CCW',lISSIONF:DFLLF COXWI'I'A' Z:URO?E:E Stabilimento di IsDra

CONCCP1'SFOR THE XJCLGATC?R.Ai'S'r'UTATIOI\I OF XADIOACTIVE Tr'ASY'EPR33 FISSION RFACT3RS AT ?RESF‘N'I IJNDPY DISCUSSICXC

~~,~~ ii*G~ md E.SCHXIDT presented to the JEXDR?C: aeeting Of RiS$ (!?a17 1975) bJ X.RIF:F

In this reDort, a survev on the xroble-ns involved in the disDosa1 is given and results for ultinate disqosal techniques, as fission reactors, sgallation reactors, ;?lld fusion reactors are reviewed.

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5.1" Desip of Spallation Reactor 5.2. Additional Costs of Nuclear 3nergv due to Incineration lx, a Snallation Eeactor 5.3. Demands Eclr Nuclear ?easurewnts

95240002 - 2 -

1. INTRODUCTION

After the fuel-oil crisis of 1973‘!74, the importance of nuclear energv for covering the energv demand increased considerablv. The Commission of the Furooean Communities established in its Wew Enerqv Policy Strategy" a nuclear target programme for the grovrth of the nuclear energv generating capacity up to the vear 2330 (Ref.1). This forecast would correspond to ,a cumulative nuclear energv generation of about

This fiqare means that until the vear 2?OD about 3500 tons of fission x?oducts and 1% to~?s of other than fuel have to be separated in re?rocessing Plants from spent fuel and will go to the waste. The management of this high-level radioactive waste associated with energy generation bv will Dresent a .formidable task to vresent and future generations of mankind. Its safe. disqosal is possibly the most important and controlling problem in the large- scale introduction of nuclear energy. ?resentlv, there does not exist a definitive solution for this qart of the cvcle. ;:lhile explo--~ ra~tion, develooment of enrichment slants, fuel element fabrication and design of advanced nuclea~r polger reactors were considered to be im?orta~nt activities alreadv since a~bout three decades, resroccssing and waste disposal arose as important tasks onlv during the last vears, iVOw, strong efforts are underwav in all countries with nuclear industrl! for ela~borating an acceptable radioactive xrastc disposal policv. -3-

The main requirements to such a policy is that a permnent removal of the radioactive substances from manls biosDhere is guaranteed. in the bast, industrial wastes were often treated applving the orincigle that "dilution is the solution of pollution*'. Apart from the fact that presentlv mblic opinion rejects this kind of treatment even for"conventional waste", it would b.J no .mans be apolicable to radioactive :rraste, Therefore, technicians have to offer convincing concmts for the treatnent of the radioactive waste, if the ob,jcctions of public opinion against the use of nuclear enerqv shall be overcome. Concerning the disposal of the radioactive waste, three: qualitativelv different concepts .qav be distin-. guished : - storaqe - long terxl disposal. - ultimate disposal Possiblv, each of these concepts will be apglied in a~ future waste disposal ~olic;~ for different classes of wa.ste, classifying the radioactive waste e.g. in - short-lived fission products (decav to innocuous 1eveX within 39 ) - internediate-lived fission products (decav to innocuous levels within about ;03 vears) - long-lived fission products - actinides and their daughters

Starace is the onlv disposal technique mulied todav for high-level radioactive waste (HAv) on an industrial scale, Xomally, it is considered as an interi>n solution and i.qp1ie.s that the waste re%ains retrievable and is under continuous surveillance. 7'hs HA:?, arising as licuid .from reprocessing slants, is stored i?: st.ainless steel tanks embedded in concrete to ~7mlts in order qain time for .mk-Ln$ d.e.finiti.ve dcci- sioiis on honi to dispose of the ~wste~

lens-t.er;r: dis;,osal refers to a disposal. of VJ?StC in salt ,ninc s , its deep buri,ai b;i injection into ground or ,undw thr: ./Ql~t?rctic:- x c:I ::::‘ ;?z so-tidi fica7:i.m of the XT is s;:~bosed~. .In

