Population Density and Use Characteristics of

Site Environs

Part 100 (Reactor Site Criteria) of Title 10, Code of Federal Regulations, is the primary regulation for evaluating the acceptability of proposed reactor sites.2

The power reactor licensing procedures which precede the issuance of a construction permit consist of four steps. First, there is usually an informal site evaluation whereby the prospective applicant discusses with the AEC the suit

The siting criteria of Part 100 are supplemented by requirements of Parts 20 and 50. Part 20 establishes allowable limits of personnel exposure to radiation and/or release of radioactive materials under normal conditions. Part 50 establishes general provisions for the licensing of power reactors. Specifically, Part 50, among other items, requires that each applicant for a construction permit describe the site on which the proposed facility would be located, including a description of the population density surrounding the site and of the use of the surrounding land.

ability of various reactor sites under consideration. Second, the application for a construction permit is prepared by the utility (usually with the help of the reactor supplier) and submitted to the AEC. This application includes the preliminary design and safety features of the proposed reactor, and comprehensive data on the proposed site. It discusses the safety features which will be provided to prevent accidents, or, if accidents should occur, to prevent hazardous exposure of the public and employees to radiation. This application is then reviewed by the AEC's regulatory staff and by the Advisory Committee on Reactor Safeguards (ACRS). The ACRS is an independent committee established by law to advise the Commission on safety aspects of reactors. It is composed of scientists and engineers who are eminently qualified in the various fields related to reactor technology.

The third step is a public hearing conducted in the vicinity of the project by an atomic safety and licensing board. The board is made up of three members, two of whom are technically qualified and one of whom is experienced in administrative proceedings. After the hearing, the board renders an initial decision as to the suitability of the proposed site for the planned use. This decision is subject to review by the Commission, either on its own initiative or upon petition by a party of the proceedings. Essentially the same type of review process occurs before the operating license is issued, except that a public hearing is not usually held.

The criteria and guidelines set forth by the AEC in 10 CFR 100 describe a number of factors bearing on the health and safety of the general public that are considered by the AEC in the evaluation of reactor sites. Specifically, in regard to land use and population characteristics of a site, 10 CFR 100 requires an applicant for a construction permit to identify:

(1) An exclusion area, which is that area surrounding the reactor in which the reactor licensee must have the authority to determine all activities including exclusion or removal of personnel and property from the area. Activities unrelated to operation of the reactor may be permitted in an exclusion area under appropriate limitations, but the licensee must be in a position to clear the area promptly in the event of an emergency. For example, the area may be traversed by a highway, railroad, or waterway, provided these are not so close to the facility as to interfere with normal operations of the facility and provided appropriate and effective arrangements are made to control traffic on the highway, railroad, or waterway in case of emergency. (2) A low population zone, immediately surrounding

the exclusion area in which the total number of residents and the population density are small enough to provide a reasonable probability that appropriate protective measures could be taken in their behalf in the event of a serious accident. AEC's regulations do not specify a permissible population density or total population within this zone because the situation varies from case to case. Whether a specific number of people can, for example, be evacuated from a specific area, or instructed to take shelter, on a timely basis will depend on many factors such as location, number and size of highways, scope and extent of advance planning, and distribution of residents within the

area.

(3) A population center distance, which is the distance from the reactor to the nearest boundary of a

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densely populated center containing more than about 25,000 residents.

As an aid to applicants in determining and evaluating these areas and/or distances, the AEC staff has developed report TID-14844, "Calculation of Distance Factors for Power and Test Reactor Sites." The analytical method outlined in TID-14844 for evaluating reactor accidents is based on a considerable simplification of the complex phenomena involved; however, the simplifying assumptions made are conservative, and it represents what is believed to be an overall conservative approach to evaluating consequences of an accident on a site. The AEC recognizes that TID-14844 may not be fully applicable to all facilities and/or sites; therefore, 10 CFR 100 states that TID-14844 may be utilized as a point of departure for consideration of particular site requirements which may result from evaluation of the characteristics of a particular reactor, its purpose, and method of operation.

The probable trend toward metropolitan siting of large power reactors requires consideration of measures to minimize the degree of risk in populated areas. The AEC is developing guidance for the selection of sites located in more highly populated regions.

Engineering and Quality Assurance Criteria

Governing Design, Fabrication, Installa tion, Testing and Operation of Reactors

The AEC's nuclear power plant siting criteria require an evaluation of plant design and operating characteristics in order to assure that the plant will be built and operated in accordance with the plans on which the siting evaluation is made. Assurance that nuclear power plants are designed, constructed, and operated to the necessary high quality standards of safety is best obtained through the specification of criteria and codes for the important plant characteristics since this technique provides the most practical way to assure compliance with agreed upon requirements.

