Rasmussen On Nuclear Safeguards

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PROBABILISTIC RISK ANALYSIS

Its Possible Use in Safeguards Problems Norman C. Rasrnussen Professor of _Nuclear Engineering Massachusetts fnstitute of Technology Canbridge, Mass.

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1.

0 Introduction

The recently conpleted Reactor Safety Study (RSS) which resulted. in the ITASH-1400 report has stimulated considerable interest in the use of this nethodology as a possible way of assessing the risk invoLved in other þa;^ts of'the nuclear fuel cycle as well as other societal activities. This paper briefly reviews the RSS nethodology and discusses its possible application to the safeguards problem. For the reasons discussed herein, the Paper'concluães that there are possible applications of these methodologies for the development of effective safeguards. Howeverr ân overall quantitative risk assessment of the safeguards issues is at present beyond the capability of the methodology. 2.0 Description of RSS Methodology

In quantitative risk analysis risk is expressed as a function of the probability of occurrence of an event and the rnagnitude of the consequence being examined. On'e of the most common definitions (but certainly not the only one) is simply the product of probabiLity and the consequence. Thus such studies must evaluate both the likelihood of certain events as well as their consequences. A variety of methodologies have been deyeloped for carrying out these evaluations. Z.L Estination of Probabilities . The principal techniques used by the Reactor Safety Study were a 'forn oi decisi.on'analysis cätt."d "eyent trees't which defined accident seguences, and a nethod ca1led "fault treesn which deternined failure probabilities, Event trees start with an i4itiating event of possible serious consequences and develop possible accident sequences depending upon the operability of various plant systerns that influence the Subsequent course of events. This logic is illustrated by the sinplified event tree for a loss of coolant accident (LOCA) shown ln Figure 1. In Figure I the values of P1 through P5 are the probability of failure of the functions at the top of [tre figure. The probability of successful function is given by (l-Pi). The size of the radioa.ctive release depends upon just úhãt systems fai1. Various pQssible consequences are indicated on the figure. For exanple, if power fails after a pipe break no other safety systens willçfectric operate and so the core will lnelt and there wiLl be à vêry

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Nuclear M¡terials Menagement

a release is ft x P2. large release. Ih" prgbSÞility.of.such it-is important to consider any In calculating the piobability into account' ãäpã"ã""cies Ëetw-"ett n1 "ttg P2 and to take them ihã-ã;p;ndencies betweËn theiå probabilities are cornrnonly referred

to as i'common mode f ailures

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As can be seen from Figure 1, a number of-possiu;le.acciFigure itr is dent sequencei--rt" identifie¿ Ui such a. diagram' version of the event trees used by actually " y"ty-ii*;iii:-e¿ ^Study to illustrate the-methodology' The event ih; Reattor Sá'teiy ii"ur actually us-ed produce many more accident sequences ' When using the event tree method the analyst must decide For reasons a1just when i"itiatiñg events nust be considered. ready discusseã, tftË principãf -concern. in reactor accidentS is ¿;;;.me1ti'g,whichcänariiefromeitheroverheating.(i...,^ fai1-. operating at tôã-higfr " po*ãi 1ãve1) or.undercooling-(i-'e'I inherent the of Because ieat). ure of plant systems to relnove-the inater reactori- C"ãgãti"" iemperature coeffíci"l!l ii'ãpãitiãi--ðt very that core rnelt by overpower wasstudy ih;'it"áy group deternined*"tt the by undercoofingl llY: unlikely conpaied, to core undercooling accidents ' analyziig effort tttu o? $;;;-;óri-

