ML20247J244

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Operating Experience Feedback Report - Progress in Scram Reduction.Commercial Power Reactors
ML20247J244
Person / Time
Issue date: 08/31/1989
From: Bell L
NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:
References
NUREG-1275, NUREG-1275-ADD, NUREG-1275-V05-ADD, NUREG-1275-V5-ADD, NUDOCS 8909200229
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b h AVAILABILITY NOTICE

' Availability of Reference Materials Cited in NRC Publications

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NUREG-1275 Vol. 5 Addendum Operating Experience Feedback Report - Progress in Scram '

Reduction Commercial Power Reactors Manuscript Completed: May 1989 Date Published: August 1989 L. G. Ilcil Office for Analysis and Evaluation of Operational Data U.S. Nuclear Regulatory Commission Washington, DC 20555 }

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j i-i ABSTRACT The U.S. Nuclear Regulatory Commission's (NRC) Office for Analysis and Evaluation of Operational Data (AEOD) evaluated U.S. Light Water Reactor (LWR) unplanned reactor scram experience in light of ongoing industry scram reduction pmgrams in NUREG 1275 Vol. 5. The purpose of this work which covered the years 1984 through 1987 was to pmvide feedback to in-dustry, the NRC staff, and the public regarding the trends in unplanned scrams at U.S. commer-cial power reactors. A primary objective of AEOD's analysis was to determine the major sources of unplanned scrams for the most recent data and to detennine whether the scram reduction programs supported by various nuclear steam supply system (NSSS) owners groups were ad-dressing the proper areas for future scram reduction. This addendum updates that work through March 1989.

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t CONTENTS Page

~ AB S TR ACT . . . .. . . . . . . . . . . .. . . . .. . . .. .. . . .... ... . . . . . . . .. . . .. . ... . .. . . . . . . . . . . . . . . .... . . .. . . . . ill 1.0 Introd u c ti on . .. . ... . . . . . . . .. . .. . . . . . . . . . . .. . . . .. . .. . . . .. .. .. . . . . . . . . .. . .. .. . .. . . . . . . .. . . .. .. . . . .. . 1 2.0 19 8 9 Estim ates . . .. . . . . .. . . . . . . . . . . . . . . .. . .... . . .... . . .. . ... . . . . . . . . .. . ... . . . . .. . . . . .. . . . . 2 3.0 19 8 8 Experience . . .. . .... .... ... ....... ......... ..... . ... . . . .... ..... .. ..... . . . . . . .... . . . 2 4.0 Westinghouse N SS S Plants ... ........................... . .. .......... ........ ...... .... .. . 3 1 l

5.0 General Electric NSSS Plants .... ..............................................4 6.0 Combustion Engineering NSSS Plants ......... ........ ... .............................4 7.0 B abcock & Wilcox NSSS Plants ... ... . . . .... . .. . . .... ........ ......... ... . ... ... . 4 8.0 Conclusions . ............ ..... . .............................................................5 9.0 Re fe rence s . . . . . .. . . . . . .. . . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . .. . . . . . . . .. . . .... 5 t

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l LIST OF FIGURES Page Figure 1. U.S. Industry Scram Improvement: Mature Plants .......... ........................... I Figure 2. U.S. LWR Unplanned Scram Trend . .. .... ................. ......................... .. 2 Figure 3. New Plant Unplanned Scram Trend ....... .... ........ ..................................... 3 Figure 4. Mature Plant Unplanned Scram Trend .... ... ...... ... ............... ................... 3 I

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LIST OF TABLES r

Page L Table 1-1 Initiating Systems at Mature Plants With E NSSSs ....... .................... 7 Table 1-2 initiating Signals at Mature Plants With E NSSSs... ............. ............... 7 1

' Table 1-3 Activities in Progress at Time of Scram: Mature Plants With Westinghouse N SS S s ....... ............ .. ......... ......... ...... .... ........... 8 Table 1-4 Causes of Unplanned Scrams: Mature Plants With Westinghouse NSSS s .... .... ....... . ......... ................... . ....... ...... 8 Table 2-1 Initiating Systems at Mature Plants With GE NSSSs ......... .......... ....... 9 Table 2-2 Initiating Signals at Mature Plants With GE NSSSs . ... .. .. ... . . ......... 9 '

