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THREAT CATEGORY I AND II FACILITIES - EMERGENCY ZONES AND
RADIUS SIZES
Table A5-II provides suggestions for the approximate radius of the emergency zones and food
restriction planning radius for threat categories I and II facilities. Site or facility specific studies (e.g.
Refs. [12,13]) could also be used to determine appropriate radii for the zones.
The suggestions are provided with recognition of the great uncertainties involved and variation by a
factor of two or more during application is reasonable. The choice of the suggested radii represents a
judgment of the distance to which making advanced arrangements is reasonable in order to ensure
effective response. In a particular emergency, protective actions may have been warranted only in a
small part of the zones. For the worst possible emergencies, protective actions might need to be taken
beyond the radii suggested.
The sizes are shown in terms of a radius of a circle centred at the source of the potential release or
criticality. However, the actual boundary of the zones should not be a circle but should be established
to conform to geographical features such as roads, rivers, or political boundaries as illustrated in
Figures 2 and 6. Following Table A5-II, there is a discussion of the basic philosophy used to establish
the size.
TABLE A5-II. SUGGESTED EMERGENCY ZONES AND RADIUS SIZES FOR THREAT
CATEGORY I AND II FACILITIES
Facilities
Precautionary Urgent
action zone (PAZ)
62, 63, 64, 65
radius
Threat category I facilities
protective
Food
action planning zone
62, 64, 65 , 66
(UPZ) radius
restriction
planning radius 67
Reactors > 1000 MW (th) 3-5 km 25 km 300 km
Reactor > 100-1000 MW (th) 0.5–3 km 5–25 km 50–300 km
A/D 2 from Appendix 8 is 10 5 (68) 3-5 km 25 km 300 km
A/D 2 from Appendix 8 is 10 4 - 10 5 ( 68) 0.5–3 km 5–25 km 50–300 km
Threat category II facilities
Reactors 10-100 MW (th) None 0.5–5 km 5–50 km
Reactors 2-10 MW (th) None 0.5 km 2–5 km
A/D 2 from Appendix 8 is 10 3 - 10 4 ( 68) None 0.5–5 km 5–50 km
A/D 2 from Appendix 8 is 10 2 - 10 3 ( 68) None 0.5 km 2–5 km
Fissionable mass possible within 500 m of
site boundary 69 None 0.5–1 km None 70
62 The radius is the approximate distance from the facility that the boundary of the zone should be established.
63 The suggested radii are the approximate distance to which the acute (2 day) dose to the bone marrow or lung could (with a
very low probability) approach those that are life threatening (exceed the values in Annex 2). A maximum radius of 5 km is
recommended as discussed elsewhere in the appendix. The source term (release) used for the reactor emergencies was typical
of that postulated for the range of low probability accidents [12] that could potentially result in severe deterministic health
effects off the site.
64 The radii were selected based on calculations performed using the RASCAL 3.0 computer model [17]. The calculation
assumed average meteorological conditions, no rain, ground level release; 48 hours of exposure to ground shine, and
calculates the centreline dose to a person outside for 48 hours.
65 These calculations probably overestimate the distance to which the relevant doses are possible because no credit is given
for dose reduction due to people performing normal activities and because the recipient is always assumed to be in the exact
centre of the plume. Under these assumptions, only a very small area would be affected to these levels.
66 The suggested radii are the approximate distance to which the total effective dose for inhalation, cloud shine and 48 hours
of ground shine will not exceed 1-10 times the GIL for evacuation with a maximum radius of 25 km as recommended for the
reasons discussed elsewhere in the appendix.
67 This represents the area that should be considered to be in threat category V.
68 Assumes that 10% of the inventory is released to the atmosphere.
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