ML20136D895

Discusses Encl Rept on DHR Problems at Us Pwrs. Implementation of Rept Recommendations Should Improve DHR Sys Reliability & Availability.Recommendations Include Improving Human Factors by Upgrading Coordination.W/O Rept

ML20136D895
Person / Time
Issue date:	12/23/1985
From:	Heltemes C NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	Harold Denton Office of Nuclear Reactor Regulation
References
REF-GTECI-A-45, REF-GTECI-DC, TASK-A-45, TASK-OR NUDOCS 8601060315
Download: ML20136D895 (3)

Text

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1 $ NE MEMORANDUM FOR:. Harold R. Denton, Director 1

Office of Nuclear Reactor Regulation FROM:

C. J. Heltemes, Jr., Director Office for Analysis and Evaluation j

of Operational Data

SUBJECT:

CASE STUDY PEPORT -- DECAY HEAT REMOVAL PP0BLEMS AT U.S. PRESSURIZED WATER REACTORS Following resolution of peer review comments, we have' completed the enclosed case study report on decay heat renoval problems at U.S. pressurized water i

reactors. Between 1976 and 1983, 130 loss-of-DHR events were reported to have I

occurred during approximately 500 reactor years of operation. Total loss of the DHR systems under certain conditions could lead to core uncovery, and resultant fuel damage. The results of scoping analyses of total loss-of-DHR 4

j scenarios presented in the study indicate that for certain postulated events, unless timely corrective actions are taken, core uncovery could result on the 3

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order of one to three hours. To date, no serious damage has resulted from the loss-of-DHR system events that have occurred at U.S. PWRs. However, many of

'the events which have occurred thus far may serve as important precursors to 1

more serious events.

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AE00's analysis of operating data indicates that the underlying or root causes i

of most of the loss-of-DHP. system events are human factors deficiencies I

involving procedural inadequacies and personnel error. Most of the errors l

were committed during maintenance, testing and repair operations.

The leading category of loss-of-DHR events (37 of 130) was the automatic l

closure of the suction / isolation valves, most of which resulted from human errors.

The report makes several recommendations based upon the potential safety significance of loss-of-DHR events.

Implementation of those recommendations l

should significantly improve DHR system reliability and availability. The recommendations include:

improving human factors by upgrading coordination, planning, and administrative control of surveillance, maintenance, and testing oparations wh*ch are performed during shutdown; providing operator aids to t

assist in determining time available for DHR recovery and to assist operators in trending parameters during loss-of-DPR events; upgrading the training and qualification requirements for operations and maintenance staff; requiring the use of reliable, well-analyzed methods for measuring reactor' vessel level 1

during shutdown modes; modifying plant design to remove autoclosure interlocks

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1 and/or~ power to the DHR suction /. isolation valves during periods which do not require valve. motion; and clarifying plant technical specifications to elimi-nate ambiguities associated with operating mode definitions.

The report acknowledges NRC's ongoing efforts to address shutdown decay heat.

removel requirements (Unresolved Safety Issue A.45). The AE0D recommenda-tions are applicable to A-45, and should be considered in the resolution of this generic issue. AE0D will track these six recommendations in its recom-mendation tracking system.

If you have any questions regardino this study, please feel free to contact Dr. Hal Ornstein at 492 4439.

Originn1 r.ir,ned ty C. J. lioltcmon, Jr.

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

Enclosure:

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J. Taylor, IE/D T. Stetka, S.R.I., RII t

l R. Minogue, RES/D B. Jorgensen, S.R.I., RIII T. Murley, Regional Administrator, RI M. Holzmer, S.R.I., PIII J. Nelson Grace, Regional Administrator, RII W. Rogers, S.R.I., RIII J. Keppler, Regional Administrator, RIII W. Johnson, S.R.I., RIV R. Martin, Regional Administrator, Region IV M. Mendonca, S.R.I., RV J. Martin, Regional Administrator, Region V S. Richards, S.R.I., RV W. Dircks, EDO R. Birkel, NRR V. Stello, ED0/DED/ROGR A. DeAgazio, NRR J. Roe, ED0/A0 L. Engle, NRR T. Rehm. E00/A0 D. Fisher, NRR

.l J. Sniezek, E00/DED/ROGR D. Jaffe, NRR F. Gillespie, RES/D/DRA0 K. Jabbour, NRR R. Bernero, NRR/D/DSI R. Lee, NRR j

T. Speis, NRR/0/ DST E. McKenna, NRR r

i J. Knight NRR/AD/DE S. Miner, NRR W. Russell, NRR/AD/DHFS H. Nicolaris, NRR i

F. Rowsome, NRR/AD/ DST J. Norris, NRR l

G. Holahan, NRR/C/DL W. Paulson, NRR i

B. Boger, NRR/C/DHFS H. Schierling, NRR W. Minners, NRR/C/ DST' C. Tramell, NRR B. Sheron, NRR/C/DSI C. Miller, NRR A. Marchese, NRR J. Gagliardo, IE/D/TTC T. Marsh, NRR L. Phillips, NRR

,w G. Mazetis, NRR S. Weiss, NRR J. Page, NRR C. Liang, NRR W. Jensen, NRR T. Dunning, NRR i

D. Chenier IP/ ADD l

H. Faulkner, IP/C/TLS l

E. Jordan, IE/D/DEPER B. Grimes, IE/D/DQAVT J. Partlow, IE/D/DINP E. Rossi, IE/C/EAB R. Starosteckt R I/0/DPRP R. Walker, R II/D/DRP C. Norelius, R !!!/D/DRP R. Denise, R IV/D/DRSP D. Kirsch, R V/0/DRP D. Queener, NSIC J. Buchanan, NOAC T. Foley, S.R.I., RI T. Kenny, S.R.I., RI W. Cook, 't. I., RI M. Branci, S.R.I., RI!

W. Orders, S.R.I., RI!

P. Skinner, S.R.I., R!!

J. Bryant, S.R.I., RII 1-

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