23 /s- 4%2

UCRL-ID-125857

Complexity Versus Availability for FusionThe Potential Advantage of Inertial Fusion Energy

L. j. Perkins

‘hiadocummt waaprepemdeaen ~ofwork qonmredbyanegency &ti UnitedStateaGVmUMm. NeMkflWunlted mGovemman-y=% - anyWarral.~,.~.’=zy=z””d~”--=d”% p~lxap~a~tktiteuea woaldnatinfriqp privately awnedri@ta Merelue yo=becig~pmductpfaeahf facdcefbyi rademtmkmarbm muktummtmceeadyca99tMaari mplyitedmemam#mmm mMm#GoWmmmtorthe univmityofcdifm$a. Ihe Vlewe and 0@nhn8a’%%!% !&!&!2!2tiM-hnDtnauamdy atateordiect tImleeofthe uldtedstet@a Government orlheulliverekyd caWoda#end!?hanmtbeuaedfar edWIkhgo?puductmdomelnmtpurpea&

lldarepatheebeeslrapmkeddirecfly fmmthebeatavdabIe copy.

AvaileMetoDOEandDOBamtmc&aEwntheOffkaczfSchtifk and Ta&tkaIMmnat&on

P.o.BoxlQ#ckkRidTNwwlPriceeavailablefrom(615)5%401, FE 626-84)1

Availdietothepubk fromtheNetimel TechnicalIn&ma&n Smvica

Us. Dqmhent of Camnerce5285PortRoyalRd.,

~ VA 22161

-.

Complexity Versus Availability for Fusion:The Potential Advantages of Inertial Fusion Energy

L. John Perkins

Lawrence Livermore National

September 5,1996

Laboratoy

SynopsisProbably the single largest advantage of the inertial route to fusionenergy (IFE) is the perception that its power plant embodiments couldachieve acceptable capacity factors. This is a result of its relativesimplicity, the decoupling of the driver and reactor chamber, and thepotential ~o employ thick liquid walls. We examine these issues interms of the complexity, reliability, maintainability and, t herefore,

‘availability of both magnetic and inertial ji.ision power plants andcompare these factors with corresponding scheduled and u nschedu ledoutage data from present day fission experience. We stress that, giventhe simple nature of a fission core, the vast majority of unplannedoutages in fission plants are due to failures outside the reactor vesselitself. Given we must be prepared for similar outages in the analogousplant external to a fusion power core, this puts sev~re demands on thereliability required of the fusion core itselfi We indicate that suchrequirements can probably be met fir IFE plants. We recommend thatthis advantage be promoted by performing a quantitative reliability andavailability study for a representative .IFEpower plant and suggest thatdatabases are probably adequate for this task.

Z. Background and Mot ivatio~

Our perception of the commercial attractiveness of future fusion power ~ .

plants is somewhat clouded by the following uncertainties:

1.

2.

3.

4The uncertainty that the physics and technol gy will work as projectedon paper today.

The uncertainty in the capital cost of the extrapolated technology. . .

The issue of complexity, reliability, maintainability — and, therefore,the uncertainty in the availability — of the fusion power core.

That is: Will they work, how much will they cost, will they break and canthey be easily repaired?

1

-——— .v— . . . ..-—,,a,,m.. ,,,,.,,.,, . ,.- .“ . . . . . e,, !,*. ~..m. ,’,Z-,W,..-”.” .-is.-*—- ----- ., .- . ._,

I.

The first category of uncertainty is the reason we have on-goingresearch and development programs. So ql!irnately we will know whetherthe physics and technology “works” before committing to commercialconstruction. The uncertainty in the second category — i.e., uncertainty inextrapolated capital costs — is more problematic, not least because of theabsence of any real data. The prospective International ThermonuclearExperimental Reactor (ITER), for example, is a one-off, state-of-the-art systemwith little substantive prior cost database to draw on. Consequently,uncertainties in this category are probably around a factor of two for next stepfusion power devices like ITER* and probably more for our ultimate powerreactors. Presumably, such uncertainties will decrease as further developmentis performed.

However, it is probably the third category which is perceived “to be themost serious concern facing prospective power plants of the conventionalmagnetic fusion energy (MFE) class. Such devices — e.g., the tokamak andstellarator — are characterized by large superconducting magnets, solid firstwalls and many complex iritegrated components within the vacuum-tightfusion power core. It is here that IFE plant concepts potentially offer thebiggest advantage and, therefore, an advantage we should seek to quantify asfar as possible. In this discussion paper, we examine this central issue ofcomplexity, ~eliability, ~aintainabfity and, therefore, Availability — referredto as “CWIIW’in the remainder of the text.

MFE reactor design studies have been performed in recent years whichsuggest that commercial reactors based on various extrapolated advancedphysics assumptions would exhibit a cost-of-electricity of about -1.5 to 2 timesthat of today’s better experience fission plants [see, for example, Refs. 2, 3, 4]. Ifour projected reactors are, indeed, only, say, 50% more expensive than presentday fission then conventional MFE fusion might appear to have somepotential in the energy marketplace of the future. On the face of it, this wouldseem to be a reasonable standpoint to take. Why then, the disquiet over recentyears regarding the state of our commercial MFE reactor product [5 - 15]? Itsuggests that, in our hearts, we either don’t really believe these numbers, or,at least, are concerned that the real situation will be considerably worse ‘because of, at least, the CRAM prospects.

