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Overview of Selective Photo-Reaction Takashi Flrisaiva Japan Atomic Energy Research Institute Tokai-Mura.Ibaraki-Ken, 319-11,Japan Tel.0292-82-5918,Fax.0292-82-5572

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Overview of Selective Photo-Reaction Takashi Flrisaiva Japan Atomic Energy Research Institute Tokai-Mura.Ibaraki-Ken, 319-11,Japan Tel.0292-82-5918,Fax.0292-82-5572 Proceedings of the 6lh International Symposium on Advanced Nuclear Energy Research -INNOVATIVE LASER TECHNOLOGIES IN NUCLEAR ENERGY- Overview of Selective Photo-reaction Takashi flrisaiva Japan Atomic Energy Research Institute Tokai-mura.Ibaraki-ken, 319-11,Japan Tel.0292-82-5918,Fax.0292-82-5572 Rbstract Selectiue reaction process Especially isotope separation is a key technology for the deuelopment of the technologies related to the nuclear energy. "Howeuer oifly a few species are separated on a production scale using the conuenuonal processes such as thermal diffusion, chemical eKchanae reaction and distillation for lighter isotopes ,and gas centrifuge and gaseous diffusion for uranium, fls these methods are based on statistical thermodunamics and haue law enrichment factors, they need repetitiue operations of separation uiith many separating units combined together. Electro-magnetic separation method known as the one with high separation factor can be applied to most of the elements ,but extremely low production rate is realized, which is uneconomical. From the aboue point of uiew, much attention has been paid to the laser process by which high selectivity is expected. This method can be applied to either gas .liquid or solid hase, and hiqn separation factors are basically realized only in gaseous phase. Since the Eeginning of the studies on isotope separation in early l97Bs, many ideas haue been proposer/for the selectiue photo-reaction process such as photoionization, muitiphoton dissociation and state selectiue chemical reaction. Rs a result of experimental and theoretical efforts, large scale production of some isotopes haue been intended. Production of deuterium Dy infrared multl-photodissociation method was studied aiming at the replacement of the conuentional dual temperature eHchange process, and lots oT experiments haue been achieued intensiuely for the uranium enrichment, fl stepwise selectiue photoionization method has also Been studied for the isotopic separation of many elements, especially uranium enrichment.To implement the laser processes on a large scale production system, aduanced performances are required not only for the tunable laser sustems bur also for many related technologies such as atomic/molecular source,pnoto-reactcr and extractor of products. Keywords:Laser Isotope Scparation.Selcctive Reaction,Photo-ionization,Photo-dissociation,SeIectivity 1.Introduction Tablet.Selectiue photoreaction by tunable IR lasers Selective photoreaction is Source Wavelength made based on the Laser Conversion "type of Reaction Working Materials spectroscopic difference CF3H,CFa2H,CF3CCIH. caused by the difference Halogenaled elements, isotopesjsomers Freonl23,CF3COH and isobars. In the field of hydrocarbon nuclear engineering, isotope Infrared Multi-photon CF2CI2,CF3I.CCI3,CF2C1H separation technique special attention is paid to TEA Dissociation Hexahalidc Si2F6.SF6,SeF6,WF6 the wide area ranging from CO, Tetrahalide SiF4.TiCl4 the uranium enrichment and isotope tailoring materials to Laser Trichloride BCI, the reprocessing of spent fuels. Among many