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Site characteristics (3.2.1–3.2.41)

Additional supporting or complementary documents to the safety analysis report

3.1.13. This section should provide a list and summary of the topical reports that are incorporated, by reference, as part of the safety analysis report. Typically, the results of tests and analyses (e.g. results of manufacturers’ material tests and qualification data) may be submitted as separate reports.

Conformance with applicable regulations, codes and standards

3.1.14. This section should provide an overview of the relevant regulations, codes and standards that collectively represent the safety rules used in the design, including information on the use of relevant IAEA safety standards. If these regulations, codes and standards have not been prescribed by the regulatory body, a justification of their appropriateness should be provided. Any deviations from existing regulations, codes and standards should be described in this section, together with a demonstration that the deviations will not be detrimental to safety.

provided in SSR‑1 [5], and relevant recommendations and guidance are provided in the following publications:

(a) IAEA Safety Standards Series No. NS‑G‑3.1, External Human Induced Events in Site Evaluation for Nuclear Power Plants [14];

(b) IAEA Safety Standards Series No. GSG‑10, Prospective Radiological Environmental Impact Assessment for Facilities and Activities [15];

(c) IAEA Safety Standards Series No. NS‑G‑3.6, Geotechnical Aspects of Site Evaluation and Foundations for Nuclear Power Plants [16];

(d) IAEA Safety Standards Series No. SSG‑9 (Rev. 1), Seismic Hazards in Site Evaluation for Nuclear Installations [17];

(e) IAEA Safety Standards Series No. SSG‑18, Meteorological and Hydrological Hazards in Site Evaluation for Nuclear Installations [18];

(f) IAEA Safety Standards Series No. SSG‑21, Volcanic Hazards in Site Evaluation for Nuclear Installations [19];

(g) IAEA Safety Standards Series No. SSG‑35, Site Survey and Site Selection for Nuclear Installations [20].

3.2.4. This chapter of the safety analysis report should provide information concerning the site evaluation as support for the design, design assessment and periodic safety review and should include potential changes to relevant site parameters expected over the lifetime of the plant. This information should include the following:

(a) The collection of site reference data for the plant design (e.g. geological, seismological, geotechnical, volcanic, hydrological and meteorological);

(b) The site specific hazard evaluation for external events of natural origin (e.g. earthquakes, meteorological events, flooding, geological and volcanic hazards, hazards from biological organisms, surface deformation relating to tectonic (i.e. faulting) and non‑tectonic causes) and of human induced origin (e.g. aircraft crashes, chemical explosions from activities performed at nearby industrial facilities and other facilities);

(c) The design targets in terms of the probability of recurrence of external events, with account taken of their severity and associated uncertainties;

(d) An evaluation of the impact of the site related issues to be considered in the parts of the safety analysis report on emergency preparedness and response and accident management;

(e) The arrangements for the monitoring of site related parameters throughout the lifetime of the plant;

(f) The potential for specific hazards to give rise to impacts simultaneously on several units in the case of a multiple unit site.

3.2.5. A description of any considerations from the site survey stage concerning the site exclusion or acceptance criteria applied in the preliminary screening of the site for suitability should be provided in this chapter of the safety analysis report.

3.2.6. Site related information represents an important input to the design process and may be one of the sources of uncertainty in the final safety evaluation. The measures employed to take into account such uncertainties should be considered in this chapter of the safety analysis report.

Geography and demography

3.2.7. This section should specify the site location, including both the area under the control of the operating organization and the area surrounding the site in which there is a need for consultation with interested parties on the control of activities that could affect plant operation (e.g. aircraft flights, associated flight exclusion zones). This should include facilities and activities in the surrounding area that could pose a hazard to the plant (e.g. pipelines, roadways, waterways).

3.2.8. Information on activities with the potential to affect plant operation should include relevant data on the population distribution and density (including, where applicable, transient populations) and on the distribution of public and private facilities (e.g. airports, harbours, rail transport centres, pipelines, roadways, waterways, factories and other industrial sites, schools, hospitals, police services, firefighting services, municipal services) around the site.

3.2.9. This section should also cover the public uses of the land and water resources in the surrounding area and should include an assessment of any possible interaction with the plant and the implications for off‑site protective actions in an emergency.

Evaluation of site specific hazards

3.2.10. This section should present the results of a detailed evaluation of natural and human induced hazards at the site that should be taken into account in the design of SSCs. The description should include due consideration of the envisaged evolution of these hazards during the expected lifetime of the nuclear power plant. SSR‑1 [5] establishes requirements for the evaluation of specific external hazards.

3.2.11. The screening criteria used for each hazard (including the envelope, probability thresholds and credibility of events) and the expected impact of each

hazard in terms of the originating source, the potential propagation mechanisms and the predicted effects at the site should be described in this section.

