05-2853. Draft Regulatory Guide; Issuance, Availability

The U.S. Nuclear Regulatory Commission (NRC) has issued for public comment a draft revision to an existing guide in the agency's Regulatory Guide Series. This series has been developed to describe and make available to the public such information as methods that are acceptable to the NRC staff for implementing specific parts of the NRC's regulations, techniques that the staff uses in evaluating specific problems or postulated accidents, and data that the staff needs in its review of applications for permits and licenses.

The draft Revision 2 of Regulatory Guide 1.92, entitled “Combining Modal Responses and Spatial Components in Seismic Response Analysis,” is temporarily identified by its task number, DG-1127, which should be mentioned in all related correspondence. Like its predecessors, the proposed revision describes methods that the NRC staff finds acceptable for complying with the NRC's regulatory requirements in Criterion 2, “Design Bases for Protection Against Natural Phenomena,” as it appears in Appendix A, “General Design Criteria for Nuclear Power Plants,” to Title 10, Part 50, of the Code of Federal Regulations (10 CFR Part 50). Specifically, Criterion 2 requires, in part, that nuclear power plant (NPP) structures, systems, and components (SSCs) that are important to safety must be designed to withstand the effects of natural phenomena (such as earthquakes) without losing their capability to perform their respective safety functions.

For several decades, the nuclear industry fulfilled Criterion 2 using the response spectrum method and the time history method for seismic analysis and design of NPP SSCs. Then, in 1976, the NRC issued Revision 1 of Regulatory Guide 1.92, which described then-up-to-date guidance for using the response spectrum and time history methods. Since that time, research in the United States has resulted in improved methods that yield more accurate estimates of SSC seismic response, while reducing unnecessary conservatism. In view of those improvements, DG-1127 describes methods that the NRC staff finds acceptable for combining modal responses and spatial components in seismic response analysis. The NRC staff initially published Revision 2 of Regulatory Guide 1.92 as DG-1108, dated August 2001. The staff subsequently considered stakeholders' feedback on DG-1108, and incorporated the necessary changes in DG-1127.

The NRC staff is soliciting comments on Draft Regulatory Guide DG-1127, and specifically on the new regulatory position regarding residual rigid response of the missing mass modes, as described in Sections 1.4 and 1.5 of DG-1127. Comments may be accompanied by relevant information or supporting data. Please mention DG-1127 in the subject line of your comments. Comments on this draft regulatory guide submitted in writing or in electronic form will be made available to the public in their entirety in the NRC's Agencywide Documents Access and Management System (ADAMS). Personal information will not be removed from your comments. You may submit comments by any of the following methods.

Mail comments to: Rules and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.

E-mail comments to: [e-mail]. You may also submit comments via the NRC's rulemaking Web site at http://ruleforum.llnl.gov. Address questions about our rulemaking Web site to Carol A. Gallagher [phone]; e-mail [e-mail].

Hand-deliver comments to: Rules and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission, 11555 Rockville Pike, Rockville, Maryland 20852, between 7:30 a.m. and 4:15 p.m. on Federal workdays.

Fax comments to: Rules and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission at [phone].

Requests for technical information about draft regulatory guide DG-1127 may be directed to Dr. T.Y. Chang, at [phone] or via e-mail to [e-mail].

Comments would be most helpful if received by April 15, 2005. Comments received after this date will be considered if it is practical to do so, but the NRC is able to ensure consideration only for comments received on or before this date. Although a time limit is given, comments and suggestions in connection with items for inclusion in guides currently being developed or improvements in all published guides are encouraged at any time.

Electronic copies of the draft regulatory guide are available through the NRC's public Web site under Draft Regulatory Guides in the Regulatory Guides document collection of the NRC's Electronic Reading Room at http://www.nrc.gov/​reading-rm/​doc-collections/​. Electronic copies are also available in the NRC's Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/​reading-rm/​adams.html, under Accession #ML050230006. Note, however, that the NRC has temporarily suspended public access to ADAMS so that the agency can complete security reviews of publicly available documents and remove potentially sensitive information. Please check the NRC's Web site for updates concerning the resumption of public access to ADAMS.

In addition, regulatory guides are available for inspection at the NRC's Public Document Room (PDR), which is located at 11555 Rockville Pike, Rockville, Maryland; the PDR's mailing address is USNRC PDR, Washington, DC 20555-0001. The PDR can also be reached by telephone at [phone] or [phone], by fax at [phone]; and by e-mail to [e-mail]. Requests for single copies of draft or final guides (which may be reproduced) or for placement on an automatic distribution list for single copies of future draft guides in specific divisions should be made in writing to the U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, Attention: Reproduction and Distribution Services Section; by e-mail to [e-mail]; or by fax to [phone]. Telephone requests cannot be accommodated.

Regulatory guides are not copyrighted, and Commission approval is not required to reproduce them.

(5 U.S.C. 552(a)).

Dated at Rockville, Maryland, this 3rd day of February, 2005.

For the U.S. Nuclear Regulatory Commission.

Michael E. Mayfield,

Director, Division of Engineering Technology, Office of Nuclear Regulatory Research.