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Control Room Habitability

On this page:

• Requirements
• History of Concerns
• Resolution Guidance
• Testing
• List of Guidance
• Public Meetings

Requirements

The required aspects of a control room for nuclear power reactors are established by General Design Criterion (GDC-19), "Control Room," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50.

History of Concerns

Since around 1980, the NRC staff and industry have been working on concerns with control room habitability. Control room habitability is the required capability of the control room to be safe for humans to remain there and work during both normal operations and accident conditions. This capability includes protection from the effects of radiation, hazardous chemicals, fire and smoke, as well as having breathable air, heating and cooling, and other facilities for human comfort. In its review of license amendment submittals over the past several years, the staff has identified numerous problems associated with the assessment of control room habitability. These problems have included the overall soundness of the control room envelope (the plant area that includes the main control room and other rooms and areas to which the operators must go to control the plant during an accident) and the manner in which licensees have demonstrated the ability of their control room designs to meet GDC-19.

For explanatory information, see the Glossary and List of Guidance.

Resolution Guidance

Since 1998, the staff has been working with industry through the Nuclear Energy Institute (NEI) and the Nuclear Heating, Ventilation, and Air Conditioning Users Group to develop guidance to address control room habitability. Also, during this time, industry and NEI have developed an industry guidance document NEI 99-03 , "Control Room Habitability Assessment Guidance," which was issued in June 2001. Although the staff agreed in concept with NEI 99-03, because of several policy and technical issues, such as frequency and method of testing, it could not endorse it fully. So, from December 2001 through March 2002, the staff issued four publicly available draft regulatory guides for comment. The public comment period for all four draft guides extended through September 2002. In May and June 2003, the final regulatory guides were issued to provide guidance on control room envelope habitability (RG 1.196), integrity testing (RG 1.197), atmospheric dispersion (RG 1.194), and radiological dose assessment with the traditional source term (RG 1.195). Also, two other regulatory guides offer guidance on control room habitability assessment: RG 1.183 on radiological dose assessment with an alternative source term and RG 1.78 on control room habitability during a hazardous chemical release.

The staff also developed a proposed generic letter on control room habitability, which was available to the public for comment from May through September 2002. The final version of the generic letter, GL 2003-01, "Control Room Habitability," was issued on June 12, 2003. This generic letter requests that licensees provide confirmation that their facility's control room meets the applicable regulatory requirements and that control room habitability systems are designed, constructed, configured, operated, and maintained according to the facility's design and licensing bases.

As a result of five workshops that took place in the summer of 2002, NEI issued Revision 1 to NEI 99-03 in March 2003. The newly issued NRC regulatory guides make reference to NEI 99-03, Rev. 0.

See List of Guidance and Guidance Development.

Testing

Since 1992, licensees for about 30 percent of the U.S. commercial power reactor control rooms have tested their control rooms to determine how much unfiltered air is leaking in. This air may be contaminated with radioactive materials or toxic gases. These licensees used methods from industrial standard ASTM E741, "Standard Test Methods for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution." Of this 30 percent sample, all except one of the control rooms tested did not meet the unfiltered air leakage limit that the plant was designed to meet. However licensees repaired, retested, and reanalyzed or took temporary compensatory measures to meet their radiological design basis.

List of Guidance

• GL 2003-01, Control Room Habitability
• RG 1.194, Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants
• RG 1.195, Methods and Assumptions for Evaluating Radiological Consequences of Design Basis Accidents at Light-Water Nuclear Power Reactors
• RG 1.196, Control Room Habitability at Light-Water Nuclear Power Reactors
• RG 1.197, Demonstrating Control Room Envelope Integrity at Nuclear Power Reactors
• RG 1.183, Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors
• RG 1.78, Evaluating the Habitability of a Nuclear Power Plant Control Room During a Postulated Hazardous Chemical Release
  

Public Meetings

The following is a list, in chronological order, of the slides and summaries documenting the public meetings held concerning the Proposed Generic Letter and Draft Guidance on Control Room Habitability.

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Monday, October 15, 2007