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Journal Articles

Comparison of antioxidative effects between radon and thoron inhalation in mouse organs

Kobashi, Yusuke*; Kataoka, Takahiro*; Kanzaki, Norie; Ishida, Tsuyoshi*; Sakoda, Akihiro; Tanaka, Hiroshi; Ishimori, Yuu; Mitsunobu, Fumihiro*; Yamaoka, Kiyonori*

Radiation and Environmental Biophysics, 59(3), p.473 - 482, 2020/08

 Times Cited Count:1 Percentile:100(Biology)

Radon therapy has been traditionally performed globally for oxidative stress-related diseases. Many researchers have studied the beneficial effects of radon exposure in living organisms. However, the effects of thoron, a radioisotope of radon, have not been fully examined. In this study, we aimed to compare the biological effects of radon and thoron inhalation on mouse organs with a focus on oxidative stress. Male BALB/c mice were randomly divided into 15 groups: sham inhalation, radon inhalation at a dose of 500 Bq/m$$^{3}$$ or 2000 Bq/m$$^{3}$$, and thoron inhalation at a dose of 500 Bq/m$$^{3}$$ or 2000 Bq/m$$^{3}$$ were carried out. Immediately after inhalation, mouse tissues were excised for biochemical assays. The results showed a significant increase in superoxide dismutase and total glutathione, and a significant decrease in lipid peroxide following thoron inhalation under several conditions. Additionally, similar effects were observed for different doses and inhalation times between radon and thoron. Our results suggest that thoron inhalation also exerts antioxidative effects against oxidative stress in organs. However, the inhalation conditions should be carefully analyzed because of the differences in physical characteristics between radon and thoron.

Journal Articles

Concentration ratios of $$^{238}$$U and $$^{226}$$Ra for insects and amphibians living in the vicinity of the closed uranium mine at Ningyo-toge, Japan

Sakoda, Akihiro; Murakami, Shoichi*; Ishimori, Yuu; Horai, Sawako*

Journal of Radiation Research (Internet), 61(2), p.207 - 213, 2020/03

 Times Cited Count:0 Percentile:100(Biology)

JAEA Reports

Research of the tasks on risk communication enforcement in fiscal year 2016 (Contract research)

Tanaka, Masaru*; Kawara, Osami*; Ishizaka, Kaoru*; Ohata, Yuki*; Fukuike, Iori*; Kawase, Keiichi; Tokizawa, Takayuki; Miyagawa, Hiroshi*; Ishimori, Yuu

JAEA-Research 2018-001, 98 Pages, 2018/06

JAEA-Research-2018-001.pdf:2.49MB

In the 2016 fiscal year, communication cases on general waste disposal facility construction plans in recent years were surveyed. Results suggested as follows: (1) Existing long-term relationships or agreements in local area promote local accepting. (2) An operator needs to consider alternative plans and explain reasons for the decision making to local stakeholders. (3) Even after first announcement of a new plan, an operator needs to review the plan depending on local concerns. (4) Announcement of a new plan will activate communications on local development including the site redevelopment.

Journal Articles

Production and detection of fission-induced neutrons following fast neutron direct interrogation to various dry materials containing $$^{235}$$U

Sakoda, Akihiro; Nakatsuka, Yoshiaki; Ishimori, Yuu; Nakashima, Shinichi; Komeda, Masao; Ozu, Akira; Toh, Yosuke

Journal of Nuclear Science and Technology, 55(6), p.605 - 613, 2018/06

 Times Cited Count:1 Percentile:74.25(Nuclear Science & Technology)

For better nuclear material accountancy, we had developed a non-destructive assay system dedicated to uranium waste drums (JAWAS-N: JAEA Waste Assay System at Ningyo-toge). The system is based on a fast neutron direct interrogation (FNDI) method. To clarify the characteristics of the FNDI method and the performance of JAWAS-N, experimental and computational mock-up tests were carried out using various dry materials that contained known amounts of natural uranium. As a result, linearity between the die-away time ($$tau$$$$_{2}$$) and the counts of fast neutrons attributed to $$^{235}$$U fission was confirmed experimentally and analytically. Moreover, the MCNP simulation was performed to discuss the radial and axial dependences of $$^{235}$$U fission probability, neutron detection efficiency, and sensitivity on uranium distributions in the drum. The simulation results agreed with the empirical results reported in a previous paper, providing valuable information on the practice of FNDI-based uranium determination. Furthermore, the nominal detection limits of natural uranium in JAWAS-N were estimated to be 15, 4, and 2 g for $$tau$$$$_{2}$$ = 0.2, 0.3, and 0.4 msec, respectively. The findings obtained here will contribute to the implementation of the FNDI method to assess the quantities of $$^{235}$$U in actual uranium waste drums.

