United States Nuclear Regulatory Commission - Protecting People and the Environment

Definition of Unplanned Release

HPPOS-254 PDR-9303020117

See the memorandum from L. J. Cunningham to J. H. Joyner (and others) dated February 18, 1992. This memo provides a definition of "unplanned release" for inclusion as a health physics position.

Definition of unplanned release: The unintended discharge of a volume of liquid or airborne radioactivity to the environment.

Guidance: An unplanned release is the unintended discharge of radioactive material from a source. Typical examples of an unplanned release are the discharge of the contents of the wrong waste gas decay tank or the wrong liquid radwaste release tank. Another example of an unplanned release is the discharge of a source, such as a turbine building sump, that is designed to divert its contents to the liquid radwaste system for processing on either the detection of the activity or a certain level of activity and, instead of being diverted, is discharged off site. It should be noted that instances as described above are rare.

Clarification: It should be noted that a change in activity level from a release source or the release from a new or different source is not necessarily considered an unplanned release. Consider the following cases.

Case 1. Inadvertent release of the contents of a waste gas decay tank through the plant vent. The release point is the same as that for other sources and although the source is new, the important fact is that the discharge is unplanned. Therefore, the release would be considered an unplanned release because no discharge of any waste gas decay tank was planned.

Case 2. Inadvertent release of the contents of the wrong waste gas decay tank through the plant vent. The release point is the same as that for all waste gas decay tanks and although the source is new, the important fact is that the discharge is not the intended one. It is the wrong tank. The release was meant to be the contents of a different tank. Therefore, the release is unplanned.

Case 3. Leakage from various pipes and valves in the Auxiliary Building are released from the plant vent via the Auxiliary Building ventilation system. The function of the Auxiliary Building ventilation system is to ventilate areas of the Auxiliary Building. While performing this function, it is designed to handle the leakage associated with various pipes and valves. This would not be considered an unplanned release since the design of the system is to treat the airborne leakage associated with the various pipes and valves. Normal expected leakage would not be considered an unplanned release since the system is designed to treat routine leakage from various pipes and valves. However, large leaks due to unexpected valve or pipe failures that resulted in a quantity of release such that a 10 CFR 50.72 or a 10 CFR 50.73 report is required, would be considered an unplanned release.

Regulatory references: 10 CFR 50.72, 10 CFR 50.73

Subject codes: 2.2, 2.3

Applicability: Reactors

Page Last Reviewed/Updated Tuesday, June 30, 2015