ML20154C974
| ML20154C974 | |
| Person / Time | |
|---|---|
| Issue date: | 03/30/1988 |
| From: | Beckjord E NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Jordan E NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| References | |
| RIL-152, NUDOCS 8809150101 | |
| Download: ML20154C974 (19) | |
Text
_ _ _ _ _ _ - _ _-_ _____ _-_-_ ____ __ __ ___ ____ - _____ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ -
[.'.y f y y ll l
l M 3 0 193g MEMORANDUM FOR: Edward L. Jordan. Director Office for Analysis and Evaluation of Operational Cata FROM: Eric S. Beckjord Director Office of Nuclear Regulatory Research
SUBJECT:
RESEARCH INFORMATION LETTER NUMBER 152; IMPROVED RISK-BASED PERFORMANCE INDICATORS
References:
- 1. SECY-86-317. "Performance Indicators. October 28, 1986,
- 2. Memorandum from Eric S. Beckjord to Victor Stello, Jr.,
"Control of NRC Rultimaking: Initial RES Review of Proposed Rulemaking to Podify Reactor Event Reporting Requirements" March 4, 1968.
- 3. Memorandum from Saruel J. Chilk to Victor Stello, Jr.,
"SECY-87-207 Policy Use of Perfonnance Indicators"
- 4. SECY-87-314. "Interim Policy Statement en Paintenance of Nuclear Power Plants " December 30, 1987.
This Research Information Letter transeits a sumary of interim results from research on risk-based perfonnance indicators. These interim results are improved Irethods for menitoring the unavailability of important safety systems. This research, which includes computer simulattens and sample data analysis free two plants, is described in reports listed in enclosure 1.
This letter sumarizes these interim results in the following order:
The regulatory issue addressed by the research
- Definition of the improved indicator of unavailability, and also a related indicator of reliability The input data needed The significance of these irdicators OI8I Fossible regulatory irplenentaticn 'I
- Planned future irpreverents.
09 /fcW / f5'032, 8lOK C/G. Q4 ,
fdward L. Jerdan 2 MAR 30 y REGULATORY ISSUE l The set of performance indicators is intended to reflect trends in safe operatiens indicated by the:
l frequency of transients or faults severe enough to challenge safety systems, f
- availability of safety systcms (i.e., the probability that safety systers will be cperational en demand).
potential for comon-cause failures, for exar.ple, due to deficiencies in maintenance.
The currently used indicator of safety-system unavailability is the number of licensee event reports (LERs) from a plant during the quarter. However, counting LERs does not directly reasure system unavailability. Also LERs occur typically less than once per quarter, so it can take a year to establish a trend.
Therefore in conjunction with AE00, RES develor>ed a rethod for an improvt.d indicator of the unavailability of safety systers (Reference 1). A methnd suitable for near term use is surrarized belcw.
_ CONCLUSIONS Unavailability Indicator The improved indicator of safety-system unavailability is: The aggregate of the total hours per year that any of six selected safety systers are estimated to be unavailable while the reactor is critical.
This indicator uses two kinds of operational data fron six selected safety sys te.ts :
the total number of hours that each train is taken out of service while the reactor is critical the nurber of failures of each train (i.e., less of train function)
A sample data sheet that could be used for a plant's monthly or quarterly report is shcwn in enclosure 2.
In addition to these monthly or quarterly perfomarce data, this ir.dicator also needs the following cre-time input of design data for the six selected safety systems:
The number of trains in each systen Success criteria; i.e., the nurber of traies that rust function to accorplish the system's safety function.
The surveillance test intervals
Edward L. Jbrdan 3 MAR 3 0 ggg For exarple, a typical AFW system centains three trains, any one of which can accorplish the AFW function, and each train is tested tronthly. A sartple data sheet for this one-tir:e input is shown in enclosure 3.
t 1he train-level data are aggregated to a plant-level indicator as follows, i first the train unavailabilities are estirated using both discovered down-tire erd undiscovered down-tire. Discovered down-tire is based on the nun.ber of ,
bours that cach train in the six selected systems is taken out of service l while the reactor is critical. Undiscovered dcwn tire is based on the nurter of train failures (i.e., loss of train functien) in each of the six selected systems. The undiscovered down-tite for each train is approximated as the number of train failures trultipled by half of the surveillance-test interval.
