United States Nuclear Regulatory Commission - Protecting People and the Environment

Recombiner Capability Requirements of 10 CFR 50.44 (c)(3)(ii) (Generic Letter No. 84-09)

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                                May 8, 1984 



          (GENERIC LETTER NO. 84-09)  

On December 2, 1981, the NRC amended SS50.44 of its regulations by addition 
of the provisions in SS50.44(c)(3). One of these provisions requires 
licensees of those light water reactors (both BWRs and PWRs) that rely upon 
purge/repressurization systems as the primary means of hydrogen control to 
provide a recombiner capability by the end of the first scheduled outage 
after July 5, 1982, of sufficient duration to permit the required 
modifications. Those plants for which notices of hearing on applications for
construction permits were published on or after November 5, 1970 are rot 
permitted by 10 CFR 50.44(e) to rely on purge/repressurization systems as 
the primary means for hydrogen control. Therefore, these plants are not 
affected by the requirement for recombiner capability; the licensees of 
these plants are being furnished a copy of this generic letter for 
information only. 

After adoption of the ar.ended rule, and as a result of the new inerting 
requirement in SS50.44(c)(3), the BWR Mark I Owners Group (incorporating 
studies performed by Northeast Nuclear Energy Company) undertook a 
substantial program to demonstrate that the Mark I plants potentially 
affected by the recombiner capability requirements of the rule do not need 
to rely on use of the safety grade purge/repressurization system required by 
the original 10 CFR 50.44 rule as the primary means of hydrogen control. 
Extensive review and independent studies by the NRC staff supported the 
findings of the Mark I Owners Group program. (This letter does not address 
PWRs because the inerting requirement of SS50.44(c)(3) does not apply to 
PWRs and, therefore, the licensees of PWRs are not likely to be able to make 
a comparable demonstration.) 

The Commission has determined that a Mark I BWR plant will be found to not 
rely upon purge/repressurization systems as the primary means of hydrogen 
control if certain technical criteria are satisfied. To avoid any 
misunderstanding, we wish to make clear that a plant that has a "safety 
grade" purge/repressurization system designed to conform with the general 
requirements of Criteria 41, 42 and 43 of Appendix A of 10 CFR Part 50 and 
installed in accordance with SS50.44(f) or SS50.44(g) must continue to have 
that system, even though it may be determined with respect to ss50.44(c)(3) 
that the plant does not rely on that system as the primary means for 
hydrogen control; thus, a decision on recombiner capability does not affect 
the requirements of SS50.44(f) and SS50.44(g) for the "safety grade" purge/ 
repressurization system. 

                                    - 2 - 

For those inerted Mark I BWR containments (for which notices on the 
construction permits were published before November 5, 1970) that do not 
rely upon safety grade purge/repressurization systems as the primary means 
of hydrogen control, the Commission determination, cited above, is 
applicable Provided the following criteria are met: 

1)   The plant has technical specifications (limiting conditions for 
     operation) requiring that. when the containment is required to be 
     inerted the containment atmosphere be less than four percent oxygen, 

2)   The plant has only nitrogen or recycled containment atmosphere for use 
     in all pneumatic control systems within containment, and 

3)   There are no potential sources of oxygen in containment other than that
     resulting from radiolysis of the reactor coolant. Consideration of po-
     tential sources of inleakage of air and oxygen into containment should 
     include consideration of not only normal plant operating conditions but
     also postulated loss-of-coolant-accident conditions. These potential 
     sources of inleakage should include instrument air systems, service air
     systems. MSIV leakage control systems purge lines, penetrations 
     pressurized with air &nd inflatable door seals. 

Accordingly, any Mark I BWR owner which has concluded that a recombiner 
capability is not required for its facility is requested to submit a 
response to this letter within 45 days. Each submittal should indicate the 
applicability of the generic studies submitted by the Mark I Owners Group to
the licensee's facility and include additional information relative to the 
three criteria cited above to enable the staff to make a comparable 

This request for information was approved by the Office of Management and 
Budget under clearance number 3150-0011 which expires April 30, 1985. 
Comments on burden and duplication my be directed to the Office of 
Management and Budget, Reports Management Room 3208, New Executive Office 
Building, Washington, D. C. 20503. 


                                   Darrell G. Eisenhut, Director 
                                   Division of Licensing 
                                   Office of Nuclear Reactor Regulation 
Page Last Reviewed/Updated Friday, May 22, 2015