Inanalyzingundercoolingaccidents,evglttreesu¡gr9 These inclucled ' developed-ior five type: of initiäting events size-pipe brea\,,snal1 vesset rupture, Large pipe-brã;k; *;lTum events. ffte first four are LoCA's ;i;;-Utè.t, aná trañsiãni Transients refer to those cases fr;î'i"g-áifi"tuttt characteristics.down for either a planned orim-unwhere the plani ir asked tã-itrut questions of planned 1.u"rorr. In the transient case the two reactor trip,.and ðo the decay heat report,ance "tu,---¿oãJ-iitu function ProPerlY inoval systems seA1-though the event trees can define the accident probathe quences they do not providJ ã"y *"iftoa for deternining probabilithe various failure tîiï;;'";'^;ír"-àccide'nt. To do' rhis been enough systens there ties must be known, Generally -have notprobabilities so the in reactor tytt"*i-tá fiovide.thes-e failures ,,fault tree,, rnethod wâs usã¿-io'deternine theie probabilities'

Thefaulttreelogicisthereyerseofthgeventtree and. final undesired eyentevent' starts with ,o*ã defined it in that this of causes possible reasons back-iã-i¿ã"tify all the pow"t to the emergency safety A sirnplified ¡;"ii-ir""'foi-"iôis'of caused 2. The iot event t1} !: AC features" is shown in Figure poler since power, or loss of DC either by tosi of AC pgwÞI power circuit' control the: operates provides ttr"-ãnãigi-"ã¿ DC is the sun of the probabilievånt .!u-i;p of piãu"uirity iiil'i;; ;ï;; ði-tit"tu tt^ro events (more accuratelv -if t i ,; ll:1"ï ì îi3. i;. :"ti: "å :$"Ïäo I 1. iis;,,";,,' ilg;,ötç" ;,i;glÀg can be caused ment of the diagram, constããi.loss of AC poï/er' which on site of loss by loss of off lite powet. "tá the simultaneousproducr of rhe is power power. Thus"ir,ã-pr"6ã¡iri;t-"i--ioii ðr AC

fall

1976

67

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the probability of loss of oll.rite,power probability of lld !h" the loss of on site power. This relätio"rrrif ii-iilustrated by the "and" svnbol on ttte figure.- i;-;;"ctice the tree is developed further until the ra:-iurãs indicat*a'ry the bottom boxes aïe such, things as "re1ay f ails to op"rr,;- ,lirlt.i, f ails ,,, or such human f ailures as "operator mista-k"sú and and. maintenance 'iiest The probabit ities of these events are trrown ir;;-;;perienceerrors. r, rvith similar systems in industrial ;;; ;;ãuy. The study has been crit icized by some for not including errors in ah: analysis. clearly tír"r" p"ãpie- Iiaye either not read or not understoôd tl.u s¡ggr.' To illüstiate this point consider Tables 1 and z rox the pwR'and BwR-;t;;;;-irilure tributions' The column marked "rtui¿rät"" includes failurescon_ various..pieces. of equip-ment, while thoie narked ,,test and of naintenance' and "human erior" áre tlpåt of rr"*u"-.ã,rr"¿ failures, lwo As noted' part of the common mod.e coílribution is also d.ue to human errors. From these tables it ïi crear that not only have mistakes bv operators and *uiniã"ãt.J-p"tsonnel been includ.ed, but il-tltl.systems. they aïe dominàni ãontributoïs to rhe overall unavailability of the system. human

Another criticísn expressed is that it is not pos_ sible to accurately predictoften very r*ät1 probabilities by these methods ' rt is true- that sma11 f ailure .;a¿;-ãr" dj.f ficult _very to predict accurately by_ fault treà *ãinoat becauie at such levels of probability very ûnritery and su¡ii" failures can be important. However, our fault tree anaiysis rã""ã that the unavailabilities of !!" systens were not in- tire ;";g;'^;"nera11y regarded as very srnal1. This is indicated Þy Table! 3'ãnd 4. 'rqotã .rrãi ;b";i'tl + *}1 systems anaryzed had'""r"ãii"¡iiiti", l{ the of more';hr;"íö:+".'' 0f 40 svstems anaryzed', 39.had. unavairaÀiiitiãi greater than" 'than'rõ:¿i-ärrä'^iö'*"r* 5 l-0- , s4 *"i" greater grearer rhan 10-s. The probabilit¡ 19-9/year ttiát-ãppããrr on îhe consequence .ofcurves is not the orobability þ{ systen faiiures but is the probability of the most serious includes the probability of "Í:.iãeni. Thisthe core melt times, the probability_of worst type'of containment failure tines. the prõbabil íty 'of-irrð'-iorrt wearher tirnes the probability.thar tiie wind is'¡i;*i;; iã,u"r¿, ? region of very high population density. since these raõtois are indeienáent, it is quite proper to- murliply their pr;b;biiiti"s tog"ir.,Ë, ro obtain such a sma11 value juit'as it i; ptof"r-to estimate the chance of obtainins heads s0 Lonsecutive vvu!¡Yv L¿rt.çr ¡rr flipping ããi", as times'in (L/2)30 I fO-g.