P These observed train uravailabilities are converted to estirates of system unavailabilities by using sirple reliability metheds based en independent r events. For exarple, the unavailability of a two-train system is calculated as the product of the unavailability of train A multipled by the unavailability of train B. These unavailabilities are sumred and ruitiplied I by 87CC heurs in a year to apptoxirate the aggrtgate number of hcurs that the six systems are expected to be cut of service. per year. The indicator is thus the aggregate of the total hours per year that any of six important safety systers are expected to be unavaileble. A sample calculation prepared by thL !
is illustrated in enclosure 4 t
Six irrportant safety systems are selected for renitorir.g Light Water Peactions:
Auxiliary Feedwater (or Reactor Core Isolation Cooling fer CWRs)
High Pressure injection (or High Pressure Ceolant Injection for EWRs)
Service water (or Standby Service Water for DVPs)
- Erergency Power-AC
- Ercrgency Pcwer-DC j Reactor Protection System [
r In a sample of five PPAs, these six systers acccunt for roughly eof of the in, pact of all single train cutages on the expected frequency of core-nelt. }
This unavailability indicator will respond about ten tirts faster to changes ,
in plant perforvance than counting LERs. This is tecause LEES involve either ;
loss of system function er loss of ruitiple trains ard, therefore, occur (
infrequently. The irproved irdicator is based on individual trains out of service; i.e., events that occur u. ore fret,tently ther cultiple train cutages.
t j Feliability Indicator By ana;yrirg these sarc data in a different way, we can produce a second irdicator. Tr.is inoicator relates to reliability; i.e., rean tire between failures. This reliability indicator is a prcbabilistic estirate cf the
. nun.ber of years betwcen systern failures (i.e., loss of syster functien) of any
! of six selected safety systers. l i !
[
1
e Edward L. Jordan 4 yAR 3 0199 I
This second indicator is calculated frem the sane train level data, but in the fo11cwing way. The cbserved train failure rate (i.e., loss of train function) <
is used to estimate the system failure rate (i.e., loss of systen function) [
using sirple reliability rothods. For exarr.ple, in a two-train system the l system f ailure rate equals the failure rate of train A n.ultipled by the .
prcbability that train B will be uravailable plus the failure rate of train B i multipled by the probability train A will be unavailable, lhen these ;
estin.ates of system failure iote are added to the the aggregated rate of :
f ailure of the six selected safety systerrs. This failure rate is ticn inverted to give the aggregated reliability indicator i.e., an estirate of the I tire between failure of any of six selected safety systeers. A serple l calculation is illustrated in enclosure 4.
Interpretation !
The irproved indicator for the unavailebility of selected safety systenis is directly related to safety, since the six systers stlected for tronitoring ,
represent about 90' of the sensitivity of core-relt frequency to outage of a I safety-system train. !
In addition, trends in this uravailability indicator also indicate rnaintenance r effectiveness, hRC defires reintenance to include "these functions aired at f preserving or restoring saf ety, reliability, and availability of plant :
4 structures, systf.rs, and ccrpenents* (reference 2). Thus one treasure of :
4 raintenance effectiveness is the availability of six important safety systctrs. [
l The reliability irdicator, on the other hand, reflects the eff&ctiveness of I i the preventive portion of the raintenance prograr.. The ob
) preventive raintenance (including predicthe raintenarce)isjective of to present !
- failures. Thus trends in this probabilistic estirate of tire between failures >
i of six inportant safety systerns reflect trerds in the effectiveness of i i
preventive maintenance. [
Therefore, the unavailebility indicator can help to track plant safety '
j pe rfonrance. In actitien, trerds in the unavailability and reliability J indicators can help to track trer.ds ir, the effectivtr(ss of the plant's i overall rnaintenance prcgram and the preventive portion of the trainterance prograrc respectively.
l REGULATORY APPLICATION !
- I l
These two ir,preved indicators of plant safety syster asailability ard ,
! reliability have been recorrended to the Inter-office Crcup cn Ferforrance l j Indicators for initial applicatien to ronitoring of plants to be restarted '
I af ter extended forced shutdown. This initial use of these two irdicaters will I l erhance NRC's ability to renitor trerds in safety syster evailebility and c.ainterance effectiseness during the first )(ar af ter restart as well as [
folic >irg years. L l f i :
i 4
i
l Edward L. Jordan 5 MAR s o y Also, these two indicators of availability and reliability of selected safety systen.s have been rectnrnded in the lcrger tern to te includtd in NRC's set cf perforrance indicaters applied to all operating plants.
