Information Notice No. 87-28: Air Systems Problems at U.S. Light Water Reactors
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
June 22, 1987
Information Notice No. 87-28: AIR SYSTEMS PROBLEMS AT U.S. LIGHT
All nuclear power reactor facilities holding an operating license or a con-
This information notice is being provided to alert recipients to potentially
significant problems pertaining to air systems at light water reactors. The
NRC expects that recipients will review this notice for applicability to their
facilities. The suggestions in this notice do not constitute NRC
requirements; therefore, no specific action or written response is required.
The NRC Office for Analysis and Evaluation of Operational Data (AEOD) has
recently issued a case study report entitled "Air Systems Problems at U.S.
Light Water Reactors," AEOD/C701.* The report discusses degradations of air
systems and plant responses to air systems losses. It also highlights more
than two dozen events in which, contrary to licensing assumptions, a safety-
related system failed as a result of an air system degradation or failure.
Operating events involving the loss or degradation of air systems were judged
to be safety significant because they may lead, under different circumstances,
to potentially serious events and conditions that have not been analyzed.
The study provides a comprehensive review and evaluation of potential safety
implications associated with air systems problems. The report analyzes oper-
ating data, focusing on degraded air systems, and the vulnerability of safety-
related equipment to common mode failures associated with air systems. The
report analyzes these data from the perspectives of trends and patterns, risk
assessments, and cost/benefit studies.
*A copy of the study report is available in the NRC Public Document Room,
1717 H Street NW, Washington, DC 20555, for inspection and copying.
June 22, 1987
Page 2 of 2
Air systems are not classified as safety-related systems at most operating
plants. As a result, plant accident analyses assume that safety-related
equipment dependent on air systems will either "fail safe" on loss of air or
perform its intended function with the assistance of safety-related backup air
accumulators. This report highlights 29 failures of safety-related systems
that resulted from degraded or malfunctioning air systems. These failures
contradict the assumption that safety-related equipment dependent on air
systems will always either fail safe on loss of air or perform its intended
function with the assistance of backup accumulators. Some of the systems that
were significantly degraded or failed were decay heat removal, auxiliary
feedwater, BWR scram, main steam isolation, salt water cooling, emergency
diesel generator, containment isolation, and the fuel pool seal systems. For
1. Leakage of 140,000 gallons of radioactive water from the spent fuel pool
at the Hatch Nuclear Plant on December 3, 1986, was caused by the
mispositioning of a single valve in the instrument air system.
2. Failure of several main steam isolation valves to close at Brunswick 2 on
September 27, 1985, was due to contaminants in the instrument air.
3. A loss of the auxiliary feedwater systems at Turkey Point 3 and 4 in July
1985 was caused by water and dirt particles in the air system.
4. The inability to scram four control rods at Susquehanna 1 on October 6,
1984, was caused by oil in the air system.
5. A loss of decay heat removal and significant primary system heatup at
Palisades in 1978 and 1981 were caused by water in the air system.
The root causes of most of the failures were traceable to design and/or
maintenance deficiencies. The design and operating problems appear to reflect
a lack of adequate attention to the design, maintenance, operation, and
administrative control of air systems.
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.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: C. Vernon Hodge, NRR
Hal Ornstein, AEOD
Attachment: List of Recently Issued NRC Information Notices
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