using reliability-analysis techniques as d.escribed above, tire Reãctor_ safetr'study conclucled that in u.s. water reactors the probability oî core melt was about I in io,oo0 per

plant per.year. The uncertainty ãrri!n"a to thís number rvas plus or minus a factor of 5. riris nrrñ¡é,,ou, obtained for the 24th and 34th plants of the first roo u.s. reactors. rt would. be expected thàt plants b*i;t uùiri'toaay *iÀrri-rr" somervhat better because of^tþu impiovenrents i; ã;;i;".

N

uclear Materials Management

The value of 1 in 20,000 per plant year is at least a factor of 10 higher than many people expected. However, to determine the significance of this number one must determine the public. consequences of a core ne1t. 2.2 Estimation of Consequences The consequences of a core melt accident are a function of a variety of factors. These include the amount of radioactivity released, the amount of heat released with the radioactive gases, the prevailing weather conditions, the population density in the contaminated area, and the value and usè of the property in the contaminated area. The anount of radioactivity released following a core nelt accident depends upon the conditions present in the core at the tirne of melting, the effectiveness of the radioactivity rernovaL, and the way in which the containment fails. Not surprisingly, the amount released can vary fron very large to quite smalln depending on these factors. Table 5, taken fron WASH-1400, shows the probability and fraction of rad.ioactivity released for 9 PWR and 5 BWR release categories which cover the spectrum of possibilities. Accidents PWR I and 9 and BWR 5 do not involve core melt; all the rest do. It should be noted that in the event of core nelt the amount of radioactivity released can yary by rnore than four orders of nagnitude (i.e., more than a factor of 10r000J. As night be expected, the smaller releases are significantly more 1ikely than the larger releases. After release fron the containment, the rate at which dilution of the radioactivity occurs is an inportant factor, This depends in part on the prevailing.meteorological conditions, Fârticularly the atmospheric stability, the nixing height, and whether or not precipitation occurs. In add.ition, if the released gases €ontain sizeable amounts of sensible heat [as they do in many cases), the reLeased gases wiLl rise, thus reducing. significantLy the exposure of the people on the ground, Finally, of course, the number of people affected will depend upon the population density in the exposed areas. fn the WASFI-1400 study a complicated conputer code rt'as developed to treat the aþove factors. It was used to calculate the likelihood and magnitude of the vari.ous accident.sr caûs€*

qr¡ences

2,3

of Core Melt Accidents There are a nunber of possible consequences of a release of radioactivity, including such early effects upon health as injury and death, and such latent effects as cancers and genetic and thyroid effects. In addition to these effects on heaLth, danage to property was considered. For each of these types of consequences, calculations lrere made to deternine the rnagnitude

F¡ll 1976

Consequences

69

ffii

of each consequence as a function of the probability of occurTence. These results \^iere obtained by using the weâther and -population. density characteristic of thã sixty- eight data sites on which the f ir,s t 100 u. s. reactors will operate. ih" curves for the various risks for an ind.ustry of 100 ïeactors in the U.S. are shown in Figures 3 through '8,

