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Journal Articles

Non-contact and selective Pd separation based on laser-induced photoreduction for determination of $$^{107}$$Pd by ICP-MS; The Relation between separation conditions and Pd recovery

Yomogida, Takumi; Asai, Shiho; Saeki, Morihisa*; Hanzawa, Yukiko; Horita, Takuma; Esaka, Fumitaka; Oba, Hironori*; Kitatsuji, Yoshihiro

Bunseki Kagaku, 66(9), p.647 - 652, 2017/09

 Times Cited Count:2 Percentile:9.09(Chemistry, Analytical)

Palladium-107 is a long-lived fission product, which can be found in high-level radioactive liquid wastes (HLLW). Determination of the $$^{107}$$Pd contents in HLLW is essential to evaluate the long-term safety of HLLW repositories. However, the $$^{107}$$Pd content in HLLW has not been reported because of difficulties in pretreatment for the measurement. In this study, we investigated applicability of laser-induced photoreduction to HLLW solution: it enables a simple and non-contact separation of Pd. The results showed the recovery of 60% was achieved at the conditions: 40% ethanol, 20 min irradiation, 100 mJ of pulse energy. Additionally, major radionuclides and potentially interfering components in ICP-MS were removed from the simulated HLLW over a wide concentration range of Pd from 0.24 to 24 mg L$$^{-1}$$, showing the applicability of the proposed separation technique to HLLW samples.

Journal Articles

Determination of $$^{107}$$Pd in Pd recovered by laser-induced photoreduction with inductively coupled plasma mass spectrometry

Asai, Shiho; Yomogida, Takumi; Saeki, Morihisa*; Oba, Hironori*; Hanzawa, Yukiko; Horita, Takuma; Kitatsuji, Yoshihiro

Analytical Chemistry, 88(24), p.12227 - 12233, 2016/12

 Times Cited Count:13 Percentile:53.5(Chemistry, Analytical)

Safety evaluation of a radioactive waste repository requires credible activity estimates confirmed by actual measurements. A long-lived radionuclide, $$^{107}$$Pd, which can be found in radioactive wastes, is one of the difficult-to-measure nuclides and results in a deficit in experimentally determined contents. In this study, a precipitation-based separation method has been developed for the determination of $$^{107}$$Pd with ICP-MS. The photoreduction induced by laser irradiation at 355 nm provides short-time and one-step recovery of Pd. The proposed method was verified by applying it to a spent nuclear fuel sample. In order to efficiently recover Pd, a natural Pd standard was employed as the Pd carrier. The chemical yield of Pd was about 90% with virtually no impurities, allowing accurate quantification of $$^{107}$$Pd.

Oral presentation

Development of analytical methods for $$^{107}$$Pd in high-level radioactive wastes using laser-induced particle formation

Yomogida, Takumi; Asai, Shiho; Saeki, Morihisa; Hanzawa, Yukiko; Esaka, Fumitaka; Oba, Hironori; Magara, Masaaki

no journal, , 

$$^{107}$$Pd contained in high-level radioactive wastes (HLW) is a long-lived fission product. The procedure for $$^{107}$$Pd determination in HLW is demanded for safety assessment of geological disposal. Radiation measurement is difficult due to very low energy of beta radiation of $$^{107}$$Pd. Chemical separations and mass spectrometry methods are superior to the radiation measurement, but it has some problems on complicated analysis processes and $$^{107}$$Ag isobar contamination. We performed a novel procedure for $$^{107}$$Pd determination by laser-induced particle formation to overcome those problems. In this study, Pd separation by laser-induced particle formation was applied to the analysis of simulated HLW solutions. ICP-MS measurements demonstrated that the recovery ratio of Pd depended on solutions and ethanol concentrations in laser irradiation. The low contamination ratio indicated the high elemental selectivity of laser-induced particle formation.