The development and promulgation of nuclear criteria, standards and codes has therefore received high priority within the AEC. The nuclear industry also is conducting an accelerated effort to develop nuclear standards and codes

The Oyster Creek Nuclear Power Plant Unit No. 1, in Lacey Township, N.J., built for the Jersey Central Power & Light Co. (a subsidiary of General Public Utilities) by General Electric Co.

through engineering code committees and technical societies.

Special Engineered Safety Features

As noted previously, 10 CFR 100 describes the criteria which guide the AEC in its evaluation of the suitability of reactor sites. One factor considered is the safety features that are to be engineered into the facility. Another is the extent to which the reactor incorporates unique or unusual features having a significant bearing on the probability or consequences of an accidental release of radioactive materials. Part 100, when used in conjunction with TID-14844, suggests a simplified potential exposure-distance relationship which can be used to determine an acceptable distance at which a nuclear plant of a given size may be located from a population center and from a low population zone. Nuclear plants which have been proposed and approved for construction by the AEC have not relied solely on this simplified exposure-distance relationship for the assurance of public safety. Rather, the trend is to increase the flexibility of siting by allowing a separation from population centers which is frequently less than that obtained by the simplified relationship given in TID-14844 by providing compensating engineered safety features.

The criteria for engineered safety features require that they be reliable and readily testable,

be provided with alternate power systems, and be protected against dynamic effects and flying objects.

The AEC takes a conservative position in evaluating the effectiveness to be assumed for these compensating engineered safety features. This conservatism is considered to be appropriate until more experience is obtained in designing, constructing, and operating the present generation plants.

It is anticipated that improved engineered safety features will be developed to substitute in part for the potential exposure-distance relationship test in reactor siting in populated areas. The AEC is supporting an extensive program of research and development that is designed to test functional system performance of these engineered safety features which is described later in Appendix C.

Natural Environmental Characteristics of a Site

Seismology and geology.-Severe earthquakes can cause extensive property damage, particularly for structures erected on material with poor earthquake response characteristics. The current trend toward larger and larger power stations is resulting in increasing structural complexity and in very large capital outlays in facilities located on a single site. Consequently, the earthquake potential of a site is an important consideration for any type of powerplant as is the provision of design features to protect the investment in the event of an earthquake.

Earthquake potential presents a special problem in the case of nuclear power plants because of providing appropriate measures to protect the health and safety of the public. A much more extensive evaluation of possible earthquakes than would be appropriate for a fossilfuel plant is required and much more conservative design requirements are used for the facility itself. Earthquake-caused vibratory motion and surface faulting, and seismically generated waves must all be considered, both as they might affect the power plant itself and the stability of the material underlying it.

Part 100.10, contains a general statement that the AEC will take the seismology and geology of the site into account in evaluating a site proposed for a nuclear power reactor.

Hydrology.-Among the factors which the AEC considers in evaluating a proposed reactor site is the hydrology of the site. For example, the AEC considers extreme flooding conditions by identifying a hypothetical flood which is considered to be the most severe flood reasonably possible on the site, based on hydrometeorological analysis of possible precipitation and also on the assumption of hydrologic conditions favorable for maximum flood runoff. In addition, the possibility of failures of nearby dams is explicitly considered. Also considered are possible floods caused by tsunami, or by seiches (large waves) in an enclosed body of water.

Meteorology. Early in the atomic energy program, it was realized that it was necessary to develop methods of determining the behavior of radioactive materials which might be released to the atmosphere as a result of the operation of nuclear facilities. The recently published report, Meteorology and Atomic Energy (Item 7 in the bibliography for this chapter), prepared by the U.S. Department of Commerce Weather Bureau for the AEC, presents an extensive treatment of meteorological considerations as they would relate to dispersion of activity from nuclear facilities.

Part 100.10 of the AEC regulations requires considerations of meteorological conditions in evaluating reactor sites. The AEC has developed conservative guidelines that may be used in lieu of experimental data when applying for a construction permit. However, during the construction stages, explicit data must be obtained that would adequately describe the site meteorology. In addition to normal meteorological conditions, the AEC also considers adverse conditions such as hurricanes or tornadoes.

Radioactive waste disposal.-Under normal operating conditions, there will be small quantitites of radioactive materials released to the environment from a reactor facility. The AEC regulations in 10 CFR 20 establish strict limits applicable to such release. If reactor facilities can demonstrate that they meet part 20 limits, normal waste disposal is frequently not an important consideration in comparative reactor siting evaluations. In the future it could be of importance when considering very large instal

lations for locations on the same waterway or in the same airshed.