.rontr.Tst to thp st:7rr7 'e, the ~~~~:ste i.5 in this casf no longer considered to be recoverable. This conceat !;uaran- tec;s i: high dqree of safetv, blxt it can not be comlitel\r ercluded that the waste !rl?~~~return in an ?mcontroll?ble ~$anncr to rrim's biosohcre, if ertraordinar- events will ot-.cur D This aossibiiit- becomes the Tore ?robable, the longer the deca.~ ?crio:?s of radioactive nucl~ides to innocuous radis~tion lr?vcls are; climatic 2nd. ~e~lon~.c;1~. zlterationsT :mdificati.on of the: wy of lift o.f wn and other un~forese able: we:its coul? occur,

rSnl:i the “uitimte diswsa!." of vast?: would wsult in the certaintv that no radioactive Iatcrial can return to .the biosThcrc after the tlis~osal of fastens has been success- .Flill~: accofl?lished. Tiacic?11',1( ix0 possibilities are l iim;iai.e lable as ultimate disoosal for selected. :~adio:~uc.ii.des D After nmtitiohih::! of the wast?, long-lived isotosses could be transmuted to stable or short-lived or‘ lesser ha,eard.ous ohi:.s bv Izxclcar nroresses as r,g, fission, (*:~:;,:I, (t- : .)? (r,Lj, p,?). As second solution these ecl.c,r-rted.

. could be shot into the deco space (extr.z- terrestria~l dicoose!?), ':'he scope of the following consi- derations is to d:iscuss the concept of the nuclear tr~wsm- tation of radioactive wste. ~?resentlv .fission reactors, intense accelera tom and fusion rextom are inn&~ rli.scussion. -5-

2, GENERAL 3N NUCLEAR TRANSXU'TATIONS

The necessitv snd feasibilitv of transmntating radioactive wastes is still under investigation, It seem, however, clear that this concept u:ill be applied only for a fevr chosen nuclides, which represent either a great radio- toxic risk or a pronounced long-tern hazard. 3ther nuclides Cl1 be disposed of by burial, The transmutation rate T of any N ~sv be described by the following equation

'The first term on the right hand side regresents the natural decal1 amd the second one the elimination bv the nuclear process in consideration. In the case of reactions z' qeans the effective absorotion cross section and ~5 the effective neutron flux. Sin-es' is a consta.nt for a. given neutron spectrum the onlv va.riable urhirh influences the transautation rate is the neutron flux. A feasibility study for nuclear transmutations involves consequently investigations on the Droduction of high neutron fields ahd sDectra in which ~7 rea~che s an 0ptitiu-n value, In addition, after a literature search, it becones apparent that the for long-lived fission Products and higher -actinides other than fuel are not well established, Finallv( technical problms mast be solved 2s e.g.mste partitioning, optinized isotope separations for nuclides to be "burned!' md daughter ,product coq?lications leading to optiqurn recvcling oeriods for given *

OUIi~/C/I S,:/f;l 7 :7 5e -5-

30 TRANSXJTATION OF FISSICN PRODUCTSW FISSION REACTORS The possibility of "burning" fission products bv recvcling the!? has been s,tudied by STEINBERG and co-workers in (R~ef.2) and (Ref.'). The contribution of individual fission product nuclides to the total fission oroduct hazard of a characteristic uranium fueled LKR is shoum in Fig.1. There the hazard measure is defined as cubic meter of water needed for diluting the isotope to concentrations that the water can be used as drinking water. "iaximum.I oermissible concentra- tions are taken from the Code of Federal Regulation (USA), The fission Troducts (FP) shall be grouped into 3 classes a) volatile FF as, e.g, KR-85 b) FT which are controlling up to decav periods of

about 830 years as ,e.g, Sh-90 and G-137 c) ion;-lived F? as, e.g. I-129 and TC-99.

Evaluations of STEINBERG dealing with the three isotopes KR-85, SR-90 Andy CS-137 to the following results:

It was estimated that releasing inventories of the noble gas isotope xR-85? generated bv the nuclear energy industrv, to the atmosphere will increase the back- ground count in the vear 2C3iC bv 4.2%. It appears therefore desirable to develoo a snecial treatment of this fission product. KR-85 is present in :

its a~bsorption cross-section is small (15 barns) compared with that of KR-83 (215b). In Pig;2, the burning cost for X12-85 as function of the enrichment is reproduced, It can be seen that o?timum conditions are reached if KR-85 becomes enriched to 90X. The burning costs for the optimum enriched Case are given as 0.321 mills,&:i':~he. -7-

