SUPPLEMENTARY INFORMATION:

I. Discussion

The NRC is issuing a revision in the NRC's “Regulatory Guide” series. This series was developed to describe methods that are acceptable to the NRC staff for implementing specific parts of the agency's regulations, to explain techniques that the staff uses in evaluating specific issues or postulated events, and to describe information that the staff needs in its review of applications for permits and licenses.

The proposed Revision 1 to RG 1.183 was issued with a temporary identification of Draft Regulatory Guide, DG-1389. (ADAMS Accession No. ML21204A065).

This revision of the guide (Revision 1) addresses new issues identified since the guide was originally issued. These include (1) using the term maximum hypothetical accident loss-of-coolant accident (LOCA) to clarify the accident that the staff finds acceptable to use to meet the description in the applicable regulations, identified in Section A of RG 1.183, Revision 1, with a clear delineation between source term assumptions and plant response; (2) adding transient release fractions from empirical data from in-pile, prompt power pulse test programs and analyses from several international publications of fuel rod performance under prompt power excursion conditions; (3) revising steady-state release fractions for accidents other than the LOCA based on a revision to the American National Standards Institute/American Nuclear Society Standard 5.4, “Method for Calculating the Fractional Release of Volatile Fission Products from Oxide Fuel”; (4) adding information to acknowledge that the RG may provide useful information for satisfying the radiological dose analysis requirements in parts 50 and 52 of title 10 of the Code of Federal Regulations (10 CFR), for new LWR applicants, including advanced evolutionary and passive LWR design and siting; (5) providing additional guidance for modeling boiling-water reactor main steam isolation valve leakage; (6) adding guidance for accident tolerant fuel, high-burnup fuel, and increased enrichment source term analyses; (7) revising transport and decontamination models for the fuel handling design basis accident; (8) adding guidance for crediting hold-up and retention of main steam isolation valve leakage within the main steamlines and condenser for boiling-water reactors; and (9) providing additional guidance on meteorological assumptions.

II. Additional Information

The NRC published a notice of the availability of DG-1389 in the Federal Register on April 21, 2022 (87 FR 23891) for a 60-day public comment period. The public comment period closed on June 21, 2022. Public comments on DG-1389 and the staff responses to the public comments are available under ADAMS under Accession No. ML23082A309.

In the notice of availability for DG-1389, Section IV, “Specific Request for Comment,” the NRC sought specific comments on the draft staff technical assessment titled, “Technical Assessment of Hold-up and Retention of Main Steam Isolation Valve Leakage within the Main Steam Lines and Main Condenser” (ADAMS Accession No. ML20085J042); the NRC staff did not receive any public comments on the draft staff technical assessment. At this time, the staff has determined to incorporate the supporting technical basis information from that draft staff technical assessment into RG 1.183, Revision 1, Appendix A, Section A-5.5, rather than finalizing the draft staff technical assessment separately for inclusion in this RG. Accordingly, the reference to the draft staff technical assessment was deleted from the final RG.

As noted in the Federal Register on December 9, 2022 (87 FR 75671), this document is being published in the “Rules” section of the Federal Register to comply with publication requirements under 1 CFR chapter I.

III. Congressional Review Act

This RG is a rule as defined in the Congressional Review Act (5 U.S.C. 801-808). However, the Office of Management and Budget has not found it to be a major rule as defined in the Congressional Review Act.

IV. Backfitting, Forward Fitting, and Issue Finality

Issuance of RG 1.183, Revision 1, does not constitute backfitting as defined in 10 CFR 50.109, “Backfitting,” and as described in NRC Management Directive (MD) 8.4, “Management of Backfitting, Forward Fitting, Issue Finality, and Information Requests” (ADAMS Accession No. ML18093B087); affect the issue finality of an approval under 10 CFR part 52; or constitute forward fitting as defined and described in MD 8.4 because, as explained in RG 1.183, Revision 1, applicants and licensees are not required to comply with the positions set forth in this RG.

V. Submitting Suggestions for Improvement of Regulatory Guides

A member of the public may, at any time, submit suggestions to the NRC for improvement of existing RGs or for the development of new RGs. Suggestions can be submitted on the NRC's public website at https://www.nrc.gov/​reading-rm/​doc-collections/​reg-guides/​contactus.html. Suggestions will be considered in future updates and enhancements to the “Regulatory Guide” series.

88 FR 71277