Preparation of carbonate slurry simulating chemical composition of slurry in overflowed high integrity container and evaluation of its characteristics

Horita, Takuma; Yamagishi, Isao; Nagaishi, Ryuji; Kashiwaya, Ryunosuke*

JAEA-Technology 2021-012, 34 Pages, 2021/07

JAEA-Technology-2021-012.pdf:2.1MB
JAEA-Technology-2021-012(errata).pdf:0.18MB

Waste mainly consisting of carbonate precipitates (carbonate slurry) from the Advanced Liquid Processing System (ALPS) and the improved ALPS at the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Holdings, Inc. have been storing in the High Integrity Container (HIC). The supernatant solution of carbonate slurry contained in some of HICs were overflowed in April of 2015. The all of level of liquid in the HICs were investigated; however, almost of the HICs were under the level of overflow. The mechanism of overflow suggested to be depending on the difference of the properties of the carbonate slurry such as the retention/release characteristics of the bubbles. Therefore, in order to clarify the mechanism of leakage, the repeatability experiment was carried out by using simulated carbonate slurry. The simulated carbonate slurry was perpetrated by using the same cross-flow filter system of the actual ALPS. Moreover, the preparative conditions for the simulated carbonate slurry were the same as Mg/Ca concentration ratio in inlet water of the ALPS (raw water) and the ALPS operating conditions. The chemical characteristics of simulated carbonate slurries were revealed by ICP-AES, pH meter, etc. The density of the settled slurry layer tended to increase depending on the calcium concentration in the raw water. The bubble injection test was conducted in order to investigate the bubble retention/release behavior in the simulated carbonate slurry layer. The simulated carbonate slurry with high settling density, which was generated by high calcium concentration solution was revealed to retain the injected bubbles. Since the ratio of concentration calcium and magnesium during the carbonate slurry generation is assumed to affect the retention of bubbles in the slurry layer, the information on the composition of raw water is one of important factor for overflow of HICs.

Direct quantitation of Cs in spent Cs adsorbent used for the decontamination of radiocesium-containing water by laser ablation inductively coupled plasma mass spectrometry

Asai, Shiho*; Ohata, Masaki*; Hanzawa, Yukiko; Horita, Takuma; Yomogida, Takumi; Kitatsuji, Yoshihiro

Analytical Chemistry, 92(4), p.3276 - 3284, 2020/02

https://doi.org/10.1021/acs.analchem.9b05161

The long-term safety assessment of spent Cs adsorbents produced during the decontamination of radiocesium-containing water at the Fukushima Daiichi Nuclear Power Plant requires one to estimate their Cs content prior to final disposal. Cs is usually quantified by inductively coupled plasma mass spectrometry (ICP-MS), which necessitates the elution of Cs from Cs adsorbents. However, this approach suffers from the high radiation dose from Cs. To address this challenge, we herein employed laser ablation ICP-MS for direct quantitation of Cs in Cs adsorbents and used a model Cs adsorbent prepared by immersion of a commercially available Cs adsorbent into radiocesium-containing liquid waste to verify the developed technique. The use of the Cs/Cs ratio and Cs radioactivity obtained by gamma spectrometry achieved simple and precise quantitation of Cs and the resulting Cs activity of 0.36 Bq agreed well with that in the original radiocesium-containing liquid waste.

Non-contact and selective Pd separation based on laser-induced photoreduction for determination of 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

https://doi.org/10.2116/bunsekikagaku.66.647

Palladium-107 is a long-lived fission product, which can be found in high-level radioactive liquid wastes (HLLW). Determination of the Pd contents in HLLW is essential to evaluate the long-term safety of HLLW repositories. However, the 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, showing the applicability of the proposed separation technique to HLLW samples.

Preparation of Sr adsorptive fiber by impregnating with crown ether derivative for Sr measurement

Horita, Takuma; Asai, Shiho; Konda, Miki; Hanzawa, Yukiko; Saito, Kyoichi*; Fujiwara, Kunio*; Sugo, Takanobu*; Kitatsuji, Yoshihiro