Journal Articles

Comparative effects of radon inhalation according to mouse strain and cisplatin dose in a cisplatin-induced renal damage model

Sasaoka, Kaori*; Kataoka, Takahiro*; Kanzaki, Norie; Kobashi, Yusuke*; Sakoda, Akihiro; Ishimori, Yuu; Yamaoka, Kiyonori*

Pakistan Journal of Zoology, 50(3), p.1157 - 1170, 2018/06

 Times Cited Count:1 Percentile:73.98(Zoology)

Cisplatin (CDDP) is widely used for treating solid cancers; however, it induces nephrotoxicity caused by oxidative stress. Here, we investigated whether radon inhalation has different effects against CDDP induced renal injury in two mouse strains differing in radiosensitivity, and determined the appropriate dose of CDDP combined with radon inhalation for highly radiosensitive mice. CDDP was administered at 20 mg/kg weight to C57BL/6J and BALB/c mice after radon inhalation at 1000 Bq/m$$^{3}$$ and 2000 Bq/m$$^{3}$$ for 24 h. Radon inhalation had a slight positive effect against CDDP toxicity in C57BL/6J mice with respect to improved hair condition, whereas radon inhalation exacerbated CDDP-induced toxicity in BALB/c mice. When BALB/c mice were treated with a lower dose of CDDP (15 mg/kg) after 1000 Bq/m$$^{3}$$ radon inhalation, the creatinine level was reduced and the superoxide dismutase content was increased. The supportive effect of radon inhalation shows its good potential as a candidate treatment to alleviate CDDP-induced renal damage.

JAEA Reports

The Annual report on the environmental monitoring around the waste rock sites 2016 Tottori

Ono, Takayuki; Kawasaki, Satoru; Ishimori, Yuu; Ando, Masaki

JAEA-Review 2017-044, 13 Pages, 2018/03

JAEA-Review-2017-044.pdf:1.17MB

The Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency performs the environmental monitoring around the Ningyo-toge and the waste rock sites according to the agreements with local governments, Okayama and Tottori prefectures. Each prefectural committee on the environmental monitoring evaluates the monitoring data annually. This report summarized the results of the environmental monitoring in Tottori prefecture in the fiscal year 2016. The results show that the levels of the radiation doses and the radioactive concentrations in the environment were within natural variations, and the waste rock sites have been well maintained. The committee concluded that the environmental impacts from the sites were negligible.

JAEA Reports

The Annual report on the environmental monitoring around the Ningyo-toge 2016 Okayama

Ono, Takayuki; Kawasaki, Satoru; Ishimori, Yuu; Ando, Masaki

JAEA-Review 2017-043, 39 Pages, 2018/03

JAEA-Review-2017-043.pdf:1.92MB

The Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency (JAEA Ningyo-toge) performs the environmental monitoring around the Ningyo-toge and the waste rock sites according to the agreements with local governments, Okayama and Tottori prefectures. Environmental monitoring of plutonium has been also performed around the Ningyo-toge regarding the practical application study on the reprocessed uranium conversion, which was carried out from 1994 to 1999 at the Ningyo-toge. Each prefectural committee on the environmental monitoring evaluates the monitoring data annually. This report summarized the results of the environmental monitoring in Okayama prefecture in the fiscal year 2016. The results show that the levels of the radiation doses and the radioactive concentrations in the environment were within natural variations, and the committee concluded that the environmental impacts from the sites were negligible. Therefore, the site of the JAEA Ningyo-toge has been well operated, and the waste rock sites have been well maintained.

Journal Articles

Knowledge discovery of suppressive effect of disease and increased anti-oxidative function by low-dose radiation using self-organizing map

Kanzaki, Norie; Kataoka, Takahiro*; Kobashi, Yusuke*; Yunoki, Yuto*; Ishida, Tsuyoshi*; Sakoda, Akihiro; Ishimori, Yuu; Yamaoka, Kiyonori*

Radioisotopes, 67(2), p.43 - 57, 2018/02

We previously reported that low-dose radiation induces the anti-oxidative function in many organ systems of mice. This results in the suppression of several kinds of oxidative stress-induced damage. This study was conducted with the objective of revealing the health effects of low-dose radiation obtained from our previous reports and searching for a new treatment based on low-dose radiation, such as radon therapy. We extracted the characteristics of the effects of low dose radiation suppressing diseases and enhancing the anti-oxidative function using fuzzy answer by self-organizing map (SOM) based on mutual knowledge. The relationship between the suppressive effect and increased antioxidative function was shown in our result, and the concentration dependence of the effect against pain was shown on the output map. Although the effect against other organs depending on concentration was unpredictable, our results indicate that low-dose radiation may also be suitable for treatment of liver disease and brain disease.

