ML20042E955
| ML20042E955 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/02/1990 |
| From: | Novak T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Rossi C Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20042E956 | List: |
| References | |
| AEOD-E90-03, AEOD-E90-3, NUDOCS 9005070022 | |
| Download: ML20042E955 (2) | |
Text
._
MAY 2: ; 1990 MEMORANDUM FOR:
Charles E. Rossi, Director Division of Operational Events Assessment
.0ffice of Nuclear Reactor Regulation FROM:
Thomas M. Novak, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data L
SUBJECT:
ENGINEERING. EVALUATION REPORT - OVERPRELSURIZATION L
OF AUXILIARY FEEDWATER SYSTEM Enclosed is an Engineering Evaluation Report of overpressure of the auxiliary feedwater system. The study was initiated following the steam driven AFW turbine overspeed event at Rancho Seco on January 31, 1989. Our review-indicates that overpressurization of the turbine-driven train due to turbine overspeed could also affect the other trains of the AFW system because the
' trains of the system are cross-connected and the isolation valves in the L
cross-connections are open during normal system operation. The turbine overspeed war caused by combined failures of the turbine governor and the l -
overspeedtripmechanism(OTM). The operational conditions.resulting from the combined failures-of both devices appear not to have been considered in the design of the AFW. system.
The events show that the consequence of turbine overspeed results'in a, condition that could overpressure the entire. AFW system and cause the system to become inoperable. Although the OTM is installed to provide protection for the AFW purp and turbine in the event of governor failure, the potential exists for both the governor and OTM to fail simultaneously due to various problems affecting their operation and reliability.. The governor, the OTM, and the turbine that experienced the overpressure events are used'in the AFW system.of nearly all operating PWRs, and the RCIC system in many BWRs.-
In view of this safety concern, it is suggested that NRR issue an information 4
notice to. inform licensees of the potential for loss' of AFW capability due to overpressurization caused by turbine overspeed. A draft of the proposed information notice is also cnclosed for your consideration.
I If you have questions, please do not hesitate to contact me or Chuck Hsu (X24443) of nty staff. We shall be happy. to meet with you.or your staff to discuss this matter.
Original signed by Thomas M. Novak, Director Division of Safety, Programs Office for Analysis and Evaluation of Operational Data cc w/ enclosure:
D. Queener, NOAC J. Wheelock, INPO 9005070022 900302
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MAY 2l 1990 -
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MEMORANDUM FOR7 Jack W. Roe, Director Division of Licensee PGrformance and Quality.Ev ation Office of Nuclear Reactor Regulation FROM:
Thomas M. Novak, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data
SUBJECT:
ENGINEERING EVALUATION REPORT - OVERPRESSURIZATION OF. AUXILIARY FEEDWATER SYSTEM Enclosed is an Engineering Evaluation Report of' overpressure of the auxiliary L
feedwater system. The study was initiated following the steam driven AFW _
J' turbine overspeed event at Rancho Seco on January 31, 1989. Our review.
indicates that overpressurization of the turbine-driven train due to turbine overspeed could also affect.the other trains of the-AFW system because the trains of the system are cross-connected and the isolation valves in'the' cross-connections are open during normal system operation. The turbine overspeed was caused by combined failures of the turbine governor and the overspeed trip mechanism-(OTM). The operational conditions resulting from'the combined failures of both devices appear not to have been considered in the-design of the AFW system..
The events show that the consequence of turbine overspeed-results in.a' condition that could overpressure the entire AFW system end cause-the system to become inoperable. Although the OTM~is installed to provide protection for the N
AFW pump and turbine in the_ event of governor failure, the potential exists for both the governor and OTM:to fail simultaneous 13.due to'various problems,
affecting their operation and reliability. The governor, the OTM, and the turbine that experienced the overpressure events are used in the AFW system of nearly all operating PWRs, and the RCIC system in many BWRs.
In view of this ' safety concern, it is suggested that NRR issue an information notice to inform licensees of the potential for loss of AFW. capability due to-4 overpressurization caused by turbine overspeed. A draft of the proposed-information notice is also enclosed for-your consideration.
If you have questions, please do not hesitate to contact.me or Chuck Hsu.
(X24443) of nty staff. We shall be happy to meet with you or your staff to g
discuss this matter.
i l
0 iginal signed by :
Thomas M. Novak,. Director.-
Division of Safety Programs.
Office for Analysis and Evaluation:
'i j
of Operational Data l
l-cc w/ enclosure:
1 D. Queener, NOAC
-J. Wheelock, INP0 DISTRIBUTION:
Central File MChiramal LSpessard RSavio, ACRS R0AB R/F JRosenthal SRubin MTaylor,- ED0 DSP R/F
'Edordan GZech KRaglin, TTC AE0D R/F Dross MWilliams, P r sky, NRR OdlC I
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