# Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release
**AGENCY:**
Nuclear Regulatory Commission.
**ACTION:**
Regulatory guide; issuance.
**SUMMARY:**
The U.S. Nuclear Regulatory Commission (NRC) is issuing Revision 2 to Regulatory Guide (RG), 1.78, “Evaluating the Habitability of a Nuclear Power Plant Control Room during a Postulated Hazardous Chemical Release.” The revision of RG 1.78 describes an approach that is acceptable to the NRC staff to meet regulatory requirements for evaluating the habitability of a nuclear power plant control room during a postulated hazardous chemical release. Releases of hazardous chemicals, onsite and off-site, can result in the nearby control room becoming uninhabitable.
**DATES:**
Revision 2 to RG 1.78 is available on December 22, 2021.
**ADDRESSES:**
Please refer to Docket ID NRC-2021-0141 when contacting the NRC about the availability of information regarding this document. You may obtain publicly available information related to this document using any of the following methods:
• *Federal Rulemaking Website:* Go to *https://www.regulations.gov* and search for Docket ID NRC-2021-0141. Address questions about Docket IDs in *Regulations.gov* to Stacy Schumann; telephone: 301-415-0624; email: *[email protected].* For technical questions, contact the individuals listed in the *FOR FURTHER INFORMATION CONTACT* section of this document.
• *NRC's Agencywide Documents Access and Management System (ADAMS):* You may obtain publicly available documents online in the ADAMS Public Documents collection at *https://www.nrc.gov/reading-rm/adams.html.* To begin the search, select “Begin Web-based ADAMS Search.” For problems with ADAMS, please contact the NRC's Public Document Room (PDR) reference staff at 1-800-397-4209, 301-415-4737, or by email to *[email protected].* The ADAMS accession number for each document referenced (if it is available in ADAMS) is provided the first time that it is mentioned in this document.
• *NRC's PDR:* You may examine and purchase copies of public documents, by appointment, at the PDR, Room P1 B35, One White Flint North, 11555 Rockville Pike, Rockville, Maryland 20852. To make an appointment to visit the PDR, please send an email to *[email protected]* or call 1-800-397-4209 or 301-415-4737, between 8:00 a.m. and 4:00 p.m. (ET), Monday through Friday, except Federal holidays.
Revision 2 to RG 1.78 and the regulatory analysis may be found in ADAMS under Accession Nos. ML21253A071 and ML21119A159, respectively.
Regulatory guides are not copyrighted, and NRC approval is not required to reproduce them.
**FOR FURTHER INFORMATION CONTACT:**
Casper Sun, telephone: 301-415-1646, email: *[email protected]* and Michael Eudy, telephone: 301-415-3104, email: *[email protected].* Both are staff members of the Office of Nuclear Regulatory Research at the U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.
**SUPPLEMENTARY INFORMATION:**
**I. Discussion**
The NRC is issuing a revision in the NRC's “Regulatory Guide” series. This series was developed to describe and make available to the public information regarding methods that are acceptable to the NRC staff for implementing specific parts of the agency's regulations, techniques that the NRC staff uses in evaluating specific issues or postulated events, and data that the NRC staff needs in its review of applications for permits and licenses.
Revision 2 of RG 1.78 was issued with a temporary identification of Draft Regulatory Guide, DG-1387.
**II. Additional Information**
The NRC published a notice of the availability of DG-1387 in the *Federal Register* on July 28, 2021 (86 FR 40661) for a 30-day public comment period. The public comment period closed on August 27, 2021. Public comments on DG-1387 and the staff responses to the public comments are available in ADAMS under Accession No. ML21253A074.
**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**
Revision 2 of RG 1.78 does not constitute backfitting as defined in section 50.109 of title 10 of the *Code of Federal Regulations* (10 CFR), “Backfitting,” and as described in NRC Management Directive (MD) 8.4, “Management of Backfitting, Forward Fitting, Issue Finality, and Information Requests”; constitute forward fitting as that term is defined and described in MD 8.4; or affect the issue finality of any approval issued under 10 CFR part 52. As explained in Revision 2 of RG 1.78, applicants and licensees would not be required to comply with the positions set forth in the RG.
For the Nuclear Regulatory Commission.
Dated: December 15, 2021.
Meraj Rahimi,
Chief, Regulatory Guide and Programs Management Branch, Division of Engineering, Office of Nuclear Regulatory Research.