In order to avoid additional neutron burning costs or enrichment costs for SR-90 which could result from the short lived SR-39, a cooling period of about 1 vear before partitioning of SR from the gross wastes should be scheduled, Then, strontium fission products can be fed dirwtlv to the reactor. After a suitable burning period, the wastes arf processed in a chemical separa- tion plant in order to remove the barium and yttrium daughter produc.ts This qurified portion is thereafter combined with SR feed ;und recvcled through the reactor, The burning costs (onlv neutron costs) amount to 0 ” 2~;. mi 11s ~/Whe ~

Unless natural Cesium wastes are enriched in CS-137 burning does not seem feasible because of the high (5.%), the low cross section (: = S,llb) of CS-137 and the large cross section of stable CS-133 (31b). A 9% enriched CS-137 gives the lowest total cost for this waste disposal. Daughter product complications are much 'more noticeable than in KR-85 burning. Optimum recycling ueriods can be determined from isotope build-w values o These periods are shorter thcan for similar XR435 vzlufis;. The build-u:, of ~koisons during a rccvcle period must be carefullv f:>llowed in order to avoid unifcessarv neutron losses. The total burning costs atriount to 3-63 mills %Vhe.

In 'i'able 3, values of important fission nuclidcs are :iiven together with irradiation times as function of the neutron flux, required in order to reduce the~ir inventorv to 0.1:;. Cross sections refer to a typical LVR.

EUR:'c~IS'~+17~75e, -8-

Apart from I-129, the times given indicate that neutron flux levels are required for burning fission products, which are much higher than those attained in ?resent nuclear reactors (10 14 to 10l5 n/cm* set) and that fluxes near IO" n./cm 2 set a.re ~probablv necessary for burning fission products like SIC-90 and CS-137.

Resulting from what has been said above the problem fission products cannot be eliminated by any svstem of fission power reactors operating in either an equilibrium or expanding power economy. The production rate will everytime exceed the consu-motion ratf bv burning and decav, A steady state between build-up and elimination CXI be onlv obtained for a srstem that includes the stockoile of fission products as part of the svstem inventory, since the stockpile will grow until i-ts decay rate and an eventual burning rate equals -the net >roduction rate of the svstem. For the orojected economv, however, this will require :a very large stockpile with its associated potential for release of la~rgc quantities of hazardous radioisotopes to the environment. An estimate of the effect of various schemes of neutron2 induced transmutation of Sh-33 is given in (Ref.q), for the case of steadv state production of electric polx:er, Since the rate of neutron induced transmutation is small compared with the rate of decav, the total quantity of SK-30within the syste:m is nearly independent on whether this isotope is recycled through th& reactor. This result is va'iid for the LYII as well as for the fast breeder. 'The only difference is that in the cause of recvclinq, &out 75'; of the radioactive ma~terial would be Cthin the reactor. It would therefore represent a greater potential hazard than without rec'~cle. 'The only solution for burning fission products in fission reactors is the development of burner reactors as gro- posed bv STEINSERG., This reactor type is designed to maximise neutron absorption in separated fission products. SE sufficient numbers of these llburnerslt are used, the fission product inventorv of a nuclear power system can re,ach eq~uilibrium and be maintained at a minimum. Although disposal of SR-90 and CS-137 wastes bv burning costs IO to 20 times as much as present buryin- techniques, it could result as an accepta~ble solution for a long term waste police in case the d;ul(ser of stored xlastes m?v become too great, The use of neutron burning would bring some negative effects to the nuclear power p&gram as a whole. The added cost of of burner reactors and the loss of breeding capacitv are the tnro major factors to be considered. Roughlv, one burner reactor will be needed for everv 9 producing reactors, But possibly retiring reactors can be used for burning fission aroducts.

