Shoichi Sato

A nickel-iodine-sulfur process for hydrogen production

Abstract A thermochemical hydrogen production process which consists of the following reactions containing nickel, iodine and sulfur (NIS process) was studied. (1.1) So 2 (aq.)+I 2 (aq.)+2H 2 O(1)→2H 2 SO 4 (aq.) (1.2) 2HI(aq.)+H 2 SO 4 (aq.)+2Ni(c)→NiI 2 +NiSO 4 (aq.)+2H 2 (g) (2) NiI 2 (c)→NI(c)+I 2 (g) (3.1) NiSO 4 (c)→NiO(c)+SO 3 (g) (3.2) SO 3 (g)→SO 2 (g)+ 1 2 O 2 (g) (4) NiO(c)+H 2 (g)→Ni(c)+H 2 O(g) This process is an improved iodine-sulfur process, and is characterized by the separation of the products of reaction (1.2) by solvent extraction, and by the absence of hydrogen or water in the high temperature reactions (3.2), (3.1) and (2). Experimental results of the main unit operations are described. The energy balance of the process is estimated, based on a simplified flow-sheet. A conceptual plant flow-sheet is discussed in connection with a VHTR.

Influence of gas flow patterns on NOx removal efficiency

Abstract Dose distribution in flue gas irradiation vessel is not uniform due to limited electron penetration range. This phenomena influence overall NO x removal efficiency is observed in the process. The remarkable increase in the efficiency can be achieved by multistage gas irradiation and gas mixing between stages. The results of modelling for longitudinal beam scanning as applied at EPS Kaweczyn pilot plant are presented in the paper. These are the basis for process vessel upscaling.

Studies on the nickel-iodine-sulfur process for hydrogen production—III

Abstract A thermochemical hydrogen production process utilizing nickel, iodine and sulfur (the NIS process) has been studied and suitable operation conditions examined. Nickel powder dissolution into acid mixtures, nickel iodide decomposition under iodine partial pressure, nickel sulfate decomposition and other steps were studied. Decomposition gas from the sulfate had near equilibrium composition as for the sulfur trioxide decomposition into sulfur dioxide and oxygen. A new process is also under study, utilizing methanol instead of nickel as the circulating reactant.

Ions in carbon dioxide at an atmospheric pressure

Abstract The formation and decay of cluster ions, (CO 2 ) n + , (CO(CO 2 ) n ) + , H 2 O(CO 2 ) n ) + , (H(H 2 O)(CO 2 ) n ) + , and (H(H 2 O) 2 (CO 2 ) n ) + in atmospheric pressure carbon dioxide are observed with a time-resolved atmospheric pressure ionization mass spectrometer (TRAPI). It was found that the reaction of the cluster ions is not always analogous to that of the corresponding bare ions, and that a trace amount of impurities, i.e. H 2 O and CO, causes a decisive effect on the reaction course of cluster ions. Relevance of these observations is discussed to the radiolysis of carbon dioxide.

Design and operational features of the low temperature fissiochemical loop

A low temperature in-pile loop for the irradiation of chemical reactants, especially by fission fragments, has been designed, constructed and operated successfully. The main features of the loop are briefly described: the capsule for sample irradiation, the design and performance of the helium cooling system and safety considerations. Gaseous chemical reactants charged in an instrumented double capsule at pressures up to 20 kg/cm2, can be irradiated in a nuclear reactor at any temperature between + 20° and – 190°C, for periods up to 5hr. The thermal performance of the helium cooling system was in good agreement with the design calculations. Irradiations of ethylene and other gases could be conducted at an absorbed fission fragment dose rate of about 20 Mrad/hr, which is several times larger than the background reactor radiation. Thus, chemical reaction studies by fission fragments can be safely conducted at. ambient to low temperatures in this loop.

Chemical Dosimeters for Mixed Radiations in a Nuclear Reactor

The dose rates due to mixed reactor radiations were measured by five gaseous chemical dosimeters – nitrous oxide (natural), 15N-enriched nitrous oxide, ethylene, ethane and carbon dioxide. The observed dose rates for these gases at the same irradiation position in a nuclear reactor were, 1.8×108, 1.5×l08, 1.9×108, 2.5×l08 and 1.0×108 rad/hr, respectively. These values were compared with those calculated from the mass stopping power of the gases for secondary electrons produced by γ-rays and those from thermal and fast neutron fluxes. No contradiction was found among them. A method of analysis of the reactor radiation dose rates into γ, thermal and fast neutron components is proposed, which is based solely on chemical dosimetry.

Radiation Chemical Reactions in Carbon Dioxide-Propane System Formation of Carbon Monoxide by Fission Fragments

Abstract Radiolysis of the CO2-C3H8 system by fission fragments (FF) was compared experimentally with those by γ- and (n+γ)-rays. Carbon monoxide formation was observed to reach maximum at 1% propane concentration with all three kinds of radiation. The G (CO) value was found consistently higher with FF than with γ- and (n+γ)-rays, whereas G(C2H6) showed the opposite tendency in the difference between FF and the other radiations. The maximum G(CO) value obtained with FF was 6.7, while only 3.6 was attained with the other radiations. The difference between the radiolysis by FF and by the other radiations was ascribed to reactions taking place within the FF tracks. The rates of in-track reactions and the diffusion out of the tracks were estimated on the basis of Mozumders track model. This estimation made it clear that, with the rise in the total pressure, CO formation could be expected to be enhanced by FF irradiation, with the reaction CO+ 2+e−→CO+O coming to predominate over other reactions constituting ...

Potential of carbon dioxide radiolysis for hydrogen production

Abstract Carbon dioxide radiolysis was investigated theoretically and experimentally, and its potential for use in hydrogen production was examined. Elementary processes in the physical, physicochemical and chemical stages of carbon dioxide radiolysis were examined from a viewpoint of energy conversion efficiency from radiation to chemical energy. The energy conversion efficiency in the physical stage was ca 70%, and in the physicochemical stage ca 40%. The back reaction in carbon dioxide radiolysis reduces product yields and lowers the energy conversion efficiency, and should be suppressed. Effects of additives, high absorbed doses and fission fragment irradiation were studied experimentally.

Effect of water on the radiolysis of carbon dioxide

Abstract Water was found to accelerate the back reaction of CO 2 radiolysis. Concentration of carbon monoxide reached only a low level( 2 ) by the radiolysis of wet carbon dioxide, while it reached much higher (>250 ppm in CO 2 ) by that of dry carbon dioxide. Clustered ions, O 2 ± (H 2 O) m (CO 2 ) n , are considered for the ixidizing species responsible for the back reaction.

Fission-fragment tracks in gases at 6–10 atm

Abstract The LET effects observed in three gaseous mixtures CO 2 -C 3 H 8 , C 2 H 6 -NH 3 and N 2 -C 2 H 4 are interpreted by competition between ion recombination and charge transfer reaction within the fission fragment tracks. A prescribed diffusion model is applied to the ionic reactions in the tracks. The competition between two reactions is related to the structure of tracks in the reaction systems. The track radius in the unit of thickness, rp , is estimated to be 0.12 and ⪅0.15 μg · cm -2 for CO 2 -C 3 H 8 , C 2 H 6 -NH 3 and N 2 -C 2 H 4 systems, respectively.