For initial use (i.e., as part of ronitcring of plant cperation after exterded forced shutdchn), irrut data can be obtained from case-by-case discussions with ir.dividual plants. For longer term use, however, data would be needed frem all crerating plants. Options for collecting the data include n.akiro arrangenents with each operating plant (pessibly thrcugh thPO), or ruleraking.
The data to be collectea are simple; e.g.: (1) The total nutter of hcurs that each train in the six selected systers is taken out of service, and (2) the nunter of failures cf each train. Pany utilities keep track of this type of inferration, at least inferrally in the centrol rect, in order to assure reeting Technical-Specification requircrents regarding Limitirg Conditiens for Operation, kESTp,ICTIChJ CN ApPLICATICh The restrictions en use of perfort.ance indicators in general also apply to use of these two irpreved indicatcrs (reference 3). These two irproved irdicators are intended to be part of a sit cf indicators to help hRC renitor trerds in the safety perforrance of individual plants. This set of indicators ccrprises one of several tools for use by senior hRC manastrent in decisicn naking regarding plant-specific regulatory progrars.
In additicn, two sirplifications used in thest irproved indicatcrs shculd be noted. One approxication in this rethod for aggregating the date is that the six selected safety systers are treate.c as equally irrertant. Within each syster, hchever, the degree of redundancy, i.e., the nurber of trains, is addressed. Ite second sirplification is that events are treated as independent events, not as pctential com en-caust events.
The reactr is also cautioned that the irdicater fcr unavailability is ret
, unavailability itself. This is a sirplifice indicator to help renitor trends in the uravailet,ility of irportant safety systers.
FUTUPE WORK The irproved indicators described in this letter are rart of several plerred irprovenents. Research en risk-tastd perfcruance irdicators is continuing to I
extend these retheds to rcre accurately risk-weight systtes, to irprove treatrent of corren-cause events, to ir; rove trenc idertificaticr., and to include initiatitg events such as transients in balance of plant. This research ccrplerents related iesearch te evaluate itproved pregramatic it.cicators.
O c
Edward L. Jordan 6 NAR 3 01999 This rcsearch is teirg performed in the Division of Peactor and Plant Systers by tbc Reliability ard Furan Factors trarch in close ccoperation ard coordination with AE00. The research contractor and subcontractor are Brookhaven fiational Laboratory and Science Applications International Corporatien. The RES staff contact is Carl Johnson, FTS 492-3548. I wculd like to encourage feedback on this R!L frorn other Offices toth at Headquarters and the Regicos. l
\ s\,
Eric S. Beckjord, Director l Office of Nuclear Fegulatory Pescarch l
Enclosures:
- 1. List of Research Reports
- 2. f'onthly Data Sheet
- 3. One-tire Data Sheet 4, San.ple Calculatier i cc: T. E. Murley, hRR J. B. Martin, R-V V. Stello, E.CC H. L. Thon psen , f. MSS R. F. Fraley, ACPS W. T. Russell, R-1 H. R. Centon, CPA J. fi. Grace R-!! J. G. reppler, CSP A. B. Davis, R-Ill W. G. PcDonald, APM R. D. Martin, R-IV R. W. Barber, COE Distrit ut ion 005 FDR RES Chron/ Circ DRPS Chron RHFB Readit.g E. Beckjord D. Ross T. Speis B. Sheron W. Houston B. Forris G. Arlotto W. Minners C. Leiber F. Coffran J. Purphy A. Rubin W. Bec6rer C. Jchnson
// ,
1 O
RHFF:0RPS PHFB:LRFS RitFE EEPS EC 0P6S D.D 00:RES d RES D:RE s'ct rson/a s / Rt.b i r, FCof fran kt'ir re rs ES' n *TSpeir
, CPgss EEcckjord L R$68 L In lib 'N)L]l88 2h1/F8 ]if E8 s) IF)> UIEE3Go/E8
Enclosure 1 RESEARCH rep 0RTS The fellcwing reports descrite the initial oploration (1) and davelopment and technical justification (1 & 3) for the uravailability irdicaters sure.arized ;
in this Research Inferrt.aticn Letter.
