ML19325E450

Reissues Rept Re Excessive Valve Body Erosion to Designate Rept as Engineering Evaluation Rept Instead of Technical Review Rept

ML19325E450
Person / Time
Site:	Brunswick
Issue date:	10/27/1989
From:	Ellen Brown NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	Rosenthal J NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
References
NUDOCS 8911070117
Download: ML19325E450 (2)

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i MEMORANDUM FOR:

Jack E. Rosenthal, Chief Reactor Operations Analysis Branch Division of Safety Programs p

Office for Analysis and Evaluation 1

of Operational Data i

THRU:

Matthew Chiramal Chief r

Engineering Section Reactor Operations Analysis Branch Division of Safety Programs i

F Office for Analysis and Evaluation J

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of Operational Data L

FROM:-

Earl J. Brown Engineering Section Reactor Operations Analysis Branch D

Division of Safety Programs Office for Analy' sis and Evaluation L

of Operational Data-

SUBJECT:

EXCESSIVE VALVE BODY EROSION AT BRUNSWICK L.

This report is being re-issued to correctly designate it as an engineering l evaluation report rather than a technical review report.

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3arlJ.Breen l

Earl J. Brown Engineering Section

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Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data

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MEMORANDUM FOR:

Jack E. Rosenthal, Chief j

Reactor Operations Analysis Branch L

Division of Safety Programs i

Office for Analysis and Evaluation j

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Matthew Chiramal. Chief Engineering Section Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis'and Evaluation l

of Operational Data Pt FROM:

Earl J, Brown Engineering Section Reactor Operations Analysis Branch Division of Safety programs Office for Analysis and Evaluation L

of Operational Data i

SUBJECT:

EXCESSIVE val.YE CODY EROSION AT BRUNSWICK i

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This report is being re-issued to correctly designate it as an engineering l

evaluation report rather than a technical review report.

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Earl J. Brown i

Engineering Section Reactor Operations Analysis Branch i

Division of Safety Programs Office for Analysis and Evaluation

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i MEMORANDUM TOR: Jack E. Rosenthal, Chief AEOD/ ESC 8 Reactor Operations Analysis Brar.ch i

Division of Safety Programs, AE00 THRV:

Matthew Chiramal Chief EngineeringSectIon Reactor Operations Analysis Branch Division of Safety Programs, AEOD TROM:

f arl J. Brown Engineering Section Reactor Operaticns Analysis Branch Division of Safety Programs, AE00

$0 EJECT:

EXCES$1VE VALVE BODY EROS 1011 AT BRUNSWICK A copy of an engineering evaluation report en excessive valve body crosion at Brunswick is enclosed for your information.

i The report indicates there is a broad scope of erosion related problems that i

could have an adverse impact on safety-related system operation or evailability.

The problers include cavitation induced valve body erosion, valve assembly degradation due to vibration, piping support damage due to vibration, piping ernsion downstream of throttled valves, severe degradation of purps in the l

service water system ard RilR service water system, low flow related damage to I

purps in other systers, and corrosion / erosion foulirp that may adversely impact heat transfer capability of service water system heat exchangers or i

piping rather than pump or valve operability. The industry action by the BWR owners group will cover " target" valves, but not pumps. Thus, it appears that low flow damage mechanisms for pumps may not be adequately covered by either the EWR owners group or Generic Letter 89-13 for Service Water Systems.

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l Earl J. Brown I

Engineering Section l

Reactor Operations Analysis Brench Divisien of Safety Programs, AEOD l

Enclosure:

As stated cc w/ enclosure:

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C. McCracLen. NRR W. Farmer, RES l

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- AEOD ENGINEERING EVALUATION REPORT g.

e UNIT.

Brunswick 1 TR REPORT NO.: AE0D/E908 i

l 00CKET NO.:

50-325 DATE: September 29, 1989 LICENSEE:

Carolina Power and Light Company EVALUATOR / CONTACT:

E. J. Brown j-NSSS/AE:.

General Electric /UE&C i

SUBJECT:

EXCESSIVE VALVE BODY EROSION AT BRUNSWICK L

EVENT DATE:' December 14, 1988 I

SUMMARY

L Excessive valve body erosion was discovered in the LPCI injection valve,

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E11-f0178, at Brunswick Unit 1.