Table 2-3 Activities in Progress at Time of Scram: Mature Plants With General Electric NSSSs ...... ..... . . . . . . . . . . . . . . . . . . . . . . . .. . .. .. 10 Table 2-4 Causes of Unplanned Scrams: Mature Plants With G encral Electric NSS S s ........ .... . .. .... ...... ...... . ........... ........ 10 Table 3-1 Initiating Systems at Mature Plants With CE NSSSs ....... ..... .... ..... 11 Table 3-2 Initiating Signals at Mature Plants With CE NSSSs........... . . . ... . . .....11 Table 3-3 Activities in Progress at Time of Scram:

Mature Plants With Combustion Engineering NSSSs . . .. ......... .... ....12 Table 3-4 Causes of Unplanned Scrams: Mature Plants l With Combustion Engineering NSSSs .. .... .. ... . . .. . ... .... ... .. .... 12 Table 4-1 Initiating Systems at Mature Plants With B&W NSSSs. . .. ... . .. . . 13 Table 4-2 Initiating Signals at Mature Plants With B&W NSSSs... . ... ... .... .. . 13 Table 4-3 Activities in Progress at Time of Scram: Mature Plants With Babcock & Wilcox NSSSs.. . . . . . . .. ... . ... .. . . .. 14 Table 4-4 Causes of Unplanned Scrams: Mature Plants i With Babcock & Wilcox NSSSs . . ......... .. . . . . . . . . . 14 i

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SCRAM EXPERIENCE

SUMMARY

JANUARY 1984 THROUGH MARCH 1989

1.0 INTRODUCTION

The reduction in unplanned reactor scram rate performance at mature plants. 'Ihe 1988 analysis from 1984 through 1988 represents a significant indicates that the learning curve of new plants l achievement by the U.S.nuclearindustry. Plant- (NUREG-1275, Vol.1) had a major effect on the specific, owne rs group, and industry-wide initia- continued lowering of the industry overall scram rate. Weexpect I. tives are. to be commended. that future re-N UREG-1275, duction will be largely depend-Volume 5, pre- u.s. Industry scragimprovement vides an analysis m . - . i, . ent on funher Sar=== par 1ooo cr=~ mature plantef-of the causes and activities underly-forts to imple-3,.

ment scram re-ing these trends.

duction lessons.

It also discusses i .e -

the individual The 1988 scram NSSS Owners i-Group scram re-experience at o8 mature plarus re-duction programs, Vealed contin- j These efforts

  • dpiffimnj "fW -

9 A SUPPORT GYSTWS should be contin-ued improve-ued in order to "'~

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ments in NSSS and BOP sys-achieve funherim-  ! isims 333-2 Mjgbu --

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tems operation Provements y,_

(see Figure 1),

through generic .'am se*YSS!M_SYS2 5 3{

activities. ,, . -

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Further im-provement in The results of our ~.'- - r*--- this area pres-ents a significant analysis, docu- ngm 1 challenge to the mented as in industry. Initial NUREG-1275.

Volume 5, indicate that the overall industry im. 1989 estimates indicate a leveling in the mature provement in unplanned scram experience from plant scram rate at about 0.46 scrams per 1000 1984 through 1987 was driven by the improved critical hours.

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2.0 1989 ESTIMATES industry reduction of 144 scrams from the 430 The results of a review of the two most recent full quaners of available unplanned scram data (the U.S. LWR Unplanned Scram Trond fourth quaner of 1988 and first quaner of 1989) sor rnm,20o0 ceme mr..

indicate that the industry scram rate is begmmng ,, ser.- am.

toleveloff. A comparisonof allquarterlyscram ca ,

rates for mature plants (plants with at least two . ,

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I years oflicensed operation) from 1984 to 1989 '

shows that in a given year, the first quaner rate " '

l tends to approximate the annual scram rate for

" ~ l that year. De table below presents the results of this comparison. u .

Comparison of First Quarter and Annual Rates for u -

Mature Plants -

1984 1985 1986 1987 1988 1989 y,,",,

First Quanet Rates 0.89 0.75 0.65 0.51 0.39 0.46 Annual Rates 0.83 0.79 0.68 0.52 0.39 0.46* Figure 2

