Yumi Sugo

Studies on hydrolysis and radiolysis of N, N, N', N'-tetraoctyl-3-oxapentane-1,5-diamide

Summary Hydrolytic and radiolytic stabilities of a promising extractant, N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA), for actinides in high-level radioactive liquid waste from nuclear fuel reprocessing were investigated in air at room temperature. Hydrolysis by nitric acid was not observed, whereas radiolysis by gamma irradiation was notably observed. The radiolysis study showed that an amide-bond, an ether-bond, and a bond adjacent to the ether-bond tended to be broken by gamma irradiation, and dioctylamine and various N,N-dioctylmonoamides were identified as the main degradation products by GC/MS and NMR analyses. The G-value for degradation of neat TODGA was 8.5 ± 0.9, which value was higher than those for N,N′-dioctyl-N,N′-dimethyl-2-(3′-oxapentadecyl)-propane-1,3-diamide and N,N-dioctylhexanamide. It was obvious that n-dodecane, which was used for a diluent, had a sensitization effect on the radiolysis of these amidic extractants. In a TODGA–n-dodecane–HNO3 system, the coexisting nitric acid showed an insignificant effect on the radiolysis of TODGA.

Extraction and separation of Am(III) and Sr(II) by N, N, N', N'-tetraoctyl-3-oxapentanediamide (TODGA)

Summary By using an extractant, N,N,N´,N´-tetraoctyl-3-oxapentanediamide (TODGA), extraction and separation of Sr(II) from Am(III) were investigated for the partitioning of high level liquid waste (HLLW). Both metal ions, accompanied with the counter anion, NO3-, and HNO3 without dissociation, were extracted by TODGA. We used two distinct methods for the separation of Am(III) and Sr(II). A mixture of TODGA and monoamide reduced the distribution ratio D of Sr(II) compared to that without monoamide, whereas D(Am) was still high value under the identical condition. After extraction of Am(III) by TODGA and monoamide, Sr(II) remaining in HLLW can be extracted by using enough concentration of TODGA at the next step. In the other method, Sr(II) was coextracted with Am(III) by TODGA. It was observed that D(Sr) decreased with an increase of HNO3 from 3 M to 6 M HNO3 at the same TODGA concentration, while D(Am) increased until 6 M HNO3. By using 6 M HNO3, Am(III) and Sr(II) were separated after coextraction.

Extraction Behavior of Metal Ions by TODGA, DOODA, MIDOA, and NTAamide Extractants from HNO3 to n-Dodecane

Four novel diamide and triamide extractants developed in our group, TODGA, DOODA, MIDOA, and NTAamide, were examined to see the extractability trends of up to 74 metal ions from nitric acid into n-dodecane. TODGA and DOODA have one or two etheric and two amidic oxygen donor atoms, and MIDOA and NTAamide have a nitrogen donor atom centered in the backbones and two or three diamidic O atoms. The former two extractants are expected to have high extractability for metal ions classified as hard acids and the latter ones have higher extractability for soft acids. TODGA and DOODA have high distribution ratios, D, for metal ions in the 2A-4A groups. On the other hand, MIDOA and NTAamide have high D values for group 5A-7A and 8 metal ions, which follows HSAB theory. The positive relation between the slope values of the extractant dependence and the extraction constant, α, is found, which suggests that a high order of successive formation of metal complexes with extractants gives high extractability.

The Effect of Alkyl Substituents on Actinide and Lanthanide Extraction by Diglycolamide Compounds

The effect of the alkyl substituents on amidic N atoms in diglycolamide (DGA) compounds on solvent extraction has been investigated. The solubility in water and n-dodecane, lanthanide loading capacity, and distribution ratios (D) of lanthanides and actinides for various DGA compounds are reported. DGA derivatives with short alkyl chains, for example, methyl and ethyl groups, are very water soluble, while DGA derivatives with long alkyl chains, for example, octyl (TODGA), decyl (TDDGA), dodecyl (TDdDGA), and 2-ethylhexyl (TEHDGA) group are moderately soluble in n-dodecane. DGA derivatives with phenyl substituents have very low solubility in both aqueous and organic solvents, which suggests that these compounds will not be suitable for solvent extraction applications in the HNO3/n-dodecane systems. The lanthanide loading capacities of DGA extractants correlate with their alkyl chain lengths according to the following order: TDdDGA > TDDGA > TODGA > TEHDGA. The branched-alkyl-chain DGA derivative (TEHDGA) exhibits both lower D and loading capacity than TODGA. The results of masking-effect and solubility tests indicate that TEDGA is the best actinide masking agent among the water-soluble DGA derivatives tested. Actinide and lanthanide extractions using ten DGA compounds in six diluents (nitrobenzene, 1,2-dichloroethane, 1-octanol, chloroform, toluene, and n-dodecane) are also reported; it was observed that lipophilic DGA derivatives with shorter alkyl chains show higher D values.