As mav be seen from Fig.4 the bulk of fission product waste decavs to innovious levels within a storage Feriod of about 630 veers, whereas actinidcs and r3 few long-lived fission products represent radio- toxic risks up to hundred thousand vears. In so far, actinides mav be considered as i: special kind of radio-

Importa~nt points which could'be dircctlv rela'ccd to the "burning" of actinides are : a. :.%. losses to the waste mst be reduced b, sqara~ti,on techniques for NP, A"I and CM must be deve- looed, which orovide decontminntion factors of 103 to l,f"k c. in order to gain a significant reduction of the long- lived active waste it will also be necessarv to treat at least the two long half-life fission products

I-123 and TC-!33,possihlv also CS-135, PD-107 and ZR-93. ,

All of the actiaidG:s exccat BK and CF reqpire containmnt for a period greater than 13.003 vems in order to decav to innoxious radiation levels, In addition to the Pu isotopes thi: most hazardous nuclidcs occurring in the LLPu fuel qcle are N?-937 s A%-231 , ,@$q-2.+3p ~~-2~44. ?~nd 9-2(-5 ~ CLAIBORNE (Ref.ii~) demonstra~ted in deta~il the feasibility of actinidns recvclving through a LW? .moving ,that the tnergv required to transmute actinidcs is a mall fraction of the energv generated in creating those actinides and the transrrluta~tion ra~te is significantlv faster than the natural r?te!

9524OO'l'l - 11 -

He found out that the decrease of the neutron multipli- cation factor for a tvpical LVR caused by actinides recyclying was only 0.8%. This loss of reactivitv can be comoensated by increa.sing the enrichment of uranium in the fresh fuel from 3-9 to about 3.4%. In the case of recvcling actinides, mixed homogeneously with fuel, an equilibrium composition for actinides is reached after about 20 cycles.

The alteration of the actinides composition bv their recyclying through a LW and the corresponding increase of the actinides inventorv is given in Table 5. Similar calculation for the increase of the actinides inventorv in the case of their recvclying through fast breeders should even give better results, since the average fission to capture ratio of the zctinides for fast is greater than for thermal ones. Ho~vever this effect has not yet been quantified because of lacking neutron cross section data for actinides in fast spectra. WeuJtechnical problems arise for the chemical reprocessing and fuel element fabrication due to the increased radio- activity of the nuclear fuel. Especially the strong of CR-252 build ur, by continuous recvcling of actinides has to be mentioned, Regarding the analysis of a maximum credible accident in the reactor svstem,no special problem is presented by actinides, since the compounds cannot be signifi- cantly dispersed into the atmosphere as, e.g. volatile fission products, On the other hand actinides recycling can have significant implicntions due to a~ strong build up of spontaneous fission neutron sources. - 12 -

Neasurcments of reactors in shut down condition and shipment of irradiated fuel get more complicated. Studies for an heterogeneous recyclying of actinides in special actinide fuel elements are underway. The main problem to be resolved in this connection is to derive reliable self-shielded and mutual-shielded effective neutron cross sections.

5s TRANS'KiTATION ,3F XADIOACTIVE YASTE BY "?EANS 2F A STALLATION REACTOR

GREGORYand STEINBERG have presented in Ref.3 the concept to use! a spallation reactor for the transmutation of the problematic fission ,products SR-90 and CS-137 into sta~ble or faster decaying isotopes. Thev proposed a complex consisting of a nuclear power reactor delivering electrical power to a high energy accelerator feeding a proton beam to a spallation reactor. The nuclear transformation reactions take place in the spallation reactor, The intermediate-level fission products CS-137 and SR-90 are separated from the!high-level radioactiv?.l?aste (i;AW) of the fuel reprocessing plants, processed and fed into the blanket of the spallation reactor, The mentioned report gives a sketch of the spallation reactor (see Fig-S) with the fission product waste blankets, information on heat transfer problems linked with the spallation core, flux distributions and

cost estimtes of the system. It was found thatasvstem urith a proton accelerator of about 500 to 9OOYWbea:m povrcr and a particle energv of 7-5 GeV, leading to a neutron flux of 2.13 17 n/cm2 set in the spallation reactor, would be ca~pable to disgose of a11 fission product waste of SR-90 and CS-137 generated in a nuclear power economy of 150 GWC?. - 13 -

According to our estimates the daily disposal rate is about 13 Kg SR-90 and 17 kg G-137. These values differ considerablv from those given in Ref.3. The complex is powered bv a 1300 'We ,

5.1. gpsiqn of Spallation Reactor . The spallation reactor consists of a circulating liquid uranium core serving as a target for the high energv (Fig,7), This target is surrounded bv a es-137 en-;~iched bl

The SrO blanket enriched in strontium 90 is separated from the cesium blanket bv a~D20 moderator !

