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[en] Complete text of publication follows. The geminate ion recombination was studied by the femtosecond pulse radiolysis system which was developed by using a photocathode RF gun LINAC in Osaka University. We found the excited radical cation as the precursor of the radical cation in the femtosecond pulse radiolysis study of n-dodecane, previously. The lifetime of the excited radical cation was very short (e.g. 7 ps in n-dodecane), and the charge transfer reaction rate constant from the excited radical cation to biphenyl was 10 times higher than that of the radical cation. That suggested that the excited radical cation affects the primary decomposition process and scavenging reaction. To confirm the excited radical cation, the time-dependent behaviors of the electron in n-dodecane were investigated by the femtosecond pulse radiolysis in this study. The geminate decay of the electron monitored at 1200 nm agreed with that of the radical cation geminately. While the electron showed the typical geminate behavior even within 100 ps, which disagreed with that of the radical cation, because of the formation process of the radical cation from the excited radical cation. Moreover, the scavenging effect on the electron was studied by the femtosecond pulse radiolysis. The initial yields of the electron were decreased by increasing of the scavenger (CCl4) concentration and the geminate decays were changed. That means that the pre-thermalized electron was captured by CCl4 and the initial distributions of the geminate pairs were changed.
[en] This document was prepared to meet FCR&D level 3 milestone M3FT-16IN030104052, “continue the study of the short chain compounds,” and, “ study the radiolysis of the non-symmetrical DGA (D3DODGA)….,” under the Radiation Chemistry FCR&D work package. Toward these goals, the short chain DGA, tetraethyldiglycolamide (TEDGA) was investigated for its hydrolytic stability in HNO3 solution, with comparisons to the less oxidizing mineral acid HCl. Initial gamma-irradiations were also performed on DGA solutions, to inform a more detailed investigation of several short chain compounds anticipated for FY17. The hydrolytic and radiolysis behavior of TEDGA is of interest for two reasons. First, previous long chain DGA radiolysis was conducted in dodecane solution since the long chain compounds are soluble in that diluent, and new radiation chemistry is expected in the aqueous environment due to reactions with •OH radical. The second reason is that this water-soluble DGA has been proposed for use as a stripping or holdback agent in both European and American fuel cycle scenarios. Therefore, this work was performed in collaboration Forschungszentrum Jülich (FZJ), and the European SACSESS program. Additionally, results are presented here regarding the radiation of chemistry the non-symmetrical DGA didodecyldioctyldiglycolamide (D3DODGA), for comparison to previous work with symmetrical DGAs such as TODGA and TEHDGA. This was also conducted in collaboration with researchers in the SACSESS program.
[en] The extraction of plutonium in 30 vol% TBP in n-dodecane was modeled based on the aqueous phase activity coefficient estimated from eNRTL model. This is the first time that the eNRTL model is applied for the plutonium extraction system. Earlier eNRTL model was successfully used for the modeling of uranium extraction by Tri iso amyl phosphate. The water activity data for Pu(NO3)4-HNO3-H2O system reported by Charrin et.al was used for the estimation of eNRTL parameter. The Root mean square deviation (RMSD) between the experimental and calculated water activity by eNRTL model is 0.44%. The formation of Pu(NO3)4.2TBP is usually considered for the extraction of plutonium. However for successful modeling of plutonium extraction, the formation of Pu(NO3)4.3TBP also needs to be included in the model as reported by Sio et.al. In this work HNO3.TBP, Pu(NO3)4.2TBP and Pu(NO3)4.3TBP are the species considered for modeling of plutonium extraction and their formation constants estimated from the experimental data are 0.214, 153 and 56042 respectively. The RMSD between the experimental and predicted organic plutonium concentration is 1.24%. The comparison of experimental and predicted organic phase concentration of plutonium nitrate is shown. (author)
[en] Tri-iso-amyl Phosphate (TiAP) is a promising alternative solvent to TBP, with near similar extraction behaviour and physical properties but lower aqueous phase solubility and does not form third phase during the extraction of Pu(IV). In addition to the solubilised extractant, inadvertent entrainment of the extractant into the aqueous stream is a concern during the evaporation operation as the extractant comes into contact with higher nitric acid concentrations and metal nitrates. Hence the thermal decomposition behaviour of TiAP-HNO3 systems has been studied using an adiabatic calorimeter in closed air ambience, under heat-wait-search mode (H-W-S)
[en] The primary purpose of this study was to understand the alpha radiolytic degradation behavior of N,N-dihexyl octanamide (DHOA) vis a vis tributyl phosphate (TBP) solutions in n-dodecane under plutonium loading conditions. These studies were carried out as a function of dose on different Pu loaded samples (containing 0.002-10 g/L Pu) from 4 M HNO3 medium. These Pu loaded solutions were evaluated for stripping behavior by contacting with 0.5 M NH2OH at 0.5 M HNO3 solutions. Organic phase analysis was carried out by gas chromatography (GC) and by visible spectrophotometry. These studies clearly indicated that Pu stripping becomes difficult with increased dose in the case of TBP system. On the other hand, no such problem was observed in DHOA system during stripping of plutonium, thereby indicating that DHOA is a promising candidate for the reprocessing of high burn up Pu rich spent fuels. (author)
[en] Novel ligand, namely, Bis-(2-ethylhexyl) carbamoyl methoxy phenoxy-bis-(2-ethylhexyl), commonly termed as Benzodioxodiamide (BenzoDODA) has been evaluated for its extraction behaviour towards plutonium and other HLW constituent elements. The extractant has shown high extractability and selectivity for plutonium over other metal ions thus making it truly plutonium selective. The radiolytic stability of the ligand shows its efficacy in separation and recovery of plutonium. (author)
[en] Filtration of a dodecane-SDS emulsion was studied in a stirred ultrafiltration cell. Dodecane-SDS emulsion formed a gel layer and was mostly rejected by the membrane(PM-30). Ultrafiltration experiments were performed in a batch cell under various operating conditions. The characteristics of the gel layer and other relevant parameters of the model were estimated. It was observed that the steady-state flux was independent of pressure