High-Purity Titanium, Zirconium And Hafnium In Nuclear-Power Engineering 1 1 1 2 3 3 M. Kotsar , S. Lavrikov , V. Nikonov , A. Alexandrov , A. Alexandrov , S. Akhtonov 1 >]SC "Leading Scientific-Research Institute of Chemical Technology" 33, Kashirskoye Shosse, Moscow, 115409, Russia, E­ mail :[email protected] 2>] SC "Interstate Association Titan" 3 ,Orshanskaya st. , Moscow, 121522, E-mail: isat91@ mail. ru 3 >] SC ''Chepetsky Mechanical Plant, 7, BeloV<I ,Glazov, 427620 ,Russia, E-mail: [email protected] Development of nuclear-power engineering is one of sess-n. The obtained metal-hydride compounds become priorities in economic activity of the Russian Federation, the sources of defects and cracking in titanium and its which increases its power potential. The share of atomic alloys. To improve the hydrogen resistance of titanium power stations in power output of the Russian Federation and its alloys for nuclear-power engineering, as well as makes 16. 7 % and will grow to 25%-30% in prospect the quality of the superconductive alloy NT-4 7 for The service life of reactors must grow to 60 yearsll. ITER reactor its additional clarification is required. The Up to 2030 optimized water-cooled power reactors method of iodide refining allows to clarify titanium (WWER) will remain the main type of nuclear reac­ from nitrogen, hydrogen, oxygen, carbon and a number tors. At present prerequisites are established for intro­ of metal impuritiess-11 >. This will increase competitive­ duction of high-efficiency fuel cycles on the existing ness of iodide titanium in relation to traditional titani­ atomic power stations with water-cooled power reac­ um-based alloys in nuclear-power engineering. tors. Introduction of such cycles is accompanied by in­ High-purity zirconium, produced by the method of crease of the service life, increase of fuel burn-up and iodide refining under industrial conditions11 >, is used as coolant void fraction, growth of claddings temperature a burden constituent in melting of alloys for reactor ap­ and strain in them2>. Titanium, zirconium, hafnium and plication. In melting of alloys of EllO, El25 and E635 alloys based on them are widely used in nuclear-power grades based on electrolytic zirconium powder for fuel engineering as constructional and absorbing materials elements and fuel clusters of WWER-1000 and RBMK- of slow neutron reactors. 1000 reactors the burden contains up to 35 % of iodide Titanium and its alloys are used in heat-exchange zirconium. El 10 opt. (basic material for fuel-element equipment of atomic power engineering. One of the main claddings) and El25 (perspective material of fuel-ele­ reasons for premature failure of titanium elements of ment claddings of PWR reactor and pipes of process power equipment of atomic power stations, including channels of high-power channel-type reactors) are con­ steam generator pipes, is cracking due to hydrogenation sidered among main alloys based on magnesium-ther­ (hydrogen pickup) of titanium and its wrought alloys, as mic sponge for fuel-element claddings and fuel cluster hydrogen content in them reaches about 0. 06 % ( - 1, parts in projects of atomic power station-2006 and 2 12 5% TiH2 ). Hydrogen content in titanium grows with TBS-PWR • >. Stable oxygen and iron content in them growth of impurity content in it3>. Presence of hydrogen with the nominal of 800 and 400-450 ppm correspondingly in titanium ingots can lead to formation of grain-bounda­ is achieved due to introduction of iodide zirconium of espe­ ry hydride layers and loss of plasticity~>. cially pure grade as per TU 95. 46-97 with hafnium con­ The reason for accelerated hydrogenation of titani­ tent, not exceeding 0. 01 % (100 ppm) into the burden. um and its alloys consists in insufficiently pure base of Metallic hafnium is used in nuclear-power engi­ titanium and use of alloying additives, contributing to neering in the form of automatic regulation and com­ intensification of this process. Fraction of impurities to­ pensation cassette plates (emergency regulating cas­ tal mass in unalloyed titanium of VTl-00 and VTl-0 settes) in WWER-440 reactors13 >. In melting of ingots grades can reach 0. 5 and 1. 0 % , including that of hy­ based on electrolytic hafnium powder up to 50 % of io­ drogen, oxygen and iron 0. 008 and 0. 01 % , 0. 1 and dide hafnium is introduced into the burden. 0. 2 % , 0. 15 and 0. 