( I:!'~:!'. .':y)= 1.23 barn),

5.2. Additional Costs of Nuclear Energy Due to Incineration --by a Spallation --.--Reactor GR%ORY and STEINRZ?$ evaluated the additional costs of nuclear enerq due to an incineration of SR-90 a,nd SE-137 in a 153 We nuclear power economv. Due to the large uncertainties of the cost of the proton accelerator v!ith a beam power of 500 NV or more the additional costs for nuclear incineration ?er generated X!$he was given as function of the accelerator 'j costs, These costs were estimated durinr: 1957 and xre below 3.03 mills/KVhe. 'They have to be considered as very prelimina~rv, because all price evaluations were based partly on sc.aiing l~aws even for componeflts of the plant for which techno].oqi-cal solu- tims not v<:t ,:::xist for a reaiization of this nuclear incineration complex, SiTR,~C/'IS'41 7,/75e 9Ij240014 - 1-I -

,:'he costs perKYhe for such an ultimate fission product waste disbosal qstem are at least a factor IO higher than the! costs for burial.

Before a more valid price evaluation is possible this nuclear incineration complex should be subject of a further assessment, For ex~nple,,H.C.CLAIBORi~F (Ref.+) states that for a~nuclear power economy of 150 GVe not one but more than 15 spallation reactors of the size as described by GREG3RY and STEINRGRG would be needed. ?.EJicGRATH (Ref,5) even writes that the utilization of this nuclear incineration process would lead to a nega- tive energy balance of the fission reactors.

Lately nuclear codes were developed which permit a much better physical assessment of the spallation reactor CoilCept. For the design of an intense (IXG) a xonte Carlo code was developed giving the angular neutron spectrum of a sgallation target as function of incident proton energy and treats the transport of neutrons and protons in the enercy range ,up to 2 GeV(Ref,6).

Xany technical problems have to be solved before a spallation reactor for nuclear incineration can be realized. Some of the Qroblems are : a , the conversion efficiency of the electric energy consumed bv the accel,er,>tor into the energv of the proton beam is at present in the order of 13-" (Ref,7) There exist hpwever acceler.Jtor projects in which this efficiencv is estimated to 0.7 (Ref,8). In this case the assumed conversion efficiency of 0,375 for the spallation reactor of GREGORYand S'i'EIN3ERG appearsto be c?;ong that L*the authors o.F high-current neutron gene- rator projects a rather conservative value.

95240015 - 15 -

b. The proton beam poxrer of the required accelcr?tox is still a factor of :about IO' hisher than Yhe beam pouier of al.ready re;-lizcd lixear acceler?tars~ 1 (L~CWF : i = p0,uA ; 3 = 800 Xiii, txrget power density 20 x!Q'&) e c. The proton be?m with i-ts power of sevwal hundred megawatts must under no circumata~nces become defocussed from its strict course and the scattered protons must not exceed durin:;< normal operation a certain limit to provide protection of material ar,d staff and this over a length of several kilometers (Ref.9). The will of particles olnt of the beam observed at present at LAM?? is in the order of 1°C and should be 'i kept in our cilse as 10~ as IO-' e d. 'The proton be:;m target will pose with respect to design and maintenance severe problems (twget ?owe-r densitv about I C! k!Ai,/cm3)a

e. 'The connection of the circulating liquid target with the vacuwn chamber zid the selection of the materials withstanding the temperature of liquid uranium in a stroncj fast ncu-tron flur will be Annother problem,

f, l'he safe containment of the spallation.fission and products of the liquid uranium target and of the blanket materials with their high invelztory of xtivated Sr *zmd Cs must be assured under ?-ny possible accident,

go 'The wall loadin? 0;c the spallation neutrons is in the order of sever& hundred W,T,!m' (mall loa.ding 5.Q' !$;:~?.T'!:~2

near the target containment) and is cornFared with 1 to IO XV;/m2 of thermonuclea~r reactor vxuum vrall loadings a r&her high v~.lue. h, il'he genera~ted neutrons reach verv high neutron .;nergies especi,allv in forward direction leading to expensive neutron shielding .

5.3. Demsnds for Nuclear Heasurements the neutron output of spa~llation targets has been measu- red by J.S.FRASER et al.(Ref.l3) for an incident proton beam range of 0.,+7 GeV to 1.47 GcV for different ta~rget materials. E.X.FUi,LT:IOOD et al,(Ref,ll) compared theo- retical results wtth experimental data and found discre- pancies in the order of 2%< to

a.bove 14. xev. For this reason, neutron cross section data uncertainties above this enerqv have little influence on .the reaction rates in the blCankets for nuclear incineration, but ar.e verv important for shielding.

