.S. NUCLEAR REGULATORY COMMISSION

Office of Public Affairs Telephone: 301/415-8200

Washington, D.C. 20555-0001

E-mail: opa.resource@nrc.gov Site: www.nrc.gov

Blog: http://public-blog.nrc-gateway.gov

No. 12-072 June 12, 2012
The report on abnormal occurrences for fiscal year 2011 is published as NUREG-0090, 

Vol. 34. It was transmitted to Congress on May 31 and is available on the NRC website at:

http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0090/v34/. It will soon be 

published in the Federal Register.

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