We note that the functional dependence of the cost-of+lectricity (COE)resulting from most reactor studies to date are determined almost entirely bythe capital co@ projections for the plant. The CRAM aspect is sidesteppedeither from reluctance or, more usually, from the lack of easily identified “formalisms for obtaining quantitative results. Accordingly, in today’s reactor

* ITEl? has an “official”cost of - $6B [1] but is considered by many to be a machine in the $1OB+class. No detailed costing uncertainty analysis has yet been performed for this device.

2

.

studies, plant capaaty factors are typically supplied as input constants withlittle or no regard to the CRAM aspects of the particular design.

In general, the uncertainty in the CRAM for a conventional MFE plantis large and is probably the Iargest single contributor to the uncertainty in theprojected COE. For example, an lTER maintenance study performed in 1991indicated that, in the event of a serious failure of a toroidal field coil, it wouldtake in the r~ge 3-5 years to replace this magnet once the machine” had beenoperating for 1 year [16]. There is no indication from our reactor studies that acommercial tokamak reactor would be substantially less complex than ITER,even those based on extrapolated advanced physics. Thus, the perception byfuture customers that a conventional MFE fusion plant is not maintainablein a finite time frame suggests that they might be considered non-viable on

i this aspect alone. That is, irrespective of our projections of potential advances~ in the physics and resulting reductions in COE through lower capital cost, thef CRAM prospects alone may be considered simply a go/no-go issue by our, future customers.4

Therefore, not only could we argue that the COE for projected IFEreactors may be lower than that of the conventional MFE approach [171but,rather, that our IFE power plant concepts could conceivably pass theirreducible test — That potential customers are suffiaently confident thatminimum acceptable capacity factors are attainable that they would be willingto entertain the possibility of ordering one.

One other related comment is in order here. Economy-of-scaleprinciples can be used to reduce the projected COE of both MFE and II% plantst

![see, for example, Refs. 2, 18-21]. Such studies typically indicate that reactorsconstructed in unit sizes significantly larger than lGWe may approach a cost-of-electriaty competitive with advanced fission projections. However, theproblem of CRAM may negate that conclusion for MFE. While the utilitystructure in the next century may be different from today, and multi-GWelectriaty reservations may become the norm, certainly in the world as awhole, it must be considered questionable that any utility — private, public orgovernment-owned — will invest in a large, single heat source which is -perceived to be vulnerable to frequent outages and significant downtimes forrepair. Hydroelectric plants are commonly found -in multi-GWe sizes.However, these have the crucial difference of redundancy where each planthas the modularity of parallel water feeds to a number of independentturbine-generator sets. Therefore, with regard to redundancy, large, multi-GWe IFE plants with multiple, maintainable target chambers presents an “additional potential advantage. Of course, they would typically be basedaround a single driver but we believe this can be sufficiently reliable based onpresent accelerator operating experience.

3

. .

Z Fission ~ce to Ftunon Pro-. . ● . ● *

Presently operating fission plants provide the best real data we have toguide our thinking on capacity factors* of potential fusion power plants.Accordingly from availability and outage data published over tie past threeyears [22-29] we can make the following observations of relevance to fusion

There are 108 present fission plants in the US each with more thanthree years of operating experience [29]. The capaaty factor performance foreach of these plants were recently published by Blake [28]. Taking Blake’s rawdata, and, neglecting the worst three plants” which otherwise wouldappreciably skew standard deviations, Fig. 1 gives a summary of theirthree-year-averaged (1993-95) capacity factors (CF) at design electric ratj.ng: -

Fig. 1. Summay of 17wee Year (1993-95) Capacity Factors for 105 out of 108*US Fission Plants at Design ElectricalRating(raw datafiom ~lab [W)

● Median capacity factor (C)?)at design electric rating= 79.0%● Mean CF = 75.4Y0, with a standard deviation of t12.3Y0“ Best is Prairie Island 1 (530MWe PWR) with CF = 90.6’Yo.. Worst* is Dresden 2 (794MWe BWR) with CF = 43.l%

● 23 units (22Y0of total) have CF > 85’%

. 80 units (76’ZOof total) have CF > 70%

● 8 plants (7.6’Yoof total) have CF c 50%c Small reactors (S700MWe) as a group had median CF = 84.3%

● Large reactors (21020MWe) as a group had median CF = 78.1’%

Bottom three plants fmm the 108 US group were dropped from averaging pmcedums here as~ey skew averages and standard deviations appreciably. These plants and capacity factorsre Indian Point-3 (10.5Yo),Browns Ferry-1 (2.7%), and Browns Ferry-2 (O%O)

“ A note on definition of availability ~ ~paciw facto~ “Availability” iS tie PWWI@Y of .time that a plant is operational and avaiiable to produce power even thou~ for masons ofload following and grid cbnands, it may not do sb at its full design electric rating (DER).“Capacity factor” is availability multiplied by the averaged fraction of DER output over theavailability period. Capacity factors of fission plants are usually quoted as three yearaverages to smooth out year-to-year variations.* ‘l%ese plants and capacity factors are Indian Point-3 (lo.s~o), Browns Ferry-1 (2.7%), andBrowns Ferry-2 (O%)

4

. .