In the literature, larr;e discrepancies were found concer- nini; the -Jerformance of a spalla~tion reactor as an u,1 .t ,j.m ; te dis?osa~l of fission products. For this reason a phx,~sical assessment of this incineration -method should be repeated and the study should include the transmuta- tion of SK-33 and CS-137, the actinides and the spalla- tion products genor,?ted b v t%e spalla.tion reactor itself, - 17 -

The first prooosal for the transmutation of radioactive wa~sti bv a controlled thermonuclear reactor (CTR) was made bv S>R.L':YNARD Jr,, !,'a C.GAUGH and D,STXNER during 197a

and I 971 respectively, w.C.VXXENHAUER (Ref.12) Der- formed the first study usin? a C'I‘R blanket for the

transmutation of fission products like SR-93 and CS-137, A more ertensive ph?isical assessment studs including the ,actinides and was made b*r

"OL[UER,LEC)NAlZD and G9RE (Ref.13s14) during 1973,

5,1> -.-.Design :lodel of C'l'R Rlanket For bench mark calculations of CTR blankets a blanket was inroduced during 1371, which has standardized dimensions ,and compositions. Such a blanket is a c-llindrical annulus (Perhaps a section through a torus) lrrith inner and outer radii of 233 c?1 and 1.33 cm respectivelv. (See Fig.9). The neutron source or plasma region is along the cvlinder axis and has a radius of 153-150 cm, It is surrounded bv a 1-O to 53 cm thick void region. The different blanket zones are cylindrical arm-uli, starting with an inner niobium v"cuum wall (9.5 cm thick), a 3 cm lavcr of F'iAixi' ( 3 ,;i'L li. tliiu::j e 5% niobium) as are11 coola~nt, ,and. an other 3.5 cm thick niobium wall. 'This va~cuum wall coolant zone is followed bv a second -/one of 5a cm thick lithium ?:ix" a 35 elm thick gra~phite reflector, and a zone of 5 cm thick lithium ">!iy:'. .The (D-'P) fusion neutron source haps a neutron current 1 <:,~ across the niobium vacuum vail of +,+.Io n/cm2 set corresoonding to a neutron energv transport wall loadinq of 10 "iy:'r$ * a val-ue which is usuall'~ used for mirror -machines. Eu.E,!c'1s'?-17~75e 9524001~ - 18 -

Conceptual design studies of T31(0:IAXS are bv a factor of 13 lOUw3?. FOXYthe tr?~nsaut?tion of fission products or actinides, the 50 cm thick Lithium "‘lix" region was replaced bv

5.2, P_erfor9ance of c' ~7TZ.2s ?n Ultirfiate Vaste Disposal Device The calculatiorswcre performed mith the one dimensional discr?:tP ordinates tr;l~ns?ort code with anisotropic sc?.ttering ANISN (Xef.15) (in ;r P3-St3 a?prorimation) and a constructed cross section file which took F~pproxi- ;nately into iiccount in some cases (;L,;), (r:,:~:,) Znd (~~:i:) reactions which are not included in the normal ENDP&'III file,

In Pig,1 it is demonstrated that the hazard level of S&z)3 ?nd ~~-137 give the dominant contribution to the total hazard of the high-level radioactive waste during the first KIO years of decav, Fig-10 gives for different tayret m&eri?ls in the blsvlket per ton of L1.T fuel viith 33.330 i"LVd,'to burn up the timc:s required for its dec

of 1 ton n3turizl ur3nium. '"all 1oAding zero is the case for 'nature: dec-?yr; 1 y!~.:jr712 and I 0 W! !n2 are the extrfmc values of considered fusion reactor v;\cuum w-,11 loadings. 'The SR-XI haz?~rd decsv time is reduced from :?-39v to 18.7V Cth D-T fusion neutrons, for the highest v:all loading, It can be seen that D-D fusion neutrons arc superior to those- of D-.T reactions, In cze onlv 2 che:micsl se??ration of the c'!e?ent Si? is performed from the high-level rsdioactive viaste (HAT), the hazard tiTe is onlv reduced b\r a factor T; -,rith the highest fusion re?~ctor nr?ll lozdin:r. c:;E'/C ys /:;17 '75e 95240019 - 19 -

CS-137 is less a waste problem as SR-93, but it is more difficult to burn it due to its small capture cross section, If onlv the CS is separated from the hi?h level ra~dioactive waste the hazard decay time is increased bv about 35 to 43% for the oral1 1oadin.q considered. This means that there is limited incentive for isotonic separation of CS--137* The advantage using D-D neutrons for the burning of

~~-137 is not so marked as in the case of burning SR-90.

