Chapter 2 The planning basis

2.1 The Hazard

2.1.1 This PNERP details the response to an ionizing radiation hazard arising as a result of:

1. a reactor facility accident (i.e., nuclear emergency)
2. a radioactive source which has either undergone an accident or over which control has been lost (i.e., radiological emergency)

2.1.2 The public is susceptible to radiation resulting from such accidents via the following exposure pathways:

1. external exposure to gamma radiation in the plume (i.e., cloudshine) or on the ground (i.e., groundshine)
2. inhalation of airborne radioactive materials
3. ingestion of drinking water, plant and animal products that may have been contaminated
4. contamination on clothing or skin leading to external exposure or absorption
5. inadvertent ingestion of contamination (e.g., contamination on face and hands, contaminated soil, etc.)

2.1.3 The primary health effect of chronic low doses of radiation could be the induction of various types of cancers with a latency period of 4 to 20 years (also known as cell modification or stochastic effects).

2.1.4 Far more unlikely is the potential for immediate effects of high doses of radiation including those associated with cell death or tissue reactions (also known as deterministic effects).

2.1.5 Radiological hazards may be measured in both Imperial and System International (SI) units. A unit conversion table is provided in Annex J.

2.2 Planning Basis for Nuclear Emergencies

2.2.1 A planning basis involves the identification of hazards that the nuclear emergency management program must address based on their impact on health and safety, property, and the environment. In a nuclear emergency, an ionizing radiation hazard could arise from an accident or event at a reactor facility.

2.2.2 Elements of the planning basis include:

1. the radiological hazard(s), i.e., the types of accidents planned for (Section 2.2.3)
2. the basis for protective action decision-making i.e., intervention levels (Section 2.2.4)
3. the potential effects on public health and safety i.e., potential radiation doses resulting from a) above
4. the geographical extent of consequences i.e., planning zones (Section 2.2.5) and planning zone distances (Section 2.2.6)

2.2.3 Reactor Facility Accidents

1. Nuclear emergency preparedness requires a planning basis which considers both design basis accidents and beyond design basis accidents (BDBAs) including severe accidents and multi-unit scenarios where applicable. For a detailed explanation regarding the basis for these reference accidents, refer to Annex L - PNERP Planning Basis Background.
2. While the planning basis should include a wide range of accidents, the amount of detailed planning should decrease as the probability of the accidents' occurrence decreases. For this reason, the planning basis for managing a nuclear emergency must strike an appropriate balance.
3. Reactor facility safety analysis and risk assessments shall be used to inform the planning basis.
4. This PNERP has been prepared in conformity with national and international standards and guidance for nuclear emergency management and as such it:
   1. Provides detailed planning and preparedness to mitigate the effects of Design Basis Accidents (DBAs) for which safety systems have been specifically designed to ensure that radiological releases are kept within authorized limits.
   2. Provides additional tools and mechanisms to mitigate the effects of Beyond Design Basis Accidents (BDBAs), including severe accidents, which are considered even more unlikely than Design Basis Accidents.
5. Design Basis Accidents (DBA)
   1. The DBA release provides the main platform for detailed planning and is generally characterized by one or more of the following:
      • Station containment systems function normally allowing radiation to decay prior to a controlled release.
      • Sufficient time would be available to alert the public and implement protective measures prior to a release.
      • The main radiological hazard to people would be external exposure to, and inhalation of, radionuclides.
      • Filter systems function to remove almost all of the radioiodine. As a result, the plume would be mostly comprised of inert noble gasses which would dissipate and do not pose a contamination hazard.
      • Radiation doses to the public would likely be below the Generic Criteria (GC) as defined in Annex E.
      • Environmental contamination would be limited to very low levels.
      • Low-level radioactive releases to the environment could occur on and off for some time (e.g., days or weeks).
   2. Planning and preparedness shall be conducted in Ontario to mitigate the consequences of releases from Design Basis Accidents and provide a basis for expanding the response as required to mitigate severe accidents (Section 2.2.3 f) ii below).
6. Beyond Design Basis Accidents (BDBA)
   1. One or more of the following may define a BDBA:
      • Station containment systems may be impaired leading to significantly reduced hold up time and decay of radioactive materials.
      • An early release of radioactivity from a BDBA with limited warning time.
      • An uncontrolled release of radioactivity from a BDBA with limited warning time.
      • The plume could include radioiodine and particulates along with noble gases.
      • Radiation doses could potentially be high.
      • Environmental contamination could be quantitatively significant in both extent and duration.
      • The area affected could extend beyond the Detailed Planning Zone.
      • A multi-unit accident (i.e., an accident involving more than one reactor).
   2. BDBAs which go unmitigated may evolve into severe accidents involving fuel degradation in the reactor core.
   3. The response to BDBAs, including severe accidents, is facilitated by the measures already in place to respond to DBAs (Section 2.2.3 e) above) and the ability to expand their function.
   4. The following additional planning and preparedness actions shall be conducted to mitigate the much less probable, but possibly more severe, off-site effects of BDBAs:
      • Automatic, default actions to initiate public alerting and to direct the implementation of protective actions, including sheltering and evacuation.
      • Priority evacuations for those closest to the hazard.
      • Radiation monitoring and, if necessary, decontamination of persons.
      • Pre-distribution of Potassium Iodide (KI) pills.
      • Timely dispatch of aerial and ground monitoring teams to determine areas of contamination.
      • Designation of a Contingency Planning Zone (CPZ).
      • Medical assessment, treatment and counselling as required.