It is instructive to select four of these plants to examine the basis forthese capaaty factors in terms of both scheduled and unplanned outages.Accordingly, extracting data from Refs 22-27, and 30, Table 1 summarizes theoutage data and contributions to the unavailability for the best US fissionplant (prairie Island 1 with CF = 90.6Yo), a plant around the mean ,(Robinson 2with CF = 76.OYO)and two poor performers (Sequoyah 2 with CF = 46.99’o, andQuad Cities 2 with CF = 46.4%)

From Table 1, we can draw the following observations and inferences:

● A typical scheduled outage for a well performing fission plant is -6-8weeks every -Mmonths, coupled with an average shutdown/startup periodbefore/after the outage at fractional power of -28days total. This wo@d resultin an averaged capacity factor (CF) of -86Y0 providing there were no otherunplanned outages. Note from above, the industry median CF of all plants is-79Y0 while about one-fifth of the 105 US plants have a CF better than 85Y0.

● If onjy refueling was to be carried out with no other serial maintenanceactivities, then, in an 18month cycle, typical theoretical unavailabilitieswould be -2weeks for core head removal and changeout of fuel assemblies,and -2-3weeks start/up shutdown. This would give a. theoretical maximumcapaaty factor of -949’0*. Note that MFE fusion plants are effectively requiredto undergo a “fueling” outage due to blanket replacement (see below); IFEplants with thick liquid walls are not.

● Refueling is one of the major activities during a scheduled outage butnot the only one. In some cases, it’s not necessarily a rate-limiting critical step.Other than refueling and loyr standard vessel inspections, all other majorroutine maintenance activities take place outside the core, i.e. prhary loopand balance-of-plant. Very importantly, the latter would be expected to applyto analogous systems in fusion plants outside the fusion power core even inthe absence of a refueling outage.

● One major reason for the differences in capaaty factors between PrairieIsland 1 (90.6’XO)and Robinson 2 (76Yo) is that the former had only one 4standard scheduled fueling outage in the 3-year 1993-95 assessment period (inthe. middle) while the latter had two (one near the beginning and one nearthe end).

● The typical projected fluence lifetime of an MFE fusion reactor blanketis -10-15MW-yr/m2, i.e. a lifetime of approximately. 3 full power yearsat “typical projected ‘neutron wall loading. Therefore, a typical blanket changeout

● Actual outages of this order have recently been recently achieved at Houston Lighting andPower due to other the-critical routine maintenance Wig performed on-line [31]

5

— ..—-.———

Table 1. Scheduled and Unscheduled Outage Contributions for Four Representative US Fission Plants

Plant andCapacity Factora

PWR, 530MWe

90.6%, 1st/105

.RotUnson 2PWR, 700MWe

76.0%, 66th/105

Seauovah 1PWR, 1148MWe

46.9%, 101st/1 05

Quad C/t es 21BWR, 789MWe

46.4%, 102nd/’

Scheduled Outages and MajorActivities 1993-95

June 94, 44days:

RF*~ loyr vessel ISI*I rmh gen. inspect., @ dMSR steambundles,SGEC, 40MOV tests,

fbtalooastdov’dstaltlp days@-42)Sept 93, 63daysRF*) SL, SGEC, RCP qkement, RHR maint.

Apri195,56daysR<(full - offbad), SGEC, MOV tests, turbineinspcbns, EDG overhaulfbtaf (mstdmwataftup da# -56)March93, 63cfaysRF’, LPT qbement, MSRV iqwtion, ILRT*,SGEC, RCP qkwment, Ioyrvessel ISI, RHR pumpmotorm@acem@

sap 95, 6odaysRF, SG mati., (Awn d 4 SG, RCP rep!,, condenser-, RHRpunp rrmtoreenMng, LPT~, -~ ppng modsfktal coastbdstadup & -56)March93, 84daysRF, ILRT, RCIC pump replacement, shroud aoxsscwer @acemnt*, systemvafvewwk”

March94, 76daysRF, rnbl plantmint

Match95, 126daysRF(full comdfbad), tiove&wf, genirwviceinepedon,tofussurfacereccet”fritalCoastdowdstartupdayt@44)ear csoaoitv factor at deskm electrical ratina. 1993-95.

Unscheduled and Over-RunningScheduled Outages 1993-95

1993-95:-21days.Miill, itemsexternalto com

Note:Onfyone rwfuelingcycle1993-95

1993-95:-8Sdays. Mill. itemsexternal tocore

NoteTwostandatdrefuelingcycles1993-96

1993-94, -334days:Eroawcomsion repailsonsewndmysideofsG

1993-95:- 68days cmother nisce!f. items external tomm

1993-95:-216 Ck3YSHP(2Itwbine bfowq. Other rrkcell. item external tocore

05

‘= Cnlkal pathtaek. a=3 ❑ Total days for SLJ/SD 1993-95 at average of 50% designelectrical rating. RF - Refuefing ISI - Itkew-ice inspection; hkR - Moisture sep%rstorrehsate~ SG - Steam generato~ SGEC - Steam generator eddy

Mach 95: TonJs surface moat (extended expected80ckq+s schd. outage to126days, but thisvmaplanned)

