Section 7: Deterministic Safety Analysis
19. A deterministic safety analysis of the design of the nuclear facility shall be made to predict the behavior of the facility in, and following, all operational states and accident conditions and to ensure that the safety criteria are met.
20. Acceptance criteria shall be specified for the deterministic safety analyses to judge the safety based on the key facility parameters and the radiological impact, as analyzed for regular operation, anticipated operational occurrences, and accident conditions.
21. A comprehensive listing of postulated initiating events shall be prepared so that the analysis of the facility response provides an envelope of all foreseeable events challenging the integrity of physical release barriers and the performance of safety functions.
22. Calculational methods and computer codes used in the safety analysis shall undergo verification and validation with appropriate experimental data and research. Uncertainty and sensitivity analyses shall be performed and accounted for when applying the results.
23. The facility's response to postulated initiating events shall be analyzed to determine whether the acceptance criteria and the safety criteria are met even with unfavorable combinations of initial conditions, equipment failures, and operator actions, as specified for the design basis and features as well as the operational limits and conditions of the nuclear facility.
Section 8: Probabilistic Risk Assessment
24. A probabilistic risk assessment of the nuclear facility shall be made to determine whether the radiation risks are as low as reasonably achievable and to guide the decisions for improving the safety of the design and management of a nuclear facility throughout the life cycle.
25. All initiating events caused by failures, errors, or hazards that could challenge regular operation and require mitigation to prevent, or events that could lead directly to severe damage to fuel, the reactor core, or other radiologically risk-significant items of the nuclear facility, shall be identified and grouped to establish the starting point of the probabilistic risk assessment.
26. The response of the nuclear facility to each group of initiating events shall be analyzed to model the alternative sequences in which the initiating events could develop further, as they are affected by the reliability of items performing their safety functions and of the operators taking correct actions.
27. Based on initiating event identification, accident sequence modeling, and detailed reliability analyses, the probabilistic risk assessment shall present the quantitative results in the form of different facility damage states and their frequencies. The total frequency of damage states involving severe damage, with appropriate uncertainty considerations, shall be viewed as a quantitative estimate of the effectiveness of the defense in depth levels and the safety functions in preventing severe accidents. The results shall be used to identify the most significant contributors to the severe damage frequency and the subsequent opportunities for safety improvements and a more balanced design.
28. The probabilistic risk assessment shall be completed by further analyzing the progress and management of severe accidents, the effectiveness of the confinement of radioactive materials released, and the consequences in terms of radioactive releases into the environment. The frequencies and characteristics of these radioactive source terms and their radiological impact, with appropriate uncertainty considerations, shall be viewed as quantitative estimates of the radiation risks associated with the nuclear facility. The assessment results shall be factored to identify the largest risk contributors and opportunities for risk reduction.
Section 9: Design Reviews and Analyses
29. The design of the nuclear facility, items important to safety, and human interactions shall be reviewed and analyzed to identify and correct design deficiencies, to assess and justify the final design solutions, and to ensure the fulfillment of the safety objectives and design basis requirements in operational states as well as in accident, design extension, and hazard conditions.
30. The defense in depth features of the nuclear facility shall be reviewed, analyzed, and assessed to determine whether adequate provisions have been made at each level of defense in depth, whether there exist such dependencies between the levels that several levels of defense could be coincidentally or consequentially lost, and whether the final design can be considered compliant with the defense in depth principle.
31. The site characteristics relating to the safety of the nuclear facility shall be analyzed to ensure that the radiological impact assumptions made in the design assessments are correct, that the facility is sufficiently protected against external hazards, and that the potential effects on a nuclear facility with multiple units, if relevant, are appropriately covered by the facility design and emergency measures.
32. The safety functions shall be reviewed, analyzed, and assessed to determine whether their failure tolerance and reliability are at a level commensurate with their importance for the defense in depth and the fundamental safety function objectives of the nuclear facility. The reviews, analyses, and assessments performed for a specific safety function shall cover the relevant operational states and the accident, design extension, and hazard conditions.
33. The design of items important to the safety of a nuclear facility shall be reviewed to determine whether they are of a robust and proven design and are suitable for their purpose. Thorough analyses and assessments shall be performed for systems, structures, and components whose safety significance, design complexity, technological novelty, or potential exposure to challenging conditions make their qualification, verification, and validation particularly demanding.
34. Human interactions with the nuclear facility or a specific activity shall be addressed to determine whether the procedures and measures for operational states and accident, design extension, and hazard conditions ensure an adequate level of safety and whether sufficient design features, administrative procedures, and control measures have been provided to prevent and mitigate the influence of human errors on the safety of the nuclear facility.