Journal Articles

Mechanisms and modeling approaches of radon emanation for natural materials

Sakoda, Akihiro; Ishimori, Yuu

Hoken Butsuri, 52(4), p.296 - 306, 2017/12

Radon emanation means the escape of radon atoms from solid grains into pore space; it is the very first process that may lead to radon exposure in the environment. Experimental and numerical studies of radon emanation have been diligently carried out since its recognition as a carcinogen. Our previous review of the measured data showed a wide range of radon emanation fractions from natural substances, and then we discussed the effects of environmental factors such as pore water. The present paper provides an overview of the approaches and progress of radon emanation modeling that may be useful for the interpretation of measured data. Recoil and/or diffusion of radon in solid following alpha decay of radium, which underlies the mechanisms of radon emanation, have been incorporated into numerical models. In the calculation based on recoil-based emanation, radium distribution and pore size were the most important parameters, which govern the magnitudes of radon ejections from the birth grain and of radon embedding into another solid surface, respectively. The solid diffusion appeared significant only at a temperature higher than a few hundred degrees Celsius. A model is now desired to be developed that incorporates the transport process of radon atoms that are still settled in solid after alpha recoil, considering radiation damage and its resulting inner path network.

JAEA Reports

Research of the tasks on risk communication enforcement in fiscal year 2015 (Contract research)

Tanaka, Masaru*; Aoyama, Isao*; Ishizaka, Kaoru*; Ohata, Yuki*; Fukuike, Iori*; Kawase, Keiichi; Watanabe, Masanori; Tokizawa, Takayuki; Miyagawa, Hiroshi*; Ishimori, Yuu

JAEA-Research 2017-003, 65 Pages, 2017/06

JAEA-Research-2017-003.pdf:2.92MB

JAEA Ningyo-toge Environmental Engineering Center and Fukushima Environmental Safety Center have same challenges in risk communication. As reference, similar domestic cases were investigated by our two Centers, and requirements for building long-term relationship were clarified. As follows; (1) Develop new relationship with various stakeholders in the region. (2) Make better use of existing resources (personnel, land and facilities, etc.). (3) Make a concerted effort to create new values with local stakeholders. (4) Make an opportunity which local stakeholders confirm safety and build confidence to the project. These efforts will enhance the opportunities for operators and residents to learn about environment management and environmental protection.

Journal Articles

Protective effects of hot spring water drinking and radon inhalation on ethanol-induced gastric mucosal injury in mice

Etani, Reo*; Kataoka, Takahiro*; Kanzaki, Norie*; Sakoda, Akihiro; Tanaka, Hiroshi; Ishimori, Yuu; Mitsunobu, Fumihiro*; Taguchi, Takehito*; Yamaoka, Kiyonori*

Journal of Radiation Research, 58(5), p.614 - 625, 2017/05

 Times Cited Count:2 Percentile:73.23(Biology)

Radon therapy using radon ($$^{222}$$Rn) gas is classified into two types of treatment: inhalation of radon gas and drinking water containing radon. Although short- or long-term intake of spa water is effective in increasing gastric mucosal blood flow, and spa water therapy is useful for treating chronic gastritis and gastric ulcer, the underlying mechanisms for and precise effects of radon protection against mucosal injury are unclear. In the present study, we examined the protective effects of hot spring water drinking and radon inhalation on ethanol-induced gastric mucosal injury in mice. Mice inhaled radon at a concentration of 2000 Be/m$$^{3}$$ for 24 h or were provided with hot spring water for 2 weeks. The activity density of $$^{222}$$Rn ranged from 663 Bq/l (start point of supplying) to 100 Bq/l (end point of supplying).Mice were then orally administered ethanol at three concentrations. The ulcer index (UI), an indicator of mucosal injury, increased in response to the administration of ethanol; however, treatment with either radon inhalation or hot spring water inhibited the elevation in the UI due to ethanol. Although no significant differences in antioxidative enzymes were observed between the radon-treated groups and the non-treated control groups, lipid peroxide levels were significantly lower in the stomachs of mice pre-treated with radon or hot spring water. These results suggest that hot spring water drinking and radon inhalation inhibit ethanol-induced gastric mucosal injury.