Note: -Three standadoutagesin 3yeara.- Regularoutageearetaking-80 daysmther

than5080 daysofbetterpetforrningplants

currenttesting MOV motor operatedvalv~ SL - Shtdgs lancing d @e&mgenerato~ RCP - Red-w ooolant ~, RHR --Residusl heat tsmovslsystem EDG - Ewrgency dieselgenerator LPT - Low press turbin~ MSRV - Main steam reliefv-, ILRT - Integratedleak ratetestingRCP - Reactorcoolant purryx RCIC - Regctorcors isolationcoolingeyetm HPCI - High preeeumcoolant injection

. .

schedule might be 50% of the modules every 18 months. This is a similarmaintenance schedule to a fission refueling outage. “However, to becompetitive in outage time, the fusion blanket changeout itself would haveto be completed in -2 weeks including torus ingress. This is not required in athick liquid wall IFE plant. Note also, that the lifetime of fission fuel istypically W3,000MWti-days/ton. By comparison, taking typical design andoperating parameters for ARIES-II-like vanadium blankets [3, 32], yields anequivalent lifetime for an MFE vanadium blanket of -18,000MW~-days/ton,necessitating the changeout of about 809f0additional fusion core mass for thesame thermal power lifetime.

● Fission outages greater than about 20Y0, i.e. capaaty factors I.ess thanabout 80’XO,are usually due to either unplanned outages or over-runningscheduled maintenance (Table 1). However, some plants have scheduledoutages more frequently than every -18months. For example, in Table 1,Quad Cities-2 plant is on 1 year refueling cycles due to the nature of. theirutility grid structie and had three such cycles during the 1993-95 capaatyfactor assessment period. Thus even with no unscheduled downtime, theirideal outages would be greater than 20Y0. In fact, this plant has always been~ble to keep its scheduled refueling outages to 40 days each, usually being atleast double this (Table 1). Coupled with significant unscheduled outages inthe balance-of-plant — e.g. over 200 days due to a blown high pressure coolantinjection turbine — gave a composite three year capacity factor of only -4670

● The vast majority of unplanned (scram) outages in fission plants aredue to failures in systems outside the fission vessel, i.e. in the primary loopand balance-of-plant. Again, these would be expected to apply to analogoussystems in fusion plants outside the fusion power core.

● The overall implication of these data is an extreme demand on thescheduled and, in particular, unscheduled outage requirements for the fusionpower core of an MFE reactor, (i.e. cryostat, PF magnets, TF magnets, vacuumvessel, shield, blankets, diverters, etc.) and its fusion-specific auxiliary systems(i.e., fueling, heating, current-drive, vacuum, cryogenics, etc.). The same ‘demands are also true in aggregate for”the core and fusion-auxiliary systemsof an IFE plant (i.e. driver, beam transport, chamber and fuel factory), but, dueto their decoupling and individual maintainability, we should realize asignificant advantage in this area.

M @ws for MFR and IF’&

IFE provides a route to a power plant embodiment which isfundamentally different in many respects from that of the standard MFE classof concepts. There are no large, expensive superconducting magnets that are

7

exposed to potentially damaging fusion radiation. This unique feature allowslifetime fusion chambers to be designed with renewable liquid coolants facingthe targets [21, 33, W], instead of solid, vacuum-tight walls that must berenewed on a frequent basis due to radiation damage. The relative advantagethat this feature affords the core of an ICF power plant (i.e. the chamber)cannot be overstated relative to the availability issue.

Moir [34] has studied the quantitative advantages of liquid walls andsuggests a res@ing tangible reduction in COE. His analyses indicate a savingof -27’Yoin the COE accruing from the impact on capital costs (--3Yo), blanketreplacement costs (--12Yo) and capaaty factor (--12Yo). Moir suggests thatliquid protection will increase capaaty factors by -12Y0 by reduang scheduledand unscheduled downtimes to replace damaged blanket modules.

For a qualitative view of CRAM issues for MFE power plants, Figs. 2and 3 show details of the design, assembly and maintenance of two in-vesselsystems for ITER, namely the blanket and divertor [35]. We note these are notnecessarily final design configurations for ITER nor are they necessarily fullyrepresentative of an ultimate power reactor embodiment. Nonetheless, ITERmust be considered the best guide we have to date of a serious engineeringdesign effort for an MFE reactor and we should note carefully the engineeringcomplexities evident in Fig. 2 and 3. Note from above that, to remaincompetitive with fission, we must be able to perform scheduled maintenanceon such configurations in a commercial reactor configuration within a -2week period every -18 months. This is notwithstanding scheduledmaintenance on other components of the fusion power core (shields,vacuum vessels, magnets, etc.).

ti the case of unscheduled outages, the required reliability ofindividual blanket segments is very high. Take, for example, a typical MFEblanket system with 16 sectors and 9 blanket segments per sector. Table 2.illustrates the required reliability of each of the 144 segments — i.e. requiredmean-time-between-failures, MTBF — if the blank& system is to contributeno more than 5’XOto the total unscheduled outage of the plant. This is shownas a function of the mean-time-to-repair MTTR, where the total blanket ooutage risk is given approximately by:

OutageRisk = 1- ~(1 + A47Tl$ I MTBFi)-1

where n is the number of blanket segments. Two observations here: First, “with a breaker-to-breaker mean-time-to-repair’ (MTTR) of, say, one month —probably near the minimum feasible for an unplamed blanket failure inside

, the high vacuum enclosure — the required reliability of each sector is -240full power years!. Second, even so, our example 59’ooutage risk due to theblanket alone is probably too large given the multiplicity of other systems

8

.