Gaseous effluents. In a pressurized water reactor, a portion of the reactor cooling water is continuously circulated through equipment that removes any gases it carries with it. The gases flow to hold up tanks where they are retained long enough to permit radioactivity to decay to a low level. The gases are then diluted with air and discharged through a stack or a vent on a controlled basis in compliance with AEC regulations.

In a boiling water reactor gases are carried with the steam into the turbine and are separated out when the steam is condensed for return to the reactor vessel. The gases flow to holdup equipment and from that point are handled in essentially the same manner as described above.

Thermal effects.-The availability of suffi cient water for cooling is important in the siting of any steam electric station. Since the utility industry is now building larger power generating stations than ever before, the amount of heat to be dissipated in a single location is correspondingly greater. The problem of discharging heat into a body of water is magnified for nuclear plants over fossil plants for two reasons: (1) the overall thermal efficiency of a present generation nuclear plant is less than that of the best fossil plant because of the lower temperature steam produced, and (2) fossil plants discharge part of their waste heat up the stack, while nuclear plants do not. This means that a present generation nuclear plant will have to dissipate 40 to 50 percent more waste heat than a modern fossil-fueled plant of the same size. Present nuclear plant efficiencies are roughly comparable to older fossil plant efficiencies. Waste heat may be dissipated in a body of water, or it may be all or partly diverted to a cooling tower, cooling pond, or other heat dissipating system.

The AEC has no present jurisdiction over the thermal effects caused by the siting of nuclear plants. However, each applicant for a construction permit is urged to: (i) Cooperate with the Fish and Wildlife Service, the Federal Water Pollution Control Administration, the State Fish and Game Boards, and other interested

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agencies in developing plans for ecological surveys; (ii) construct, operate, and maintain such fish protective facilities over the water intake structures as are needed to prevent significant damage to fishery resources; and (iii) make such modifications in project structures and operations as may be found necessary as a result of ecological surveys. Many individual state legislatures have adopted water quality regulations. When selecting a site for a reactor facility, a utility must satisfy its particular state that it can comply with these regulations during the operation of the facility. The problem of thermal effects is discussed in detail in Chapter V.

Siting Trends

The first nuclear power plants were sited in locations chosen primarily for their low population density. These plants were primarily built for demonstration purposes. Additional transmission costs which may have been imposed by remote siting could be properly considered to be research and development costs. However, as nuclear power plants gain commercial acceptance, economic considerations, including those associated with siting, are becoming a more important factor. It is more attractive financially to place large commercial reactor plants close to load centers, including locating them in metropolitan areas. To date, however, licensed plants have not been located in areas of such high population density that appropriate protective measures in an emergency would be impractical.

The evaluation of an application to license a reactor on or near a metropolitan site (an area where take-cover or evacuation actions may not be practical in view of the large population density) must take into consideration the amount of experience with large power reactors of the type now being constructed. Until there is more experience in the design, construction, and operation of these plants, the AEC plans to maintain a conservative approach in evaluating plant safety and in establishing requirements for engineered safety features.

Obtaining the necessary experience is not considered to be restricted simply to the accumulation of operating time. The experience gained

in designing and building reactors will lead to improved standards and better systems of quality assurance in construction, component fabrication, and installation. This experience and these improved standards, in turn, may allow greater flexibility in reactor siting. In-service inspection techniques to permit early detection of conditions which could lead to failure are also being improved. Another important source of experience is to be found in the current and future reactor safety research programs, both those sponsored by the AEC and by the nuclear industry. As this large body of experience is developed, analyzed, and applied, meaningful decisions on the evolution of more liberal siting policies can be expected.

Development of Codes and Standards

The foregoing discussion underscores the importance of documenting proven engineering practices and procedures and using them in the design, siting, development, construction, and operation of nuclear power reactor plants to provide maximum assurance that these plants are reliable, safe, and economical. Such documentation may be in the form of engineering codes, standards, criteria, or specifications.

Current emphasis on engineering codes and standards focuses attention on the plant characteristics, including its engineered safety features, and minimizes reliance on the availability of sites having a unique combination of highly favorable natural environmental advantages. Perfecting codes and standards to be employed in the design, construction, and operation of nuclear plants will thus permit greater freedom in site selection without compromising public health and safety.

Sources of Engineering Codes and Standards for Nuclear Plants

The nuclear industry which supplies the facilities, equipment and services required by the AEC and its licensees (e.g., electric utilities) has traditionally obtained its engineering codes and standards from the following sources:

(a) Voluntary industry and professional standards bodies.

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