Bunseki Kagaku, 66(3), p.189 - 193, 2017/03

https://doi.org/10.2116/bunsekikagaku.66.189

A Sr-selective adsorption fiber was prepared for rapid analysis of Sr content by using radiation-induced emulsion graft polymerization and subsequent chemical modification. A polyethylene fiber with a diameter of 13 m was first immersed in a methanol solution of an epoxy-group-containing vinyl monomer, glycidyl methacrylate (GMA), and polyoxyethylene sorbitol ester (Tween20) as a surfactant for graft-polymerization of GMA. Octadecylamine was then bound to a polymer chain extending from the fiber surface providing hydrophobicity to the polymer chain. Dicyclohexano-18-crown-6 (DCH18C6) was finally impregnated onto the polymer chain via a hydrophobic interaction between the octadecyl moiety of the polymer chain and the cyclohexyl moiety of DCH18C6. The fiber surface structure, characterized by DCH18C6 molecules loosely entangled with polymer chains, afforded realizes the rapid and selective adsorption of Sr ions with an adsorption rate approximately 100 times higher than that of a commercially available Sr-selective resin (Sr Resin).

Preparation of crown ether derivative-impregnated fiber based on the radiation-induced emulsion graft polymerization for rapid analysis of Sr-90

Horita, Takuma; Asai, Shiho; Hanzawa, Yukiko; Saito, Kyoichi*; Fujiwara, Kunio*; Sugo, Takanobu*; Kitatsuji, Yoshihiro

no journal, , 

There has been an increasing demand for rapid analysis of Sr to ensure a prompt action against the contaminated water in the Fukushima Daiichi NPP. Precedent works demonstrated that Cs adsorption fibers prepared by utilizing graft polymerization technology achieved high-speed removal of Cs in the contaminated water. In this study, we have investigated the applicability of such proven technology to the preparation of a Sr adsorption fiber specialized for the selective extraction of Sr. In the prepared fiber, an extractant for Sr,dicyclohexano-18-crown-6-ether (DCH18C6) was impregnated via hydrophobic interaction between DCH18C6 and the hydrophobic polymer chains attached onto the surface of the fiber. To increase the adsorption capacity, emulsion graft polymerization which promotes the polymer chains to grow longer was applied. The densely-packed DCH18C6 inside the interfacial phase formed by the polymer chains facilitates the efficient adsorption. The amounts of Sr adsorbed is comparable to those of conventional adsorbents, indicating that the prepared fiber has a feasible performance for Sr adsorption.

Determination of 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, , 

Pd is a long-lived radionuclide that can be found in HLW. The estimation of the amount of Pd in HLW is considered crucial for long-term safety evaluation of HLW. However, experimentally determined concentrations of 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 Pd with ICP-MS. The amount of Pd per 1 mg of U in the sample was 2399 ng/mg-U.

Direct measurement of 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, , 

Preparation of Sr adsorption fiber for beta-ray measurement

Horita, Takuma; Asai, Shiho; Hanzawa, Yukiko; Saito, Kyoichi*; Sugo, Takanobu*; Fujiwara, Kunio*; Kitatsuji, Yoshihiro

no journal, , 

There has been an increasing importance of the development of rapid Sr analysis technique, responding to needs in Fukushima Daiichi NPP. We have been trying to achieve a rapid analysis using a fibrous Sr adsorbent which has high selectivity for Sr. The fiber we prepared that has a high-density Sr adsorption phase on its surface, and so it can adsorb Sr on the fiber surface. On the other hand, base material of a conventional Sr adsorptive resin for Sr analysis (Sr Resin) is bead-shaped resin, and Sr is adsorbed inside pores. The fiber allows highly efficient counting by minimizing the self-attenuation effects. The adsorption capacity and selectivity of the fiber was nearly the same as those of the Sr Resin. From these results, we confirmed that the fiber has performance for efficient counting of Sr.

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 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 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.

Separation of platinum-group metals from radioactive waste liquid by laser induced particle formation

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

no journal, , 

Platinum-group metals (PGMs), such as Pd, Ru, and Rh are generated by nuclear fission of U and can be found in spent nuclear fuel (SNF) and high-level radioactive waste (HLW). Separation techniques for PGMs from HLW have been investigated for the safety assessment of HLW and the reuse of PGMs as resources. Among such PGMs, only Pd has a long-lived radionuclide Pd. Accordingly, the precise measurement of the amount of Pd in HLW is essential for the long-term safety management of HLW. The determination of Pd requires a reliable separation technique that allows selective Pd recovery with high purity. We developed a new separation technique specialized for PGMs. The technique involves UV-laser irradiation that induces selective reduction of ions of PGMs. The reduced PGMs can be readily recovered as precipitates. At the conference, the separation performances of PGMs and some applications of our technique will be discussed.