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Figure 3 is the risk curve for fatalities that occur in the one- to two-month. period following tir" accid.ent. In Figure 4 -medical the curves represent iilnesses thar wõu1d t"q,titå care sometine during the first year following the accident. Figurå shows the increase in the íunber of cancers per year durin! iiru-s thirty-year period-b_eginning about tãn years^after the These cancers would bé addeã to the nornal incidence ".ãî¿ã"t. of about 17,000^per year in the_exposed. population. Figure 6 rate is a sinilar cuïve for the^nunber of_gènetic- effects per yeãr d.uring tfrã-¡irsi generatíon. Only a smal1 fraction thèse îre the oblious de--fects and most_are-e{pressed as an of increased. susceptibility t; genetically related diseases. The normal incid.encã rate of such effects i: 8,000 per I9ar. The number of cases of thyroia-nããuïes per year during !h" lJtirty-year period. following ifrã is shown in Figure 7. Thyroid.'nod.uies are smal1 giowthsaccident on trrã-trryroid gland that can be effectively treated by simpte surgery. such_ growths are quite common.and'occur spontanéô-u;iy at a rate of about 81000 per year in a normal populätíon the size of the exposed population,

It is,intere_sting to note that eyen the largest accident identified (which haã a 1g-9 per year perin reactor occurrence rate), the increase in the number äf cânce.t and genetic is so sna1l that it could not be srarisrically- id.Ëniifi.u¿defects ih; presence of the normal occurrence rate. Tliis is not true, i;however, for-thyroid nodules,, since in the largest acðident the normal rate would be doubled. Thus, although a lãrge nuclear accident ;õ"1ã" be a yery serious event, it is ñot an aãcíd.ent of the unprecedented proportions some nuclear critics suggest. In all cases , ãs wourd be expected, the magnitude of the possible consequences varies over a conÁiderablã range for the reasons alr-eady discussed.. It is also i*potiãài to that all the curves-have a sharply d.ecreasing negutive s1ope.note This means that smaller cons-equènces are mucñ rnoie 1ikely ïtr".t i"iãu, ones. Risk curves of this general type for any of tn" histori_ g?1ly observed risks show tñe same cÍräructerisiic Thus, fires that ki11.ten pgopre aïe much nore ritery-th;; slope. those ki11 one hundred peopre. This characteristic äf tist curvesthat has been noted nany authors and generally reflects the fact that a nurnber of-by indepenclent factors-affect ihe cons.q,r"tã"r and it

70 N

uclear Materials Management

is very unlikely that the worst conditions would prevail at given time.

any

Figures 9, 10, and 11 illustrate this point. In these figures historic risk curves for a number of man-caused and natural risks are plotted and compared to the nuclear risk curve for fatalities and property damage. Such curves for the other consequences are not shown because no reliable historical data exist for then. There seens 1itt1e doubt., horvever, that modern technological society produces cancers and genetic effects by other means. one obvious example is the radiation dose received by victins of accidents as a result of X rays. There are many other examples.

3.0 Safeguards Applricâtions of Quantitative Risk Assessment In regard tô the nuclear polarer issues, the WASH-1400 study has stimulated the question of whether these methods can be used to assess risks in the other parts of the fuel cycIe. There is no reason that they could not be applied to the reprocessing plant. For a number of reasons, horvever, f do not believe that the safeguards risks can be quantified using these procedures. One of the basic assumptions ín the RSS nethodology is that failures are basically random in nature. 0f course, such studies must recognize that some of the failures may haye dependencies. The dependencies between these failures are referred to as the "common mode failure problem" in reactor safety. Neverthe1ess, except for these corrections, the basic assumption of randornness is made. This assumption allows one to estimate a system failure by an appropriate mathematical combination of the failure rates of its parts. In the case of deliberate huinan action, âs in inagined diversion scenarios, such an assunption is surely not

val id

.

This is not the only problern. As we have discussed, a risk assessment also requires a prediction of the magnitude of the consequences. Such an assessment requires knowing at least a probability distribution of the possible yield of a nuclear explosion and infornation as to rvhere the detonation rnight occur. Clearly, the point of detonation would not be random relative to híghly populated areas. Thus, in the consequence analysis we are also faced with problems that seen to be beyond the capability of present techniques.

