Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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December 31, 1992
TO: ALL HOLDERS OF OPERATING LICENSES OR CONSTRUCTION PERMITS FOR
NUCLEAR POWER REACTORS
SUBJECT: LIMITED PARTICIPATION BY NRC IN THE IAEA INTERNATIONAL NUCLEAR EVENT
SCALE (GENERIC LETTER 92-09)
PURPOSE
The U. S. Nuclear Regulatory Commission (NRC) is issuing this generic letter
to inform licensees of its recent decision to participate in the International
Nuclear Event Scale (INES) of the International Atomic Energy Agency (IAEA).
The NRC decided to participate in this program in a limited way to foster
international cooperation. The NRC expects that the limited use of INES will
have a negligible effect on its licensees or on State and local governments.
The participation of the NRC is not intended to affect emergency classifi-
cations, event reporting to the NRC, or communications with the public.
Nevertheless, usage of the INES could lead to confusion with the existing
four-level emergency response scale used in the United States. This generic
letter discusses the measures and conditions of the limited participation to
prevent any adverse effect. It supersedes the previous position of the NRC
not to participate in the INES program (letter from E. L. Jordan, Director,
NRC Office for Analysis and Evaluation of Operational Data, to NRC licensees,
dated August 22, 1990).
DESCRIPTION OF THE SCALE
The INES is a tool intended to promptly and consistently communicate to the
public the safety significance of reported events at nuclear installations by
providing a common terminology among the nuclear community, the media, and the
public for describing the events. The INES was designed by an international
group of experts convened jointly by the IAEA and the Nuclear Energy Agency
(NEA) of the Organization for Economic Cooperation and Development. The group
was guided in its work by the findings of a series of international meetings
held to discuss general principles underlying such a scale. The INES also
reflects the experience gained from the use of similar scales in France and
Japan as well as from consideration of possible scales in several other
countries.
Events are classified in the INES at several levels. Events of greater safety
significance (levels 4-7) are termed "accidents," events of lesser safety
significance (levels 1-3) are termed "incidents," and events of no safety
significance (level 0 or below scale) are termed "out-of-scale deviations."
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Generic Letter 92-09 - 2 - December 31, 1992
DISCUSSION OF LIMITED NRC PARTICIPATION
The IAEA adopted certain precautions on the use of the INES. They are given
in a leaflet describing the structure and use of the INES (Attachment 1). NRC
licensees or state or local governments do not need detailed instructions for
event rating because the NRC will complete and submit event rating forms
(Attachment 2) to the IAEA.
The NRC will limit its participation by classifying and submitting forms only
for events at nuclear power plants that are classified as an alert or higher
on the emergency response scale used in the United States. Not every alert
will necessarily have an INES classification, as some may be rated below the
INES scale.
When the NRC receives a report of an event, it will delay the assignment of an
INES level number for about a week after termination of the event, to consider
subsequent developments in assigning the number. This time delay will help
prevent any confusion with the U.S. emergency classification. The NRC will
notify State and local governments and the affected licensee of its INES
classification. The NRC will not request of any of these parties a review or
concurrence with the NRC classification. The NRC does not plan to issue a
press release associated with the classification, but will provide copies of
the transmitted event rating form to the concerned licensee and to the NRC
Public Document Room.
The NRC remains bound to the early notification and assistance conventions
formally approved by the IAEA General Conference in September 1986. These
conventions provide for an international exchange of information, data, and
assistance during a nuclear accident or serious radiological emergency.
BACKFIT DISCUSSION
This generic letter conveys information about the participation of the NRC, an
agency of the United States, in the international program of the IAEA for
classification of nuclear events. By this generic letter, the NRC staff does
not request any licensee or applicant to submit information to the NRC, does
not recommend any new regulatory action, and does not modify any existing
regulatory position of the NRC staff. Consequently, this generic letter does
not represent a backfit.
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Generic Letter 92-09 - 3 - December 31, 1992
This generic letter requires no specific action or written response. If you
have any questions about this information, please contact the technical
contact listed below, who is the NRC INES Coordinator.
ORIGINAL SIGNED BY
James G. Partlow
Associate Director for Projects
Office of Nuclear Reactor Regulation
TECHNICAL CONTACT: Denwood F. Ross, Jr., Deputy Director
Office for Analysis and Evaluation
of Operational Data
U. S. Nuclear Regulatory Commission
Mail Stop 3701 MNBB
Washington, D.C. 20555
Telephone (301) 492-7361
Attachments:
1. INES Description
2. INES Event Rating Form
3. List of Recently Issued Generic Letters
