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
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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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