' Linear esumate two years of licensed operation (new plants) ex-perienced 99 fewer unplanned scrams than the This correlation provides the capability to proj- comparably defined populationin 1987. De re-ect that the rate for mature plants may level off or duction in this number at new plants can be at-evenincrease slightly from 1988 to 1989. His tributed to the smaller number of plants that is only a projection. Industry scram experience started up in 1988, and a large improvement at a during the remainder of calendar 1989 could number of plants that staned up in 1987. A offset the rate observed during the first quarter number of these plants behieved a significant and yield an annual rate that is less than the 1988 reduction in their scram rate from a relatively rate. De attached Tables include data thmugh high value (e.g., greater than 3.0 scrams per 1000 the first quarter of 1989. critical hours). A large portion of the overall industry reduction in 1988 stemmed from this 3.0 1988 EXPERIENCE source. Figure 3 displays the scram rate trend for The overall U.S. LWR unplanned scram rate declined by 39% between 1987 and 1988 (from he number of unplanned scams at mature plants 0.71 to 0.43 scrams per 1000 critical hours), re- (plants with at least two years oflicensed opem-spectively. Figure 2 illustrates the trend at all tion)in the population declined from 2761n 1987 U.S. LWRs for the five-year period starting with to 231 in 1988 - a net reduction of 45 scrams.

1984, showing the contribution from both man- l Combined, plants with Combustion Engineering i ual and automatic scrams. (CE)- and General Elecuic (GE)-designed NSSSs l'

accounted formost of the reduction from 1987 to In 1988, a total of 286 unplanned scrams oc- 1988.

cuned at U.S. LWRs, which represents a net 2

l New Plant Unplanned Scram Trend scram. per sooo concan Hr.. matunty m 1988 kept the overall rate slightly elevated. During 1988, these plants had 31

  • scrams (which represents 14 percent of the total a ,_

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= - - scram count for mature plants), with an average rate of 1.01 scrams per 1000 critical hours.

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At various points in time this declining rate can be traced to improvements in the performance of u -I

mature plants of a particular NSSS design . In 1985 and 1987, theimproved performance of the

' main feedwater system at plants with Westing.

I house (E)-designed NSSSs drove the decline in o

theindustry scram rate. In 1986,the reduction of

. . . .. .. .7 io..

v, RPS system-initiated scrams at plants with GE-designed NSSSs was the most significant con-Figure 3 tributor to the decline. In 1988, the improved performance of the main feedwater and main turbine systems at plants with CE-designed NSSSs Figure 4 displays the general downward trend in combined with the overall improvement in per-the scram rate for mature plants. During 1988, formance of GE-designed NSSSs to yield a sig-the scram rate for all mature plants (plants that nificant reduction in the unplanned scram rate.

operated for all or part of 1988 as mature plants) Detailed discussion by NSSS designer follows.

was 0.39 scrams per 1000 critical hours.

4.0 WESTINGIIOUSE NSSS PLANTS in 1988, mature plants with E-designed NSSSs

[Aature Plant Unplanned Scram Trend welu responsible for 40 percent of all critical scram. por ,ooo concai sr.. hours logged by the industry and 52 percent of all

.. unplanned scrams. There was a small reduction a ,, in this group's rate (due primarily to an increase

" - - in the number of critical hours) from 1987 to

" 1 1988-fram 0.49 to 0.45 scrams per 1000 critical I

l hours, respectively.

OS i In prior years, reductions in scrams initiated by o

o

- lpll the main feedwater system at these plants had been the leading source of scram reduction. In 1988, the main feedwater system contribution to the rate increased. The small decline in the over-all 1988 rate for this group of mature plants can

. be attributed to a general reduction across all sys-tems (with the notable e xception ofmain feedwa-Figure 4 ter) and an increase in the number of critical 3

w______________.___ _

hours for these plants during that year. The rates a reduction in the rate from 0.67 to 0.28 scrams for mature plants with E-designed NSSSs as a per 1000 critical hours. Most of this reduction I

function ofinitiating system, cause, activity in can be attributed to decreases in scrams initiated progress at time of scram, and initiating signal by secondary side systems, primarily the main are shown in Tables 1-1,1-2,1 'i and 1-4. feedwater, main turbine, and main generator sys-tems.

5.0 GENERAL ELECTRIC NSSS j PLANTS The main feedwater system's contribution to the

]

overall scram rate for this group of plants de- 1 Mature plants with GE-designed NSSSs experi- clined by approximately 60 percent in 1988 -

enced a significant reduction in unplanned scram from an essentially constant rate of 0.22 scrams rate from 1987 to 1988 - from 0.54100.39 scrams per 1000 critical hours to 0.09 scrams per 1000 per 1000 critical hours, respectively. This im- critical hours. The contribution from main tur-provement in performance during 1988 can in bine system-initiated scrams averaged 0.09 scrams large measure be attributed to five plants that per 1000 critical hours from 1985 through 1987, operated in both 1987 and 1988, and experienced and then dropped to zero in 1988. Fmm a cause no scrams in 1988. This resulted in a net reduc- perspective, the reductions in the scram rates for tion of 20 scrams. A total of 12 of the 25 plants plants with CE-designed NSSSs especially those in this group that operated in 1988 experienced a for 1988, can be attributed to a reduction in the reduction in their scram rate. During this year, number of scrams due to equipment failures.