.

eB

lanket

sewn

ent

Tro

n*p

ort~f

●k

L

i:.I/

E

..

co--

..

..

.

1.

m.1

Diverter

Cassette

Storage

Con

cept

forR

and

omA

ccess

\

-..

Ill

I

Table z Required Blanket Reliability to Limit hscheduled titages to S5~o(Tokamak blanket With 16 sectors and 9 segments per sector)

MITR = mean-time-to-repair

MTBF = mean-time-between failures ( = [failure rate(yrl)]-1)

Req’d MTBF for Each Blanket Segment

MITR = 1 week 55 full power years

M17_R= 1 month 240 full power years

MJTR = 6 months 1440 full power years

inside the fusion power core. Abdou [36] has addressed similar issues in termsof the reliabili~ requirements of the DEMO and beyond, and its impact on therequirements for a volumetric neutron source.

For a more quantitative view, we refer to a bla’hket availability studyperformed in 1991 by Bunde et al. [37J Fig. 4 gives an illustration of an MFEreactor blanket similar to that analyzed by Bunde et al and is of a water-cooled, solid ceramic breeder design with stainless steel structure and heliumtritium purge (no detailed blanket illustrations were explicitly available inBunde et al.’s pap&). They approached the problem as generally as possibleusing a bottoms-up approach. First, this entailed an accounting of theindividual components ~d assembly details of the blankets themselves, i.e.number of welds, total length of piping, number of pipe bends, etc. Followingthis, they applied a failure database for analogous components in present daysystems such as fission reactors where an extensive database exists. Whencoupled with a fault tree analysis and estimates of mean down times forrepair (i.e. MTI’R), they were able to estimate an overall outage risk.

...

Fig. 5 illustrates the failure database employed by Bunde et al. in thesestudies, while Fig. 6 shows a breakdown of their estimation of the outage riskcontributions between elements. Firstly note, unsurprisingly that the outagerisk of this blanket system is high, i.e. greater than 40% alone. Second, abouttwo-thirds of this outage is due to weld failures, particularly those betweentubes and plates/tanks. Again, perhaps not surprising in view of there being-37,000 butt welds and greater than 5 km of longitudinal welds (Fig. 4). BothBunde et al and Abdou [36] have tinderlined the severe demands put on theblanket reliability for MFE power plants.

11

LOhfR

$s’.1

,/,,,’0 ,.

. .

L.

A6Ksmw helium gop

—outer cladding

k=

bery[lium

L pressure tube

not er

2nd c lodding

spocer

Y“ Ist c~oddingv L iA[02

wruwwcm

Ceramic (LiAIOz) Tz breeder, HScooled,He T2purge, Be neut. multiplier, 316 s.steel structure

Total length of straight pipes= 220km

No. pipe butt welds = 37,000

No. pipe bends = 2300

Total length of longitudinal welds= 5.3km

Fig. 4. Tokamak Solid Breeder Blanket similar to that Anal~ed by Bunde et al. in the Availability Study of Ref. 37.

LONGITUDINALI

V&m[14]

A [l/(h’m)][13]

● ********# ● ****O******* 1**** *.*m Oe *** (I ● 9******* [13]● *e******, ) ● **, **m*m **e* )************* D...****** [13]

+——. .-- —- ___

BU7TWELDSOFPIPES

[14, 16, 17], . [18]

i [1/(h’weki)] [1]

PIPES(STRAIGHT) *

L [l/(h’m)]k [14]

[17, 30, 31][18]

+[1]

——..---— ——

[14, 17]PIPEBEND [18](1 BENDAT l@j +1 [l/(h*bend)]

. . .- –. .I&ll I&lo 1(P l@ W’ 10* 10-s ‘

FAILURERATE A [dimqisiott dapending.on ttem]

MIN REF MAXMSICDATA: –——+——- valii fw Small Ieaica,low loadedmaterial,nucleartechnology,‘conventionalnuclear’welds,

prc-operadonshop welds (forchangesdueto devi~ions from theseconditionssw Table1)

Thetypesof linesandcorrespondingdotsdesignatethevariousareasof informationsources:* nucleartechnology,especiallysodium-heatedsteamgeneratorsvarietyof heattransferequipmentreactorpresaumvesselsvarietyof nucleartechnologyheattransferquiprncnt ( x = meanvalue)ccmventiondandnuclearvcsadsandpiping,national(USSR) andinlcmalional(IAEA)

Fig. 5. Examples of Failure Databases Employed by Bunde et al. [W]

1134

s

6

II

13

13

14

15M171819

SIX.AIGHrPll=.$U31@NBEslltAlGHTPrPB(3utPlJRmlsmAmTPIPEF3PSBlD(D,90dWPIPBWELDPIPSMAINI’ENANC3?WELDsmAIGHr T(JB4 Immnnu?rWELD,WAIJS VACMGTANKWELD,WALL9HBIWAl=t TASK

