ML20311A004
| ML20311A004 | |
| Person / Time | |
|---|---|
| Issue date: | 11/10/2020 |
| From: | Robert Beall NRC/NMSS/DREFS/RRPB |
| To: | |
| Beall, Robert | |
| Shared Package | |
| ML20289A534 | List:
|
| References | |
| 10 CFR Part 53, NRC-2019-0062, RIN 3150-AK31 | |
| Download: ML20311A004 (7) | |
Text
THIS PRELIMINARY RULE LANGUAGE AND ACCOMPANYING DISCUSSION IS BEING RELEASED TO SUPPORT INTERACTIONS WITH STAKEHOLDERS AND THE ADVISORY COMMITTEE ON REACTOR SAFEGUARDS (ACRS). THIS LANGUAGE HAS NOT BEEN SUBJECT TO COMPLETE NRC MANAGEMENT OR LEGAL REVIEW, AND ITS CONTENTS SHOULD NOT BE INTERPRETED AS OFFICIAL AGENCY POSITIONS. THE NRC STAFF PLANS TO CONTINUE WORKING ON THE CONCEPTS AND DETAILS PROVIDED IN THIS DOCUMENT AND WILL CONTINUE TO PROVIDE OPPORTUNITIES FOR PUBLIC PARTICIPATION AS PART OF THE RULEMAKING ACTIVITIES.
THE STAFF IS PRIMARILY SEEKING INSIGHTS REGARDING THE CONCEPTS IN THIS PRELIMINARY LANGUAGE AND SECONDARILY SEEKING INSIGHTS RELATED TO DETAILS SUCH AS NUMERICAL VALUES FOR VARIOUS CRITERIA.
STAFF DISCUSSION OF SUBPART B - PRELIMINARY RULE LANGUAGE, NOVEMBER 2020 Preliminary Language Discussion Subpart B - Technology-Inclusive Safety Subpart B is part of the Part 53 structure and format described in Requirements previous public meetings. In sum, Subpart B defines the safety criteria that other areas of Part 53 (e.g., design & analysis (Subpart C),
operations (Subpart F)) will use as performance metrics.
§ 53.20 Safety Objectives. This section provides the overall qualitative safety goals based on both
§ 182 (adequate protection) and § 161 (protect health or minimize Each advanced nuclear plant must be designed, danger) of the Atomic Energy Act, as amended (AEA). This two-tier constructed, operated, and decommissioned such structure of the AEA is articulated in a decision of the U.S. Court of that there is reasonable assurance of adequate Appeals for the D.C. Circuit (Union of Concerned Scientists v. NRC, protection of the public health and safety and the 824 F.2d 108, (D.C. Cir. 1987)).
common defense and security. In addition, each advanced nuclear plant must take such additional The justification of NRC requirements since the 1980s has not always measures to protect public health and minimize been described in the context of this two-tiered approach. However, danger to life or property as may be reasonable when the NRC has clearly explained the bases for more recent agency considering technology changes, economic costs, actions as being needed either for adequate protection (e.g., NRC operating experience, or other factors identified in the post-Fukushima order on mitigation strategies (EA-12-049)) or to assessments performed under the facility safety protect health or minimize danger (e.g., post-Fukushima order on program required by § 53.80. severe accident capabilities for BWR hardened vents (EA-13-109)).
This preliminary rule language proposes to use the two-tiered concept to support the development of a technology-inclusive, risk-informed, and performance-based regulatory framework for advanced nuclear plants.
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A topic for discussion in developing this Subpart and the remainder of Part 53 is the proposed relationship between the first and second tier safety criteria and the two-tiered structure related to § 182 (adequate protection) and § 161 (protect health or minimize danger).
§ 53.21 Safety Functions. (a) Limiting potential offsite consequences (i.e., dose to an individual)
(a) The primary safety function is limiting the release will be used as the primary performance metric throughout Part 53.
of radioactive materials from the facility and must be maintained during routine operation and for licensing (b) Requires the applicants identification of supporting safety functions basis events over the life of the plant. such as controlling heat generation, heat removal, and chemical (b) Additional safety functions supporting the retention interactions that will be essential for a particular design to ensuring of radioactive materials during routine operation and retention of radionuclides within a facility; and (c) requires licensing basis eventssuch as controlling heat development and maintenance of design features and programmatic generation, heat removal, and chemical interactions-- controls to fulfill the identified primary and additional safety functions must be defined. over the life of the facility. Note that the safety functions and the (c) Design features and programmatic controls serve design features and programmatic controls used to fulfill them will be to fulfill the primary safety function and additional the means to satisfy the first and second tier safety criteria.
safety functions and must be maintained over the life of the plant. These requirements are similar in concept to current requirements for LWRs to address the general design criteria and non-LWRs to provide principal design criteria; however, these safety functions are broad in order to support any technology. Subsequent Part 53 Subparts on design, analyses, and operations will require measures (i.e., design features and programmatic controls) to support the primary and additional safety functions.