Fall 1976

71

with problems of this type it is sonetimes possible assuming conservatively q9s:imistic to make a useful anaiysis by 'exist. In sone cases one f inds that .rvhere uncertaiities values is sti11 smal1 enough to l{ay obtained in this the risü of the prob"ifirãru be acceptable. Horvever, in the safeguards case many if they are only *Incõnservative holvever, abilities can be d^efendéd as being if one case, this aisigned valuei of nearly unity. probability high fairly a considers the maximum consequeice to have the risks are certainly unacceptable ' From r¿hat has been said So far it rnay appear that we are is no way to concaught in a nuclear "catch 22." That isr_there in an acceptproblern vince oursefves that rtIe have dealt with this case. able way. Horvever, I do not believe this is the be followed is It seems to me that thê approach that mustmaterial VeTy nuclear to make the unautho rizeð. access to special so access In essence we must make the probability.of difficult. sma11 that u"'rãr, if all other probabilities in the risk assessment ãi"-""ity ttre-Uenef it of nuclèar power st111 outrveighs the risk. Faced

the Ifwefocusonjustthispartofthe.problem,l?19iy reliability believe I syËtern, effectivenerr-oi the safäguards I notice thât t]rere ã"ãryrir techni[uåt-.utt bã very vã1uab1et on just this topic ' sessions are three papurd in tomorrow rnôrning -s papers_i yet seen_ any -of*these Ãiirr",iãñ-r'rrã"* not-4-ãr l-:1:"T:-tl: basä¿ o1-tl'1:^::::l: ?:Y*T.fo:-11:", i' representt K.;ä;i.u; ;ä;ä;-ã; u-P11Ti:li$^l'i:tii..:tT:"?:l Ñsi, 'rriår'^'i"r'å"ã--i""ð.-rt iä"räËiiity äãiðguãras an-arysi-s . From tireìr, !1:1"t it appears the

other two þapers are on the same general subj ect' needed to I do not belieye the basic input infornation is system eguardsaf accuratery q,rattiify-itrã ef fectiveness õf a â's the such efforts currently availablb. However, I beligveroad of fornulating- these the down uå started have Kendrick'paper we can better understand just whlt ¡;;b1ems in^ r".it-a-way that tyP.e of . work continues, ii"áa àf information âre lacking ., I f tothis hope that tnese à"á I hope it wi1l, it is reasonable quantitative assessments *"tfrod, *ay sorneaay produce neaningful would assessments These of the effectiv.eness of vari'ous syltens. design facility eârty stages of be particu1""iy"ïuf"rU1"'itt-thu nade ' readily be can *ft"it modifications of safeIt is comforting that to date the effectiveness recognize, guards systems has been essentially perfect. i|ie allnumber of ever-increasing an' ñorru,r"t , that there Seens to be it thist 1ight.of In violence. of senseless and irrational acts .' technique: safeguard:. .1 is essential to continually improve of reliability believe the development "ttâ ptop"t inpleñentation *"thods cãn contribirte^ to thõse improvernents which have ;;;itti, alrvays been the goal of this society' .

Nuclear Materials Managemenl

CONTRTBUTIONS TO PT¡R SYSTÐM UNAVÀIIÀBILTITES

Table 1

Contribution (t) Hulûan Test and

System

Reactor proÈection ÂuxiliarY feedwater¡ 0-8 hours after sma1l LOCÀ 8-24 houls after s¡nall LOCÀ 0-8 hours without' offsite Pofler Contairunent spray lnjection

tirniting control¡ Ht; single train Hi; both tralns Hl-Hl; singte traln Ht-Ili; both trains

65

35

5

9

86


56

l4

6

80

74

I

27

6

67

61

26 2

92

100

6

Low-pressure injection High:pressure inJectlon

Safety lnJectlon cont¡ol¡ Single t¡aln Both trains Contaf.nnent spray reci¡culation

coNlRrBUTroNs

59 16 80

41

57

42

l3 7

23

60

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19

68

56

37

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31

68

75

23

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77

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Contrlbuti.on (t) Hu¡ÍaD Test and Reactor protection vapor suppresslon: l,arge LOCÀ S¡nall LOCÀ E