Oral presentation

Development of Pd separation technique based on laser-induced particle formation for determination of $$^{107}$$Pd in HLW with ICP-MS

Yomogida, Takumi; Asai, Shiho; Saeki, Morihisa; Hanzawa, Yukiko; Esaka, Fumitaka; Oba, Hironori; Magara, Masaaki

no journal, , 

Inventory estimation of long-lived fission products (LLFPs) in high-level radioactive waste (HLW) is indispensable for the long-term safety assessment of geological repository. Reliability of the estimated inventory is verified with actual measurement values which are drawn from proven analytical techniques. There has been increasing interest in the development of new determination methods of Pd-107 which is one of the LLFPs with a half-life of 6.5$$times$$10$$^{6}$$ y because little measured data has been reported. Major difficulty in determination of Pd-107 involves the poor recovery of Pd in separation step required prior to measurement. In this study, a highly selective separation technique based on laser-induced microparticle formation has been applied to Pd separation. The recovery percentage of Pd from a simulated HLW solution were affected by irradiation time and laser pulse energy. The maximum recovery percentage of 60% was achieved by 20-min irradiation at the energy of 100 mJ.

Oral presentation

Development of Pd separation technique based on laser-induced particle formation for determination of $$^{107}$$Pd in radioactive wastes with mass spectrometry

Yomogida, Takumi; Asai, Shiho; Saeki, Morihisa; Hanzawa, Yukiko; Esaka, Fumitaka; Oba, Hironori; Kitatsuji, Yoshihiro

no journal, , 

Palladium-107, which is one of the long-lived fission products in high-level radioactive waste (HLW), is a pure beta emitter with a half-life of 6.5$$times$$10$$^{6}$$ y. The inventory estimation of $$^{107}$$Pd is demanded for the long-term safety assessment of geological repository. ICP-MS is suitable for the determination of $$^{107}$$Pd because radiometry with a low beta energy of 33 keV is practically inapplicable. However, cumbersome chemical separation accompanied with highly radioactive sample treatment is still necessary prior to the measurement with ICP-MS. To minimize radioactive contamination and radiation exposure, simplified procedure is desirable. In this study, a simple separation technique based on laser-induced microparticle formation has been applied to Pd separation in a simulated HLW solution. Sufficiently high decontamination factors of coexisting elements ($$>$$ 1000) were observed, indicating that the proposed method achieved highly-selective separation of Pd.

Oral presentation

Non-contact Pd separation based on laser-induced particle formation for determination of $$^{107}$$Pd with ICP-MS

Yomogida, Takumi; Asai, Shiho; Saeki, Morihisa; Hanzawa, Yukiko; Esaka, Fumitaka; Oba, Hironori; Kitatsuji, Yoshihiro

no journal, , 

Oral presentation

Determination of $$^{107}$$Pd in Pd recovered from spent nuclear fuel solution by laser induced photoreduction

Asai, Shiho; Yomogida, Takumi; Saeki, Morihisa*; Oba, Hironori*; Hanzawa, Yukiko; Horita, Takuma; Kitatsuji, Yoshihiro

no journal, , 

$$^{107}$$Pd is a long-lived radionuclide that can be found in HLW. The estimation of the amount of $$^{107}$$Pd in HLW is considered crucial for long-term safety evaluation of HLW. However, experimentally determined concentrations of $$^{107}$$Pd in HLW has not been reported due to the difficulty in recovering significant amount of Pd from HLW which has high radioactivity. In this study, we have focused on remotely operated separation technique based on laser-induced photoreduction, which allows to keep the distance from samples. To validate the applicability of the proposed method, spent nuclear fuel with a traceable irradiation history was employed instead of HLW. The resulting Pd precipitate contained almost no impurities, such as actinides (U, Np, Pu, Am, Cm), major fission products (Zr, Mo, Tc, Ru, Rh, Ba, Cs, Ce), resulting in the interference-free measurement of $$^{107}$$Pd with ICP-MS. The amount of $$^{107}$$Pd per 1 mg of $$^{238}$$U in the sample was 239$$pm$$9 ng/mg-$$^{238}$$U.