3.2.12. Hazards identified as potentially affecting the site can be screened out if they would be incapable of challenging the safety of the plant or if they are considered, with a high degree of confidence, to be extremely unlikely. The arguments in support of the screening process should be justified and described in this section of the safety analysis report.

3.2.13. The target probability levels for design against external hazards should be defined, and a comparison with the acceptable limits should be presented. Attention should be paid to the external hazards that could lead to common cause failures of the safety systems and the safety features for design extension conditions.

3.2.14. The evaluation presented in this section should also take into account unlikely natural hazards exceeding those considered for design, derived from the hazard evaluation for the site, to ensure adequate margins to avoid cliff edge effects. The reliability of the heat transfer to the ultimate heat sink should be given special attention.

3.2.15. This section should confirm that appropriate arrangements are in place to periodically update the evaluations of site specific hazards in accordance with the results of updated methods of evaluation, monitoring data and surveillance activities.

3.2.16. This section should also include results from the evaluation of potential combinations of site specific hazards that could affect the safety of the nuclear power plant.

3.2.17. Where administrative measures are employed to mitigate the adverse effects of hazards (especially for human induced events), information should be presented on their implementation, together with the roles and responsibilities for their enforcement.

Proximity of industrial, transportation and other facilities

3.2.18. This section should describe the locations and transport routes that represent potential risks for the plant and the results of a detailed evaluation of the effects of potential accidents at industrial, transportation or other facilities in the vicinity of the site. Projected developments in the vicinity over the envisaged

lifetime of the nuclear power plant relating to this information should also be presented and updated, as required, in future stages of the safety analysis report.

3.2.19. Any identified risks considered in determining the design basis should be included to help determine whether any additional measures are necessary to mitigate the adverse effects of potential incidents.

Activities at the plant site that might influence the safety of the plant

3.2.20. In this section, any processes or activities at the site that, if incorrectly carried out, could affect or influence the safe operation of the plant should be presented and described. Examples of such processes or activities include vehicular transport in the plant area; storage of fuels, gases and other chemicals;

and activities potentially leading to intakes of or contamination by harmful particles, smoke or gases (e.g. intakes of air through ventilation systems).

3.2.21. Measures for site protection (e.g. dams or dykes for flood control and drainage) and any modifications to the site (e.g. soil substitution, modifications to the site elevation) are usually considered at the site characterization stage, and their assessment in relation to the design basis should be included in this section of the safety analysis report.

Hydrology

3.2.22. This section of the safety analysis report should present sufficient information to enable evaluation of the potential implications of hydrological conditions at the site for the plant design and safe operation, with special attention devoted to conditions that potentially affect residual heat removal to the ultimate heat sink. Cooling water channels and reservoirs to be used for cooling the plant should be described. Low water conditions and the possibility of using groundwater sources in extraordinary situations should also be considered.

3.2.23. The conditions that should be taken into account in this section include potential floods resulting from phenomena such as abnormal ice effects and heavy rainfall, as well as runoff floods from watercourses, reservoirs, adjacent drainage areas and site drainage. This section should also include consideration of flood waves resulting from dam failures; flooding caused by landslides; ice jams and other ice related flooding; and seismically generated, water based effects on and off the site. For coastal and estuary sites, evaluations should include storm surge, tsunamis and seiches. For both coastal and riverine flooding, reasonable

combinations of hazards (e.g. tides, strong wind) and potential effects of climate change should be considered.

3.2.24. The information given in this section should be prepared in such a way as to enable the assessment of (i) the transport of radionuclides in groundwater and the surface water system and (ii) the dispersion of radionuclides through the environment. This information should also include a characterization of the hydrogeological subsurface properties and surface water features to enable an assessment of the measures taken to preclude the release of radionuclides to the environment.

Meteorology

3.2.25. This section should provide a description of the meteorological aspects relevant to the site and its surrounding area, with account taken of regional and local climatic effects. Data derived from on‑site meteorological monitoring or other meteorological stations should be documented.

3.2.26. This section should include information relevant to the assessment of (i) the hazards from meteorological events potentially affecting the plant and (ii) the transport of radioactive material to and from the site and the dispersion of radionuclides through the environment.

3.2.27. The extreme values of meteorological parameters or meteorological events — such as temperature; humidity; rainfall; wind speeds for straight and rotational winds, including tornadoes (owing to the sudden pressure drop that accompanies the passage of the centre of a tornado); waterspouts (owing to their potential to transfer large amounts of water to the land from nearby water bodies);

dust storms; sandstorms; and snow loads and ice (see SSG‑18 [18]) — should be evaluated in relation to the design, with account taken of the envisaged evolution of such extreme parameters over the lifetime of the nuclear power plant. The potential for lightning and windborne debris to affect plant safety (including the design basis missile hazard from hurricanes and tornadoes) should be considered, where appropriate.

