United States Nuclear Regulatory Commission - Protecting People and the Environment

Resolution of Generic Safety Issues: Item B-66: Control Room Infiltration Measurements ( NUREG-0933, Main Report with Supplements 1–34 )


The control room area ventilation systems and control building layout and structures are reviewed to assure that plant operators are adequately protected against the effects of accidental releases of toxic and radioactive gases and to assure that the control room can be maintained as the backup center from which technical center personnel can safely operate in the case of an accident. A key parameter affecting control room habitability under the conditions described in GDC-19 and SRP11 Section 6.4 is the magnitude of control room air infiltration rates. Current estimates of these rates are based on data relating to buildings that are substantially different than typical nuclear power plant control room buildings. Additional experimentally measured air exchange rates of operating reactor control rooms are needed to develop an improved data base. This NUREG-04713 task will facilitate compliance with the following staff requirements and guidance: (1) GDC-19 of Appendix A to 10 CFR Part 50,197 "Control Room," and (2) SRP11 Sections 6.4, "Control Room Habitability System," and 9.4.1, "Control Room Area Ventilation Systems."

Work performed by NRR, including experimental measurement of air exchange rates of selected operating reactor plant control rooms, resulted in revised review procedures and have been incorporated into Rev. 2 of SRP11 Section 6.4 (July 1981) and is being applied to plants under licensing review. The review of this issue with respect to operating plants is also being implemented in accordance with TMI Action Plan Item III.D.3.4, "Control Room Habitability Requirements," as required by NUREG-0737.98

On August 18, 1982, the ACRS issued a letter435 on control room habitability which presented recommendations for staff consideration. These recommendations that relate to control room infiltration aspects of control room habitability pertain primarily to achieving more effective implementation of existing criteria rather than to revising technical and design criteria. The staff response436 to the ACRS on January 31, 1983 did not recommend revising existing design criteria but made the following comments: (1) recommended increased training of NRC and licensee personnel on control room habitability systems inspection and test procedures, (2) stated that assistance has been requested from INPO on tests conducted by industry organizations on control room HVAC systems, and (3) provided results of an LER review of control room HVAC system surveillance testing over the past 5 years, which established a profile on component failure but did not reveal any total loss of control room habitability.


Based on the accomplishments above, this issue has been RESOLVED and is being implemented.

Page Last Reviewed/Updated Thursday, March 29, 2012