- 1.
- Evaluation of Reliability technology applicable to LWR operaticral i safety," Craf t huREG/CR 4618, l'ay 1556. '
i Chapter 4 of this draf t recort explores a concept for ri>L-tased perforrerce :
i ir.d t ca tors . Appendix F u.,us WP905 historical data for the Pavis Cesse auxiliary feedwater sysics to illustrate the feasibility cf develeping an trdicator cf safety sptem availability.
E. Vesely. W.E and A:are, MA., "System Unavailability Irdicaters - Interin
/.ralysis," Bf;L "echnical lieport A-3295 9-30-87, Septer.ber 1987. l l (
1his technical repcrt intrcduces a rcthed fer evaluating uravailtbility cf systen:s ustrg cbse"vaticns of the frequency ard length of dcwntires of the i systers's trains. Specific fonts for the dcwntire frequency indicatcr and for !
the systerr uravailability irdicater are defired. The attributes of these i specific fertrulatiens are discussed which previde tae basis for checsing one l approach for further study. Comparisons of alternative ferrulations cf l unavailet.ility indicators are providcc using statistical simulations fer l l testing the pcher of the apprcach in tracking systerr unavailability. A i precedure guide, software specifications, and flowcbart for the calculatico cf cyclc tased perforrrance indicators using ctservaticos of train ard systen.
l failures and dcwntines is also decurrented as well es delineatir.g the general .
l steps requirtd for irplerrerting the approach.
- 3. Yesely. W.E. and Azarn, ti. A. , "Incicatore of Syster Uravailebility ard l' Unreliability; Technical Justification and Prececures Cuide for traplernentation," Ehl Technical Feport A-32?E ? 28 88, February 1968. ;
1his report ecosolicate-s letter reports anc current work en the develeptrent of sio lified indicators of unavailet'ility fcr possible rear tern use. The work inc.udes pilot at:alyses cf data frcn. Surry ard Susquetar.na.
L l
I l
r h
I f
\
l Enclosure 2 NLd@$507 $9$9 Hours Out of Service Number of Failures Total hours this month when train was out of Number of kein failures service while reactor (ie, loss of train function)
SYSTEM TRRIN was critical this rnanth.
i HFW 2 (RCIC)' 3 I
IIPl I H P C I,'H P CS) 2 3
I
... s g g ,
2 (SSLUS) 3 1
EPS/f1C 2 :
3 1
2 EPS/DC ,
3 l 4
RPS j Trip Breakers 2 i
Logic 3
4 t
BWC system in parenthesis
2 :
Enclosure 3 See VGalle Baba Surveillance Number Success Criteria Test of Trains (t! umber of Trains fleeded to Perform SYSTEM Interval in System the System Function)
HPI (HPCl/HPCS)
. =
, Trip j Bres>1rs Logic
' BWR system in parenthesis -
-1
)
Enclosure 4 SAMPLE CALCULATIONS J.F. Carbonaro, BNL Train Level Calculation A sample are presented calculation below. of the indicators for unavailability and unreliability-The derivation and technical justification for these indi-- $
cators can be found in BNL's Technical Reports A-3295 9-30-87 and A-3295
- 2-18-88.
These are r6fereness 2 and 3 as listed in Encloesta 1.
To facilitate the calculations of these indicators a etaple spreadsheet model was developed. This model incorporates the existing equations for these two indicators. Automating these calculations using this sof tware model removes the burden among other of calculation 1;on the user and also assures consistency of results users.
The tuo measures of systen performance presented here are unavailability and unreliability.
level of the system. The data zor these indicators will be collected at the train Tha variables being sessured are as follows:
fa the number of train f ailures in a given time period da 1: the downtine of the train Tn h the time per~1od increment (i.e., quarter)
For tuas sample calculati~.
for three safety systema for te train level data for f and d were collected surry-1 plant. These systans ares taergency Power (EPB), High-pressure fejection (EPIS), and Auxiliary 7eedwater (AFW5).
D, and L.