=y’=wTg~msP’

WW2S, TANK ~~wuDsoFoRIvHt7t?BEsWED, WAILSVACMB-TANKWELD.WALUHJVWA~TAf4K

t- +—--- ---- ---— ---- —-—- ——-+1- ---—- --- L —— -- - I

& _+VJATERTAti~SJ?@P.--—21 S’lRAlOHTPIPe 1-

-—— -— -- ——

mmsm, 180d?gHOOKBREAKSIXA3GHTPIPSFDZBEND, l:OdcIPIPBWRDFiPBUAlhWAN(X WLDsTuAlOmnmBmTue.em’ue.e3g

● m**** *e **a** ● *O******* I——-- —--- --—-

b*e**O **O***** d* OO*s*O***m O*

———— .-●*0 **********8a ● *m *****m-———- ---- ,-

——

● ☛☛☛

---

33 STRAIQUI’IRPSSIJRETUBE

4

snwaHTPIPB(HsPuRc?E)~BomoDPIPE

WUJSEOFm/WAUVm.OSTnAlalrr F&EFIFsaml),$low_ WELDm MAINIENANCS WEI.DSilW(3HT’lUB~ lN3J31’~W@ID,WALLSVACA@TANKWUO,WA1.ISHWWATTXTANK

----— --- - ----— —— -- .--- —- ---——-— ---— ---- —---

l**** e**** **es# ● ***o ***D**”

---—- --- -— —-- —-

b00**9e **b**** ● ee**e***a **w D“*●

t

--—- —

,BLANm

}1 1 1t r I

~owA’l=TA?W3AlSED SP. t 1 1

MOP DR~TUBES_,TANK triummmm, wAUS VACMGTANKW* ‘uWA~TANKWLD,WA7ZfiTANKS3.OBEDSP.WM OFOWV~TUBI?S I

102 10-t

WELDs

sTRAIGlrT PIPEs

PIPE BIXX

TVTAL1

-———— ---

104

OUTAGERISKGM [ =] = FAILURE RATE [l/h] ● MEAN DOWN TIME [h]

Fig. 6. Breakdown of Outage Risk Contributions Among Blanket Design Elements (Bunde et al [37])

.

. .

As an alternative illustration of the “complexity” issues in MFEblankets, Table 3 compares some parameters for a generic MFE fusion blanketwith analogous quantities for the core of typical fission pressurized waterreactor. Note that, for a fair comparison, the MFE analogy to the core of afission reactor inside the reactor pressure vessel should really, include thecomplete fusion power core inside the cryostat boundary, including blankets,shield, divertor, vacuum vessel, TF coils, PF coils, etc. In the case of WE, theequivalent “heat source” is the target chamber, beam transport and driver.Again, whether in terms of number of welds, amount of piping, number ofpenetrations, heat fluxes, etc., Table 3 underlines the “complexity” concernssurrounding the CRAM for MFE cores, especially since we really should alsoadd the corresponding quantities for all the other systems internal to thecryostat.

Given the simple nature of a fission core, it is not surprising that thevast majority of unplanned outages in fission plants are due to failuresoutside the reactor vessel itself. Consequently because, like fission, a fusionpower core comprises a heat source to boil water for a steam cycle, we must beprepared for similar outages external to the fusion power core for analogoussystems. Again, this puts extreme demand on the scheduled and, inparticular, unscheduled outage requirements for the fusion power core itself.

conclusions andRec ommendat ions

Probably the single largest potential advantage thatconventional MFE power plants is in the perception that itcredible capacity factors. This accrues from three main sources:

WE has overcould achieve

1.

2.

3.

The relative simplicitydecoupling the driversystem. Projected MFEfusion power core with

of the ICF reactor chamber made possible byfrom the nuclear-grade thermal conversionreactors, by contrast, are a single integratedinterlinked, hard to maintain components

The potential to use thick liquid wallsl thus providing for lifetime ~structural components and low activation inventory.

The potential to multiplex reactor chambers to provide operationalredundancy*.

? ws ~d liquid wall W@d be ba&ed by a low StNSS, rum-nuclear steel wall

* ~Is also has the associated advantage of permitthg capital cost phasing. Note that MFEreactors could, m principle, also be multiplexed but as each fusion power core is essentially aself-contained unit, economy-of-scale penalties tend to negate any redundancy advantage.

15

Table 3. Comparison of the “Complexity” of a Generic MFE Fusion Blanketwith a Fission Cor@

Design

Total length of straight

P* (km)

No. pipe butt WddS

No. of Pipe bends

Length of longitudinal

w,elds

Penetrationsb

Surface power density

$AW/r#)

Peak fast neutron power

fluxh(rulw/r#)

Generic MFE

Fusion Reactor

ceramic(LiAlo2)breeder, waterooofed, Be multiplier,He triiiumpurge,ferriticsteel struoture,concentrictubularconfigurat”mn

-220k

-37,000k

-2300k

-5kmk

-800

~0.5c/ z5d

-3h

Typical PWR

Core

-180 fuel olusterseach witha -17x17fuel rod matrix.Fuel=O.&m d~ U02pellets insidezircaloyCladdhlgof wallthickness 0.57mm@2milis)