Journal Articles

Measurements of radon activity concentration in mouse tissues and organs

Ishimori, Yuu; Tanaka, Hiroshi; Sakoda, Akihiro; Kataoka, Takahiro*; Yamaoka, Kiyonori*; Mitsunobu, Fumihiro*

Radiation and Environmental Biophysics, 56(2), p.161 - 165, 2017/05

 Times Cited Count:4 Percentile:64.02(Biology)

In order to investigate the biokinetics of inhaled radon, radon concentrations in mouse tissues and organs were determined after mice had been exposed to about 1 MBq/m$$^{3}$$ of radon in air. Radon concentrations in mouse blood and in other tissues and organs were measured with a liquid scintillation counter and with a well-type HP Ge detector, respectively. Radon concentration in mouse blood was 0.410$$pm$$0.016 Bq/g when saturated with 1 MBq/m$$^{3}$$ of radon concentration in air. In addition, average partition coefficients obtained were 0.74$$pm$$0.19 for liver, 0.46$$pm$$0.13 for muscle, 9.09$$pm$$0.49 for adipose tissue, and 0.22$$pm$$0.04 for other organs. With these results, a value of 0.414 for the blood-to-air partition coefficient was calculated by means of our physiologically based pharmacokinetic model. The time variation of radon concentration in mouse blood during exposure to radon was also calculated. All results are compared in detail with those found in the literature.

Journal Articles

Current status of decommissioning activities at Ningyo-toge Environmental Engineering Center

Ishimori, Yuu

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04

This paper illustrates the current status of decommissioning activities at four facilities in the Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency. (1) The Test milling facility was dismantled from 1999 to 2002. The dismantled materials are stored, and surveyed to determine the quantities of contaminants in the Dismantled materials storage facility. (2) Major equipment at the Refining and conversion facility was dismantled and removed from 2008 to 2013. About 530 t of dismantled materials were generated. Measures of other materials and equipment are taken for easier area managements. (3) A part of centrifuges in the Enrichment engineering facility was decontaminated with 5% of dilute sulfuric acid, and some of them were reused after clearance. Major equipment except centrifuges at the facility has been dismantled and removed since 2014. Dismantling activity will end in 2022. So far, about 270 t of dismantled materials were generated. (4) Centrifuges in the Uranium enrichment demonstration plant have been flushed by $$mathrm{IF}_7$$ gas since 2002 before dismantling. Decontamination efficiencies for DOP-1 and for DOP-2 were about 91% and 99%, respectively. Further plans for dismantling of centrifuges are under review. (5) Related techniques such as measurements are also explained.

Journal Articles

Comparison of classification performances between Random forests and Support vector machine for $$gamma$$-ray spectral data of uranium-bearing waste drums

Hata, Haruhi; Ishimori, Yuu

Radioisotopes, 66(4), p.149 - 158, 2017/04

For the estimation of radioactive inventory, the radioactive waste drums should be classified based on their radioactive composition. We compared the classification performances between random forests and support vector machine, both of which are machine learning methods. The tested uranium in waste drums included natural uranium from uranium ore, reprocessed uranium from nuclear fuel, and natural uranium with rich radium from the impurities in yellow cake. A total of 75 data in 1037 $$gamma$$-ray spectral data of these drums were trained, and 962 data were applied in the classification models. It was found that the random forests were advantageous in the shift of the channels.

JAEA Reports

Enforcement management system for decommissioning project in Ningyo-toge Environmental Engineering Center; Results of activities in fiscal year 2015

Ema, Akira; Ishimori, Yuu

JAEA-Review 2016-034, 84 Pages, 2017/03

JAEA-Review-2016-034.pdf:8.96MB

The Ningyo-toge Environmental Engineering Center of the Japan Atomic Energy Agency has managed the decommissioning projects since 2013. In 2015, Enforcement Management System (EMS) was established to enforce the project management systematically. The project management based on EMS was started in 2015. This report summarized the state of management activities in FY 2015.

