Low population zone

Liquid Nitrogen Liquid Nitrogen System Low Pressure Low Population Zone Local Radiation Processor Low Temperature Adsorber Light Water Reactor... 

Population data are site specific and will be presented at the time of application for a specific site. However, for purposes of estimating population doses, a population density is assumed to average 500 persons per square mile over a radial distance out to 30 miles. A bounding low population zone of 425 meters (i.e. coincident with the exclusion area boundary) has been selected for purposes of safety analyses. 

A program of onsite data collection, supplemented by National Weather Service (NOAA) summaries from locations near a specific site, will be conducted. Information from the onsite program will be used to confirm that the limiting offsite dose analyses and annual average X/Q values are adequate relative to exclusion area boundary radius and low population zone requirements. 

The numerical dose values given in lOCFRlOO for determining the extent of the exclusion area and low population zone (LPZ) are consistent with all of the selection bases and have been applied, without modification, to the licensing of the FSV-HTGR plant. Therefore, these dose values have been included as top-level regulatory criteria. 

Two-hour exclusion area boundary and 30-day low population zone accident doses less than 25 rem whole body and 300 rem thyroid. 

The existence of a low population zone around the plant, which could be quickly evacuated (within hours) in case of accident to the plant. 

Dose limits equal to the preeeding ones for the whole aeddent duration at the external border of the low population zone. 

The exelusion zone was estabhshed at a radius of 800 1000 m around the plant and the low population zone at roughly 5 km from the plant (US Code of Federal Regulations, 2004a). 

An exclusion area and a low population zone are necessary. Also, a distance from the reactor to population center has to be kept in order to meet the above requirement. 

Residents in the low population zone are protected by emergency evacuation plans. 

No need for exclusion zone beyond the plant boundary and no need for evacuation plans. The site boundary can be identified as low population zone per lOCFRlOO. Emergency planning will be limited to on-site responses and informing authorities of the plant status even following a severe accident. 

The exclusion area does not have to be owned by the licensee, merely controlled. The low population zone is... 

CFR 100 stipulates that neither an individual located at any point on the outer boundary of the exclusion area for two hours immediately following onset of the postulated fission product release nor an individual located at any point on the outer boundary of the low population zone for the duration of the accident should receive a total radiation dose in excess of 25 rem to the whole body or 300 rem to the thyroid. Thus, the design-basis LOCA, whose consequences were not to be exceeded by any other credible accident, became the focus of siting evaluations. 10 CFR 100 also stipulates that the... 

The San Onofre 1, Connecticut Yankee, Oyster Creek, Nine Mile Point, and Dresden 2 plants were approved for construction from 1963 to 1965 using ESFs to permit relaxing previous requirements on the size of the exclusion area and low population zone. In 1962 an application was submitted for a construction permit for the Ravenswood plant essentially in the heart of New York City. The AEC staff rejected this application however, metropolitan siting was still seriously considered as late as 1970. ... 

The potential doses at the exclusion area boundary and the low population zone are calculated assuming that the accident occurs when the meteorological conditions are worse (from the standpoint of the calculated doses) than those that would be expected to prevail at the site approximately 95% of the time [Regulatory Guides 1.3 and 1.4]. Table 2.1-4 presents the results from typical calculations of potential offsite doses due to several kinds of design basis accidents. Even with the considerable number of pessimistic assumption employed, the calculated doses that a person out-of-doors in the vicinity of the plant might receive for the entire course of the accident are usually well below the 10 CFR Part 100 guidelines. 

Doses are calculated for a hypothetical person standing outside in the radioactive plume, for 2 hours at the exclusion area boundary and during the entire period of plume passage at the low population zone outer boundary. [10 CFR 100 (d)]... 

Accident Two Hour Exclusion Boundary (3200 feet or 975 meters) Duration of Accident Low Population Zone (4 miles or 6.4 km) ... 

Evacuation time estimates should be used with great caution. Often they apply to the full Emergency Planning 2jQnt rather than to the nearby low-population zone. 

As discussed in Section 5.2, risk decreases rapidly up to a distance of about 2 to 3 miles and decreases more slowly thereafter. Thus, in a core melt accident, early evacuation of the first 2 to 3 miles would markedly reduce individual risks (i.e., the payoffs would be greatest within this distance). Second, the population within this distance is small (at many sites, a few hundred people), and there are normally few impediments to immediate evacuation of the area. Indeed, this area encompasses the low-population zone around most reactor sites. Third, the individual risk of early deaths or injuries for the most severe accident is, in most cases, confined to this area. Immediate evacuation of people near the plant could well prove to be precautionary because most severe accidents (like the Three Mile Island accident) would not be expected to lead to a major release. On the other hand, core damage accidents are expected to be extremely rare, so that precautionary evacuations would also be rare and the results of not taking immediate protective actions could be tragic. 

---