Safety Categorization and Design Criteria for Nonreactor Nuclear Facilities
|Publication Date:||1 January 2014|
This standard specifies criteria for categorization of SSCs and SACs that have a safety function based on radiological and/or chemical dose and exposure levels for the public and workers. The safety categorization leads to codes and standards that are needed for reliable design, construction, and operations commensurate with the safety categorization.
The safety categorization criteria specified in this standard will
(1) establish an objective and technically based rationale for the determination of safety categorization;
(2) ensure that all hazard controls required by the safety design basis are appropriately categorized;
(3) establish a basis for consistency (i.e., minimize categorization differences among similar items in a facility).
The purpose of this standard is the following:
(1) Specify criteria for categorization of safety SSCs;
(2) Select industry codes and standards for reliable design, construction, and operations commensurate with the safety categorization.
To meet these objectives, the standard specifies the requirements in the following steps:
(1) identification of hazards;
(2) evaluation of hazards;
(3) selection of DBEs;
(4) unmitigated accident analysis of DBEs;
(5) identification of safety functions and categorizations;
(6) selection of safety SSCs to fulfill safety function requirements;
(7) evaluation, selection, and implementation of applicable industry codes and standards to ensure safety SSCs are designed, constructed, and maintained to fulfill the intended safety functions.
It should be noted that the methodologies for steps (1) through (4) are not in the scope of this standard. A proposed, new ANS standard, ANS- 57.11-201x, "Integrated Safety Assessments for Fuel Cycle Facilities," that addresses integrated safety assessment is being developed and will specify requirements for steps (1) through (4). Steps (1) through (4) are essential for the identification of safety functions and selection of safety SSCs (stated in steps 5 and 6). The discussions of methodologies for steps (1) through (4) are briefly addressed in Appendices A, B, and C.
To meet the requirements in steps 5 and 6, this standard specifies the categorization criteria in Sec. 4.1. The results from unmitigated accident analyses of DBEs are used together with the criteria in Sec. 4.1 to categorize safety functions and safety SSCs.
The criteria noted in Sec. 4.1 are qualitative and as such, need to be converted into quantitative criteria. Quantitative criteria are expected to be established by the regulators/users using the qualitative categorization criteria in Sec. 4.1.
For clarification, Appendix A provides some representative quantitative criteria (Table A.2). Regulators/users should establish their own criteria as appropriate. Using these quantitative criteria (set by the regulator/user), safety SSCs are categorized (i.e., SC-1, SC-2, and SC-3), with SC-3 being the most stringent safety class.
Step (7) is the selection of appropriate industry codes and standards for design, construction, and operation of safety SSCs to ensure that the SSCs are robust and reliable to fulfill their intended safety functions. Since the design requirements for safety SSCs could vary widely, so can the selection of appropriate industry codes and standards. Section 5 lists industry codes and standards that are widely used for safety SSC design, construction, and operations. Codes and standards are selected based on design specifications that SSCs must meet to fulfill safety function requirements. However, the listed codes and standards cannot be mandated until their applicabilities are determined. Therefore, selection and application of codes and standards is a two-step process:
(1) The regulator/user must evaluate and select applicable industry codes and standards;
(2) Once the applicable codes and standards are selected, the regulator/users must implement the requirements of the codes and standards to ensure the SSCs are designed, constructed, and maintained to fulfill their intended safety functions.
Appendix B provides additional details for the safety categorization process.
This standard is intended for design activities associated with nonreactor nuclear facilities and can be applied for categorization of hazard controls controls in many types of facilities, including, but not limited to, fuel fabrication and enrichment facilities, as required by 10 CFR 70  and other nuclear and radioactive material storage and processing facilities as required by 10 CFR 830 . The standard should be applied within the limits of the authority of the regulator for the facility.