Information Notice No.79-08 – Interconnection of Contaminated Systems with Service Air Systems Used as the Source of Breathing Air

                                 UNITED STATES
                         NUCLEAR REGULATORY COMMISSION
                            WASHINGTON, D. C. 20555

                                              Information Notice No. 79-08 
                                              Date: March 28, 1979         
                                              Page 1 of 2


Description of Circumstances:

This Information Notice describes an event which occurred at the Peach Bottom 
Nuclear Power Station; however. the generic implications may be applicable
to  other power reactors and selected fuel cycle facilities.

On October 4, 1978, the Philadelphia Electric Company (PECO) reported that,
on  two occasions at Unit 2, contamination had leaked from the radwaste
system to  a system used to provide the plant source of breathing air. The
leakage  occurred through an interconnection of the radwaste system with the
plant  breathing air source. PECO established that no personnel were
subjected to  contaminated breathing air as a result of this leakage.

One of the functions of the service air system at Peach Bottom is to provide
a  source of breathing air for personnel using supplied air respiratory 
protective equipment. By means of an interconnection to the radwaste system, 
the facility also uses the service air system to provide a source of 
compressed air during the backwash cycle of the demineralizer filter element. 
The compressed air provides the motive force for reverse water flow through 
the filter element and was being used to perform this function when the two 
incidents occurred. Liquid from the radwaste system leaked past a check valve 
and a process valve.  PECO determined by analysis of liquid samples that 
contamination had leaked into the service air system. Valves in the leakage 
path were subsequently dismantled and examined. The examinations revealed the 
presence of dirt deposits in the check valve and air operated ball valve.
PECO  attributes the specific cause of the leakage to these dirt deposits
which  prevented the proper seating of the valves.

NRC contacts with other operating power reactors have indicated that other 
facilities also use service air as a source of breathing air. In several 
cases, the service air system is physically interconnected to other systems 
which carry radioactive material and relies on valves or other barriers to 
prevent contamination of the plant source of breathing air.


                                              Information Notice No. 79-08
                                              Date: March 28, 1979         
                                              Page 2 of 2

NUREG-0041, "Manual of Respiratory Protection Against Airborne Radioactive 
Materials," which supplements the stipulations of Regulatory Guide 8.15, 
states in Section 9.8, "A separate breathing air supply and distribution 
system shall be used. The ordinary plant supply of compressed air in any 
building shall not be used for breathing purposes . . . unless it has been 
specifically modified and properly adapted for such use and specifically 
approved for this purpose by the qualified person supervising the respiratory 
protective equipment program."

At those facilities where service air is used as a source of breathing air, 
certain precautions can be taken to minimize the potential of a problem 
similar to the one described. By review of the service air system and as-
built  or design drawings, interconnections between contaminated systems and
the  source of breathing air can be identified.  Where interconnections are 
identified, the design should assure that adequate separation is provided.
In  addition, operating procedures should provide for controls to prevent 
contamination of the breathing air source.

No specific action or written response to this Information Notice is
required.  If you desire additional information regarding this matter,
contact the  Director of the appropriate NRC Regional Office.


Page Last Reviewed/Updated Thursday, March 25, 2021