Novel Extractant, NTAamide, and its Combination with TEDGA for Mutual Separation of Am/Cm/Ln

A novel extractant, N,N,N′,N′,N′′,N′′-hexaalkyl-nitrilotriacetamide (NTAamide), was developed for the extraction and separation of actinides (An) and lanthanide (Ln). NTAamide has a nitrogen atom in the center of a backbone and is bonded to three acetamide groups; the nitrogen and three amide oxygen atoms can work as the donor atoms. NTAamide extracted Am and Cm with a low distribution ratio of Ln in diluted HNO3, and the separation factor (SF) for An/Ln was equal to or higher than 23.6 using 0.5 M NTAamaide/n-dodecane and 0.2 M HNO3. The addition of N,N,N′,N′-tetraethyldiglycolamide as a masking agent to the NTAamide extraction system was effective for separating Am from Cm; the maximum SF was 6.5, one of the highest SF values obtained using the HNO3 and n-dodecane system.

Simultaneous analysis of silicon and boron dissolved in water by combination of electrodialytic salt removal and ion-exclusion chromatography with corona charged aerosol detection

Selective separation and sensitive detection of dissolved silicon and boron (DSi and DB) in aqueous solution was achieved by combining an electrodialytic ion isolation device (EID) as a salt remover, an ion-exclusion chromatography (IEC) column, and a corona charged aerosol detector (CCAD) in sequence. DSi and DB were separated by IEC on the H(+)-form of a cation exchange resin column using pure water eluent. DSi and DB were detected after IEC separation by the CCAD with much greater sensitivity than by conductimetric detection. The five-channel EID, which consisted of anion and cation acceptors, cathode and anode isolators, and a sample channel, removed salt from the sample prior to the IEC-CCAD. DSi and DB were scarcely attracted to the anion accepter in the EID and passed almost quantitatively through the sample channel. Thus, the coupled EID-IEC-CCAD device can isolate DSi and DB from artificial seawater and hot spring water by efficiently removing high concentrations of Cl(-) and SO4(2-) (e.g., 98% and 80% at 0.10molL(-1) each, respectively). The detection limits at a signal-to-noise ratio of 3 were 0.52μmolL(-1) for DSi and 7.1μmolL(-1) for DB. The relative standard deviations (RSD, n=5) of peak areas were 0.12% for DSi and 4.3% for DB.

Preparation and biological evaluation of 3-[76Br]bromo-α-methyl-l-tyrosine, a novel tyrosine analog for positron emission tomography imaging of tumors

INTRODUCTION 3-[(18)F]fluoro-α-methyl-l-tyrosine ([(18)F]FAMT) is a useful amino acid tracer for positron emission tomography (PET) imaging of malignant tumors. FAMT analogs labeled with (76)Br, a positron emitter with a long half-life (t(1/2)=16.1 h), could potentially be widely used as amino acid tracers for tumor imaging. In this study, 3-[(76)Br]bromo-α-methyl-l-tyrosine ([(76)Br]BAMT) was designed, and its usefulness was evaluated as a novel PET tracer for imaging malignant tumors. METHODS In this study, both [(76)Br]BAMT and [(77)Br]BAMT were prepared. The in vitro and in vivo stability of [(77)Br]BAMT was evaluated by HPLC analysis. Cellular uptake and retention of [(77)Br]BAMT and [(18)F]FAMT were evaluated using LS180 colon adenocarcinoma cells. Biodistribution studies were performed in normal mice and in LS180 tumor-bearing mice, and the tumors were imaged with a small-animal PET scanner. RESULTS [(77)Br]BAMT was stable in vitro but was catabolized after administration in mice. Cellular accumulation and retention of [(77)Br]BAMT were significantly higher than those of [(18)F]FAMT. In biodistribution studies, the tumor accumulation of [(77)Br]BAMT was higher than that of [(18)F]FAMT. However, some level of debromination was seen, which caused more retention of radioactivity in the blood and organs than was seen with [(18)F]FAMT. PET imaging with [(76)Br]BAMT enabled clear visualization of the tumor, and the whole-body image using [(76)Br]BAMT was similar to that using [(18)F]FAMT. CONCLUSIONS [(77)Br]BAMT showed high levels of tumor accumulation, and [(76)Br]BAMT enabled clear visualization of the tumor by PET imaging. Although an improvement in stability is still needed, (76)Br-labeled FAMT analogs could potentially serve as PET tracers for the imaging of malignant tumors.

Development of extraction chromatographic adsorbent using alkylpyridinedicarboxyamides as extractant for separation of trivalent minor actinides from lanthanides – stability and separation ability against nitric acid exposure and gamma-ray irradiation

Toward the development of a practical separation method for trivalent actinides and lanthanides, we used extraction chromatography with alkylpyridinedicarboxyamides as the extractant. The results confirmed that the performance degradation of the adsorbent caused by contact with HNO3 and/or irradiation with gamma-rays would be very small during the operation of column chromatography. The optimal conditions for the column separation were also determined: eluent, 5 M HNO3; flow rate, 0.1 mL min−1. In addition, the change of average particle size of inert support material from 250–850 μm (XAD4) to 25–45 μm (Gelpack A040) brought about the improvement of separation between trivalent actinides and lanthanides.