the feedwater system contribution to the scram rate at plants with GE-designed NSSSs experi- 'Ihe rates for mature plants with CE-designed enced the first significant redtiction since 1984. NSSSs as a function of initiating system, cause, The m ain turbine and RPS systems contributions activity in progress at time of scram, and initiat-I to the overall scram rate have remained essen- ing signal are shown in Tables 3-1,3-2,3-3 and tially corutant since 1986. From a cause perspec- 3-4.

tive, the reduction in the overall scram rate at this group of plants in 1988 resulted from a large re- 7.0 BABCOCK & WILCOX NSSS duction in the number of scrams caused by equip- PLANTS ment failures.

In 1988,14 unplanned scrams occurred at mature The scram rates for mature plants with GE- plants with B abcock & Wilcox (B &W)-designed designed NSSSs as a function ofinitiating sys- NSSSs. Nine of these were initiated by the main tem, cause, activity in progress at time of scram, feedwater system. In 1988 the main feedwater and initiating signal are shown in Tables 2-1,2- system continued to be the most significant 2,2-3 and 2-4 scram-initiating system at this gmup of plants.

As noted in Table 4-1, the main feedwater sys-6.0 COMBUST 10N ENGINEERING NSSS tem's contribution to the rate has declined from a PLANTS maximum of 0.42 scrams per 1000 critical hours in 1985 to an approximately constant rate of 0.14 Mature plants with CE-designed NSSSs achieved scrams per 1000 critical hours since 1986. The a 54 percent reduction (a reduction of 30 un- overall rate for this group of plants declined fmm planned scrams) in the number of unpirnned 0.33 t00.27 scrams per 1000 critical hours from scrams from 1987 to 1988. This corresponds to 1987 to 1988.

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m The rates formature plants with B&W-designed scram reductions in 1988. Some of these plants NSSSs as a function ofinitiating system, cause, operated during 1988 without any unplanned activity in progress at time of scram, and initiat- scrams. The results of a review of the most recent ingsignalarcattachedinTables4-1,4-2,4-3and two quarters of available scram data (fourth 4-4. quaner of 1988 and the first quaner of 1989) indicate that the industry scram rate may be

8.0 CONCLUSION

S leveling off. The results of our review of the

unplanned scram data suggest that scram reduc-

'Ihe U.S.nuclearindustry's unplanned scram rate tion efforts by owners groups and individual op-trended down in 1988 compared to 1987. In . eratingplantsshouldbecontinuedwithagoalof o contrast with earlier years, most of this reduction furtherimprovements through generic activities.

was the result ofimproved performance at plants that have less than two years oflicensed opera-tion, with a number of these plants achieving a scram rate reduction from a relatively high value (e.g., greater than 3.0 scrams per 1000 critical 9.0 REFERENCE -

hours).

1. NUREG-1275, Volume 5 "OperatingExpe-A review of scram data for mature plants re- rience Feedback Repon - Progress vealed that these plants experienced significant in Scram Reduction," March 1989.

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TABLE 11 r.

INITIATING SYSTEMS AT MATURE PLANTS MTTH E NSSSs Scrams per 1,000 Critical Hours .

. Systems 1984. 1985 1986 1987 1988 1989*

Main Feedwater . 0.34 0.18 0.21 0.10- 0.14 0.19 Reactor Protection 0.16 0.14 0.13 0.09 0.10 0.04 Electrical Distribution 0.16 0.16 0.10 0.05 0.04 0.01 Main Turbine 0.11 0.05 0.12 0.10 0.06 0.09 Main Generator 0.08 0.05 0.02 0.04 0.02 0.03 .

Control Rod Drive - 0.02 ' O.06 0.05 0.04 0.04 0.03 Other 0.02 0.04 0.05 <0.01 0.02 0.01

- Reactor Coolant 0.06 ' O.03 <0.01 0.03 0.01 0.03 Main Steam - 0.03 0.02 0.03 0.03 0.02 0.07 Condensate 0.04 0.04 0.02 0.01 0.01 0.03

  • First quarter of 1989.