Metal Zr(OC(CH3)3)4. conventional isotope Alkoxide Ge(OC(CH3)4) separation methods the laser method is most Others OsO. promising as a technology of Infrared Excitation +UV Ammonia NH, next generation in terms of Dissociation both energy efficiency and Halogenated selectivity. Laser Isotope Optical CC13H Separation experiments Pump Single-colored IRMPD hydrocarbon NH3 have long been achieved Hexafluoride UFfi since early 70's. In convenience the laser Raman Multi-colored IRMPD Hexafluoride UFA isotope separation methods p-H. CW Laser I nduced Thermal are divided according to the Hexafluoride SF< wavelength range used. Diffusion co2 One of these is the Halogenated Laser CCI2FH selective photoreaction by Laser Assisted Nozzle hydrocarbon tunable infrared laser and Method the other is the one made by Hexafluoride SF, tunable visible or ultra-violet laser. CO Laser Induced Chemical Hexafluoride UF, Laser Reaction (CRI SLA) 1.1 Selectiue Reaction with Tunable Infrared Lasers (1) TEA C02 laser based reaction Infrared Multi-photon Dissociation method (IRMPD) is most widely used by taking advantage of — 255 — discrete tunability of C02 laser irradiating special molecules which have resonant spectroscopic absorption peaks. Especially halogenated hydrocarbon, hexahalide, tetrahalide .trichloride and even metal alkoxide are used. Dissociation of molecule like ammonia by infrared excitation with ultraviolet excitation was also applied. In order to convert wavelength of C02 TEA laser, optically pumped NHo or CF4 lasers .especially Raman p-H? lasers are used for the dissociation of uranium hexafluoride based on the multi-colored IRMPD. (2) Reaction by the other types of lasers Continuous wave C02 laser is used for laser induced thermal diffusion and laser assisted nozzle method. In the very special case CO Laser is used for the laser induced chemical reaction (CRISLA). HEATER WMlffl Wavanumberf cm"' 1 HCI 00^7"^/ ^^^^^ fiacharound "101 USER UNIT IMC . loco 8 Wavenumberf cm"' 1 Fig. 1 Laser Induced Thermal Diffusion ) Fig.2 IR Multi-photon dissociation and hydrogen isotope eitchange process8^ UF -F Basic Reacti 5 UFSCI 235 235 UF6 +3hv3-> UF6 ->UF5CI + HF 5.33 it rn by CO laser 235 a =6x2\8 a V-T relaxation ../2 235| _/i UFfi + HCI -» ^UF. + HCI + =/ 0 \V-V scrambling ^UF, + ^UF, B5UF * Fig.3 CRISLfl method(IR Laser Induced 6 6 Photochemical Reaction) 1.2.\Selectiue Reaction with Tunabl^ Uisible or Ultrauiolet lasers Photochemical reaction by tunable visible\lasers is made by a dye laser.which can emit tunable photons with many colors of dyes. CW laser pump dye lasers are used for laser induced chemical reaction photochemical reaction in gaseous/U,quid phase and atomic beam deflection. Diode CW lasers dre also used for radiation pressure. Pulled laser are used for photo-dissociation, especially single photon dissociation and for laser induced chemical reaction, but most popular ana widely applicable selective reaction is a multistep photo'ipnization. (1) Single photon dissociation \ Single photon dissociation is seen in visible and ultra-violet wavelength region. Typical reaction systems are given forthe dissociation of symmetric tetrazine and formaldehyde. a.Dissociation by Visible Photon s-Tetrazine(H2C2N4) + hv -*HCN+N2 b.Dissociation by Ultra-Violet Photon H2CO+ h v -*H2+CO Combination of ultraviolet dissociation and cascade is proposed by LLNL1> Physical and — 256 — operational parameters are given as follows. Table 2. Selectiue photoreaction using tunable uisible/ultra-uiolet lasers Source