§ 53.22 First Tier Safety Criteria. The first-tier safety criteria are metrics that establish a level of safety (a) Design features and programmatic controls must or backstop based on current requirements in (a) Part 20 limits on be provided for each advanced nuclear plant to doses to members of the public and (b) the Sections 50.34, 52.79, ensure the contribution to total effective dose 100.11 reference values related to the safety assessment of a site and equivalent to individual members of the public from radiological consequences from a major accident in terms of possible normal plant operation does not exceed 0.1 rem (1 dose to an individual at defined distance and duration of exposure mSv) in a year and the contribution to dose in any 2
unrestricted area does not exceed 0.002 rem (0.02 A topic for future discussion will be the degree to which the first-tier millisievert) in any one hour. safety criteria for an important subset of licensing basis events (i.e.,
design basis accidents) will be fulfilled through design requirements (b) Design features and programmatic controls must such as classification of safety-related SSCs or operational be provided for each advanced nuclear plant such requirements such as technical specifications; the expected level of that analyses of licensing basis events in accordance detail in safety analysis reports; and staffing requirements. Related with § 53.24 demonstrate with high confidence that discussions will also address an applicants analyses related to the events with an upper bound frequency greater than first-tier safety criteria - for example, will the analyses more resemble approximately once per 10,000 years meet the the traditional, deterministic approach in Chapter 15 and the design following: basis accident category within NEI 18-04?
(1) An individual located at any point on the boundary of the exclusion area for any 2-hour period following Section (c) was added to address longstanding desire to maintain the onset of the postulated fission product release some flexibility for the NRC to determine that an action is needed to would not receive a radiation dose in excess of 25 provide reasonable assurance of adequate protection.
rem (250 mSv) total effective dose equivalent; and (2) An individual located at any point on the outer boundary of the low population zone who is exposed to the radioactive cloud resulting from the postulated fission product release (during the entire period of its passage) would not receive a radiation dose in excess of 25 rem (250 mSv) total effective dose equivalent.
(c) Design features and programmatic controls beyond those needed for paragraphs (a) and (b) of this section must be provided for each advanced nuclear plant to satisfy additional requirements established by the NRC for ensuring reasonable assurance of adequate protection of the public health and safety and maintaining common defense and security.
§ 53.23 Second Tier Safety Criteria. The second-tier safety criteria establish a process - similar to current (a) Design features and programmatic controls must requirements on maintaining doses as low as reasonably achievable be provided for each advanced nuclear plant to for normal operations/routine effluents. The preliminary language for 3
ensure the estimated total effective dose equivalent to normal operations is taken from Part 20 and the higher level (dose individual members of the public from effluents values) from Appendix I to Part 50. One topic for discussion is the resulting from normal plant operation are as low as is appropriateness of the Appendix I performance goals for a technology-reasonably achievable taking into account the state of inclusive regulation.
technology, the economics of improvements in relation to the state of technology, operating The second-tier safety criteria for licensing basis events (b) experience, the economics of improvements in establishes the connection to licensing basis events and defense in relation to benefits to the public health and safety and depth (1) and is taken from the NRC safety goals (2). These other factors included in the assessments performed requirements will provide a basis for Subpart C which will be on design under the facility safety program required by § 53.80. and analyses as well as Subpart F on operations (maintaining Performance objectives for design features and capabilities and reliabilities, facility safety program, etc.).
programmatic controls must be established such that:
(1) The calculated annual total quantity of all radioactive material above background to be released from each advanced nuclear plant to unrestricted areas will not result in an estimated annual dose or dose commitment from liquid effluents for any individual in an unrestricted area from all pathways of exposure in excess of 3 millirems to the total body or 10 millirems to any organ.