TABLE 1-2 INITIATING SIGNALS AT MATURE PLANTS WTTIIE NSSSs Scrams per 1,000 Critical Hours Signals ' 1984 1985 1986 1987 1988 1989*

l Turbine Trip - 0.23 0.17 0.16 0.11 0.10 ' O.10 Safety Injection - 0.02 0.00 0.05 0.01 0.01 0.01 Loss of Power 0.07 0.02 0.02 0.02 0.01 0.00 low Reactor Coolant Flow 0.02 0.02 0.02 0.01 0.03 0.00 Manual 0.05 0.09 0.09 0.04 0.08 0.07 MSIV Closure 0.01 0.00 0.00 0.00 0.00 0.00 Low Steam Generator level 0.26 0.18 0.12 0.09 0.11 0.19 High Reactor Power 0.02 0.02 0.02 0.01 <0.01 0.01-Other 0.02 0.00 0.01 0.01 0.02 0.00 IRM 0.04 0.01 0.01' O.01 0.01 0.01 Steam Flow / Feed Flow Mismatch 0.10 0.04 0.06 0.02 <0.01 0.04 P-7 Premissive . 0.04 0.01 0.01 0.03 0.00 0.03 High RCS Temperature 0.02 0.03 0.02 0.00 0.01 0.00 RCP Breaker Open 0.02 0.01 0.01 0.00 0.01 0.00 Source Range Monitoring 0.05 0.02 0.01 0.04 0.00 0.01 low RCS Pressure 0.01 0.00 0.00 0.00 0.00 0.00 Pressurizer High Pressure 0.01 0.01 0.01 0.00 'O.00 0.00 High Negative Flux 0.00 0.02 0.03 0.04 0.03 0.01 High Steam Line Flow 0.00 0.01 0.00 0.00 0.00 0.00 High Steam Generator level 0.00 0.01 0.01 0.00 0.01 0.00 Missing 0.01 0.03 0.00 0.00 0.00 0.00 High Steam Line Pressure 0.00 0.00 0.00 0.00 0.00 0.00 Reactor Trip Breaker 0.02 0.01 0.02 0.00 0.01 0.00 Pressurizer Low level 0.00 0.00 0.01 0.00 <0.01 0.00 low Negative Reactor Power 0.00 0.00 0.00 0.00 0.00 0.00 Undervoltage RCP 0.00 0.00 0.00 0.01 0.00 0.00 High RCS Pressure 0.00 0.00 0.00 0.01 0.00 0.00 Under Frequency RCP 0.00 0.00 0.00 0.00 0.00 0.00 Iligh Containment Pressure 0.00 - 0.00 0.00 0.00 0.00 0.00

  • First quarter of 1989.

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TABLE 1-3  !

ACTIVITIES IN PROGRESS AT TIME OF SCRAM i MATURE PLANTS WITH WESTINGHOUSE NSSSs )

Scrams per 1,000 Critical Hours Activities . 1984 1985 1986 1987 1988 1989*

Testing - 0.18 0.06 0.15 0.08 0.11 0.15  ;

Transition 0.30 0.25 0.20 0.15 0.11 0.06 Steady State 0.31 0.26 0.25 0.20 0.17 0.25 Calibration - 0.02 0.02 0.01 0.00 <0.01 0.00 l Undefined 0.06 0.01 0.01 0.00 0.00 0.00 l Troubleshooting 0.09 0.06 0.04 0.02 0.02 0.04

-Maintenance 0.04 0.09 0.08 0.05 0.04 0.04

  • First quarter of 1989.

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l TABLE 1-4 CAUSES OF UNPLANNED SCRAMS MATURE PLANTS WITH WESTINGHOUSE NSSSs Scrams per 1,000 Critical Hours L Causes 1984 1985 1986 1987 1988 1989*

Equipment 0.67 0.45 0.45 0.31 0.27 0.23 l Human Error 0.25 0.24 0.21 0.13 0.12 0.19 l SG Level 0.07 0.03 0.02 0.01 <0.01 0.00 Procedure <0.01 0.03 0.05 0.02 0.05 0.06
  • First quarter of 1989.