1

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ContaÍnment heaE re¡noval Lort-Pressure reclrculation High-pressure recirculation Contal.nnent leakage Sodl.r¡¡n hYdroxide adldit'ion 2

t3

I'njectlon;

åccr¡mulators

fable

Conullon . Hodes {at

Mainteriance

Conseguence

Emergency coolanÈ

ErroË

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coolant injecÈlon: Icw-pressure coolant. injection core- apraY tnjection

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ßergency

ÀutodteþressurL zatLon

xigh-plessure coolant Lnjection RCICS

1?

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85 86

ContaLnment leakage:

targe

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Dr¡nrcII >6 ln.2) Drlnrell 1-4 tn.2) lletwell >6 in.2) ?feÈwe].l (r-4 ln.2) S¡nall LOCÀ ãigh-pressure servLce wafer: nequired within 30 ¡¡lnutes neáuired withín 25 hours .úPCBS anit CSIS punp cooling (ES9l) SeconåarY sontain$ent

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98 100

2


96

r00

100 ?

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100

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73

Table3P!.{RCAT,CUTJ\TEDSYSÍEMUNÀVÀII,ÀBTLITIES(22SYSTEMS) Median unavailability

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o,

Nu¡nber

of systens

Percentage of Systerns in

Each UnavailabiLiÈy Range

to-l<e.,<10-'t ¡'¡ ro-4:Qr,l .to-3

5

238

4

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Tabte 4

EwR CAIÆIr,ÀTED SySTEM

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I'NÀVÀILIBILITrES (L8 svsrEMs)

l.: ì

Median

t.l,,i ''i

: ,i,i 'il, ,

unavailability O,

Number

of systens

Percentage of Systems in Each unavailabiríty Range

ro-6 S o¡{ < 1o-5 ro-5 Í Q¡¡ < to-4 ro-4 3 Q" < 1o-3 ro-3 < Qu < 1o-2

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TABLE

SU}LV¡¡\RY OT' AECTDENTS INVOÍJVXNG CORE

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C't

DT'îÅTION

9¡ÂRN¡NG

ELWÀIIO¡¡ coNtÀtNEENl

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4.0 t0.0.

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130

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of Èhe J.totopac uscd ln thc study ls ls fo.¡nil ln Àppcndlx Vtt.

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Cor

Ptr lar llbr l¡ir Cltr lu, llp, Zlr

.

lo$Gr Gncrgy ¡cle¡se ttte than thl¡ vatue appitcr to palt o! ttrc Þcrlo{ oves rhlch thc r¡dllo¡etlvlry fs bclng :oloascd. the effect of lowcg energy role¡sÇ tatct on consequencês ts foun¿l ln þpenilt:c vt.

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Probabitiry Ðistribution f.or Early Fatalitics per year for LOO Reactors

Approxirnate uncertainties are estírnatecl to ba represented by factors.of 7i4 anrl n rnagnîtr¡clcs and by factors "T-:-"lrrQuene_ oi 1/5 and 5 on probaLrilities.

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probability ÞistribuLion for Iiarly ll-ì.ness per Year for IOO Iteactors

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79

Fall 1976

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cf

80

of

to be rcpresented by UG and 3 on consequrnce magnituclus and by factors

115 and 5 on probobïlities"

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fall1976

81

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lor

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85

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1.

Property damage rlue to auto accidents is not included lrec¿use data are not avaîlable for lov.r probabil;ty events. Auto accïdents cause ebout $15 billion dam.rge each year.

2.

See sectïon 6-4

lor a discussion of conf ícl¿ncu. bounds applicable to the non nucleðr curve. See sectisn 5.5 for the confidence bsuncts on the nuclear ctrrve.

