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IMPACT ON RADIOLOGICAL BARRIERS AND CONTROLS AT FACILITIES
Radiological barriers and controls

WHAT THE CRITERIA LOOK LIKE

 

Now let’s look at the criteria themselves. Beginning with

Criteria related to reactors, both power reactors and research reactors.

 

To rate an event at Level 5 based on this criterion requires either
melting > equivalent of a few % of the fuel of a power reactor
or
release from the fuel assemblies > few % of the core inventory of a power reactor

It is important to note that the percentages are relative to the total for a power reactor, i.e. of about 3 000 MW(th).

The criteria, on the other hand, apply equally to a research reactor. However, even for a 10 MW(th) research reactor it would be impossible to reach a Level 5 accident.

 

To rate an event at Level 4 based on this criterion requires a
release from the fuel assemblies > 0.1% of the core inventory of a power reactor

The fraction of 0.1% is relative to the inventory of a power reactor. Thus, the total melting of the fuel of a 10 MWTh research reactor would be rated at Level 4.

Equally, an event resulting in the failure of the cladding of more than about 10% of the fuel assemblies, even without any fuel melting, would also be rated at Level 4 due to the release into the primary circuit of the free fission product gases normally held within the cladding.