(2) The calculated annual total quantity of all radioactive material above background to be released from each advanced nuclear plant to the atmosphere will not result in an estimated annual air dose from gaseous effluents at any location near ground level which could be occupied by individuals in unrestricted areas in excess of 10 millirads for gamma radiation or 20 millirads for beta radiation.
(b) Design features and programmatic controls must be provided to:
(1) Ensure plant SSCs, personnel, and programs provide the necessary capabilities and maintain the necessary reliability to address licensing basis events 4
in accordance with § 53.24 and provide measures for defense-in-depth in accordance with § 53.25; and (2) Maintain overall cumulative plant risk from licensing basis events such that the risk to an average individual within the vicinity of the plant receiving a radiation dose with the potential for immediate health effects remains below five in 10 million years and below two in one million years for a radiation dose with the potential to cause latent health effects.
§ 53.24 Licensing Basis Events. This section establishes the requirement to define and address Licensing basis events must be identified for each unplanned events (both internal and external hazards) to ensure advanced nuclear plant and analyzed in accordance estimates of offsite consequences are below the safety criteria and with § 53.[3x] to support assessments of the safety that SSCs, personnel and programs address the safety functions.
requirements of this Subpart B. The licensing basis This section provides a starting point for subsequent requirements to events must address combinations of malfunctions of be developed in design and analysis (Subpart C) and related plant SSCs, human errors, and the effects of external operational requirements (Subpart F) for topics such as configuration hazards ranging from anticipated operational control, reliability programs/metrics, etc.
occurrences to highly unlikely event sequences that are not expected to occur in the life of the advanced nuclear plant. The evaluation of licensing basis events must be used to confirm the adequacy of design features and programmatic controls needed to satisfy first and second tier safety criteria of this Subpart and to establish related functional requirements for plant SSCs, personnel, and programs.
§ 53.25 Defense in Depth. This section establishes requirements based on the longstanding Measures must be taken for each advanced nuclear nuclear philosophy to ensure defense in depth to address plant to ensure appropriate defense in depth is uncertainties. Additional requirements will be included in design and provided to compensate for epistemic and aleatory analysis (Subpart C) which will address requirements for both 5
uncertainties such that there is high confidence that probabilistic risk assessment (PRA) and deterministic analyses and the safety criteria in this Subpart B are met over the related operational controls. This is an expected topic for discussion life of the plant. The epistemic and aleatory in terms of both the concept and then subsequently the wording.
uncertainties to be considered include those related to the ability of barriers to limit the release of radioactive materials from the facility during routine Definitions operation and for licensing basis events and those Epistemic - relating to knowledge or to the degree of its validation Aleatory - depending on chance; random related to the reliability and performance of plant SSCs and personnel, and programmatic controls.
Measures to compensate for these uncertainties can include increased safety margins in the design of SSCs and providing alternate means to accomplish safety functions. No single design or operational feature, no matter how robust, should be exclusively relied upon to meet the safety criteria of 10 CFR part 53.
§ 53.26 Protection of Plant Workers. This section incorporates Part 20 limits on occupational exposures as (a) Design features and programmatic controls must a way to ensure that protection of plant workers is included in the exist for each advanced nuclear plant to ensure that higher level safety criteria for Part 53.
radiological dose to plant workers does not exceed the occupational dose limits provided in Subpart C to 10 CFR part 20.
(b) The licensee must use, to the extent practical, procedures and engineering controls based upon sound radiation protection principles to achieve occupational doses and doses to members of the public that are as low as is reasonably achievable.
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Other Possible Topics for Discussion
- DOE orders and ANS 2.26, Categorization of nuclear facility structures, systems, and components for seismic design, include consideration of unmitigated consequences from event scenarios to determine equipment classification. This type of approach is also used in non-reactor consensus standards to determine appropriate design features and programmatic controls. Some recent discussions related to seismic design have indicated that such an approach can be aligned with the methodology described in NEI 18-04. Is there a role for such an approach within Part 53?
- An important feature of Part 53 will be embedded mechanisms to apply analytical safety margins to gain operational flexibilities in areas such as emergency planning, siting, and staffing. A question is whether provisions for doing the assessments and putting in place the needed design features and programmatic controls for alternative criteria should be in this Subpart or in subsequent Subparts. The initial plan is to provide these mechanisms in Subpart C (design and analysis) to lay out the basic process of establishing design goals more restrictive than the second-tier criteria - and using margins established by the defined threshold to justify alternatives in other sections/Subparts.
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