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_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ _ _ . _ . _ _ . _ _ _ _ _ _ . _ _ . _ _ _ _ _ . _ . _ . . _ _ _ _ .3

l TABLE 2-1 INITIATING SYSTEMS AT MATURE PLANTS M1TH GE NSSSs i Scrams per 1,000 Critical Hours Systems ' 1984 1985 1986 1987 1988 1989*

i Main Feedwater 0.11 0.10 0.12 0.13 0.06 0.02 I Main Turbine 0.13 0.13 0.09 0.08 0.08 0.09 RPS 0.12 0.17 0.07 0.07 0.06 0.07  ;

Main Steam 0.13 0.07 0.06 0.05 0.02 0.09 I

Electric Distribution 0.05 0.10' O.07 0.05 0.02 0.09 Condensate 0.07 0.07 0.09 0.04 0.03 0.02

' Other 0.05 0.03 0.05 0.03 0.02 0.02 Main Generator <0.01 0.05 0.02 0.06 0.07 0.00 Reactor Recirculation 0.04 - 0.03 0.03 0.01 0.02 0.00 Control Rod Drive - 0.02 0.04 0.03 0.01 0.01 0.02

  • First quarter of 1989.

TABLE 2-2 INITIATING SIGNALS AT MATURE PLANTS WITH GE NSSSs Scrams per 1,000 Critical Hours Signals 1984 1985 1986 1987 1988 1989*

High RCS Presstue 0.04 0.02 0.03 0.02 0.01 0.00 High Negetive Flux 0.01 0.00 0.00 0.00 0.00 0.00 MSIV Closure 0.10 0.09 0.09 0.04 0.02 0.07 Turbine Trip 0.10 0.20 0.15 0.16 0.15 0.16 Manual 0.05 0.11 0.08 0.04 0.04 0.11 Missing 0.07 0.03 0.00 0.00 0.00 0.00 High Reactor Power 0.05 0.04 0.06 0.05 0.04 0.02 Main Steam Line Radiation High 0.02 0.01 0.01 0.01 0.01 0.00 IRM 0.05 0.02 0.05 0.03 0.01 0.02 Low Reactor Water Level 0.16 0.17 0.12 0.16 0.07 0.02 Loss of Power 0.05 0.03 0.03 0.02 0.01 0.02 1.ow Reactor Coolant Flow 0.01 0.01 0.00 0.00 0.00 0.00 Other 0.02 0.03 0.00 0.01 0.02 0.00 SRM 0.00 0.01 0.00 0.00 0.00 0.00 Scram Volume High 0.00 0.01 0.01 0.00 0.01 0.00 High Steam Line Flow 0.00 0.01 0.00 0.00 0.00 0.00

  • First quarter of 1989.

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TABLE 2-3 ACTIVITIES IN PROGRESS AT TIME OF SCRAM MATURE PLANTS WITH GENERAL ELECTRIC NSSSs Scrams per 1,000 Critical Hours Activities 1984 1985 1986 1987 1988 1989*

Testing 0.17 0.15 0.14 0.08 0.08 0.00 Maintenance 0.02 0.12 0.08 0.05 0.03 0.09

- Transition 0.20. 0.19 0.19 0.12 0.09 0.21 Steady State 0.16 0.21 0.19 0.28 0.18 0.11 1~

Undefined 0.14 0.06 0.01 0.00 0.00 0.02 Calibration 0.02 0.03 0.00 0.00 0.01 0.00 Troubleshooting 0.01 0.02 0.02 0.01 0.00 0.00 l *First quaner of 1989.

l TABLE 2-4 CAUSES OF UNPLANNED SCRAMS MATURE PLANTS WITH GENERAL ELECTRIC NSSSs Scrams per 1,000 Critical Hours l C:auses 1984 1985 1986 1987 1988 1989*

Equipment 0.46 0.51 0.38 0.37 0.24 0.21 i Human Error 0.19 0.22 0.19 0.10 0.08 0.11 l- Procedures 0.05 0.06 0.05 0.03 0.04 0.09 Unknown 0.02 0.01 0.01 0.04 0.02 0.02

  • First quarter of 1989.

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L________m.________.____.___ .__m. - - - _ _ _ . -

TABLE 31 INITIATING SYSTEMS AT MATURE PLANTS WITII CE NSSSs Scrams per 1,000 Critical Hours Systems 1984 1985 1986 1987 1988 1989* ,

Main Feedwater 0.23 0.23 0.18 0.22 0.09 0.05 Main Turbine 0.07 0.09 0.08 0.11 0.00 0.05 )

Electrical Distribution 0.09 0.05 0.11 0.07 0.03 0.05 i Control Rod Drive 0.13 0.15 0.03 0.02 0.00 0.00 i Reactor Protection 0.13 0.05 0.08 0.05 0.03 0.14 Reactor Coolant 0.09 0.08 0.08 0.04 0.02 0.00 Main Generator 0.00 0.08 0.05 0.07 0.04 0.00 Main Steam 0.05 0.06 0.04 0.02 0.01 0.00 Condensate 0.00 0.02 0.07 0.04 0.02 0,00 Other 0.05 0.02 0.01 0.04 0.01 0.00 )