The licensee investigation indicated that valve i

3 throttling was a major contributor to the erosion. A review of previous AEOD reports, the Sequence Coding and Search System, and 16RDS identified four previous AEOD reports that addressed erosion events and more than 200 other j

n erosion events. The event data indicate a pattern of erosion damage and i

degradation of components in several safety systems (RHR, HPCI, RCIC, service

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. water,andRHRservicewater). The primary causes appear to be cavitation i

related to either throttling devices such as valves, orifices, and reducers or i

low flow conditions. An NRC information notice, IN 89-01, was issued on the valve erosion event and Generic Letter 89-13 was issued on service water j

system problems.

It appears that action by the BWR owners group will concentrate on " target" valves in various systems.

However, it appears that i

low flow damage mechanisms for pumps may not be adequately covered by either i

the BWR owners group action or Generic Letter 89-13 for service water systems, l

Also, it is not clear that industry efforts to monitor FWR plants have evolved j

as anticipated.

J DISCUSSION J

1 On December 14, 1988, the licensee discovered excessive erosion of the valve I

body downstream of the seat during disassembly of the LPCI injection valve, E11-F0178, for Brunswick Unit 1.

The valve disassembly was being conducted as i

l part of the plant long term maintenance program. The valve body had erosion l

pockets with a minimum wall thickness of 1.7 inches. The origira1 wall thickness was between 3.5 and 4 inches.

Inspection of the identical valve, E11-017A, on the other LPCI train revealed a wall thickness of 1.4 inches in the same area of the valve body. Preliminary investigation by the licensee

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indicated that'a major contributor to the erosion of these valve bodies could be l

the throttling operation of the valves. The licensee discovered erosion in other throttle valves in the LPCI system. NRC Information Notice IN 89-001 (Ref. 1) was issued on this event.

The effort to ascertain the extent of this problem included a review of previous AE00 reports, a search of the SCSS LER database, and a search of the

.NPRDS equipment failure database. This review identified three engineering evaluation (EE) reports that addressed erosion and effects of valve tnrottling i

in nuclear plants and one case study that included erosion as a degradation

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WQ 2-v mecher.hm. The three EE reports are:

• Misuse of Valve Resulting in Yibration Demage to the Valve Assnbly(and Pipe Supports," E315 (Ref. 2); " Erosion in l

Nuclear rower Plants," E416 Ref. 3); and

• Pump Damage Due to Low flow Cavita.

i tion"E807(Ref.4). The case study report was:

• service Water System Failures l

ar.d Degradations in Light Water Reactors, C801 (Ref. 5). The LER search using the Sequence Coding Search System (5C55) identified 64 valve erosion events i

from 1980 through 1988. The NPRDS search identified over 140 events covering the period from 1985 to 1988.

AE0D_ Reports AEOD/E315 This report was an evaluation of two events involving operation of the residual heat removal system (RHR) in the shutdown cooling mode at the Susquehanna l

Unit 1 plant. The f0178 valve (the same valve with erosion at Brunswick) was used to throttle flow in the shutdown cooling mode of the RHR systein.

This valve was observed vibrating severely. The packing was lost, the position

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indicator had f alltn off, the adjacent pipe hanger had two broken welds, and another pipe hanger had cracked welds. Several pipe hanter weld cracks were observed on the other train also. Four months later the valve disc separated from the stem. The investigation found that RHR flow for the shutdown cooling i

mode could be distributed as a minimum 1/4 hett exchanger flow and 3/4 bypass flow. This flow distritution in combination with a very low level of decay heat l

created a situation in which it was desirable to reduce flow through the RHR l

heat exchanger, but this could only be accomplished by throttling valve F017B.

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The report suggested that an information notice be issued.

1E IN 83-055 (Ref. 6) was issued on the event.

It was concluded that the severe damage to the LPCI system injection valve, F0178, wass directly related to RHR system flow l

limitations that result from a combination of system design, configuration, flow l

control, and the low level of decay heat. The report suggested that NRR review system' operation for compatibility of valve assenibly design and qualification including frequency of operation and vibration, together with the adequacy of i

l the shutdown cooling mode system flow control.

l-l AEOD/E416 i

This study was an evaluation of more than 140 reports involving erosion in i

There were 31 reports about valves 1

p(umps, valves, heat exchangers, and piping.a report may include several valves) dis l

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HTGR. The erosion events involved both steam and water systems.

