ML20011E659
| ML20011E659 | |
| Person / Time | |
|---|---|
| Site: | Braidwood, Haddam Neck, 05000000 |
| Issue date: | 02/12/1990 |
| From: | Novak T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Rossi C Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20011E660 | List: |
| References | |
| AEOD-E90-02, AEOD-E90-2, NUDOCS 9002220113 | |
| Download: ML20011E659 (2) | |
Text
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FEB 121990 MEMORANDUM FOR:
Charles E. Rossi, Dirtetor Division of Operational Events Asssement, NRR FROM:
Thomas M. Novak Director Division of Safety Programs, AE0D
SUBJECT:
CROSBY LOW PRESSURE RELIEF VALVES The enclosed study of Crosby low pressure relief valves highlights a significant issue regarding deficient maintenance of these protective devices that can lead to degradation of important safety systems.
The recent extended blowdown of the primary system at Draidwood, Unit 1 is directly related to a problem with a Crosby low pressure relief valve in the residual heat removal system. The loss t
of coolant event represented a significant reduction of safety margin at the plant.
All relief valves have some type of adjustable ring thet surrounds the nozzle l
discharge area and affects the lift and resent characteristics of the valve.
As discussed in the study, extended blowdown events observed at two piants were related to setting the ring too high, while observed valve disc assembly failure observed at a third plant was attributed to too low a ring setting.
Both of these phenomena degrade the valve and impact the performance of the system to which they are attached. These rystems include RHR and component cooling water.
The mantfacterer dxs not routinely receiva operational cata on these valves ar.d hat, not issued any ady'.scries on prob hms with these low pressure valves. The TPI eccident stimalsted signifie. ant of fort on high pressure safety and relief valves attached to the reactor or steam generetors, but this work has not carried over to valves on low pressure systercs importent to safe.y.
Also enr.losed is a draft of a proposed information notice that we recommer;d be sent to all licensees to inform them of the benefits of proper paintenance of t
low pressure relief valves.
For further inforriation regarding this study, plea:ie contact S. Israel (x24437) of rty staff.
p gtnc1 U U g w '
ppaa.e y.7 Thomas N. Novak, Director Division of Safety Programs, AE0D
Enclosure:
As stated Ab
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cc w/enclossure:
Distribution:
T. Sullivan, NRR 4PDRr 1_,
,o JRosenthal CHeltemes HFaulkner F. Cherney, RES TCentral,Filef VBenaroya EJordan r
M. Wegner, AE0D SIsrael TNovak MTaylor
@hI E. Brach, NRR Plam LSpesserd CHaughney I'
9002220113 900212 PDR ADOCK 05000213 S
PNU
- SEE PREVIOUS CONCURRENCE ROAB:DSP:AEOD*
ROAB:DSP:AEOD*
ROAB:DSP:AE0D*
ROAB:DSP:AEOD*
DSP:AE0D SIsarel:as Plam JRosenthal VBenaroya TMNovak 1/ /90 1/ /90 1/ /90 1/ /90 2/f2./90
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i KEMORANDUM FOR: Charles E. Rossi, Director Division of Operational Events Asssement, NRR FROM:
Thomas M. Novak, Director Division of Safety Programs AE00
SUBJECT:
CROSBY LOW PRESSURE RELIEF VALVES The enclosed study of Crosby low pressure relief valves highlights a significant issue regarding deficient maintenance of these protective devices that can lead to degradation of important safety systems. The recent extended blowdown of the primary system at Braidwood, Unit 1, is directly related to a problem with a Crosby low pressure relief valve in the residual heat removal system. The loss of coolant event represented a significant reduction of safety margin at the plant.
All relief valves have sone type of adjustable ring that surrounds the nozzle discharge area and impacts the lift and reseat characteristics of the valve.
As discussed in the study, extended blowdown events observed at two plants were related to setting the ring too high, while observed valve disc assembly failure observed at a third plant was attributed to too low a ring setting.
Both of these phenomena degrade the valve and impact the performance of the system to which they are attached.
These systems include RHR and component cooling water which are important to plant safety.
The manufacturer does not routinely receive operational d6ta on these valves and has not issued any advisories on problems with these low pressure valves.
The TMl accident stimulated significant effort on high pressure safety and relief valves attached to the reactor or tteam generators, but this work has not carried over to valves on lcw pressure systems important to safety.
Also enclosed is a draft of a proposed information notice that we reccntend be sent to all licensees to inform them of the benefits of proper maintenance of low pressure relief valves.
For further information regarding this study, please contact S. Isrici (x24437) of ry staff.
Thomas M. Novak, Director Division of Safety Programs, AE0D
Enclosure:
As stated cc w/enclossure:
Distribution:
T. Sullivan, NRR PDR JRosenthal CHeltemes HFaulkner
- f. Cherney, RES Central file VBenaroya EJordan M. Wegner, AE0D SIsrael TNovak HTaylor E. Brach, NRR Plam LSpessard CHaughney ROAB:DSP:AEOD ROAB:DSP-.0D R04B:DSP:AE00 DSP:AE0D D:DSP:AE0D SIsarel:as 5T Plam JRosenthal VBenaroya TMNovak 1/'J//90 Igl/90 1/8/90 1/ I /90 1/ /90
.