To retain ?.he history of these measures, the accumulated variables are F.
period:
These values can be expressed in the following equations for the nth l
fn"In + 1/2 F,,g train failures D, = d, + f n . u + 1/2 Dg g train downtine hrs L, = i n + 1/2 L,,g quarters where ff , das is are the number of train failures , the observed train downtime and the time interval for the nth period respectively. Tha f actor "u" is the undetected downtLas associated with each failure, conventionally assumed to be one-half of the periodic test inte rval .
The factor of 1/2 is taken here arbitrarily to provide an attenuation f aca '
tor for the past history. Vhile this f actor can range between sero and one, the median value of 1/2 will be used in the trial application.
The following example is used to illustrate updating of the variables.
- t e
S a w
~ . . , - - . .-
. ,w Trata Level Busesle Calculation PowerGiven 8ystem, theTra;a following 1: quarterly data for i and d from ens surry-1, Emergency
$UERY EP8 TRAIN-t Tr-Ouarter fail'ures f(f) Downtine d(bre) 86-1 0 6
- H-2 0 0 88 -3 1 19.5 86-4 0 0 87-1 1 17.5 87-2 0 0 For the purpose of this calculation, the values for Fo, De, and Lo were assumed to be 1 train failure, 36 train downtine hours, and 1.88 quarters, respectively. These values were assumed by the author based on a review of the collected data, however, initial values for these variables .ould have been set to aero an well to show that no past history is being .>etained. The calcula-tione of Fn, Dn, and Ln aret 70 = 1 failure Ft = 0 failures + 1/2*(1 failure) = 0.5 failures ft = 0 + 1/2*(0.5) = .25 failures F3 = 1 + 1/2*(.25) = 1.125 failures Fg = 0 + 1/2*(1 125)
- 0.56 failures Do = 36 hrs Di = 6 hrs + 0 f a11ures*(15 days)*24 hrs / day + 1/2*(36 hrs) = 24 hrs D2 = 0 + 0*(15)*24 + 1/2*(24) = 12 hrs Ds = 19 5 + 1*(15)*(24) + 1/2*(12) = 385.5 hrs i Dg = 0 + 0*(15)*(24) + 1/2*(385.5) = 192.75 hre to = 1.88 quarters Li = 1 quarter + 1/2*(1.88 quarters) = 1.94 quarters L = 1 + 1/2*(1 94) = 1.97 quarters l
t La = 1 + 1/2*(1.97) = 1.98 quarters L4 = 1 + 1/2*(1.98) = 1.99 quarters I
.e. n . .nm ~~
-s-The train level indicators for unavailability and unreliability arr determined using the in110 wing equationes qn
- Dn/Ie Probable train downtina hrs /qtr r n = F,/La probable train failures /qtr. I From the previous asample, tha' resultant values for go, and rg, ares ~l l
g4 = 192.75 train downtine hrs /1.99 quarters = 96.7 train downtime hrs /qtr r
4 = 0.56 train fa11utes/1.99 quarters = .28 train failures /qtr.
If it te desired to show q or r in other imits, this is easily done by '
changing the units of F, D or L accordingly. t Bretes Larei calculations The following information with regard to system level calculations as '
required n a the number of trains in the system, and X: the numb 6r of trains required for success.
For example, if n=3 and p1, the "logte" is stated as 1 out of 3 (X out of 'A).
The system level equations for r and q are as followes
- s ys," #1, ' 92, 93, 2, 9 [93, 1
3, 91, 92, Probable system failures /qtr q,7, "g g
- q2, *9 3, pr bable systen downtime brs/qtr The results of the train level indicator calculationo for the 8drry-1 EPS, are shown in Table 1 These are used for the systes level saloulations. The resui:s for the EPIS and Anf8 are presented in Tables 2 and 3, respectively.
The systen logic for the EPS is 1 out of 2.