The erosion l

problems included wear through the wall of valve bodies, deterioration of rubber seats, and wear of retaining devices. A major finding was that " erosion events appear related to the specific water source with suspended solids (raw l

water, radwaste, etc.), the use of throttling devices (valves and orifices), or a combination of these effects." This study also indicated that piping erosion events were related to use of throttling devices such as valves, orifices, and reducers. Approximately 40 percent of the 60 piping erosion reports were related to flow throttling.

Thus, if valve throttling is used, the program to monitor erosion shnuld include both the valve and downstream piping.

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The report concluded that constructive actions to address erosion problems could include:

(1) cognizance of the phenomenon for certain systems and i

sites (2) identification of specific plant equ4pment and configurations that may be susceptible to erosion, and (3) physical impicmentation of

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monitoring programs to detect degradation of equipaent (pumps, valves, heat i

exchangers,andpiping).

AEOD/E807 Erosion and vibration resulted in failure of an emergency service water pump at Susquehanna Unit 1.

Subsequent disassembly of the pump revealed that the i

bottom portion of the pump suction bell had separated from the body and had fallen into the pump pit. Inspection of the residual heat removal service water pumps revealed cavitatien damage similar to that found in the service water pumps. The cavitation was caused by flow recirculation due to operating 3

the pumps at low flow rates. The RHRSW pumps had been operated at less than 50 percent flow most of the time. A search of operational experience database i

files identified similar pump degradation from low flow operation at Yermont Yankee, H. B. Robinson 2, Turkey Point 3, Haddam Neck, and a foreign plant.

The study concludes that operation of centrifugal pumps at low flew conditions l

tor extended periods of time can cause cavitation damage fron flow recirculation.

The cavitation erodes the impeller and the internal pumo casing wall. The icw

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flow conditions could occur during performance of the inservice surveillance tests by restricting flow through the mini flow bypass line, or running the purops in a low flow mode for a system designed for a wide range of flows, hRC Bulletin 88-04 (Ref. 7) addressed the miniflow test configuration. NRC Informa.

tion Notice 89-008 (Ref. 8) was issued to highlight purrp damage caused by low-flow operation.

AEOD/C801

- This report was a comprehensive review and evaluntion of service water systtm failures and degradations observed in LWRs from 1980 to 1987. The causes of failures and degradations include various fouling mechanisms (sediment deposition, biofouling, corrosion and erosion, pipe coating failures, calcium l

carbonate, foreign material and debris intrusion); single failure and other i

design deficiencies; flooding; multiple equipment failures; personnel and t

procedural errors; and seismic deficiencies. Of 980 operational events during i

this p*iod, 276 were deemed to have potential generic safety significance.

A majority (58 percent) of the events involved system fouline. The fouling mechanisms included corrosion and erosion (27 percent), biofouling (10 percent),

foreign material and debris intrusion (10 pe-cent), sediment deposition (9 percent), and pipe coating failure and calcium carbonate deposition (1 percent).

The recommendations from the study were:

(1) Conduct, on a. regular basis, performance testing of all heat exchangers which are cooled by the service water system 6nd grform a safety function to verify heat er. changer heat transf er c6pability.

(2) Require licensees to verify that their service water systems are ret r

vulnerable to a single failure of an active component.

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o (3) Inspect, on a regular basis, important portions of the piping of the

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service water system for corrosion, erosion, and biofouling.

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(4) Reduce humcn errors in the operation, repair and reintenance of the l

service water system.

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Generic letteer 89-13 (Ref. 9) was issued July 18, 1989 to address the issues i

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identified in Case Study C801.

LERSCSSSearg l

AllLERsweresearchedusingtheautomateddatabase(SCSS)toidtntifythose i

LERs in which the words " erosion" and " valves" both a ppear. Sixty-four LERs from 1980 through 1988 were identified. About half tie events identified by this search occurred af ter our 1984 study of erosion, E416. These events did i

not appear to include excessive wear similar to that reported at Brunswick, i

In general, the data was similar to that reviewed in the E416 study. There were many events with valves that failed leek rate tests due to erosion of the disc. This was corrected by lapping. Other reported causes were erosion due i

to steam cutting, and expansion of a small lock from a gasket, "0" ring, or i

steam packing.