1

  • First quarter of 1989. )

TABLE 3-2 INITIATING SIGNALS AT MATURE PLANTS %TTH CE NSSSs Scrams per 1,000 Critical Hours Signals 1984 1985 1986 1987 1988 1969*

tow Steam Generator Level 0.16 0.14 0.13 0.16 0.08 0.05 Turbine Trip 0.07 0.22 0.15 0.10 0.04 0.09 High Steam Generator Level 0.07 0.03 0.03 0.05 0.01 0.00 Manual 0.18 0.09 0.12 0.17 0.04 0.00 low DNBR 0.15 0.12 0.13 0.01 0.03 0.05 low Reactor Coolant Flow 0.02 0.02 0.03 0.01 0.00 0.00 Other 0.05 0.03 0.00 0.06 0.02 0.05 MSIV Closure 0.04 0.03 0.00 0.00 0.00 0.00 Loss of Power 0.04 0.02 0.04 0.06 0.01 0.00 High RCS Pressure 0.00 0.03 0.04 0.04 0.01 0.00 Pressurizer High Pressure 0.00 0.02 0.01 0.00 0.01 0.00 High Reactor Power 0.04 0.05 0.03 0.01 0.00 0.00 Steam Flow / Feed Flow Mismatch 0.00 0.03 0.00 0.00 0.00 0.00 Pressurizer Low Level 0.00 0.00 0.00 0.01 0.00 0.00-Under Frequency RCP 0.00 0.00 0.01 0.00 0.00 0.00 Reactor Trip Breaker 0.02 0.00 0.00 0.00 0.00 0.00 Missing 0.02 0.00 0.00 0.00 0.00 0.00 Source Range Monitoring 0.00 0.00 0.00 0.00 0.00 0.05

  • First quarter of 1989.

11

TABLE 3-3 l

ACTIVITIES IN PROGRESS AT TIME OF SCRAM MATURE PLANTS WITH COMBUSTION ENGINEERING NSSSs Scrams per 1,000 Critical Hours Activities 1984 1985 1986 1987 1988 1989*

Testing 0.15 0.05 0.13 0.07 0.02 0.05 Transition 0.24 0.20 0.18 0.16 0.05 0.05 Steady State 0.31 0.31 0.32 0.38 0.13 0.18 Undefined 0.11 0.06 0.00 0.00 0.00 0.00 Troubleshooting 0.02 0.08 0.01 0.00 0.01 0.00 Maintenance 0.04 0.11 0.08 0.06 0.05 0.00 Calibration 0.00 0.02 0.00 0.00 0.00 0.00

  • First quaner of 1989.

l l

TABLE 3-4 CAUSES OF UNPLANNED SCRAMS MATURE PLANTS WITH COMBUSTION ENGINEERING NSSSs Scrams per 1,000 Critical Hours Causes 1984 1985 1986 1987 1988 1989*

l Equipment 0.55 0.46 0.45 0.34 0.12 0.09 l

Human Enor 0.13 0.26 0.13 0.14 0.08 0.05 SG Level 0.07 0.01 0.05 0.02 0.00 0.00 Procedure 0.05 0.06 0.03 0.07 0.05 0.05 l Unknown 0.05 0.02 0.05 0.07 0.02 0.09

  • First quarter of 1989.

l l

l 12

{

TABLE 41 INITIATING SYSTEMS AT MATURE PLANTS WITII B&W NSSSs Scrams per 1.000 Critical Hours 1984 1985 1986 1987 1988 1989*

Systems 0.19 0.42 0.14 0.14 0.14 0.08 Main Feedwater 0.04 0.17 0.08 0.02 0.04 0.17 Main Turbine 0.08 0.07 0.05 0.04 0.00 0.08 Reactor Protection Electrical Distribution 0.04 0.12 0.05 0.04 0.02 0.17 0.02 0.00 0.08 0.02 0.02 0.00 Condensate 0.02 0.02 0.02 0.02 0.00 0.08 Main Generator 0.00 0.02 0.00 0.02 0.02 0.08 Control Rod Drive 0.02 0.02 0.00 0.02 0.00 0.00 Main stram 0.00 0.00 0.00 0.02 0.00 0.08 Other

'First quarter of 1989.

t I

TABLE 4-2 INITIATING SIGNALS AT MATURE PLANTS WITII B&W NSSSs Scrams per 1.000 Critical Hours Signals 1984 1985 1986 1987 1988 1989*