21

01

0

0

o.6e

-o.o15h

Approximate

ratio:

Fission/Fusion

—

“0.1

3‘(l .41)

3

3

-o.oo5i

a. For a fairer comtwison to the core of a fission reactor inside the reactor messure vessel, theMFE analogy sho~d really include the complete fusion power core inside&e cryostatboundary, including blankets, shidd, diverter, vacuum vessel, TF coils, PF coils, etc.b, i.e. through bulkheads, shieldin~ cryostat, and pressure boundariesc Peak, at first wail.d Peak, at divertor.e At fuel cladding surface.f Relative to fusion first wallg. Relative to divertorh. Power flux of fast neutrons through the first wail (fusion) or cladding (fission)i. Reason for this surprisingly small ratio is twofold. First, surface/vohune ratio advantage forfission rel to fusion is a factor of -350; second, only -5% of me 200MeV fission reaction energyappears as fast neutrons (<k>-2MeV) whereas in fusion, WO of the 17.6MeV fusion reactionenergy appears as fast neutrons (En=14.1MeV)

j. Control rodsk. Data on pipe lengths and welds taken from Bunde et al [37’JL There are&d caps welded at the each of fuel rod, i.e. a total number of -52,000 end capwelds. However, these are factory installed and inspected and considerably more reliable thanon-site butt welds between tubes and plates.

.

What, therefore, should be do~ to further quantify and, therefore,promote the CRAM advantages of prospective IFE power plants? There havebeen several , quantitative studies of tokamak reactor reliability andavailability based on bottoms-up accounting [see, for example, Refs 3740]. TheIFE program should consider performing analogous studies for an IFE powerplant to highlight the advantages in as quantitative a manner that designsand databases will permit. This is a complex task as it requires full componentdocumentation, fault tree construction, a failure and repair database, andMonte Carlo-like sampIing analyses. Note, however, that we cannot, andshould not, argue that databases are insufficiently developed for this task. Forexample, the II% reactor chamber — probably the source of greatest concernregarding outage risk — is basically a steel vessel containing plates, tubes,pumps, and liquid coolant flows. Operating data is available at some level foraIl these individual components, much of it from direct power plantexperience [371

Accordingly, taking the HYLIFE-11studies of Moir et al. [21, 33, 34] as anexcellent point-of-departure, we - recommend the following work beperformed:

1.

2.

3.

4.

Perform a comparative listing of the number of critical systems in arepresentative IFE power plant with analogous quantities for a typicalMFE power plant and a representative fission plant. For example:length of straight pipe, number of welds, number of pipe bends,number of valves, number of pumps, number of parallel coolingsystems, etc. Good detailed discussions of chamber fabrication anddesign can be found, for example, in Ref. 41.

Quantify, as far as possible, the CRAM advantages this IIFE power plantby calculating total outage risk in terms of MTBF/M’ITR for thecomplete fusion specific plant defined in #l above.

Quantify, as far as possible, the advantages of thick liquid wallprotection in terms of both scheduled and unscheduled (failure) outage ,of the chamber. Compare with thin wetted wall protection.

Quantify, as far as possible, the issues of multiplexing an IFE powerplant, where a sin@e driver is coupled to several reac~or chamb~rs, topromote the advantages of WE regarding redundancy. This includesboth the systems aspect of multiple chambers and capital cost phasing .[see, for example, Refs 18-20] and also bottoms-up availability studies.

In closing, we underline that probably the single largest advantage ofthe WE route to fusion energy is its potential for adequate reliability,maintainability and, therefore, availability of the fusion power plant. Wesho@d strive to promote this advantage on as quantitative a basis as possible.

17

.

Acknow edgments1

The author takes pleasure in acknowledging informative discussionswith Ralph W. Moir, Wayne R. Meier, Ronald L. Miller, B. Grant Logan andRoger W. Carlson. This work was performed under the auspices of the U.S.Department of Energy by the Lawrence Livermore National Laboratory underContract W-7405 -Eng-48.

References

[l] ITER Technical Advisory Committee,(TAC-8), ITER San Diego Joint Work Site,

[2] J.D.Galambos, et al., “Commercial

Report on the Eighth TAC MeetingSan Diego, CA, June 1995 -

Tokamak Reactor Potential withAdvanced Tokamak Operation’’, lJucl. Fusion 3s,551 (1995).

[3] R.A.Krakowski, et al., “Lessons Learned from the Tokamak AdvancedReactor Imovation and Evaluation Study (ARIES)”, Los Alamos NationalLaboratory, LA-UR-93-4217 (1993)

[4] C.G.Bathke et al., “A Systems Assessment of the Five Starlite TokamakPower Plants” to be published in Fusion Technology (1996)

[5] J.P.Holdren, Science, 200,168 (1978)

[6] L.M.Lidsky, “The Trouble With Fusion”, Technology Review, p33,Massachusetts Institute of Technology (Ott 1983)

fl K.H.Schmitter, “The Tokamak: An Imperfect Frame of Reference”, p47 inUnconventional Approaches to Fusion, B. Brunelli and G. G. Leotta (Eds),(Plenum Press, NY, 1981)

[8] RCarruthers, “Criteria for the Assessment of Reactor Potential”, I&id., p39

[9]. R.L.Hirsch, J. Fusion Energy, 5,101 (1986).,

[10] D.Pfirsh and K.H.Schmitter, “On the Economic Prospects of Nuclear.Fusion with Magnetically Confined Plasmas”, Max Planck Institut FurPlasmaphysik, Garchin~ IPP 6/271 (1987)

[11]: C.Sweet, “Criteria for the Assessment of Fusion Power”, Energy Policy, 17,419 (Aug 1989)

. .

