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Defence in depth: sources



Finally, we get to the third table—Table 8, the full version can be found on page 54 of the Manual. This table covers events that do not readily fit into the other two tables.

As shown here, the table covers three types of events:

  • Non-compliance issues, rated at Level 1 based on safety culture,
  • Possible safety culture issues, depending on the circumstances, rated at Level 0 or 1, and
  • Wrong packaging issues, potentially rated at the maximum under defence in depth, depending on the packaging provided.

Cat 4

Cat 3/2

Cat 1

e.g. Exceeding dose limit, authorization, non-compliance with transport licence conditions, serious failure in record keeping

Possible safety culture issues
e.g. Inadequate surveys, labelling errors

Wrong packaging
e.g. Source in supposedly empty container, source in wrong packaging


Now let’s consider the table in a bit more detail.

If you look at the full table, you will see that the first five examples are non-compliance issues. They are all rated at Level 1, based on safety culture issues. The next (6th) example is similar, but some judgement is required about the significance of the non-compliance. The other examples are also similar, although in a couple of cases there is a need for judgement as to whether the safety culture issues justify a Level 1 rating. The last couple of examples related to transport are different. As correct packaging is the main safety provision during transport, these events can lead to the maximum defence in depth rating. There is a choice of rating depending on the deficiency of the packaging.

Type of events Event rating depending on the source category
Cat 4 Cat 3/2 Cat 1

Member of the public receiving a dose from a single event in excess of annual statutory dose limits.

1 1 1

Workers or members of the public receiving cumulative doses in excess of annual statutory dose limits.

1 1 1

Absence of or serious deficiency in records such as source inventories, breakdowns in dosimetry arrangements.

1 1 1

Discharges to the environment in excess of authorized limits

1 1 1

Non-compliance with licence conditions for transport.

1 1 1

Inadequate radiological survey of transport.

0 or 1a 0 or 1a 0 or 1a

Contamination on packages/conveyance where the resulting contamination is of little or no radiological significance.

0 or 1 0 or 1 0 or 1

Contamination on packages/conveyance where a number of measurements reveal excessive contamination above the applicable limits, and there is potential for the public to be contaminated.

1 1 1

Shipping documents, package labels or vehicle placards incorrect or absent. Marking of packages incorrect or absent.

0 or 1 0 or 1 0 or 1

Radioactive material in a supposedly empty package.

1 1 or 2b 1, 2 or 3b

Radioactive material in the wrong type or in inappropriate packaging.

0 or 1c 1 or 2c 2 or 3c

a - The rating should take into account the degree of inadequacy of the surveys as well as any safety culture implications.

b - The choice of rating should take into account the safety provisions that might still be in place even though the package was supposed to be empty.

c - The higher rating in each category reflects situations where the wrong or inappropriate packaging could reasonably result in inadvertent exposures.