The hydrogen isotope radiolytic yields, G(H2), G(HD) and G(D2) were determined in H2O/D2O mixtures under chemical conditions close to a LOCA in a PHWR like Atucha I Nuclear Station, that is 2·10–3 MH3BO3 and p(H+D)=8.5±0.2. The total hydrogen radiolytic yield G(H2+HD+D2) as a function of the deuterium atom fraction goes through a flat maximum at about 0.58. This result in dicates that the 4% flammability limit for hydrogen in the reactor's containment with be reached sooner than what is expected assuming a linear combination of pure H2 and D2 radiolytic yields. Hydrogen radiolytic production in 10–3 M KBr in H2O/D2O mixtures gives the same results as in the boric solutions suggesting a bimolecular B(OH)
+OH reaction. Identical isotope concentration factors were calculated for both solutions.
The mechanism of the step I and step II of thermal decomposition of 3CaO · Al2O3 · 6D2O was studied. The presence of Ca(OD)2 was proved in the products of the first step of decomposition. In the calorimeter cell of the Dupont 990 thermoanalyser the enthalpy changesΔHr,I=59.2kJ/mole D2O for step I (210–410°) andDHrII,1=69.0 kJ/mole D2O for the first fast part of the step II (“stage 1 of the step I”, encompassing the temperature interval 410–560°) were measured. This indicates that the dissociation of Ca(OD)2 is not the only transition taking place in the first fast part (stage 1) of the step II.
This paper reports the results of an investigation into the solvent extraction of uranium from technical grade phosphoric acid using industrially available extractants as D2EHPA and TOPO diluted in technical grade kerosene. Preliminary tests showed that, the effect of different parameters such as uranium oxidation stage, temperature and the molar ratio of D2EHPA/TOPO on the uranium recovery was in good agreement with those of previous investigations. However, a detailed investigation into the effect of phosphoric acid concentration, organic concentration and acid/organic phase ratios suggested that the mechanism of D2EHPA/TOPO synergism was rather complex and it presented a different character depending on the acid concentration.
Authors:Y. Sayi, K. Ramakumar, Rajendra Prasad, C. Yadav, P. Shankaran, G. Chhapru and H. Jain
A hot vacuum extraction technique for the determination of hydrogen in metal and alloy samples has been standardised. After
measuring the total pressure of the evolved gases, individual hydrogen and deuterium intensities are measured using an on-line
quadrupole mass spectrometer. Synthetic mixtures of H2 and D2, in known concentrations, have been analysed by QMS and an analytical expression correlating the measured [D2]/[HD] intensity ratio with the mole fraction of deuterium in the synthetic mixture has been arrived at. The precision and
accuracy in the measurement of hydrogen is about 10% at 50 ppmw level.
Authors:M. Yagi, T. Mitsugashira, I. Satoh, M. Hara, Y. Shiokawa, K. Inoue, K. Masumoto and S. Suzuki
As a new fact, the neutron emission from the d-d nuclear fusion reaction in a SiO2–D2 system has been confirmed as well as that in the Ti–D2 system. By using a liquid scintillation detector, the neutron emissions from 8 sample materials consisted of SiO2, in which a small amount of deuterium was adsorbed chemically on the surface layer, were measured in the range of temperature between liquid nitrogen temperature and 400 °C. As a result, it was demonstrated that the neutron-emission reactions take place predominantly on the surface layer of sample material.
Neutron emission has been examined in a system in which the recently reported phenomenon of fracto-fusion might be occurring. No positive evidence has been obtained for cold fusion. The upper limit of the fusion has been 0.0112 events/sec in each specimen containing 0.33 g D2O.
The excitation function of the89Y/d,2n/89Zr reaction was determined by the stacking foil technique below 13.5 MeV. The measured dependence has a threshold energy of Ethr=6.0 MeV. An estimation by the Keller, Lange and Münzel tables is in good agreement with the experiment.
The determination of uranium in liquid samples using energy dispersive X-ray fluorescence was investigated. The organic phase di-(2-ethyl hexyl) phosphoric acid and trioctyl phosphine oxide (D2EHPA-TOPO)/kerosene, which resulted from first and second cycles of uranium extraction from commercial phosphoric acid, was directly analyzed using 109Cd as a primary excitation source. Copper was used as an internal standard, which led to a linear relation between relative intensity of uranium and its concentration. Three calibration curves, 0–100, 100–1000 and 1000–6500 g· ml–1, according to uranium concentration in the studied samples, were constructed. The effect of different molarities of D2EHPA and TOPO was considered. The detection limit, precision and accuracy were 1.1 g · ml–1, 3% and 1.4%, respectively. The obtained results were compared with other techniques such as -ray spectroscopy, UV spectrometry and volumetry.
Authors:V. Chakravortty, S. Perevalov and Yu. Kulyako
Extraction of californium/III/ with di-/–2-ethylhexyl/ phosphoric acid /D2EHPA/ in heptane from pyrophosphate media is almost quantitative between pH 4 and 5. From tripolyphosphate media, however, two to three extractions are needed in the pH range of 3–5 to isolate Cf3+ completely. Reextraction experiments show that 1M H2SO4 can back-extract Cf3+ completely while two to three reextractions with 5M HNO3 can only separate californium/III/. Reverse phase partition chromatography experiments were performed to recover 300 g of californium/III/. From slope analysis of the extraction data the composition of the extracted species has been found to be Cf/H2P2O7/A.HA and Cf/H4P3O10/.A2.2HA from pyrophosphate and tripolyphosphate solutions, respectively, where D2EHPA is abbreviated as /HA/2.