Wavelength Laser Conversion Type of Reaction Working Materials Dye Laser Laser Induced Chemical Reaction IC1 CW Laser Photo-dissociation H2CO,C2H2N4 (Pump) Photochemical Reaction (Liq.) U02F2+HF+CH3OH Atomic Beam Deflection Ba CWLD Radiation Pressure Rb Pulse Photo-dissociation H2CO,Br2 Li+CCl FH,Yb+HCl,CSCl ,U(BH ) , Laser Dye Laser Laser Induced Chemical Reaction 2 2 4 4 (Pump) U02(HCOO)2H20 Multistcp Photoionization Li,Mg,K,Ca,Ti,Fe,Cu,Ru,Zr,Pd,Ba,Hg,Tl, Nd,Sm,Eu,Gd,Dy,Er,Tu,Yb,U,Pu Pulse Eu3+H 0 Laser Element Selective Photochemistry 2 And the following enrichment is expected. 13c 1.1 %->~70%(single stage),95%(2 stages) 180 0.208%->—40%(single stage),95%(2 stages) 17,0 0.038%->~7%(single stage),95%(3 stages) Table 3. Cascaded single photon dissociation process Physical parameters Operational Parameters Wavelength 290-355nm Laser power 129W Photoabsorption cross section 5xl0'17cm2 Laser PRF 4350Hz Spectroscopic selectivity 200(13C,17O),300(18O) Laser pulse width 40ns Quantum Yield 0.95 Temperature 300K Photolysis cell length 10m Geometry Number of passes 10 + \ELF + H2O" -»- -OH Reaction Coordinate ^cavenagr 340 360 380 400 420 440 460 480 500 320 WAVELENGTH (nm) Fig.4 Oxygen isotope separation in liquid Fig.5 Element selectiue photoreaction in liquid phase phase (2)Laser Induced Selectiue Chemical Reaction Photo-decomposition was made with Uranium Boro-hydride (-deuteride)by 2-step Scheme by — 257— E.R.Bernstein(COO-4118-1),in which 2-5% U(BH4)4/Hf(Zr)(BH4)4 was irradiated by tunable laser at low temperature to decompose it as follows;U(BH4)4+h v -*U(BH4)3.Photochemical reaction was also observed in Uranyl Formate in the following way2), +4 +2 U02(HCOO)2H20+h v -*U ,U02 (3)0ther reaction methods Laser induced sputtering of SF6 from the cold Kr matrix are made using TEA C02 laser ,and Isotopic Selectivity A3 was obtained when laser illuminated non-target molecules.3' Isotope separation in liquid phase was carried out for hydrogen isotope separation based on the photolysis of formaldehyde in liquid xenon"' 2+ 5 Oxygen isotope separation was made with U02 in methanol solution as follows. ) U02F2+2HF+CH3OH-+UF4+Organic Products Photochemical reaction selective to elements but not to isotope was achieved in liquid phase for europium.6' 3+ 2+ 2+ + Eu H20+h v -s.[Eu H20]*Eu +H +'OH 2 Eu^+SO.JA - —L.UVJV--»EuSO4, 2. Htomic Uapor Laser Isotope Separation As this method is based on the resonant multiple photoionization process, atoms can easily be ionized with low photon flux.which is related to the high utilization efficiency of photons, and the atomic spectrum is enough narrow so that the photons with tunable wavelengths are easily absorbed by the 235U without being absorbed by 238U atoms.Therefore ,this method . could achieve separation at high separation factor by one single operation. could be economical. could enrich uranium from the reprocessed uranium .which leads to the effective utilization of natural resources. Tabie4.MPI schemes for RIMS Cilliclot to dtpltfed UWIIIIB Element Ionization . Types of RlSScheme»a»erc<l [a 1 Icniied IIBII PotentlaKcm" ) n,e 4,11 ,)*„ |or this eltmeni AJ ««278 o,»o, "L*»I" Itilxr AJ 78930 2»,*«, J-,"-!*" Idtwdbbslgte to 7«40S> 2U.4U, "'*"' Al D tent IMircrihlt C 90820 2o,«., ntllei C 49306 2",4». 2",4U," Siltcllii J'oli Cd 12140 UL+U)4W| "|4»l*"l bokpt shift 2»,+u, Co 63364 ",+•>, U,4»,40, Q 54576 «'*»' U,4U, -,•>»,"' MiMIc Cnud slate a 31406 C,40, ».*».*». 2u,+u, state exciter ticiler Cu 62317 U,4U, »l*».
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