[12]. J.Reece Roth, “A Critical Evaluation of the DT Tokamak as a Power Plantfor the Electric Utilities”, Proc 13th Syrnp on Fusion Engineering, Knoxville,TN, Ott 1989, IEEE, 89CH2820-9 (1990)

18

—w.—.. —.,------ —,.

. .

[13]. W. D.Kay, “The Politics of Fusion Research”, Issues in Science andTechnology, p40, Winter 1991-92

[14] C.G.Bathke et al., “A Need for Non-Tokamak Approaches to MagneticFusion Energy”, 17th Symp. ‘on Fusion Technology, Rome, Italy, Sept 1992

[15] L.~.Perkins, “The Restructured Fusion Program and the Role ofAlternative Fusion Concepts”, Testimony to the US House ofRepresentatives Committee on Science, Lawrence Livermore NationalLaboratory, UCRL-ID-123417 (1996)

[16] T.Sweeney and L.Goldman, “Toroidal Field Coil Replacement for theInternational Thermonuclear Experimental Reactor”, Bechtel Inc, September1991

[17J R.W.Moir, Lawrence Livermore National Laboratory, privatecommunication (1996)

[18] W.RMeier et al., “Economic Studies for Heavy Ion Fusion Electric PowerPlants”, Lawrence Livermore National Laboratory UCRL-94335 (1986)

[19] W. R.Meier et al. “Economics and Other Figures of, Merit”, Chpt 7 inEneq# fiorn Inertial Fusiim, International Atomic Energy Agency (1995)

[20] B.G.Logan et al, “Requirements for Low-Cost Electriaty and HydrogenFuel Production from MuRiunit Inertial Fusion Energy Plants with a SharedDriver and Target Factory”, Fusion Technology,28, 1674 (1995)

[21] R.W.Moir et al., “HYLIFE-IL A Molten-Salt Inertial Fusion Energy PowerPlant Design”, Fusion TecnoZogy 25,5 (1994)

[22] List of Scheduled Outages at US Nuclear Power Plants, Nuclear News 36,No. 1,31 (1993)

[23] List of Scheduled Outages at US Nuclear Power Plants, Nuclear News 36,No. 9,37 (1993)

[24] List of Scheduled Outages at US Nuclear Power Plants, Nuclear News 37,No. 1,40 (1994)

[25] List of Scheduled Outages at US Nuclear Power Plants, Nuclear News 37,No. 9,33 (1994)

[26] List of Scheduled Outages at US Nuclear Power Plants, Nuclear News 38,No. 1,35 (1995)

19

. .

[271 List of Scheduled Outages at US Nuclear Power Plants, Nuclear News 38,No. 9,26 (1995)

[28] E.M.Blake, “US Capaaty Factors: Crowding the Ceiling”, Nuclear News39, No. 6,24 (1996)

[29] World List of Nuclear Power Plants, Nuckar News 39, No. 3,40 (1996)

[30] D.Cook, Commonwealth Edison Co., Quad Cities Power Plant, Cordorva,IL, private communication (1996)

[31] S.Rosen, Houston Lighting and Power Co., private communication (1996)

[32] L.El-Guebaly, University of Wisconsin, Madison ~, pri@e

communication (1996)

[33] R.W.Moir, “hnprovements to the HYLIFE-11 Inertial Fusion Power PlantDesign”, Fusion Technology, 26, 1169 (1994)

[34] R.W.Moir, “IF%Power Plant Design Strategy”, to be published in FusionTechnology (1996)

[35] ITER Technical Advisory Committee Informal Technical Review on In-Vessel Systems and Related Physics, TAC-95-16, ITER Garching Joint WorkSite, Garching, Germany (1995)

[36] M.A.Abdou, “A volumetric Neutron Source for Fusion NuclearTechnology Testing and Development”, Fusion Eng. and Design, 27, 111(1995)

[371 R.Bunde at al., “Reliability of Welds and Brazed Joints in Blankets and itsInfluence on Avafiability” Fusion Eng. and Design, 27, 111 (1995)

[38] R.Bunde, “Reliability and Availability of the Next European Torus”,Fusion Technology, 14197 (1988)

[39] Z.Musicki, “Availability Analysis of Fusion Plants Employing a MonteCarlo Simulation Computer Code”, PhD Thesis, University of Wisconsin,Madison (1984) WI, University Microfilms International, AnnArbor, MI

[40] Z.Musicki et al, “The Fusion Engineering Database”, proc llth IEEE Symp.on Fusion Engineering, Austin, TX (1985)

[41] P.A.House, “l+YIJFE-11 Reactor Chamber Design Refinements”, FusionTechnology 26, 1178 (1994)

I

20

Technical Inform

ation Departm

ent • Lawrence Liverm

ore National Laboratory

University of C

alifornia • Livermore, C

alifornia 94551