Effect of preparation conditions and storage time on characteristic and rheological properties of carbonate slurries

Kato, Tomoaki; Yamagishi, Isao

JAEA-Technology 2023-018, 53 Pages, 2023/11

JAEA-Technology-2023-018.pdf:2.6MB

In the decommissioning of Fukushima Daiichi Nuclear Power Station, radioactive carbonate slurry waste was generated using the Advanced Liquid Processing System (ALPS) pretreatment and temporarily stored in a high integrity container (HIC). In 2015, overflow of supernatant from HIC estimate as bubble retention in the carbonate slurry was discovered, increasing the need for a safety assessment of the carbonate slurry stored the HIC (HIC slurry). In this study, a carbonate slurry (simulated slurry) was prepared according to the Mg/Ca mass ratio in the ALPS inlet water of the HIC slurry which overflew the HIC. The effects of reaction time during the pretreatment process, suspended solids concentration (SS concentration), and settling time on the particle composition, morphology and rheological properties of the slurry were investigated. Evaluating the effect of reaction time and concentration process on chemical properties in slurry production, the effect of the reaction time was not confirmed in the simulated slurry that had undergone the concentration process, and slurry prepared at SS concentration of 150 g/L was composed of formless particles have a particle diameter of 0.4 m or less. We also investigate the effect of SS concentration on sedimentability, decrease in SS concentration by dilution with processing solution contributed to an increase in the initial slurry settling velocity. Furthermore, two different flow characteristics were observed depending on the settling time, suggesting that the slurry at the initial settling time has non-Bingham flow properties, whereas it changes to Bingham flow properties as the settling time becomes longer. In addition, yield stress was increased with settling time, and this yield stress was found to be exponentially proportional to the density of the slurry. These results provide knowledge to estimate the current state of HIC slurry and are expected to contribute to the safety assessment.

Effect of gamma-ray irradiation on corrosion of stainless steel contacted with Zeolite particle

Kato, Chiaki; Yamagishi, Isao; Sato, Tomonori; Yamamoto, Masahiro*

Zairyo To Kankyo, 70(12), p.441 - 447, 2021/12

https://doi.org/10.3323/jcorr.70.441

Zeolite particles have been used in a Cs adsorption vessel for purification of contaminated water in Fukushima Dai-ich Nuclear Power Station (1F). The used Cs adsorption vessels were kept in storage space on 1F site. The risk of localized corrosion of stainless steel used in the vessel was worried. To evaluate the risk of localized corrosion, using specially designed electrochemical testing apparatus was used under gamma-ray irradiation test. And, real size mock-up test conducted. The results showed the potential change caused by creation of HO by water radiolysis decreased by zeolite particles and the enrichment of chloride ion concentration in the vessel do not propagate during dry up procedure of Cs adsorption vessel. These data indicate the risk of localized corrosion of Cs adsorption vessel may stay at considerably low level.

Decision making in protection against radiation from nuclear disaster; Risk trade-off and stakeholder involvement

Kanda, Reiko*; Homma, Toshimitsu*; Takahara, Shogo; Tsubokura, Masaharu*; Osako, Masahiro*; Kawaguchi, Isao*; Kato, Takaaki*

Risukugaku Kenkyu, 30(3), p.133 - 139, 2021/04

https://doi.org/10.11447/jjra.SRA-0353

Almost ten years have passed since Fukushima nuclear accident. Our experience should be used to improve current emergency protective measures and preparedness. A review of the protective measures implemented in the aftermath of Fukushima nuclear accident has revealed problems such as paternalistic intervention for inhabitants and increased health risks due to the evacuation of vulnerable groups. The risk trade-offs in environmental recovery actions are more complex and ongoing; the stakeholders are the next generation and residents outside of the prefecture. Since one of the characteristics of nuclear disasters is the distance and time dependency of the risk, countless individual cases need to be addressed. While generalization of protective measures is essential, the appropriate deployment of personnel in a variety of roles may require to really address individual cases. To improve nuclear emergency preparedness in the future, it is necessary to incorporate both a top-down approach and a bottom-up approach in a well-balanced manner.

