United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-06: Contamination of Breathing Air Systems

                                                    SSINS No.: 6835 
                                                         IN 85-06       

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555

                              January 23, 1985

Information Notice No. 85-06:   CONTAMINATION OF BREATHING AIR SYSTEMS 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or 
construction permit (CP). 

Purpose: 

This information notice is provided to alert licensees to two events 
resulting in the radioactive contamination of compressed air systems used to
supply breathing air to respirator users at nuclear power plants. It 
supplements information previously provided in Information Notice 79-08 
which discussed similar events. Licensee corrective actions and lessons 
learned from the two relatively recent events and other previously 
documented occurrences are discussed. It is expected that recipients will 
review this information for applicability to their facilities and consider 
actions, if appropriate, to preclude similar problems occurring at their 
facilities. However, suggestions contained in this notice do not constitute 
NRC requirements; therefore, no specific action or written response is 
required. 

Description of Circumstances: 

Event 1 

During September 1984, portions of the Browns Ferry service air system (SAS)
were contaminated with gaseous radioactivity directly from the station's 
augmented offgas system (AOG). The SAS and AOG were cross-connected via a 
rubber hose (with a single check-valve). Air from the SAS was being supplied
to remove moisture from the AOG hydrogen analyzer sample line downstream of 
the AOG hydrogen/oxygen recombiner. Evidently this was a routine maintenance
activity. When the SAS on-line and backup air compressors failed and the air
receivers bled down, freshly produced radioactive offgas entered the service
air through the temporary hose connection. This condition existed for 
approximately 2 1/2 hours; fortunately, no one used the system as a 
breathing air supply during this period. 

Plant personnel became aware of the problem after the air compressors were 
once again operable. Apparently the offgas in a portion of the SAS line near
an area radiation monitor (ARFI) was compressed and caused the ARM to alarm 
(10mR/hr alarm set point). Only short-lived noble gases and their daughter 



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                                                          IN 85-06        
                                                          January 23, 1985 
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products were found in the SAS, and no explosive or flammability problems 
were reported. Along with tightened administrative controls, double 
check-valve backflow protection is now required when cross-connecting to the
SAS. 

Event 2 

On July 19, 1983, workmen while cutting up spent fuel racks inside a 
tent-containment structure at H.B. Robinson were wearing air-line 
respirators fed by the plant's instrument air system (IAS). While attempting 
to connect the air manifold assembly to a different IAS supply point before 
putting on their respirators, two workers were exposed to dust and rust 
particles from the initial air surge. When "frisked," the two workers found 
themselves contaminated. Air sampled from the contaminated air line 
contained about 6.6E-8 Ci/cc (corresponding to an MPC fraction of 14.1). 
On the basis of these air samples and the whole-body counting, the workers 
involved were assigned radioactive intakes of less than 40 MPC-hrs. 

The licensee investigated the incident, sampled other portions of the IAS, 
and found no other radioactive contamination problems. The source of the IAS
contamination could not be definitely determined. Therefore, as part of the 
corrective actions taken, the licensee now samples and analyzes for 
radioactivity at each air supply connection point before the breathing air 
is used. 

Discussion 

The NRC staff is aware of other instances where installed service air 
systems used to provide personnel breathing air have been contaminated (see 
Attachment 1 for references). On the basis of a review of licensees' 
corrective actions and discussions with the licensees' operating staff, the 
lessons learned from the referenced events are summarized as follows: 

1.   Radiological air sampling before use can help prevent inadvertent 
     intakes of radioactivity when infrequently-used portions of 
     service/instrument air systems are used as breathing air sources. This 
     precautionary radiological sampling of the air system would complement 
     the periodic radiological sampling and industrial hygiene sampling 
     necessary to ensure continued Grade D quality (or better) for supplied 
     air as required by 30 CFR 11 and 10 CFR 20. 

2.   Operating procedures can provide for effective administrative controls 
     and establish physical separation criteria to prevent 
     cross-contamination when air systems are temporarily connected to 
     contaminated systems. To minimize the potential for 
     cross-contamination, some licensees use intermediate air motors (driven 
     by service air) to directly supply air to a contaminated system. This 
     approach is applicable only when the air supply loads are low enough to 
     be supplied by the air motors. 

3.   There is that potential for "an unreviewed safety question" situation 
     when system operations are changed from what is described in the Safety
     Analysis Report, such as cross-connecting contaminated and 
     noncontaminated systems. IE Circular No. 80-18, "10 CFR 50.59 Safety 
     Evaluations for
.

                                                          IN 85-06        
                                                          January 23, 1985 
                                                          Page 3 of 3     

     Changes to Radioactive Waste Treatment Systems" discusses general 
     principles and philosophy of the 10 CFR 50.59 safety evaluation 
     guidance and provides insight as to when safety evaluations are 
     necessary to ensure that changes to SAR-described systems are properly 
     evaluated. 

4.   For permanent, as-designed interconnections between installed 
     compressed air systems and contaminated systems, periodic function 
     checks and maintenance of the system separation protection features 
     (e.g., check valves and air operated ball valves) can help ensure 
     continued integrity of the separation. 

5.   Procedures governing the startup, operation, and maintenance of 
     "add-on" air handling equipment (e.g., pressure regulating/filtration 
     manifold) can ensure proper air purging (blowing down) to remove 
     contaminants such as dead-leg water and rust before the air is used for 
     breathing. 

While a separate breathing air supply and distribution system is the ideal 
source of worker-supplied air and this can be justified for plants at the 
design stage, the physical and economic constraints of installing a separate
breathing air system in an existing facility might be overly burdensome. 
Properly modified plant SASs and IASs, with attendant maintenance and 
sampling surveillance programs, can be adequate, reliable sources of 
breathing air for plant workers. 

No specific action or written response is required by this information 
notice. If you have any questions about this matter, please contact the 
Regional Administrator of the appropriate regional office or this office. 


                                   Edward L. Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  J. E. Wigginton, IE 
                    (301) 492-4967 

                    R. L. Pedersen, IE 
                    (301) 492-9425 

Attachments:
1.   References
2.   List of Recently Issued IE Information Notices
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