The problem for the disposal of the actinides is diffe- rent frond that of disposal of the fission products, InitiallxT their hazard is lower but of much longer duration. 'ihe transmutation of actinides in a fusion reactor blanket occurs throu?h the fission process, rather than the process of cnnversion to stable isotopes hv ( :, in ) ) ('.~,~..~) ) ( '. ) , (':,:j.::x) or similar wocesses. The objective of actinide trxwnutation is to convert the waste fro2 an actinide composition to a fission product composition. In general a controlled thermo- nuclear reactor is an efficient actinide Surner, However, there are some actinides like NP-2.77 whose hazard levels are low originallv but can reach a significant level i-n case a neutron induced transmu- tation is tried. s,3* Additional Costs of Nuclear Gnerq Due to Incineration in a Controlled Thermo-Nuclear Reactor A detailed economic analvsis of the controlled thermo- nuclear reactor as a fission Droduct and xtinide burner has not yet been made due to lack of design definitin. - 20 -

The cost of burning W-90 and '?S-137 in a fusion reactor was indicated in Ref.12 as being at least IO times as expensive as the estimated cost of a storage of all fission products in deep salt formations (price about 3,.9.$5 mills ?er,k~@To this value, an unknown price for the burning of actinides has to be added. The transmutation rates obtained for SR-90 end CS-137 especially at 10 ~'i"rn~ vacuum wall loadings, are suffi- cientlv high to use the blanket of a controlled thermo- nuclear reactor as an ultimate waste disposai.device,About 20 m of standardized torus length would be required to burn the waste of a 150 G:ie power economy. For the actinides, the achieved transmutation rates sure even more favourable.

The a~pplication of a fission reactor as a means for the ultimate radioactive waste disposal seems to be technically possible for the actinides. Eecycling studies of particularisotopes in s?ecial snectra and optimized cyclirq times are not yet performed such that the full advantage of actinide burning in fission reactors can be demonstrated,

The use of spallation reactor as a waste burner is not vet sufficiently investigated neither for fission product nor for nctinide burning. Feasibility studies for controlled thermonuclear reactor blankets as ultime radioactive waste disposal have demonstrated, that this method could be used for fission ,products and actinides.

95240021 - 21 -

All results concerning the burning of S?-';3 ad CS-137 suffered from the uncertainties of the mailable therm.1 neutron cqture cross sections zt the date of the fexibiiitv stadv.

These uncert::inties iaight le?d to the conclusion that a burning of SR-93 is ?.s difficult as the blaming of cs-137. ,Yhe burning of CS-137 could even become i!xpossible.

95240022 - 22 -

REFERE3CES

(1) A.DECRESSIX, B.HUBER tiuclear Fuel Cycle Qowth 1975-1930 in the European Communitv Yorkin: ?aper III 1031'7m (1974) ( 2,) ';I. STFINBERC-,. G ~W0TZAX , B . 'YANOFITZ Neutron Burning of Long-Lived Fission laroducts for T,"aste DiSnOsal &L 9553 (19Q)

(3) X.V.GXEGC)?~ and $4.STEINBERG A nuclear transmutation system for the disposal of long-lived fission product waste in an expanding nuclear power economy BNL 11315 (1957) ( c) H. C acmnmmT: Neutron induced transmutation of high-level radioactive waste

(5) P.F.UCGw4TH Radioactive -*Taste management, Potentials and hazards from a risk point of view. KFX 1992 (1?7:i) (6) !:', A. COLl3TANNs R. G. A.LSWK,L5:R Thermal neutron flux generation by high energy protons Nucl, Sci. and Eng., 31 (13;S) (7) F.X0;3ARD 6th Zntern.Conf on high energy acceler>tors; (19

95240023 - 2’3 -

95240024 m3WATER AT RCG 10'2 I ---_ / --N \ Sr 90 \ (WASTES FROM 1 METRIC TON OF FUEL \ p \ AT 34000 MWDITI \ \

/FISSION PRODUCT ,TOTAL - ‘.\ I \\ ‘1 \’ \ ! \ 1 I \’ \ L \I \ ’ I \ I ‘,I-129 1 I 1, 1C / I. --- a ---a--. l - .-w-w----- r-\------’ H-3 \ ” -L, \ :\

-\ \ II Tc-9!