Laser storage ring with high power for realization of laser stripping injection

Harada, Hiroyuki; Yamane, Isao*; Saha, P. K.; Suganuma, Kazuaki; Kinsho, Michikazu; Irie, Yoshiro*; Kato, Shinichi

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.684 - 688, 2017/12

http://www.pasj.jp/web_publish/pasj2017/proceedings/PDF/TUP1/TUP117.pdf

The high-intensity proton accelerator adopts a charge exchange injection scheme, which injects with exchanging from negative Hydrogen ion to proton by using carbon foil. This scheme can realize high intensity proton beam but the uncontrolled beam losses are caused by scattering between beams and the foil. Additionally, the collision may occur the foil beak. Therefore, a new injection scheme for higher intensity is needed as an alternative to the foil. In the J-PARC 3GeV RCS, we newly propose and develop a laser stripping injection scheme. However, it is necessary that laser power is two order higher than latest laser one. To realize this big issue, we develop the laser storage ring, which can provide laser pulse of high repetition rate by recycling one. In this presentation, we will introduce the laser stripping injection scheme and describe the concept of the laser storage ring with high repetition rate and report the current status.

Laser storage ring with high power for realization of laser stripping injection

Harada, Hiroyuki; Saha, P. K.; Yamane, Isao*; Kato, Shinichi; Kinsho, Michikazu; Irie, Yoshiro*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.983 - 986, 2016/11

http://www.pasj.jp/web_publish/pasj2016/proceedings/PDF/TUP0/TUP051.pdf

The high-intensity proton accelerator adopts a charge exchange injection scheme, which injects with exchanging from negative Hydrogen ion to proton by using carbon foil. This scheme can realize high intensity proton beam but the uncontrolled beam losses are caused by scattering between beams and the foil. Additionally, the collision may occur the foil beak. Therefore, a new injection scheme for higher intensity is needed as an alternative to the foil. In the J-PARC 3GeV RCS, we newly propose and develop a laser stripping injection scheme However, it is necessary that laser power is two order higher than latest laser one. To realize this big issue, we develop the laser storage ring, which can provide laser pulse of high repetition rate by recycling one. In this presentation, we will introduce the laser stripping injection scheme and describe the concept of the laser storage ring with high repetition rate.

Effects of gamma-ray irradiation on spontaneous potential of stainless steel in zeolite-containing diluted artificial seawater

Kato, Chiaki; Sato, Tomonori; Ueno, Fumiyoshi; Yamagishi, Isao

Proceedings of 17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, Vol.2, p.1357 - 1374, 2016/05

With respect to the long-term storage of the zeolite-containing spent Cs adsorption vessels used at the Fukushima Daiichi Nuclear Power Station, the corrosion of the vessel material is one of the most important issues. In this study, we performed electrochemical tests on stainless steel specimens in zeolite-containing artificial seawater under gamma-ray irradiation. The spontaneous potential ESP and critical pitting potential VC of the type 316L steel in systems in contact with various zeolites were measured in order to evaluate the corrosion resistance of the steel. In addition, the water sample was analyzed after being irradiated, in order to determine the concentrations of various dissolved oxidants such as oxygen and hydrogen peroxide, which can accelerate the corrosion process. The steady-state rest potential increased with an increase in the dose rate; however, the increase was suppressed in contact with the zeolites. The VC value of the steel when in contact with the zeolites was slightly smaller than the VC value in bulk water; however, the choice of the zeolite used as herschelite, IE96 and IE911 hardly affect the VC value. The concentration of HO in the bulk water under irradiation also increased with the increase in the dose rate. This increase was suppressed in the systems in contact with the zeolites, owing to the decomposition of the HO by the zeolites. A clear relationship was observed between ESP and the HO concentration. As contact with the zeolites caused the increase in ESP under irradiation to be suppressed, it can be concluded that the presence of zeolites in the spent Cs adsorption vessels can reduce the probability of the localized corrosion of the stainless steel in the vessels.

