\N Nuclear Graphite Based on Coal Tar Pitch Behaviour

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\ N NUCLEAR GRAPHITE BASED ON COAL TAR PITCH BEHAVIOUR UNDER NEUTRON IRRADIATION DLTVEEN H 00 AND 1100°C P.MOTTET, A.FILLATRE, R.SCHILL, G.MICAUD Commissariat a l'Energie Atomique, CEN Saclay (France) J.LORE, P.CORNUAULT Groupe Péchiney Ugine Kuhlmann, Paris .(France)

13. Biennial confaranca on cor bon. Irvine, Calif., USA, 18-22 July 1977 CEÀ-CONF—4030

ABSTRACT Two nuclear grades of coal tar pitch coke graphites have been developed and tested under neutron irradiation. The neutron irradiation induced dimensional changes between MOO and 1'i00°C, at fluences up to l,2.1022n.cm-2 4FG shew a behaviour comparable to anisotropic petroleum coks graphites* Less than 10% variation in thermal expansion, itaxiromn decrease by a factor four in thermal conductivity, and large increase of the Young moaulus have been observed. NUCtfAR GRAPHITES RASED CN COM. TAR PITCH H3MVXOUR UNDER KLVTKOH IRRADIATION BETttEQ» 100 AND 1 *©0»C p.nmrr, A.FIILATRI:, R.SCHILL, G.IICAUD Oonnissariat à l'Energie Atomique, CBI Saclay(France) J.LORE, P.CORStUAULT Groupe Pechiney Ugine Kuhlaacn,'PARIS (France) i. arraopucTK» Figures 3 and * show the degradation of lbs ceiai-isotropic graphites based on coaltar the thermal conductivity of P3JHMI graphite in pitch coke have been developed for use as a nodc- the axial and radial directions respectively. rwtor in IfTCR. This paper suesnarizes the diren- A saturation appears at approximately 2*10" sional changes and the evolution of the physical n.c»~* •rc.although the decrease in conductivity and mechanical properties of P3JKMI and P>JHA?N is smaller at ir eased irradiation temperatures. graphites under the effect of neutron irradia• tion, • The fraction change in Young's Modulus 7. IPttERIALS versus fluencc for P^IilAN graphite is shown on figure &. The increase in the modulus of elas• PyHIMi and P)iI/C,K graphites based on coal y ticity is greater Jhen the irradiation tempera• tar pitch coke arc numtfactured by extrusion ture is lower. according to a classical process. Ifceir physical and eoctetnical properties are described in Stress-strain curves have been drawn frora table I. The anirotropy factor of these gra• irradia ed specimens, we observed two different phites falls between 1.3 and 1.4, with coeffi• types of behaviour depending on the irradiation cients of thcTKtil expansion (CIE) between these temperature. Between SQ0 and 900°C the graphite of anisotropic petroleura coke graphites- and strains with a constant energy /3/, while above ilsocoke graphites. If the therw«l conductivity 900°C the energy changes without strain varia• fs slightly lower than that of petroleum coke tion M. graphites, the density and rceehïnical charac• teristics arc improved due to the excellent compatibility between the filler and the binder 1. ÇUKWSVXI The pitch coke graphites studied are less stable than petroleum coke graphites of compa• 3. mvmouR WICK KTOTRCH IRPADIATIOW rable CTE and anisotropy. This sceros to indi• Kbrc than 1200 samples of P3J1KJ, taken from cate that the fibrous structure of the coke has both the axial and radial directions, have been a preponderant effect under neutron irradiation. irradiated in the Osiris (Saday), HfK (Petten), «nd ORR (Oak Ridge) reactors. Tec r.exintxi flu• ence thus far readied is 12*10 n.ctr.-2 $PS* it» Bibliography the case of PjJfiA»! arts! 4x10' *n.cni~2 for PjJtftjN. l\l J.P. AUK3T, J. !AK/\YL\ A. BUSCAIU/W Irradiation teryoratures for both graphites have Nouillabilité des cokes par le brai ranged from f00°C to W00°C. Carbon Conf. Baden-Baden S.J. nipçnsion3l_çhanges preprints'p 375, 1972 The dimensional behaviour of P^JKtff and PjJhAjN graphites is shown in figures 1 and 2. IV G.B. HSSLE, J.C. B0KK03 Wo significant ef/ect of the itnprogr.-ition has 10th Biennial Conf. on Carbon been otcerved between the two graphites. Bethléem, Penn., 1971 The BBxirum axial shrinkage is '»,5% atl350°C IV J.S. OCHARD, H.H.W. I-OST* with a turnaround near 7.10"n.cm"7 $FC. At . Free, fifth Carton Conf. lower temperatures, between SCO and 1100°C» Vol 1, p 619, 196? shrinkage continues up to ï»**ri.cm"' $FG. In the radial direction, the maxitrum shrin• /•»/- M.R.E. EVERETT, Y. RIDEALGH kage is about 2.2* at 1350°C and 5*10*'n.cn"'. Carbon Conf. Baden-Baden The turnurourid occurs at higgler fluencies when preprints p 191, 1972 the irradiation temperature is decreased. Expansions arc observed above approximately 10**n«aif ' fTC as new porosity is generated 111. 3.2. Eyoluï içn_of __ph'/siçal _ j^ropert i es The CTE, tmasurrd between 25 and 125°C, increase slowly with fluence at low temperatures and dccrccisc at trwjjeraturcs higher than 700°C. The variation dees not exceed 10Î..

• graphite damage flucnee « 1.2& flucnce I > 0.18 W:V «.1.85 EM fluence T*b)e X Physical and »?chanieal properties of the fjBW and PjWi^H cr*phites Qrvtyhire ^V9* *âxTâï fiSIâï' *âxîâï~~?SdîâV t Bulk density 1.73 1.73 1.79 .1.79 Thorcrtl expansion 3.8S *.2Î 3.08 «.23

ïhenul conductivity l.M 1.1S 1.70 1.29

Young Kod^us 100S 709 11H3 772 daN war2 Tensile stretch 1.12 0.70 l.V» 0.90 daH tin-2

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