NpRDS Search l

The search strategy for the NPRDS was to identify valves with normal / abnormal wear.

It was further refined with a narrative search for the word

• erosion."

There were over 140 reports identified f rom 1985 through 1988 for all safety classes (1,2,3,and4). The type of reported erosion was similar to that in the MOD studies and the recent SCSS review. There were no narrative descrip-tions that indicated erosion as extensive as that at Brunswick Unit 1.

However, there were reports that identified other valves in the RHR system with erosion damage. Some of the valves were F015B (this valve is in series with F017B),

l F024B (RHR test line control valve), 1001-28AandB(outboardisolationvalves),

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and 1001-36A (RHR pump test line). Thus, the events reported to NpRDS illustrate erosion patterns similar to those previously identified in the AEOD reports E315, E416, and E807.

l Industry Program l

The BWR Owners Group (BWROG) has established an effort to address valve crosion l

due to cavitation induced by valve throttling. The BWROG objective is to i

" Provide a guidance document for individual utilities to establish and implement 1

a valve assessment / inspection program in order to eliminate valve erosion pro-i blems." The BWROG program is a multistep prc;ess including meeting with NRC sttff to present the plan, schedule, and discuss results pr.or to final disposi-I tion for use by licensee; surveying all BWROG participating utilities to identify safety-related valves used for throttling; rcquest/ collect data on l

cavitation erosion; identify methods used by utilities to eliminate erosion problems; and prepare a BWROG Guidance Report.

Information about the program was presented to ACRS on April 27, 1989.

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Based on data reviewed to date, the effort has identified approximately 15 or 16 " target" valves in EWR safety-related water systems. The appropriate L

number of valves depends on whether the BWR has HPCI or HPCS. The approach addresses eight valves in the RHR system, two in the RHR service water system,

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two in the core spray system, one to three in the HPC1/HPCS systems, and one in the RCIC system.

For all systems other then RHR, the " target" valves are i

test return valves except for two heat exchanger flow control valves.

I AEOD staff have participated with NRR during the BWROG prcsentations. The previously cited AE00 reports E315 E416, and E807 were identified for industry y

information. The concerns expressed by AE0D were that cavitation induced damage has exhibited a broader scope than simple valve body erosion.

In addition to i

valve body erosion, the AE0D studies have identified cavitation induced damage t-as valve assembly degradation due to vibration, piping support damage due to vibration, piping erosion downstream of throttled valves, severe degradation of pumps in the service water system ana the RHR service water system, and low flow reinted damage to pumps in otnar systems.

It is our understanding that the j

BWROG program will be limited to tuget" valve body erosion, further, it was indicated by the BWROG that pumps will not be addressed and, if service water pumps are a concern, they should be covered as part of any NRC action related to service water systems.

In addition, a representative from NUMARC indicated that efforts to address cosion in PWR plants would be reviewed with the various owners groups. We are not aware of subsequent action (after April 1989) by any PWR owners group.

OVERVIEW The AEOD reports have identified a relatively broad scope of erosion related problems involvin the RHR system service water system, and RHR service water system. The prob ems include cavitation induced valve body erosion, valve assembly degradation due to vibration, piping support damage due to vibration, piping erosion downstream of throttled valves, severe degradation of pumps in the service water system and RHR service water system, low flow related damage to pumps in other systems, and corrosion / erosion fouling that may adversely impact heat transfer capability of service water system heat exchangers or pising rather than pump or valve operability. NRC generic communications t1st certain to these issues include Information Notices83-055, 89-001 and 89-008;Bulletin 88-04, and Generic Letter 89-13.

j It appears that there are two efforts established to address these p'roblem areas, first, the BWROG has established an effort to cover " target valves in systems such as RHR, HPCI, RCIC, and HPCS as we?1 as two RHR service water system valve.

This BWROG effort appears to be a tho opoh effort that will concentrate on valve erosion and cavitation but will nc. address other components. Presumably, if valve cavitation is reduced, there is the potential for btneficial reduction in vibration probitas with piping supports and valve assembly operation.