\ .--m-s- m-m -‘p’+ - - -/ - T --- -- . \ I 1 . \ I I’ \ KJ- 85 I ” \ \ \ \ :’ Nb-9?m

------2.

--w-----,‘-,- -. ---

-*

100 AGE OF WASTE / XR- EURATOM FlSSIOti PRODUCTS HAZARDS FIG. 1 ‘: ISPRA FROM A U-FEEDED LWR 95240025 j I I I I I I I I I I 0 I 0 20 40 60 80 100 ‘lo KR -85

:CR-EURATOM COSlS FOR KR-85 AS FIG. 2 ISPRA CIFlS0lWlC ENRlCHMENT I 95240026 5-l I

1. 18I 12 I 11 I ?WATER AT RCG)

10” \\ ,)” ‘I% PRODUCTS IdO /1\’ \ I IIDES QTHE HAI l+Pul 7 ( rERS

P + 0.55% (U+Pu) \ ‘ERSi 4 ld ” -

FlSSiON ~PRO!kCTS WITHOUT~I-129 AND TC-99 . ./ ...... +...... + ...... I.’ -

DECAY TIME (YEARS) * ,,, XR-EURATOM RADlDAc;TtiE WASTE HAZARD FIROM FIG. 4 .~ ISPRA A lJ-FEEDED LWR 95240028 FIRST CYCLF * Tw!NTrm CYCLF

PLFMENT MASS (GRAMS) RRR VASS (GRAMS) RRR

TH 2.3 (-4) 1.1 (-3) 2.1 (-3) 1.2 C-3)

PA 4.3 (-5) 1.7 (-4) 1.3 (-4) 4.7 (-4) -I

Change of Actinides' Concentntians' I LOW LEVEL

1 POWER - ’ 1 REACTORS 1 I PLANTS I I 4GW(e)

STORAGE I I ICHEMICAL I 1 3 FRESH FUEL

1.3 GW (e) SPALLATION I REACTOR : I CORE PROTON ACCELERATOR . PROCESSING PROTON BEAM -800 MW

CR-EURATO SPALLATION REACTOR FPT- COMPEX I SPRA PROTON BEAM -75 GeV mA

ENTIRE SYSTEM IN D20 MODERATOR XJ EXCHANGERS

39.5-29.4 kg

DIMENSIONS: x CORE- 1Ocm DIAM 350 cm LENGT SRO BLANKET 26.5 cm TO INSlDE RADIUS 292 cmT0 OUTSIDERADIUS 60.0 cm LENGTH CS,o, BLANKET

THE SPALLATION REACTOR -- U-238 CYLINDER Pb CYLINDER

-6 10

w 10.0 ,qNERGY &Id)

xR-EmATOM 4w rg~irifggh SPECTRA FOR ISPRA u-238 AMP ,Pb TARGET ,, IV :’ ” LITHIUM MIX (94% Li (6% Nb)

GRAPHITE REFLECTOR

BENCH MARK BLANKE T

SOURCE REGION

300 cm LITHIUM MIX (94%Li,6% Nb)

TARGET ZONE

MODERATOR(C, Be) CTR TRANS UTAT~ION LANKET NEUTRON SOURCE REGION R

ISO 200 300 cm

CCR-EURATOM FIG. 9 ISPRA CTR BLANKETS 9524f~o32 ,. ,,, sotopes of tme to reach ha_r_ard of lto of to LWR Fuel Vnat [Y] t 33000 MWd/to Wall Loading of RFMARKR ! 1 w’m2 10 MW’rn2

Sr -90 439 104 17.8

64.5 6.6

27.5

21.5

,ctinides 462(l) 2.73 0.254

462(l) 1.05 0.166

(1) &n . 241 only

? (2) 0.5%of actinides not recovered

c. c. R. Time to reach the FInsara of 1 *on of EDRATOM u nat 1 Different Tarqet Materials