e-learning view The Manual here
IMPACT ON PEOPLE AND THE ENVIRONMENT
Release

SUMMARY OF RELEASE CRITERIA

 

We have now seen and applied the two different types of release criteria. They are summarized here.

This information can be found in section 2.2.2, page 1718 of the Manual.

Perhaps you are wondering, why stop at Level 4?

 

Radiologically equivalent to the order of more than tens of thousands of TBq of 131I

> 50 000
TBq

 

Radiologically equivalent to the order of thousands to tens of thousands of TBq of 131I

5 000–50 000

TBq

 

Radiologically equivalent to the order of hundreds to thousands of TBq of 131I
OR
Greater than 2 500 times the D2 value

500–5 000

TBq

 

Radiologically equivalent to the order of tens to hundreds of TBq of 131I
OR
greater than 250 times the D2 value

50–500

TBq

2.2.2. Definition of levels based on activity released*

Level 7
"An event resulting in an environmental release corresponding to a quantity of radioactivity radiologically equivalent to a release to the atmosphere of more than several tens of thousands of terabecquerels of 131I."
This corresponds to a large fraction of the core inventory of a power reactor, typically involving a mixture of short and long lived radionuclides. With such a release, stochastic health effects over a wide area, perhaps involving more than one country, are expected, and there is a possibility of deterministic health effects. Long-term environmental consequences are also likely, and it is very likely that protective action such as sheltering and evacuation will be judged necessary to prevent or limit health effects on members of the public.

Level 6
"An event resulting in an environmental release corresponding to a quantity of radioactivity radiologically equivalent to a release to the atmosphere of the order of thousands to tens of thousands of terabecquerels of 131I."
With such a release, it is very likely that protective action such as sheltering and evacuation will be judged necessary to prevent or limit health effects on members of the public.

Level 5
"An event resulting in an environmental release corresponding to a quantity of radioactivity radiologically equivalent to a release to the atmosphere of the order of hundreds to thousands of terabecquerels of 131I."
or
"An event resulting in a dispersed release of activity from a radioactive source with an activity greater than 2 500 times the D2 value, for the isotopes released."
As a result of the actual release, some protective action will probably be required (e.g. localized sheltering and/or evacuation to prevent or minimize the likelihood of health effects).

Level 4
"An event resulting in an environmental release corresponding to a quantity of radioactivity radiologically equivalent to a release to the atmosphere of the order of tens to hundreds of terabecquerels of 131I."
or
"An event resulting in a dispersed release of activity from a radioactive source with an activity greater than 250 times the D2 value, for the isotopes released."
For such a release, protective action will probably not be required, other than local food controls.

*These criteria relate to accidents where early estimates of the size of release can only be approximated. For this reason, it is inappropriate to use precise numerical values in the definitions of the levels. However, in order to help ensure consistent interpretation of these criteria internationally, it is suggested that the boundaries between the levels are about 500, 5 000 and 50 000 TBq 131I.