25 % correspondingly. Wrought al­ The process of iodide refining ensures deep clarifi­ loys based on titanium of different grades, developed cation of titanium, zirconium and hafnium from impuri­ mainly for the needs of the aircraft and sea industry, ties and allows to produce metals in the form of metal 10 are alloyed with aluminium, vanadium, manganese, mo­ bars, convenient for subsequent processing • 1 n. The ad­ lybdenum, tin and zirconium in different proportions. vantage of the process of iodide refining of metals (Ti, V, Mn, Fe, Mo are ~-stadilizators of titanium and form Zr, Hf) consists in the idea that it allows to process dif­ the IMC with it, which, being concentrated mainly on ferent waste metal, forming in manufacturing of main grain boundaries, are getters and accumulators of hy­ products, and to produce high-purity metals hereby. drogen, as well as catalysts in hydrogenation proces- The base of the process of iodide refining of met- • 2238 • Proceedings of the 12'h World Conference on Titanium als (Ti, Zr, HO is the chemical transport reaction8>: units. This allows to use raw materials both in the form of chips, and in the compact form (tablets, pieces, grist, + 200-soo·c 1100-1soo·c Cl) t cuttings of sheet material). There are 4 threads in the unit Me,.+ 21 2r ---------- Mel4c;. -------------- 41 r + MeT in the form of wire pins with the diameter of - 4 mm, and conducted in enclosed volume in two different tempera­ there is no charge of the· raw material in the central part. ture zones. The effect of clarification from impurities is Such a construction allows to produce bars of iodide hafni­ achieved due to difference in thermodynamic and physi­ um and titanium with the diameter of 17-22 mm cal and chemical properties of Me-I and IE-I systems The required temperature of raw materials is ad­ (IE-impurity element). justed and maintained in the units using the cooling 14 15 The works • > establish linear dependence of clar­ system. The air is used as a cooling agent, which tem­ ification factors (I<.,1=C.,.,"'"""-1 C.,.,cnd) on the content of perature is equal to the ambient temperature at the impurities in source materials CCmi,,.,urcc) ,zirconium and thermostat input. Before iodide refining the raw materi­ hafnium: als, charged in the industrial units, are subjected to de­ I<.:1 = a • (Cm., """""' - Cm., min ) + 1 (Zr) ( 2) gasation, and, when titanium and hafnium are pro­ lg l<.,1 =a lg Cmi,,,,,"""' + b (Hf) (3) duced, this operation is conducted twice. The most complete clarification of titanium, zirconium Table 1 give the results of comparison of the chem­ and hafnium from impurities is achieved after triple io­ ical composition of iodide titanium, zirconium and hafni­ dide refining. Hereby the total of impurities in bars um, produced of practically equivalent raw materials in changes far less from the second to the third refining metals units of HN78T alloy under industrial condi­ than from the first to the second one, and the refining tions10·1D. It follows from the given data that the actual effect appears in growth of the electric resistivity ratio content of total impurities in bars of all metals is by 2-4 (y=fl29sK/p4.2K) from 140 to 190,from 165 to 198 and times lower than the technical requirements, and the from 21 to 33 for titanium, zirconium and hafnium cor­ content of individual impurities, as a rule, corresponds to respondingly9·16>. their detection limits in used methods. The microstruc­ Under industrial conditions the process of iodide ture of iodide metals is grain one with radial pores, loca­ refining is carried out in metallic units, made of ted from peripherals to the center. Microhardness values chrome-nickel alloy of CN78T grade10 ·1D. Industrial at the section of bars of titanium, zirconium and hafnium 2 unit Z-40, applied for iodide refining of recycles of me­ vary within 1090-1178 MPa ( 111-120 kgf/mm ), 2 tallic zirconium, its alloys with niobium and titanium. 1080-1444 MPa ( 110-147 kgf/mm ) and 1757-1934 2 1 Hafnium and titanium are produced in H-20 shelf-type MPa (179-197 kgf/ mm ) correspondingly D. Table 1. Chemical composition of titanium.zirconium and hafnium Titaniumiodide, Titaniumiodide, Hafniumiodide Zirconiumiodide, Zirconiumiodide Hafniumiodide No Element in Z-40 and TU48-4-282-86. COST 22517-77 in Z-40 TU 95. 46-97 in H-20 H-20 grade Tl-I grade HFl-1 Fraction of total mass,% Maximum Maximum Maximum l Nitrogen 0.0018 - <0.002 0.005 <O. 002 0.005 2 Aluminium 0.0018 0.005 0.001 0.005 <O- 003 0.005 3 Beryllium - - 0.0003 0.001 - - 4 Boron - - <0.00003 0.00005 - - 5 Hydrogen 0.0001 - - - <0.0008 - 6 Hafnium - - 0.03 0. 05 (0,01 * *) > 99. 94 (Zr out) > 99. 86 (Zr out) 7 Iron 0.0014 0.005 0.004 0.03 <O. 007 0.04 8 Cadmium - - 0.00003 0.00005 - - 9 Calcium - - 0.00032 0.02 <O. 003 0.01 10 Oxygen <0.01 - 0.007 0.05 <0.007 - 11 Silicium <0.0008 0.009 0.002 0.008 <0. 003 0.005 12 Lithium - - 0.0001 0.0002 - - 13 Magnesium <0.001 0.004 - - <O. 003 0.004 14 Manganese <0.001 0.004 0.0003 0.001 <0.0003 0.0005 15 Cupper <0.001 - 0.0003 0.003 - - 16 Molybdenum - - 0.003 0.005 <0-003 0.