ML20209A986

Submits Case Study Rept, Air Sys Problems at Us Lwrs. Rept Presents Five Recommendations Which Would Reduce Reactor Accident Risks by Reducing Likelihood of Common Mode Failure of Safety Sys.W/O Stated Encls

ML20209A986
Person / Time
Issue date:	03/31/1987
From:	Heltemes C NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	Harold Denton Office of Nuclear Reactor Regulation
References
AEOD-C701, NUDOCS 8704280332
Download: ML20209A986 (4)

Text

~AE0D/C701 MEMORANDUM FOR: Harold R. Denton, Director Office of Nuclear Reactor Regulation FROM:

C. J. Heltemes, Jr., Director Office for Analysis and Evaluation of Operational Data

SUBJECT:

CASE STUDY REP 0PT -- AIR SYSTEMS PROBLEMS AT U.S. LIGHT WATER REACTORS Following resolution of peer review coments, we have completed the enclosed case study report on air systems problems at U.S. light water reactors. A copy of the report is enclosed for your information and action, as appropriate.

The study analyzes and evaluates the operational experience related to, and the safety implications associated with failures and degradations of air systems at U.S. LWRs.

The report presents aspects of air systems degradations and plant responses to air systems losses which are not addressed in previous studies.

It also highlights more than two dozen events in which, contrary to licensing assumptions, a safety-related system failed due to an air system degradation or failure. Operating events involving the loss or degradation cf air systems were judged to be safety significant because they may lead, under different circumstances, to potentially serious events and conditions which have not been analyzed in the FSARs.

The report presents five recommendations which, if implemented, would reduce reactor accident risks by reducing the likelihood for common mode failure of safety systems and by enhancing plant recovery from anticipated and unanticipated transients. The recommendations in the study address:

(1) ensuring that air system quality meets the requirements specified by the manufacturers of the plants' air-operated equipment; (2) ensuring adequate operator response by formulating and implementing anticipated transient and system recovery procedures for loss-of-air events; (3) impro'/ing training to ensure that plant operations and maintenance personnel are sensitized to the importance of air systems and the vulnerability of safety-related equipment served by the air systems to common mode failures; (4) confirming the adequacy and reliability of safety-related backup accumulators; and (5) verifying equipment response to gradual losses of air to ensure that such losses do not result in events which fall outside FSAR analyses.

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Harold R. Denton If you have any questions regarding this study, please feel free to contact me or Dr. Hal Ornstein at 492-4439 tigem seusap C. J. Hemunes,&

C. J. Heltemes, Jr., Director Office for Analysis and Evaluation of Operational Data

Enclosure:

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Multiple Addressees 2-The report presents five recommendations which, if implemented, would reduce reactor accident risks by reducing the likelihood for common mode failure of safety systems and by enhancing plant recovery from anticipated and unanticipated transients. The recommendations in the study address:

f (1) ensuring that air system quality meets the r manufacturers of the plants' air-operated equi,equirements specified by the ent; (2) ensuring adequate operator response by formulating and impleme ing anticipated transient.and i

system recovery procedures for loss-of-air ents; (3) improving training to ensure.that plant operations and maintenan e personnel are sensitized to the.

importance of air systems and the vulner ility of safety-related equipment served by the air systems to common ro failures; (4) confirming the adequacy and reliability of safety-related bac p accumulators; and (5) ~ verifying equipment response to gradual losse of air to ensure that such. losses do not result in events which fall outsi FSAR analyses.

If you have any questions regap ing this study, please feel free to contact me or Dr. Hal Ornstein at 492-44 9 4

1 C. J. Heltemes, Jr., Director

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