Effect of zeolites on the corrosion potential of type 316L stainless steel in diluted artificial sea water under gamma-ray irradiation

Kato, Chiaki; Sato, Tomonori; Ueno, Fumiyoshi; Yamagishi, Isao; Yamamoto, Masahiro

Zairyo To Kankyo 2015 Koenshu (CD-ROM), p.83 - 86, 2015/05

In relation to the consideration for long-term storage of spent Cs adsorption vessels containing zeolites in the Fukushima Daiichi Nuclear Power Station, corrosion of the vessel material in the spent Cs adsorption vessel is one of important issues. We performed electrochemical tests of stainless steel (SUS 316L) in the zeolites containing artificial seawater under gamma-ray irradiation. The spontaneous potential (ESP) and critical pitting potential (VC), of SUS316L were measured to understand the corrosion resistance of the stainless steel in this study. The rest potential of the stainless steel increased with increasing time after gamma-ray irradiation. The ESP, defined as the steady rest potential, increased with increasing dose rate, while increasing ESP was suppressed by contact with the zeolites. Concentration of HO in bulk water increased with increasing dose rate. The concentration increasing was suppressed by contact with the zeolites due to decomposition of HO. There was good relationship between ESP and the concentration of HO. The VC of SUS316L contacted with the zeolites decreased with increasing Cl ion concentration and is slightly smaller than the VC in the bulk water. The contact with the zeolites causes the suppressant of increasing ESP under the irradiation. The contact with the zeolites can reduce probability in the localized corrosion for SUS316L.

Corrosion of the stainless steel in the zeolite containing diluted artificial seawater under -ray irradiation

Kato, Chiaki; Sato, Tomonori; Nakano, Junichi; Ueno, Fumiyoshi; Yamagishi, Isao

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10

As a part of consideration for long-term storage of spent zeolite adsorption vessels in the Fukushima Daiichi Nuclear Power Station, corrosion of vessel material in the spent zeolite adsorption vessel is one of important issue. We performed electrochemical tests of stainless steel (type 316L) in the zeolite containing artificial seawater under -ray irradiation. Steady spontaneous potential (Esp) and pitting potential (VC), of type 316L was measurement. Co -rays source was used under irradiation. Dose rate of -ray irradiation was controlled for 5 kGy/h and 400 Gy/h. In anode polarization curves, there was no clear difference under irradiation and non-irradiation. The corrosion potential of type 316L increased with increasing time after -ray irradiation. The Esp was shifted to nobler by -rays irradiation, while increasing Esp was suppressed by contacted with zeolite.

An Investigation for long-term storage of a spent zeolite adsorption vessel; Estimation of washing out salt component in a spent zeolite adsorption vessel, 1

Sato, Hiroyuki; Terada, Atsuhiko; Hayashida, Hitoshi; Kamiji, Yu; Kobayashi, Jun; Yamagishi, Isao; Morita, Keisuke; Kato, Chiaki

JAEA-Research 2013-042, 25 Pages, 2014/03

JAEA-Research-2013-042.pdf:5.13MB

Spent zeolite adsorption vessels in the Fukushima No.1 nuclear power plant are kept for long-term with washing out with fresh water for prevention of corrosion remaining salt component in vessel. However, corrosion result is concerned by residual concentration of salt component, washing out experiment is carried out using actual and unspent adsorption vessel (KURION). KURION adsorption vessel is filled with 1,650 ppm of sodium chloride (1,000 ppm of chloride ion) and washed out with pure water for estimating washing effect in this experiment. Pure water is streamed with volume flow rate 4.5 m/h, chloride concentration in vessel is measured with drainage sample water. 1,000 ppm of chloride concentration is decreased till 0.5 ppm and below by washing out with about double pure water volume of adsorbing material filling volume in vessel, washing out is more effective in KURION adsorption vessel.

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

http://accelconf.web.cern.ch/AccelConf/IPAC10/papers/tupe091.pdf

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.