Systes Level Example Calculations
- 9 " " I#
sysg4) "S1 4) i
- 9 ' * " I# *
- 2(4) 2f bre q, = 4,9.8 probable systest domrtime hrs /yr
'Y8(4) I(4) 2(4) * '2(4) N (4) ,
. e
' - w wp - W
. \
4
, .28 fger ailures , 281.7 bra , .72 failurea , _96.7 hrs
,sysg4) qtr qtr gtr
, 78.88 failures-hr' . 3LJuuuL . I atr qtr I' 3AIU " ,69.6 failures-hre gtr
, 4 etre , , at r .
yr 2L90 Trs'
- r,7, = .27 probable system failures /yr;
. Note:
The bracketed numbers below the indicator variable represent the time period that the values correspond tot the designation for the train values has no brackmas.
quarter number The 4: sample below represents the unavailability (g) of train 1, for 9
1(4)
Plant Laval Indicators Dpon completing the train and systen level calculations for the indicators, the aggregate plant level indicators were calculated.
tion ofThetheaggregate systen level of the usavailability indicator, q, is obtained by the suuna-calculations t agg
- 9EPS
- 9FWS
- SEPIS probable downtina hrs /yr in 3 selected safety systems The essregate summation of the system of thelevn1unreliability valueet indicator, r agg, to also taken as the r,,, arEP8 * #AFW3 * 'RPIS probable failures /yr in 3 selected safety systems The aggregate for mean time between failures (NTEF), is equal to the recip=
rocal of the unreliability aggregate, r agg.
, NTBF,,, = 1/r,,, years / failure of any of 3 selected safety systens
,In this example three safety systaae were selected, however this number can either be inorgased or decreased depending on the application.
MTSFaggTheare results shown in forTable the4.sinFigurequarters 1 is aofgraphical data collection forrnaqagg,io representat gg, and of the 9agg indicator, and Figure 2 represents a graph of the NTBFagg indicator.
t e e
-% _ w
- - .3.
~5-Trend of Amareaste Indicators The trend of the aggregate indicator is calcular.;sd as the mean of the previous four quarters (X ) ainus the mean of the itst two quarters (Y1 ). I divided by the standard d,eviation of the previous four quarters (ag). This is expressed in the foranlas I',- II Trend = -
o The results are expressed in torna of deviations from the previous four quarter unans measured in standard deviations. .
A sample calculation of the trend indicator for q.gg is shown below.
Quarter Sagg*
N-1 4.33 86-2 4.08 N-3 64.64 M-4 31.90 87-1 143.21 87-2 38.34
- iktet (probable downtimes brs/yr in 3 selected sa(ety systems)
I,= q,,g o = O.33 + 4.08 + 64.64 + 31.90)/4
= 31.29 hrs /yr Yg = q, = (143.21 + 38.34)/2 l
i = 90.88 bes/yr 1
, 2 o , [(4.33-31.29)2 + (4.06-31.29 4
)2 + (64.64-31.29)2 + (51.W31.2O )2 e,= 27.36 probable downtime hrs /yr in 3 selected safety systems q = . 0.88 assgg,,,g) 27.36 = -2.18 standard deviations .
5 i
Figure 3 is a finger chart of the gagg and NTSFgg indicators calcu-lated in this example application as well se the esistIng performance indicators Commercial ifuelear Plants published1987. Augustas reported in the AROD quarterl data through June 1987.
In this initial trial application the aggregate indicators for unavaila- l bility and mean time between f ailures are trended against their own past perfor--
mance.
In the future, given a largs enough application, a plant's performance can also be trended against the industry average. -
Sunportins Dats .
Table 1. Surry-1378 Train and Systen Level Indicators Train Lavel Indicators Systaa Levet Indicators Train-1 Train-2 Failure Este Unavailability Tr/ Quarte r r* q** r* q** rt qtt 86-1 0.26 12.4 0.77 200 3 86 -2 0.11 4~. 5 0.13 6.1 0 89 34 7. 1 0.09 86-G 1.37 194.2 4.1 0.44 182.2 0.34 64.6 86 -4 0.28 96.7 0.72 281.7 0.27 49.8 67-1 0.64 237.4 0.86 329.7 87-2 0.76 142.9 0 32 118.6 0.43 177 7 0.20 38 5
- in i of train failures per quarter _
- 1n train downtime hours per quarter fin units of probable system failures per year ttin units of probable systen downtime hours per year Table 2. Surry-1 EPIS Train and Systen Level Indicators Systan' Level Surry EPID Train Level Indicators Indicators Tr/ Train-1 Tratn-2 railure Unavail-r* q** Trata-3 Rate ability Quarter r* qa* r* qa* rf (ft 86-1 1.378-06 1 55 E+00 1.371-06 1 55E+00 86-2i 1.371-04 1 55E+40 8 20E-12 3.083-06
- 6. 75 E-07 7.61I-01 6.73E-07 7.61E-01 86-3 6.73E-07 7.61E-41 9.791-13 3.68E-07 3.35E-07 3.78E-01 3.332-07 4 168+00 3.335-07 86-4 1.67E-07 9.41E-01 1.671-07 3.755-41 9 173-13 4.955-07 3.43E+00 1.673-07 1.84E-41 5.635-13 5. 06 E-07 87-1 8.33E-08 4.70E-01 8.33E-08 1.71E+00 87-2 8 33E-08 9.393-02 7.002-14 6.29E-08 4 16E-08 2.353-01 4.161-04 8.34E-01 4.168-04 4.693-02 8 72I-15 7.643-09
- in f of train failures per quarter
- in train downtime hours per quarter ,
fin units of probable system failures per year ttin units of probable system downtina hours per year e o e an -n --.- - - - - - - - - - - - - ~ - - - - '
.y.