Oral presentation

Recovery and determination of Pd in nuclear fuel used for electricity generation

Asai, Shiho; Yomogida, Takumi

no journal, , 

Palladium found in spent nuclear fuel is characterized by having radiopalladium $$^{107}$$Pd (Half-life: 6.5$$times$$10$$^{6}$$ y). With its long half-life, accurate determination of the amount of $$^{107}$$Pd in spent nuclear fuel is essential for estimating the radiation effects. However, no experimentally determined concentration has been reported due to the difficulties in obtaining pure palladium form spent nuclear fuel with conventional separation techniques. In this study, Pd in spent nuclear fuel solution was separated by precipitation triggered by photoreduction of Pd(II) with pulsed laser irradiation. About 20 min of the irradiation to the spent nuclear fuel solution provides high Pd recovery of more than 90%. The prepared Pd precipitate was dissolved with aqua regia and measured with ICP-MS. Almost no impurities were detected in the Pd precipitate, resulting in the accurate determination of $$^{107}$$Pd.

Oral presentation

Direct measurement of $$^{107}$$Pd in Pd metal recovered from spent nuclear fuel with laser ablation ICP-MS

Asai, Shiho; Ohata, Masaki*; Yomogida, Takumi; Saeki, Morihisa*; Oba, Hironori*; Hanzawa, Yukiko; Horita, Takuma; Kitatsuji, Yoshihiro

no journal, , 

Oral presentation

Isotope ratio measurement of Pd recovered from spent nuclear fuel with LA-ICP-MS

Asai, Shiho; Ohata, Masaki*; Yomogida, Takumi; Saeki, Morihisa*; Oba, Hironori*; Hanzawa, Yukiko; Horita, Takuma; Kitatsuji, Yoshihiro

no journal, , 

Safe and cost-effective disposal of radioactive wastes requires reliable evaluation of the amount of the radionuclides found in such wastes. Measurement of $$^{107}$$Pd, one of the radionuclides that are necessary to be evaluated, is associated with highly radioactive sample (e.g., spent nuclear fuel sample), resulting in only a few data in published forms. We separated Pd as a precipitate from a spent nuclear fuel sample and then determined the precise amount of $$^{107}$$Pd. However, the method needed dissolution of the Pd precipitate to carry it to the sample introduction system of ICP-MS. In this study, we tried direct measurement of the Pd precipitate with laser-ablation (LA)-ICP-MS that enables solid sample measurement. The diameters of the recovered Pd precipitates were less than 500 nm, which is much smaller than the ablation spot. This allowed Pd to be uniformly vaporized, leading to sufficiently stable signals with high precisions equivalent to those of conventional ICP-MS.

Oral presentation

Interference removal for high-sensitivity rapid analysis of $$^{107}$$Pd in radioactive rubbles by ICP-MS/MS

Iwahashi, Hiroyuki; Do, V. K.; Furuse, Takahiro; Ota, Yuki; Homma, Shunta; Kurosawa, Kiyoko*; Motoki, Yoshiaki*; Hirosawa, Takashi

no journal, , 

The radiometric determination of beta emitting $$^{107}$$Pd (half-life of 6.5 million years) requires a multiple-step chemical separation and a time-consuming radioactive measurement. Inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) with recent technological advances in interference removal by two quadrupole mass filters and a collision/reaction cell could be an alternative for highly sensitive analysis of long-lived radionuclides. In this study, we have developed an analytical method for the determination of $$^{107}$$Pd in concrete rubble by ICP-MS/MS combined with single-column chromatographic separation. A simplified procedure for the separation of Pd from concrete matrices was developed. The measurement condition was optimized to completely suppress the interference including the isobar $$^{107}$$Ag and the sample matrices. The application of the developed method to radioactive concrete rubble is under consideration.

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