Other 0.08 0.12 0.00 0.02 0.04 0.08 bss of Power 0.04 0.00 0.00 0.02 0.00 0.00 High RCS Pressure 0.15 0.42 0.11 0.10 0.10 0.17 bw Negative Reactor Power 0.02 0.00 0.00 0.00 0.00 0.00 MSIV Closure 0.02 0.00 0.00 0.00 0.00 0.00 Turbine Trip 0.08 0.07 0.22 0.10 0.04 0.34 Manual 0.00 0.10 0.03 0.02 0.02 0.17 Under Frequency RCP 0.00 0.05 0.00 0.00 0.00 0.00 bw Steam G.nerator Level 0.00 0.05 0.03 0.00 0.00 0.00 bw Reactor Coolant Flow 0.00 0.02 0.00 0.00 0.00 0.00 High Reactor Power 0.00 0.02 0.03 0.04 0.02 0.00 Missing 0.00 0.05 0.00 0.00 0.02 0.00 High Steam Generator level 0.00 0.00 0.03 0.00 0.00 0.00 Undervoltage RCP 0.00 0.00 0.00 0.02 0.02 0.00 RCP Breaker open 0.02 0.00 0.00 0.00 0.00 0.00 Power imbalance 0.00 0.00 0.03 0.00 0.00 0.00

  • First quarter of 1989.

l 13

TABLE 4-3 ACTIVITIES IN PROGRESS AT TIME OF SCRAM MATURE PLANTS WITH BABCOCK & WILCOX NSSSs Scrams per 1,000 Critical Hours Activity 1984 1985 1986 1987 1988 1989*

Transition 0.15 0.25 0.11 0.08 0.08 0.08 Maintenance 0.06 0.12 0.03 0.02 0.00 0.17 Steady State 0.08 0.30 0.19 0.18 0.12 0.25 l Testing 0.08 0.10 0.05 0.02 0.04 0.25 Undefined 0.02 0.02 0.00 0.00 0.00 0.00 Troubleshooting 0.02 0.10 0.08 0.00 0.00 0.00 Calibration 0.00 0.02 0.00 0.02 0.02 0.00 6

  • First quaner of 1989.

TABLE 4-4 CAUSES OF UNPLANNED SCRAMS MATURE PLANTS WITH BABCOCK & WILCOX NSSSs Scrams per 1,000 Critical Hours Causes 1984 1985 1986 1987 1988 1989*

Equipment 0.31 0.72 0.30 0.25 0.22 0.34 Human Error 0.10 0.10 0.08 0.08 0.02 0.17 SG Level 0.00 0.05 0.03 0.00 0.00 0.00 Procedures 0.00 0.05 0.03 0.00 0.02 0.00 Unknown 0.02 0.02 0.00 0.04 0.00 0.25

  • First quaner of 1989.

14 i

U E.NUOLE AR REGULATORY COMMISSION sie T h> EE qqg sgay 335 .no Ana,noum hemtises e, ony p 2E9 127'$ BIBLIOGRAPHIC DATA SHEET NUREG-1275 w ,,,,r ron,,,,, ,,, , , ,-,, , Vol . 5, Addendum

2. TIT LE AND SUBT&T LE Operating Experience Feedback Report - Progress in Scram
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Commercial Power Reactors August 19"9" 8

4 FIN CR GR ANT Num*BER 6 TYPE CF REPORY 5 AUTHORLS, L. Bell i es a,Ou Ca. tusD .. . 39g, January'1984 - March o'***a* U***"o" O't.co or see.on. a s naces heoues.orv Lomm,u.on *"a man,*ne nao**u ,* cons'*;ror croco B pt,,A F O..VMtNG.CRG

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10 SUPPLEMENT ARY NOTES 11 AB5T R ACT .200 = ores or en' The U.S. Nuclear Regulatory Commission's (NRC) Office for Analysis and Evaluation of Operational Data (AEOD) evaluated U.S. Light Water Reactors (LWR) unplanned reactor scram experience in light of ongoing industry scram reduction programs in NUREG-1275, Vol. 5. The purpose of this work which covered the years 1984 through 1987 was to provide feedback to industry, the NRC staff, and the public regarding the trends in unplanned scrams at U.S. commercial power reactors. A primary objective of AEOD's analysis was to determine the major sources of unplanned scrams for the most recent data and to determine whether the scram reduction programs supported by varicus nuclear steam supply system (NSSS) owners groups were addressing the proper areas for future scram reduction. This addendum updates that work through March 1989.

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