The second effort inv:1ves licensee response to Generic Letter 89-13 pertaining to service water systems. As previously indicated, the corrosion / erosion aspect of this effort appears to emphasize fouling that may impact heat transfer capability rather than degradation of components such as pumps and valves. Thus, it would seem that. low flow pump erosion may net receive appropriate monitoring to address the concerns identified in E807 (Ref. 4).

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FINDINGS l

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AEOD studies have identified a broad scope of cavitation related component damage. These include valve body erosion, valve assembly degradation due i

to vibration, piping support damage due to vibration, piping erosion i

downstream of throttled valves, severe degradation of pumps in the service j

l water system and RHR service water system, low flow damage to pumps in i

other systems, and service water system failures and degradations involving fouling mechanisms that include corrosion and erosion.

2.

The conclusions, suggested actions, and recommendations in AEOD reports l

E315 E416. E807, and C801 appear to be reasonable approaches to minimize j

effects of this damage in the future.

3.

NRC has issued several generic communications addressing these erosion issues. These documents are Information Notices83-055, 89-001 and i

89-008;Bulletin 88-04; and Generic Letter 89-13.

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4 The BWROG effort appears to be a thorough effort pertaining to erosien of

" target" valves.

NRk is following thit effort. We understand the effert i

will not include monitoring of pumps.

5.

It does not appear that any formal effort has been established by FWR owners i

groups to rev hw these erosion issues.

t 6.

The damage mechanism to centrifugal pumps under low flow conditions identified in E807 (Ref. 4) does not appear to t'c appropriately addressed by either the BWROG action or Generic Letter 8943.

4 CONCLUSIONS The event data from 1980 through 1988 exhibit a consistent pattern of erosion

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damage and hgradation of components in several safety related systems. The priinary causes appear to be cavitation related to either throttling devices such as valves, orifices, and reducers or low flow conditions. This results in either long term erosion wear or a more immediate destructive vibration problem.

However, the root causes leading to erosion or cavitation damage appear related to system flow limitations with special concern at low flows relative to full system capacity. A combination of system design, configuration, flow control and low flow requirements conspire to cause ecuipment damage. The conclusions, suggested actions and reconmendations in AE0D reports E315, E416, i

E007, C801, and the NRR Generic Letier 89-13 appear useful to monitor damage l

and degradation due to erosion.

However, it appears that flow damage mechanisms for pumps may not be adequately addressed by either the EWROG or GL 89-13.

Also, it is not clear that industry efforts to monitor FWR plants has evolved t

as anticipated.

REFERENCES 1.

U.S. Nuclear Regulatory Commission, NRC !nformation Notice No.89-001, Valve Body Erosion," January 4,1989.

2.

U.S. Nuclear Regulatory Commission, E. J. Brown " Misuse of Valve Resulting in Vibration and Damage to the Valve Assembly and Pipe Supports, "AECD/E315, July 7, 1983.

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• 7-3.

U.S. Nuclear Regulatory Comission, E. J. Brown, ' Erosion in Nuclear Power i

Plants," AE0D/E416, June 11, 1984 4

U.S. Nuclear Re ulatory Comission, C. Hsu, " Pump Dinage Due to Low flow i

Cavitation," AE D/E807, October 18, 1988.

5.

U.S. Nuclar Regulatory Comission, P. Lam and E. Leeds, " Service Water 3

System failures and Degradations In Light Water Reactors," AEOD/0801, August 1988.

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6.

U.S. Nuclear Regulatory Comission, IE 1rfomation Notice 83-055, "Mitapplication of Valves by Throttling Beyond Design Range," August 22, 1983.

l 7.

U.S. Nuclear Regulatory Comission, NRC Bulletin No. 88-04, ' Potential Safety-Related Pump Loss," May 5,1988.

8.

U.S. Nuclear Regulatory Comission, hRC Information No.89-008, "fump Damage Caused by Low-flow Operations," January 26, 1989.

9.

U.S. Nuclear Regulatory Comission, J. G. Partlow to All Licensees " Service 1

Water System Problems Affecting Saf ety-Pelated Equipment (Generic Letter l

89-13)," July 18,1989.

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