Table 3. Surry-1 AFW8 Train and Systen Level Indicators Systes Level
$1rry AWS Train Level It,!.icators Indicators Yr/ Tra.n-1 Tra:,n-2 Failure Unavail-
- Trann-3 Esta Quarter r* q'* r* q** re qa* rf ability.
qtt -
8I6-! 0.26 2.1 0.26 5.2 0.52 18.6 3.34E-05 1.645-04 86-2 0.13 1.0 0.13 7.1 0.25 42.1 3.775-05 2 54E-04 86-3 0.06 4.0 0.06 71 2.14 850.4 86-4 0.03 26.6 5.463-04 2.02I-02 0.53 213.8 1.07 448.2 1.295-02 87-1 0.0l: 13.3 0.27 2 13E+00 106.7 0.33 223.7 1.60E-03 2.64I-01 87-2 0.01 9.1 0 13 60.1 0.27 111.7 2.793-04 5.113-02
- in i of train failures per quarter *
- in train downtime hours per quarter tunitt of probable system failures per year ttin units of probabla system downtime hours per year Table 4. Surry-1 Aggregate Measures Yr/
s 1 86-2 f5 4.1 bf 0 10 10.5 86-3 64.6 0.35 86-4 2.9 51.1 0.29 3.5 87-1 141.2 0.76 1 87-2 1.3
.t d.5 0.20 5.1 !
- probable downtine hrs /yr for 3 selected safety systems
- probable failures /yr in 3 selected safety systems tprobable yrs /f ailure in 3 selected safety systems
. l l
l e /'h ab $n n b A
- - W--.---------------------- --
il
- b. -
I .
l l 1so .
0 140-
- 120-
?
, I i 100-H o 80-Y -
. a 60-I f
y 40 -
? 20-O-
86-1 86-2 88-3 86-4 87-1 87-2 Year - Quarter Figure 1.
Safety System DaavatImbility Aggregate 3,
1 (EPS, ABES, EPIS)
O l .
i __ _ _ __ _ _ _ _ - - . _ _ - . _ - . - - - _ - - - _ _ - - - _ _ _ _ _ - - _ _ _ _ _ _ _ _
12 Y
- io- ,
/ 8-a Y
6- -
a s
. p 4- T
~
II y 2-O-
86-1 88-2 86-3 88-4 87-1 87-2 Year - Quarter '
Figure 2. Safety Systema 3EEF Aggregata i (ns. AFRS, EFIS) I'
^
. s
- e
-to-Declined Improved 5 j
Automallo Scrame While Orltloal 0 .
Safety System Actuatione
.5 1
2,9 Signifloant Eventa
~ 1.7 Safety System Fallures 3,7 Ferced Outage Rate
.5 Equipment Fuced Outagea /1000 crit hra
(
i$;%s'hh[ sis. 2,2 Aggregate System !
e w' x s ,:'*
. i Unavellbillty (nretyr)
- 1.0 Aggregate 8yoom MTBF i
i i r i i . . .
1.5 -1 i
-25 - 0.5 0 0.5 0 1 1.5 2.5 1
( Deviations frorn Previous 4 Otr. Means (Measured in Standard Deviations) 1 l
\
Figure 3. Surry-!: Trends - 2nd Quarter India; 97-2 l
l l
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