Protective Actions

Definition of Protective Actions

Protective actions are those that are taken to avoid or reduce radiation exposure to members of the public and emergency workers in emergency response situations.

Goals of Protective Actions

The goals of protective actions are to minimise the duration of any exposure to ionising radiation, to move people a safe distance away from a radiation source, and to use shielding when appropriate to protect people from radiation.

Factors Determining Protective Actions

The specific protective actions taken in a nuclear emergency will depend upon a number of factors, including:

• The nature of the radioactive source or the damage to the nuclear facility;
• The amount of radiation in the environment;
• The type of radiation being released;
• Where people are in relation to the source of radiation; and
• The time available to take protective actions.

In general, the sooner protective actions are taken, the more effective they are. People who are close to the source of radiation may need to take protective actions before those who are further away. In all cases, it is important that protective actions be taken as instructed.

Types of Protective Actions

There are two types of protective actions:

• Urgent protective actions; and
• Longer term protective actions.

Urgent protective actions

Urgent protective actions are those which, to be most effective, should be taken before or immediately after a release of radioactive material. Types of urgent protective actions include entry control, sheltering, evacuation, thyroid blocking, and monitoring and decontamination.

Entry Control

Entry control is preventing non-essential persons from entering the affected area.

Sheltering

In certain situations, the safest course of action is to remain inside with all doors and windows closed, and air conditioners and furnaces turned off. This is referred to as sheltering. Sheltering reduces the dose to people inside for a period of a few hours to a few days.

Evacuation

Evacuation means leaving the affected area as soon as possible. If a release is imminent, sometimes it is safer to shelter first, and evacuate later. Officials will order evacuation when it will help people avoid a significant radiation dose, and when it is safe to do so.

Thyroid Blocking

This is a method for protecting the thyroid gland, which readily absorbs iodine. A stable, or non-radioactive, iodine such as potassium iodide, is taken in pill form to reduce the absorption by the thyroid gland of radioactive iodine-131, which may be present in the environment after a radioactive release. However, taking stable potassium iodide when it is not necessary, or in the wrong amounts, can be harmful.

Contamination Monitoring

Contamination monitoring refers to the process of checking for radioactive material that may be on people or objects; decontamination is the process of removing it. In many cases, the decontamination process may be as simple as washing with soap and water.

Longer-term Protective Actions

Longer-term protective actions are those that need to be taken in the days, weeks, and months following a release of radioactive material, and are expected to be in force for an extended period. Longer-term protective actions include food control measures, temporary relocation, and resettlement.

Food Control

If food is suspected of being, or proven to have been, contaminated with radioactive material, measures will be taken to ensure that it is not consumed. Food control measures also encompass livestock feed.

Temporary Relocation

Inhabitants may have to be kept out of an area for a period of more than a week, but not more than a few months. It is expected that people will eventually be able to return to the affected area.

Resettlement

Resettlement refers to keeping people out of the affected area permanently. Residents would not be able to return to their homes.

Rationale for Protective Actions

The rationale behind the decisions made regarding protective actions taken in a particular emergency considers:

• The action that is effective against the type of radiation present, and that is safe to take in the particular emergency situation;
• The amount of radiation dose that can be averted by taking the action; and
• The risk and cost of taking the action.

The benefit of the protective action must be weighed against the potential risk of the action.

Intervention Levels

Intervention levels (IL's) are specified levels of radiation dose that would justify the introduction of certain protective actions during a nuclear emergency. These levels are not based upon regulatory dose limits: the two sets of levels are applied in different circumstances and are based on different rationales.

Regulatory Dose Limits Versus Intervention Levels

Regulatory dose limits and intervention levels are based upon international guidelines. Regulatory dose limits keep routine public and worker exposures to radiation from licensed sources extremely low. There is no risk and no direct cost to the public in maintaining these levels. However, protective actions do involve risk or cost to the public, and therefore authorities must be guided by intervention levels to avoid introducing a risk or cost to the public that is greater than the protective benefit offered by the protective action.

Decisions Regarding Protective Actions

During a nuclear emergency, decisions regarding protective actions are made by emergency response specialists from municipal, provincial, and federal government organisations. Information from many varied sources is assessed and analysed rapidly in order to determine the best course of protective action for each situation.