Geology, seismology and geotechnical engineering

3.2.28. This section should provide information concerning the geological, tectonic, seismological and volcanic characteristics of the site and a sufficiently large region surrounding the site. The evaluation of seismic hazards should be based on a suitable seismotectonic model, substantiated by appropriate

seismological evidence and geological or seismological data. The results of this evaluation that will be used further in other sections of the safety analysis report (including structural design and seismic qualification of components) should be described in sufficient detail. The potential for volcanic phenomena to affect plant safety should be considered, where appropriate.

3.2.29. Site reference data relating to the geotechnical properties of soil and rock underlying the site (both static and dynamic properties, including damping and modulus degradation properties) should be elaborated on in this section.

Geological hazards such as slope instability, subsidence or uplift of the site surface, soil liquefaction, instability of subsurface materials, and the long term performance of subsurface materials and foundations over the lifetime of the plant should be characterized in this section. The processes for the following should be described: the collection of data for the design of foundations, the evaluation of the effects of site response and soil–structure interaction, the construction of earth structures and buried structures, the evaluation of the effects of groundwater conditions, and the evaluation of soil improvements at the site.

3.2.30. This section should present the relevant data for the site and the associated ranges of uncertainty, including the spatial variability used in the site seismic response analysis and in the structural design. Reference should be made to the technical reports that provide a detailed description of the conduct of the investigations and their planned extensions, as well as of the origin of the data collected through site surveys on a regional basis or through bibliographic surveys.

3.2.31. The design of subsurface material and buried structures, as well as site protection measures, if relevant, should also be documented.

A description of projected developments relating to the information described in paras 3.2.28–3.2.30 should also be provided and should be updated as required.

Site characteristics and the potential effects of the nuclear power plant in the region

3.2.32. The characteristics of the site and the surrounding environment relevant to the dispersion of radioactive material in water, air and soil should be described in this section. The relevant requirements for evaluating the dispersion of radioactive material are established in section 6 of SSR‑1 [5].

Radiological conditions due to external sources

3.2.33. This section should describe the radiological conditions in the environment at the site and in the surrounding area, with account taken of the radiological effects of other nuclear installations on the site and any other external radiation sources. The radiological conditions should be described in sufficient detail to serve as an initial reference point and a basis for future assessments of radiological conditions at the site and in the surrounding area.

3.2.34. A description should be provided of the available radiation monitoring systems and the corresponding technical means for the detection of any radiation or radioactive contamination. If appropriate, this section may reference other relevant sections of the safety analysis report concerned with the radiological aspects of licensing the plant.

Site related issues in emergency preparedness and accident management 3.2.35. The issues regarding feasibility of emergency preparedness in terms of plant accessibility and transport of any equipment necessary in an emergency, including a severe accident, should be described in this section, with account taken of all reactor units and other nuclear and non‑nuclear installations on the site, as applicable. The information provided should include the availability of adequate access and egress roads for the evacuation of personnel, including access to and around the site, and supply networks in the vicinity of the site.

3.2.36. The availability of local transport networks, communications networks and other infrastructure external to the site, during and after an external event, and issues regarding the feasibility of implementing emergency response actions should be described in this section.

3.2.37. The need for any necessary administrative measures should be identified, together with the relevant roles of bodies and response organizations other than the operating organization.

Monitoring of site related parameters

3.2.38. The strategy for monitoring site related parameters and the use of the results in preventing, mitigating and forecasting the effects of site related hazards should be described in this section.

3.2.39. The provisions to monitor site related parameters affected by earthquakes and surface faulting, geological and volcanic phenomena, meteorological events, flooding, geotechnical hazards, hazards from biological organisms and human induced hazards (e.g. aircraft flight activities, chemical explosions, activities at nearby industrial and other facilities) should be described in this section. These provisions may be used for the following purposes:

(a) To provide the information necessary for operator actions taken in response to external events;

(b) To support the periodic safety review at the site;

(c) To develop models for the dispersion of radionuclides;

(d) To confirm the completeness of the set of site specific hazards taken into account.

3.2.40. This section should contain a description of the on‑site meteorological monitoring programme, which can potentially be used for updating meteorological data in the future, for predicting the dispersion of radioactive substances during plant operation, or for providing early warning against extreme meteorological events. The monitoring of demographic and hydrological conditions over the lifetime of the plant should also be described in this section (see SSR‑1 [5]).

3.2.41. Long term monitoring programmes should include the collection of data from site specific instrumentation and data from specialized institutions for use in comparisons to detect significant changes from the design basis, for example changes due to the possible effects of climate change.

CHAPTER 3: SAFETY OBJECTIVES AND DESIGN RULES FOR