United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Definition of Unplanned Release

HPPOS-254 PDR-9303020117

Title: Definition of Unplanned Release

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 Thursday, March 29, 2012