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Nucle¡r M¡terial¡ Managen

DI SCUSS I

ON

SILVE KALLMAN - LEDOUX COMPANY: You mentioned that a number of persons are kil1ed by airplane accidents. -You specified that ä nurnber of those weïe kilfed on the ground by airplanes falling ,rpon ih"t. Your next category stated-the number of peoqle ki11ed

by falling obj ects. l4y. question is: Were the number of pe9P1e tiffe¿ by-faliing airplanes included in the second category? DR. RASMUSSEN: I?d like to give that gentleman a gold star. frve presented that slide several-hundred tines in the last few years änd no one has asked that question. Frankly, I d.ontt know the answer. Those numbers were taken directly fron the United States Statistical Abstracts where they are categorized that wâI

'

Perhaps another way of illuminating by the j.nterveners: Looking recently used been iir" q,r"ttdary has to a counte'r-part of the "maximun credible acci.dent." Do you have a viewpoint on this kind of transference? DAVE RUD0LPH

-

EDTOW COMPANY:

DR. RASMUSSEN: Our worst hypothetical airplane crash ki11ed EOTOOO becausÀ it cráshed iito the stands i^¡hen thgy were crowded. to If'you assune the maximum credible accident in safeguards of a heart the in detonated weapon iabricated be ; successfuiiy *á¡õr-ðity, i-i'i'obvious that thè consequences are horrendous. I dontt know if thatts a neaningful exeicise at all, and T donrt see how it hetps cope with the problem.

rve go! to deny terrorists access is required io iftii kind of material. We have tõ do whatever I donrt be..made. rnigft that threats viable ;; ã;f;"d-;g"itt"f "tty (which is acðident" credible see how the .õ"ð"pi-ôf "***imurn a that so defined is and accident" Uasis now dalled th;--;á'e;ign with it) can be applied set of equiproãrrt-ðátt"Uu designed-to deal in a city' explosive large-nuclear io thê ¿eitoñaiion of a tank car FRED SCHMIDT - UNIVERSITY OF WASHINGTON: Last year a. rniddle in the loaded with cfrfoiinã rolled off a railroad trackThe event received open.. break ãidtt't it of Seattle. fãriü"átãfy someone when tatei rnonths 1it,tle publi.iiy until !everal io*".thousands of peonlepointed might our rhat, if ii'itää-b;"k;;-ópã"' éven ki11eà. Su,ch tñinss ro11 have been rhoroughly gass"¿-ãiii',."and ver through searrï;it;iå Ëiåtãtri """if ði.rl*årr"iñ" be a target' easily It'áou1d terr'orists. they are not targets 9f organi zation can- relatively It also seens to ne that a terrorist ãnd use ii to blow up the Chicago easily buy ro,ðõ0"'ão"i-of.TÑT-why don't rltgse rhings_g:.rt if we rrade center ii;; ;;;piãl . tô vulnerable to teirori'sts? really believà ã,rr ,ociety is some and I!ve looked at this question DR. RASMUSSEN: ltrell Fred., quite vul.nerable to derrorist acts ' have concluded that we are rir"-answer to your question seen some on a smal1 ;;;ià.

We know

what the problen is.

We

we,ve

Fall 1976

87

is that most terrorists do not set out to kiLl or naim or damage the. largest possible nunber. of people they could" nàineir-iñ-;iwant to draw attention to.themsèlvès or their cause. Theú d.o-'

of course, :oTe yeII danaging_ things (look at rrerãn¿, ioí -.. ' example) ánd-have õ¡ten stated, thât if faced " I do be]ieve,we with terrorist-problens have a lot of thingé to worry other than nuclear power ,lalggt-:. I further Èelieve thâtabout will not knuckle under" ltlerll ttput in the reserves, as wesoiiety need' to defend ourse.l-ves, and_wi1l not give up nuclear power because of terrorist threais" That would-not UË lggi.rf iince we would next .have to giye up every other technology [hat a threat could be made_ upgn and that inciudes most tächnõiogies. I do think it nay be logical to put some effort into defend.ing ourselves if we see a threat. devel_oping.

88

Nucle¡r M¡teriele Menegement