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TABLE 10.2 EMERGENCY REFERENCE
LEVELS FOR
INGESTION
COUNTERMEASURE
TABLE 10.3 EMERGENCY REFERENCE
LEVELS FOR RELOCATION
Projected Dose Equivalent (mSv) in the first year
Countermeasure
Whole Body
Individual Organs Preferentially Irradiated
Control of Foodstuffs
Upper Level Lower Level
50
5
500
50
Projected Dose Equivalent (mSv) in the first year
Individual Organs Preferentially Irradiated
Not anticipated
Countermeasure
Whole Body
Relocation
Upper Level Lower Level
500
50
ed
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The actual level of predicted dose at which a particular countermeasure should be introduced will depend upon a number of local factors prevalent at the time of the incident.
10.2 Derived Emergency Reference Levels
Having established a level of dose at which a countermeasure should be introduced it is necessary to relate this to some measurable quantity. For example, it may be a requirement of a contingency plan to ban milk if its consumption would lead to individual doses in the first year exceeding 5 mSv. It is therefore necessary to calculate, amongst other things, the level of radioactive iodine per litre of milk which would give rise to a dose of 5 mSv. This figure is known as a 'Derived Emergency Reference Level', (DERL).
The calculation of DERLs is not simple since not everyone consumes the same quantity of a given foodstuff per year, and also the dose to a person from a given intake of radioactivity will vary a little from person to person dependent upon a number of factors, in particular the age of the person. DERLs are calculated by assuming a greater than average consumption of a given foodstuff and then calculating the doses which may arise in three
upon the different age groups, viz, one year old infants, ten year old children and adults. The DERI is then based age group which gives rise to the most restrictive DERL.
Advice on the principles and procedures for establishing DERLs has been given by the International Atomic Energy Agency, (IAEA), (ref 14). (It should be noted that the IAEA use the term 'Derived Intervention Level' rather than 'Derived Emergency Reference Level' but the two terms are synonymous). This IAEA document also gives some examples of DERLS.
The numerical values for derived emergency reference levels have been published by the United Kingdom's National Radiological Protection Board (ref 38). This document does not, however, give details of DERI. values. for radioactivity in meat. Following the Chernobyl accident a number of organisations offered advice on DERI values for meat and these were typically at a level of about 1 000 Bq kg ̈1.
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