2.2.4 Intervention Levels – Generic Criteria and Operational Intervention Levels^{footnote 4[4]}

1. Protective action decision-making involves the comparison of radiation doses (actual or modelled) to internationally accepted Generic Criteria (GC) and Operational Intervention Levels (OILs).
2. The application of GC and OILs is dependent on timing and the availability of actual off-site radiation monitoring data:
   1. Generic Criteria (GC) provides decision-makers with reference levels for the early stages of an emergency, when modelling is used to estimate projected doses. When the projected dose exceeds a GC level for a specific protective action, that action should be directed (subject to operational considerations) to protect the public from potential exposure to radiation. GC are expressed in terms of doses over a specified time period.
   2. Operational Intervention Levels (OILs) are derived from the Generic Criteria and allow decision-making based on actual, measured levels of radioactivity following a release. When the actual dose rate exceeds an OIL for a specific protective action that action should be directed (subject to operational considerations) in order to protect the public.
3. Numerical values for the Generic Criteria and Operational Intervention Levels are detailed in Annex E.

2.2.5 Emergency Planning Zones (EPZ)

1. Planning zones define the areas beyond the boundary of a reactor facility, in which implementation of operational and protective actions are or might be required during a nuclear emergency, in order to protect public health, safety, and the environment. Planning zones shall include the following:
   • Automatic Action Zone (AAZ)
   • Detailed Planning Zone (DPZ)
   • Contingency Planning Zone (CPZ)
   • Ingestion Planning Zone (IPZ)
2. While each of the above zones are distinct and do not overlap, when measures are initiated for the Ingestion Planning Zone, they should be implemented for all other zones noted in Paragraph 2.2.5 a) above.
3. Automatic Action Zone (AAZ)
   1. A pre-designated area immediately surrounding a reactor facility where pre- planned protective actions would be implemented by default on the basis of reactor facility conditions with the aim of preventing or reducing the occurrence of severe deterministic effects.
   2. Additional planning and preparedness shall be undertaken for the AAZ to prevent or reduce deterministic effects for this zone, including the implementation of automatic, default protective measures during General Emergencies and some On-site Emergencies (e.g., evacuation, sheltering-in-place and Iodine Thyroid Blocking).
4. Detailed Planning Zone (DPZ)
   1. A pre-designated area surrounding a reactor facility, incorporating the Automatic Action Zone, where pre-planned protective actions are implemented as needed on the basis of reactor facility conditions, dose modelling, and environmental monitoring, with the aim of preventing or reducing the occurrence of stochastic effects.
   2. Detailed planning and preparedness shall be conducted for the DPZ to ensure that evacuations can be implemented and that the associated needs and requirements of the evacuated public can be met.
   3. Detailed planning and preparedness measures for the DPZ are described in Chapter 3.
   4. The DPZ around a reactor facility shall be divided into a number of response sectors. All emergency response measures, both operational and protective, shall be planned and implemented in terms of these sectors.
   5. The desirable pattern of response sectors in a DPZ is illustrated in Figure 2.1. Response sectors lie within two rings around the reactor facility: an inner ring (which lies beyond the Automatic Action Zone) and an outer ring. Within each ring it is desirable to have as few sectors as possible, while maintaining the need for flexibility and practicability in the application of the operational response strategy.
   6. The actual demarcation of the response sector boundaries shall be such that, as far as practical, they lie along clearly recognizable features, such as roads, waterways and railway tracks. Other factors to be taken into account shall be municipal boundaries, population densities, and availability of appropriate evacuation routes.
   7. These divisions are illustrated in Figure 2.1. Actual zones and response sectors for each reactor facility are shown in the appropriate site-specific Implementing Plan.
