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Ionising radiation

Environmental Radioactivity - Medicine - Occupational Radiation Protection - Nuclear Hazards Defence

Ionisierende Strahlung

Intervention reference levels

  • Intervention reference levels indicate what civil protective measures should be taken from what expected radiation exposure to man in the event of a radiological emergency.
  • For the protective measure "Sheltering" or, respectively, "Evacuation", the intervention reference level is an effective dose of 10 and, resp., 100 millisievert within 7 days.
  • For the protective measure "Intake of iodine tablets", the intervention reference level is an organ-specific dose of 50 millisievert for children up to age 18 and pregnant women and, resp., 250 millisievert for persons between age 18 and age 45 within 7 days.

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In order to be able to act quickly and appropriately in the event of a radiological emergency, it is necessary to determine in advance, from what expected radiation exposure to man measures should be taken. That is the reason why "intervention reference levels" have been established; these are values where measures are taken in case they are exceeded.

The dose of radiation serves as valuation standard. It states how much radiation a person – in relation to their mass – has taken up. Thus, the intervention reference level is a dose value; it is given in the unit millisievert (mSv).

Dose values can be estimated through prognoses prior to or during a release of radioactivity. For this purpose, the BfS operates the RODOS prognosis system.

Why are intervention reference levels needed?

In the event of a radiological emergency different civil protective measures can be taken:

  • Evacuating people,
  • Sheltering and
  • Intake of iodine tablets.

Fixed intervention reference levels indicate what measure must be taken when. The dose type is also important for different measures:

  • For the administration of iodine tablets, solely the organ dose of the thyroid is relevant. That is the dose which only affects the thyroid. In order for the thyroid to not be able to take up radioactive iodine in the event of a radiological emergency, iodine tablets should saturate the thyroid with non-radioactive iodine beforehand. The intervention reference level for this measure is thus an organ dose level for the thyroid.
  • The effective dose is taken as a measure for "Evacuation" and "Sheltering". The effective dose is the sum of all organ doses. It describes the effect of the radiation on the whole body.

Intervention reference levels serve as a measure for the justification of certain measures from the radiation protection point of view. However, when taking a decision about such measures, further aspects must be taken into account, e.g. whether the measure is feasible and what additional risks may come from it. Exceeding of an intervention reference level does not automatically trigger a measure.

If the dose levels are below the respective intervention reference level, the civil protective measures must be discussed with regard to proportionality. In any case, the radiation exposure to the public should be kept as low as reasonably achievable.

Overview of intervention reference levels

MeasureOrgan-specific dose (thyroid)Effektive doseIntegration time and exposure pathways
Sheltering 10 millisievertExternal exposure in 7 days and committed effective dose due to radionuclides inhaled during this period
Administration of iodine tablets

50 millisievert (children up to age 18 as well as pregnant women)

250 millisievert (persons between age 18 and 45)

Radioiodine inhaled over a period of 7 days including the committed equivalent dose
Evacuation100 millisievert External exposure in 7 days and committed effective dose due to radionuclides inhaled during this period

Civil protective measures

Sheltering / Evacuation

Measures "Sheltering" and "Evacuation"

For the civil protective measure "Sheltering", the intervention reference level is an effective dose of 10 millisievert; for the civil protection measure "Evacuation" the intervention reference level is an effective dose of 100 millisievert. This effective dose is composed of

  • The dose an adult person would receive when they would permanently stay outdoors for seven days during the accident: In this case both the radiation from the outside ("external exposure") and the radiation from inhaled radioactive particles ("inhaled radionuclides") have an effect
  • And the dose this adult person would receive from the radiation emitted by the radioactive particles over the following months and years, which was taken up by the body during these seven days via breathing air and food and would not have been excreted immediately (committed effective dose). Some radioactive particles remain inside the body for a short time only and are quickly excreted by the metabolism, others are built into the bones where they remain until they decay. Depending on the half-life of the respective radionuclide, seconds to years pass until decay.

Intake of iodine tablets

Measure "Intake of iodine tablets"

For the civil protective measure "Intake of iodine tablets" the intervention reference level for children up to age 18 and pregnant women is an organ-specific dose of the thyroid of 50 millisievert, for adults between age 18 and 45 an organ dose of the thyroid of 250 millisievert. The organ dose is composed of

  • The dose of radioactive iodine (radioiodine) individuals would inhale when staying outdoors permanently for 7 days during the release
  • And the dose that would result from the radiation of the iodine deposited in the thyroid in the following 3 months (iodine has a half-life of 8 days and has nearly completely decayed (99.9 %) after 80 days).

Persons over age 45 should do without taking iodine tablets, since metabolism dysfunctions of the thyroid occur more frequently with increasing age. That increases the risk of side effects of an iodine blockade. Furthermore, the probability to develop thyroid cancer caused by ionising radiation decreases with increasing age.

Who determined the intervention reference levels?

The currently valid intervention reference levels were recommended by the German Commission on Radiological Protection (SSK) in 2014. Based the Radiation Protection Act, they are currently being enshrined in ordinances.

The SSK is an advisory body of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) and comprises voluntary, independent experts.

State of 2018.07.23

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