NRC Regulatory Issue Summary 2002-01 Changes to NRC Participation in the International Nuclear Event Scale

January 14, 2002



All holders of operating licenses for nuclear power reactors, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vessel.


The U.S. Nuclear Regulatory Commission (NRC) is issuing this regulatory issue summary (RIS) to inform addressees of impending changes in the NRC's level of participation in the International Nuclear Event Scale (INES). This RIS does not transmit any new requirements or staff positions and does not require any specific action or written response.

Background Information

The INES promotes prompt and consistent communication regarding the safety significance of reported events at nuclear installations by defining a consistent framework and common terminology for describing events to the nuclear community, the media, and the public. The INES was designed and developed by an international group of experts convened jointly by the International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency (NEA) of the Organization for Economic Cooperation and Development (OECD). 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 consideration of possible scales in several other countries.

The INES classifies events at several levels. Events of greater safety significance (levels 4-7) are termed "accidents," while events of lesser safety significance (levels 1-3) are termed "incidents," and those of no safety significance (level 0 or below) are termed " deviations." A description of the INES, including an explanation of the various classification levels, can be found at <>.

The NRC has participated in the INES in a limited fashion since 1993. The NRC issued Generic Letter 92-09, "Limited Participation by NRC in the IAEA International Events Scale", dated December 12, 1992, to inform licensees that the agency had agreed to use the INES to rate all reactor events that result in the declaration of an "Alert" or higher emergency classification. Pursuant to that decision, from February 1993 through September 2001, the NRC transmitted a total of 32 reactor-related INES reports to the IAEA.

Issue Summary

In order to be even more responsive to international stakeholders, the NRC has elected to increase its participation by evaluating all reported nuclear events (reactor, fuel cycle, materials, and transportation events) for possible rating on the INES. Medical misadministrations are outside the scope of the INES and will not be reviewed by the NRC for possible rating. Only events rated at Level 2 or higher will be reported to the IAEA, unless another member country specially requests the rating of a particular event. The NRC estimates that this reporting threshold will result in approximately one reactor report and fewer than five materials reports being filed per year. The NRC staff is unaware of any negative impact upon licensees as a result of the NRC's participation in the INES to date, and the agency expects that its increased level of participation in the INES will have a negligible effect on licensees or State and local governments.

Licensees should continue to report events in accordance with the regulations. The change in policy regarding the NRC's level of participation in the INES is merely a response to increasing interest by foreign government agencies and media in events occurring at facilities in the United States. The INES is not intended to supersede the existing four-tiered emergency classification system described in NUREG-0654, Revision 1,"Criteria for Preparation and Evaluation of Radiological Emergency Response Plans and Preparedness in Support of Nuclear Power Plants", February 2001. Nonetheless, many countries throughout the world have adopted the INES as a consistent framework for communicating the significance of events involving nuclear facilities.

Backfit Discussion

This RIS does not require any action or written response, or any modification to plant structures, systems, components, or facility design; therefore, the staff did not perform a backfit analysis.

Federal Register Notification

This RIS is informational and pertains to a staff position that does not represent a departure from current regulatory requirements and practice. Consequently, the staff did not publish a notice of opportunity for public comment in the Federal Register.

Paperwork Reduction Act Statement

This RIS does not request addressees to collect any information and therefore is not subject to the requirements of the Paperwork Reduction Act.

If you have any questions about this matter, please telephone or e-mail the technical contact listed below.


Donald A. Cool, Director
Division of Industrial and Medical Nuclear Safety
Office of Nuclear Materials Safety and Safeguards


David B. Matthews, Director
Division of Regulatory Improvement Programs
Office of Nuclear Reactor Regulation

Technical contact: Robert J. Stransky, Jr., IRO
(301) 415-6411
Attachments: List of Recently Issued NRC Information Notices

ADAMS Accession Number ML013200502

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