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Federal Register / Vol. 86, No. 124 / Thursday, July 1, 2021 / Rules and Regulations
that it is not necessary to impose an additional limitation for standardization similar to that imposed on Tier 1
departures by 52.63a4 and b1
because it would unnecessarily restrict the flexibility of applicants and licensees with respect to Tier 2
information.
An applicant or licensee referencing this DC rule may request an exemption from Tier 2 information as set forth in paragraph VIII.B.4. The applicant or licensee would have to demonstrate that the exemption complies with one of the special circumstances in regulations governing specific exemptions in 50.12a. In addition, the NRC would not grant requests for exemptions that would result in a significant decrease in the level of safety otherwise provided by the design. However, unlike Tier 1
changes, the special circumstances for the exemption do not have to outweigh any decrease in safety that may result from the reduction in standardization caused by the exemption. If the exemption is requested by an applicant for a license, the exemption would be subject to litigation in the same manner as other issues in the licensing hearing, consistent with 52.63b1. If the exemption is requested by a licensee, then the exemption would be subject to an opportunity for hearing in the same manner as license amendments.
Paragraph VIII.B.5 allows an applicant or licensee to depart from Tier 2
information, without prior NRC
approval, if the departure does not involve a change to or departure from Tier 1 information, Tier 2 information, or the technical specifications, and the departure does not require a license amendment under paragraph VIII.B.5.b or c. The technical specifications referred to in B.5.a of this paragraph are the technical specifications in Chapter 16 of the generic DCD, including bases, for departures made prior to the issuance of the COL. After the issuance of the COL, the plant-specific technical specifications would be controlling under paragraph VIII.B.5. The requirement for a license amendment in paragraph VIII.B.5.b is similar to the requirement in 50.59 and applies to all of the information in Tier 2 except for the information that resolves the severe accident issues or that affects information required by 52.47a28 to address aircraft impacts.
The NRC concludes that the resolution of ex-vessel severe accident design features should be preserved and maintained in the same fashion as all other safety issues that were resolved during the design certification review refer to SRM on SECY90377, Requirements for Design Certification
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Under 10 CFR part 52, dated February 15, 1991, ADAMS Accession No.
ML003707892. However, because of the increased uncertainty in ex-vessel severe accident issue resolutions, the NRC has adopted separate criteria in paragraph VIII.B.5.c for determining if a departure from information that resolves ex-vessel severe accident design features would require a license amendment. For purposes of applying the special criteria in paragraph VIII.B.5.c, ex-vessel severe accident resolutions are limited to design features where the intended function of the design feature is relied upon to resolve postulated accidents when the reactor core has melted and exited the reactor vessel, and the containment is being challenged. These design features are identified in Section 19E of the DCD but may be described in other sections of the DCD. The location of design information in the DCD is not important to the application of this special procedure for ex-vessel severe accident design features. However, the special procedure in paragraph VIII.B.5.c does not apply to design features that resolve beyond-designbasis accidents or other lowprobability events. The important aspect of this special procedure is that it is limited to ex-vessel severe accident design features, as defined above. Some design features may have intended functions to meet design-basis requirements and to resolve ex-vessel severe accidents. If these design features are reviewed under paragraph VIII.B.5, then the appropriate criteria from either paragraph VIII.B.5.b or VIII.B.5.c are selected depending upon the function being changed.
An applicant or licensee that plans to depart from Tier 2 information, under paragraph VIII.B.5, is required to prepare an evaluation that provides the bases for the determination that the proposed change does not require a license amendment or involve a change to Tier 1 or Tier 2 information, or a change to the TS, as explained above. In order to achieve the NRCs goals for design certification, the evaluation needs to consider all of the matters that were resolved in the DCD, such as generic issue resolutions that are relevant to the proposed departure. The benefits of the early resolution of safety issues would be lost if departures from the DCD were made that violated these resolutions without appropriate review.
The evaluation of the relevant matters needs to consider the proposed departure over the full range of power operation from startup to shutdown, as it relates to anticipated operational occurrences, transients, DBAs, and
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severe accidents. The evaluation must also include a review of all relevant secondary references from the DCD
because Tier 2 information, which is intended to be treated as a requirement, is contained in the secondary references. The evaluation should consider the tables in Sections 14.3 and 19.8 of the generic DCD to ensure that the proposed change does not impact Tier 1 information. These tables contain cross-references from the safety analyses in Tier 2 to the important parameters that were included in Tier 1.
Paragraph VIII.B.5.d addresses information described in the DCD to address aircraft impacts, under 52.47a28. Under 52.47a28, applicants are required to include the information required by 50.150b in their DCD. A COL applicant or licensee that departs from this information is required to consider the effect of the changed design feature or functional capability on the original aircraft impact assessment required by 50.150a. The applicant or licensee is also required to describe in the plant-specific DCD how the modified design features and functional capabilities continue to meet the assessment requirements in 50.150a1. Submittal of this updated information is governed by the reporting requirements in paragraph X.B.
During an ongoing adjudicatory proceeding e.g., for issuance of a COL
a party who believes that an applicant or licensee has not complied with paragraph VIII.B.5 when departing from Tier 2 information may petition to admit such a contention into the proceeding under paragraph VIII.B.5.g. As set forth in paragraph VIII.B.5.g, the petition would have to comply with the requirements of 2.309, Hearing requests, petitions to intervene, requirements for standing, and contentions, and show that the departure does not comply with paragraph VIII.B.5. If on the basis of the petition and any responses thereto, the presiding officer in the proceeding determines that the required showing has been made, the matter would be certified to the Commission for its final determination. In the absence of a proceeding, assertions of noncompliance with paragraph VIII.B.5
requirements applicable to Tier 2
departures would be treated as petitions for enforcement action under 2.206, Requests for action under this subpart.
Paragraph VIII.B.6 provides a process for departing from Tier 2 information.
The creation of and restrictions on changing Tier 2 information resulted from the development of the Tier 1
information for the Advanced Boiling
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