Journal Articles

Current status of uranium measurements and their related techniques at JAEA Ningyo-toge

Ishimori, Yuu; Yokoyama, Kaoru*; Hayakawa, Tomoya; Hata, Haruhi; Sakoda, Akihiro; Naganuma, Masaki

Dekomisshoningu Giho, (55), p.36 - 44, 2017/03

This paper gives an outline of the current status of uranium measurements and their related techniques at the Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency. The JAWAS-N and the Q$$^2$$ system have been adopted to evaluate uranium contents in the wastes. About 10 g or more of uranium in a 200 $$ell$$ drum can be evaluated by these systems. The equivalent model developed to correct the evaluation results with Q$$^2$$ system is not available to less than dozens of grams of uranium in a 200 L drum. The paper illustrates the advantage of use of the improved equivalent model which evaluates uranium content from full energy peak of 1001 keV and its Compton spectrum in order to correct the inhomogeneous distribution of uranium in measuring objects. The use of model achieved the limit of uranium quantitative determination under one tenth of those of previous evaluation methods. To determine $$^{235}$$U, it was demonstrated that the shielding factor, $$X_{geometry}$$ for evaluation of 1001 keV $$gamma$$-ray is also possible to use for evaluation of 186 keV $$gamma$$-ray. The measurement systems adopting the model have been introduced to other nuclear operators in Japan. In addition, it is also examined to use for clearance. As a related technique, feasibility studies on machine learning algorithms have been performed to classify the waste drums depending on their $$gamma$$-ray spectrum.

Journal Articles

Verification of the quantitative method of caesium radioactivity concentration of decontamination wastes

Yokoyama, Kaoru; Suzuki, Atsuo*; Ishimori, Yuu

Radioisotopes, 66(3), p.117 - 125, 2017/03

Decontamination wastes contaminated with radioactive cesium ($$^{134}$$Cs, $$^{137}$$Cs) are housed in the flexible container bags. Canberra manufactured flexible container concentration measurement car has been developed for the radioactivity measurement of decontamination waste. For reduction of background, the flexible container bags is mounted to the frame, it is measured from the lower side. In the flexible container bag, if there is uneven distribution of the source, it is estimated that quantification error increases. We proposed the method quantifying the shielding situation of $$gamma$$ rays. Then, it demonstrated that quantification accuracy of radioactivity can be improved.

JAEA Reports

Research of the tasks on risk communication enforcement (Contract research)

Tanaka, Masaru*; Aoyama, Isao*; Ishizaka, Kaoru*; Ohata, Yuki*; Fukuike, Iori*; Miyagawa, Hiroshi*; Ishimori, Yuu

JAEA-Research 2016-017, 76 Pages, 2017/01

JAEA-Research-2016-017.pdf:10.57MB

From 1955 to 2001, Japan Atomic Energy Agency (JAEA) carried out research and development projects related to uranium exploration, mining refining, conversion and enrichment at/around Ningyo-toge in Japan. Subsequently, JAEA has been conducting projects related to decommissioning of nuclear fuel cycle facilities and remediation of closed mine sites. JAEA had opportunities of communication with local stakeholders through the projects. Consensus building with local stakeholders and maintain it for over decades are important challenges for JAEA Ningyo-toge Environmental Engineering Center. For this aim, similar domestic case were investigated and compared, and evaluated about required measures for long term relationship with local stakeholder.

Journal Articles

Classification of radioactive waste drums using random forests for their $$gamma$$-ray spectra

Hata, Haruhi; Ishimori, Yuu

Radioisotopes, 66(1), p.1 - 10, 2017/01

The feasibility of Random Forests, one of machine learning methods was examined for the classification of radioactive waste drums. It was carried out using 954 $$gamma$$-ray spectra of drums which were already classified to natural or reprocessed uranium. After 300 spectra were selected at random to reassemble training datasets, the percentages of correct classification by Random Forests were evaluated with another 654 spectra. When the counts of spectra were reprocessed as the difference of their logarithm, Random Forests accurately classified 654 drums.

Journal Articles

One-year measurements of $$gamma$$-ray background using a high-purity germanium detector

Sakoda, Akihiro; Tanaka, Hiroshi; Ishimori, Yuu

Hoken Butsuri, 51(4), p.245 - 250, 2016/12

In the present work, the natural $$gamma$$-ray background was thoroughly measured using a high-purity germanium detector in a year (283.5 days in total, $$n$$ = 271). The data was first discussed in relation to radon concentrations in the laboratory. No correlations were found between the $$gamma$$-ray count rates from $$^{214}$$Pb and $$^{214}$$Bi and radon concentrations, meaning that radon just around the germanium detector was reduced to the negligible level by the introduction of nitrogen gas. Also, the count rates of major nuclides appeared to fluctuate with the coefficient of variance of a few up to several tens of percent, without seasonal variations. Furthermore, summing of all $$gamma$$-ray spectra allowed us to see neutron-induced peaks that cannot be detected in usual short-term measurements. All data obtained here would be the knowledge useful for the practice of $$gamma$$-ray measurements.

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