5. The Contingency Planning Zone (CPZ)
   1. A pre-designated area surrounding a reactor facility, beyond the Detailed Planning Zone (see Section 2.2.6), where contingency planning and arrangements are made in advance, so that during a nuclear emergency, protective actions can be extended beyond the Detailed Planning Zone as required to reduce potential for exposure.
   2. The planning measures undertaken in the CPZ are described in Chapter 3.
   3. Plans and arrangements for this CPZ include considerations for:
      • division into sub-zones
      • population estimates for each sub-zone
      • development of mechanisms, processes and procedures to provide for environmental radiation monitoring and data analysis by the PEOC Scientific Section
      • familiarization sessions with impacted municipalities, as required
      • identification of existing response centres that fall within the CPZ and development of a list of possible alternates located outside the CPZ
      • Iodine Thyroid Blocking (ITB) requirements consistent with those stipulated for the Ingestion Planning Zone
      • Public awareness and education requirements consistent with Ingestion Planning Zone requirements
      • No requirement for designation of additional emergency response centres (e.g., EOCs, EIC, Reception and Evacuation Centres, personal monitoring and decontamination facilities, etc.) beyond those designated for Detailed Planning Zone
      • No additional public alerting and communications requirements beyond those established for the Detailed Planning Zone
6. Ingestion Planning Zone (IPZ)
   1. A pre-designated area surrounding a reactor facility where plans or arrangements are made to:
      • protect the food chain
      • protect drinking water supplies
      • restrict consumption and distribution of potentially contaminated produce, wild-grown products, milk from grazing animals, rainwater, animal feed

        Note: Wild-grown products can include mushrooms and game.

      • restrict distribution of non-food commodities until further assessments are performed
   2. The IPZ is divided into concentric sub-zones in order to facilitate implementation of protective measures:
      • Sub-zone A lies between the Contingency Planning Zone and 30 km.
      • Sub-zone B lies between 30 km and 50 km.
   3. Ingestion Control Sub-Zones A and B are each divided into eight sub-zones.
   4. Ingestion control measures are further discussed in Chapter 6.
7. The divisions described above are illustrated in Figure 2.2. Actual zones and response sectors for each reactor facility shall be described in the appropriate site-specific Implementing Plan.

2.2.6 Planning Zone Distances

1. Planning zone distances for reactor facilities are established based on a number of factors including but not limited to, reactor design and the number of reactors on site. Consequently, planning zone distances may vary from site to site.
2. The outer radii of the planning zones surrounding the reactor facilities (listed in Annex A), as measured from the venting or release stacks, are as follows^{footnote 5[5]}:

2.3 Planning Basis for Radiological Emergencies

2.3.1 Radiological emergencies arise as a result of:

1. Accidents or occurrences at nuclear establishments.
2. Accidents or occurrences during the transportation of radioactive material.
3. c)Radiological Dispersal Devices (RDD)/Radiological Exposure Devices (REDs)
4. Radiological Device (RD)
5. Lost/stolen/orphan sources
6. Satellite re-entry
7. Nuclear weapon detonation

2.3.2 Radiological Emergency Intervention Levels

Intervention levels described in Section 2.2.4 above should be used as the basis for decision-making in a radiological emergency.

2.3.3 Radiological Emergency Zones

Field monitoring will inform the delineation of zones to be used as the basis for protective measures in a radiological incident (Note: zoning for radiological incidents arising on-site at a reactor facility shall be delineated pursuant to Section 2.2.5 above):

1. The Restricted Zone is the area within which exposure control measures are likely to be required.
2. The Buffer Zone provides a buffer area beyond the Restricted Zone where limited measures of radioactivity are detected. This is the area within which ingestion control measures may be necessary.
3. The divisions described above are illustrated in Figure 2.3.